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Car's an '84 GSL-SE, and the short of it is that I've got a fast idle problem and a severe surging/bucking problem.
Recent Background: On my way to take it for an inspection, I noticed it idled high at 3,000 RPM, and I got a bit of surging in second gear; when I'd coast, it'd suddenly accelerate gently for a couple of seconds, and then coast, and then accelerate, etc… Nonetheless, I dropped it off. It passed the inspection, but they told me the throttle body was bad. They're just an oil-and-tires shop, and I don't put much stock in what they say. Anyway – the car didn't throw any codes. The shop said they performed a smoke test and there were no vacuum leaks, and that they also cleaned the throttle body (I wish they'd asked me first). I went to get the car. Now it was idling at 4,000 RPM. I took it for a spin, and not long after it began surging and bucking so violently – under acceleration, and while coasting, in several gears, everything – that I thought it was going to put me through the windshield. The shop was close to home, so I coasted into my apartment lot. The next day I got fairly sick and wasn't able to make it outside for four weeks, and the car sat, which brings us to today.
Today: My first thought was a bad TPS. I grabbed a multimeter to measure the TPS' voltage from idle to full throttle, but when I popped off the air intake hose, I saw the throttle plates were stuck wide open. I checked and adjusted the accelerator cable, which didn't help. I had someone gradually press the accelerator pedal with the key in accessory position, and the throttle lever/linkage smoothly rotates all the way forward, and when the pedal lifts off it smoothly rotates all the way back, but the throttle plates don't budge. The throttle body doesn't look dirty, and since the plates are open it wouldn't be the plates' edges sticking. Anyone want to help me figure what to check first?
First off, surprised a shop would pass a vehicle with a condition like this for a safety inspection...i know i wouldn't. Tps defect a good guess,but would need some diagnostics before condemning it as cause for your problem. Not certain why you removed air intake for tps check.
What you saw as throttle plates stuck wide open are #2secondary throttle valve,with engine not running they are normally in this position. This(these)are controlled by the double throttle diaphragm located to the right of throttle body facing front of car.
A look a little further into throttle bore will show you the primary &secondary throttle valves which should be closed(mostly) in engine off and idle speed condition. The throttle body although complicated is a very reliable unit. Most driveability complaints by what is believed to be the throttle body are actually components that control it and require a logical diagnostic approach to uncover the problem. Hopefully the shop that cleaned it didn't make any adjustments to it in the interest of lowering the excessively high idle. I know you adjusted the throttle cable,would suggest returning it to previous adjustment. Next you need to make sure there's no mechanical reason for the condition. Need to remove air intake hose once again and look into back of throttle housing at throttle valves-should all be same,essentially closed. Operate throttle and watch opening/closing of these. This is best done on a warmed engine as thermowax pellet will engage fast idle cam and prop throttle slightly open. This is your fast idle mechanism that elevates idle speed til engine warms and is engaged til coolant is warm enough to act on pellet. I for one wouldn't want a cold engine to scream at 4k on startup,so before you touch the throttle(without starting) look in throttle body at throttle valves and see if all are closed,then operate throttle open/close. All should move smoothly and return consistently,though primary throttle may stay open a few degrees due to aforementioned fast idle mechanism which you should hear click into position as throttle is initially opened. Check these things and post back results for direction on how to proceed.
Much appreciate the tip to check farther inside the TB. As an aside, taking the air cleaner hose off the TB didn't have anything to do with the TPS check; I figured I'd check the TB for grime while I was under the hood. Anyway, the primary and secondary throttle valves open and close smoothly with the accel. pedal, and there's just the normal bit of clearance for the primary valve at a rest while the engine is off. I didn't get the chance to run the car today, but before I lost my sunlight I began the TPS check. It appears to have no ground on any of the three pins. Once I get my lighting back in the morning, I'm going to take a closer look at whether the PO or shop messed with the adjusting screw.
That TPS isn't showing any life. I played with the adjustment screw as much as I could, and it still didn't show even a fraction of a volt through either the TPS connector or the green checking connector, and then I returned the screw to the adjustment it started with.
The tps is a variable resistance unit,needs reference voltage to send appropriate voltage back to ecu. Disconnected from wire harness at connector should show @1k ohms at idle position and @5k ohms wot and have smooth readings throughout with no glitches or dropouts. This is another item in the system that historically is very reliable. Never say never but... Two voltmeters are necessary to adjust it or a pair of 3.4 watt bulbs made up into a tester that plugs into that green connector,the latter is my choice. Quicker,easier. Strange there is no voltage at check connector,as the car starts and runs. Time for fsm and wiring diagram. Look at wire harness from connector and follow it back and see if any signs of damage(rodent damage always a favorite for something like this),break in wire,etc. Any history of water leaks in pass side footwell area? Maybe pull back carpet and put eyes on ecu,not hard to pull out to check continuity of wires to tps and back.
No water leaks, and nothing electrical looks chewed in the car. I went back over all the vacuum tubing to make sure the shop, PO, etc. didn't mis-route any of them or that any have cracked or slipped off, but every vac hose goes where it should and looks to be in fine shape. I'm working from the '85 FSM, plus a Haynes and Chilton for cross-reference. I took off the BAC/IAC valve, took them apart from each other, and had a peak. The valve inside the BAC opens and closes as it should. I attached a piece of clean vac hose to the BAC and sucked in as well, and the valve works fine that way, too. I'll hook the IAC up to the battery to see if it engages/disengages as it should, but if I eliminate vac hoses, TB function/grime, TPS, and BAC/IAC, I've eliminated the easy culprits. Part of what had me suspecting electricals was how unpredictable the bucking/surging was. The idle stays a constant 4000RPM and doesn't fluctuate at all, but the bucking, during the drive home, came and went without any noticeable pattern.
Stay focused on throttle position sensor. Voltage(lack of?),adjustment & operation. One of most important sensor inputs ecu uses to calculate fuel for a given mode of operation. Try to figure out what's not right with this and make it right before moving on to something else as a possible cause. Trust fsm for specifications and wiring diagrams. Haynes manual is a good resource but have found inconsistencies in some wiring diagrams. Following this thread.
Ok, my apologies for the radio silence. Pneumonia came back and took away all my willpower to see this through the past couple of weeks. So I checked the IAC valve out a few weeks ago, applied 12V battery power, and it works perfectly. I reinstalled it and the BAC. Then I wanted to check the TPS one more time, so this evening I warmed up the car to operating temp to get started. A few observations:
- Upon starting, it goes straight to 4000 RPM. And then it steadily climbs over the next minute to 4900RPM and stays there. Turning on the A/C drops the RPM very slightly.
- I turned the engine off, took the key out of the ignition, and then put it back to ON position, as according to this helpful nugget. I disconnected the TPS plug and hooked up my multimeter. I should be getting 1k ohms at idle, gradually rising to 5k ohms at full throttle as my wife worked the gas pedal. Instead, I got a consistent 2.26k ohms at idle, and then as she pressed the gas pedal it skipped erratically down to 0.37k ohms at full throttle. As she gradually let the gas pedal up, it skipped back up until it was at 2.08k ohms at idle.
- For kicks, I kept the key in ON, plugged the TPS back together, and got two multimeters, set them to 20 V DC. I hooked them up to the green connector plug, and both registered 0 V. No amount of adjusting the TPS screw registered voltage on either one. I realize later I'm going to have to check the TPS adjustment once all is said and done, but I took a picture of the screw's position before I started and turned it back to where it was. It's very close to where it was, if not exact.
Bad TPS, me thinks, unless someone sees an operator error somewhere.
Sorry to hear about your recurring health issues. I'm familiar with the article you refer to in your post and suspect i know the reason you're not reading any voltage on tps circuit at test connector.
There is no need to remove key from ignition AFTER you shut the car off. You then need to turn the key to ON position,same position it's in when car is running. All warning lights will be lit across bottom of instrument cluster,this position powers up ecu and provides the reference voltage to test connector among other things. If you do this and go back to test connector i'm very sure you will find voltage there.
Would also revisit ohm testing of tps. Also somewhat certain you have a mechanical problem with throttle body and or a massive air leak causing that 5k rpm idle. Do you hear any air rushing/sucking sound when engine is running? The complaint in your original post sounds like could be tps related in association with something else. It is possible to have more than one problem causing this.
Ah, I'm referring to it as ACC out of habit, but I believe it was in ON when I did the two-multimeter test. The key was turned as far as it goes without cranking, and I got the row of warning lights and gauges came online. I'll make the edit in the last post so that it doesn't throw anyone off. So it was in ON, car had been warmed up, and it still read 0 volts at the green connector at any setting. I tested the TPS several times and always got 2.xxK ohms at idle and <0.4K at full throttle, which is odd and backwards. As far as the TB goes, I don't see any binding in the linkage when the throttle is operated. The dashpot works, the return spring works, the accel cable is adjusted, and the plates close and open smoothly. Vac hoses are all routed correctly and in good shape - some are new - and the upper/lower intake gasket is new. I'm leaning toward ordering a new TPS since the ohm test is so screwy.
Time to look into wiring diagram in fsm,follow circuit back to ecu in car and put eyes on connector that wire is in and look at the associated pin in ecu for corrosion etc. Continuity test should be done from ecu connector back to test connector by tps. Check to make sure the circuit doesn't go to ground.
Disconnect ecu and remove from bracket to look at closely for corrosion or any damage. Depending on what you find with tps reference wire you may want to do a pin out test for all the wires coming/going from ecu. Make certain power going in and power coming out is as it should be. Check all ecu grounds for resistance. Most everything controlled by ecu is done thru grounds.
Quick question: should my primary throttle plate be open at all, even a little, when the car is off? The FSM doesn't explicitly say, but it seems to imply that it should be fully closed at idle/off. Here are a few pics of that top, primary throttle plate, and you can see the gap at the bottom. It looks to be 0.25 inch or so open.
Your first post you stated the shop that did inspection cleaned the throttle body... that throttle body is filthy,throttle blade looks propped open further than should be. Probably coked,carboned up. Subscribe to kiss philosophy-keep it simple s***** Do the basics first and rule that out before jumping to conclusions with other components being bad. In one of my previous posts i mentioned that i believed this to be a mechanical problem and/or a vacuum leak.
That picture shows a mechanical problem,you need to figure that out before you do anything else-starting with thoroughly cleaning of throttle bore and plate and shaft. VERY good chance this is only problem,very certain there's a ring of sludge/dirt in throttle bore not allowing plate to open/close fully.
Open throttle fully and look at the bore,should be shiny/clean,same with throttle plate-should look just like those secondary air valves. Throttle body assly should be cleaned approx every 30k-doubt that's ever been serviced.
Cleaning: what you'll need..Throttle body cleaner(CRC makes a good product),old toothbrush,clean lint free(shop) rag,light spray oil (CRC Power Lube) works good. Open throttle fully and spray throttle body cleaner into throttle bore,onto throttle plate and shafts. Use toothbrush and scrub deposits off throttle body bore both sides and edges of throttle plate and throttle shaft. Spray more cleaner onto all scrubbed parts and follow up with some cleaner sprayed on rag and do a final wipedown of all cleaned parts-everything should be shiny new looking. Spray power lube onto throttle shaft and work throttle open/closed. Throttle plate should now be in base idle position-noticeably more closed than it is currently. Look at secondary throttle valves and do the same if needed. Put everything back together and start car and see what results you have. Worst case scenario,throttle shaft may be bound up with sludge where it passes thru throttle body housing and will need more cleaning to free up. If idles normally,then go thru tps check/adjustment once warmed up.
That's an old pic from before it was cleaned. Here's a newer batch of pictures. The first pic shows the car cold, not warmed up, with the primary throttle plate propped open (is it too far open?). The last pic shows the car still cold, but I manually flipped the throttle lever off fast-idle, to where the throttle plate would be after the car is warmed up.
1st,really hard to tell in pics. I can see the opening on bottom 1/2 of throttle plate, i can't see the top of throttle plate/bore. You need to look at that closely,it should mirror the opening you see on the bottom as in exactly the same. If it's not,something's out of whack. Bent throttle plate,loose bolts on throttle shaft allowing throttle plate to move out of centered position. It does look to be open excessively. If that all checks out, while throttle plate/linkage is in warm position(base idle) look at throttle stop tab to be sure it's resting on threaded adjustment stud. Leaning over right fender,it is to left of throttle body air intake hose. Look carefully to see that tab that contacts stud(throttle stop) is actually resting on it.
There is another possibility in event the two aren't in contact with each other. The idle dashpot could be misadjusted,seized or its attaching bracket is bent not allowing throttle to fully close.
Will post some pics in a bit of the above.
Much appreciate you going out to take pictures. It's a PITA to get a picture of the top half of the primary throttle plate, but it looks straight and not bent. Here are a few pics I managed to take while the engine was cold (no time to warm it up today):
As the engine sits normally when off and cold:
With me manually taking the throttle lever off fast idle:
Again, as it sits normally. This time the dashpot, which has daylight between the bracket and the dashpot:
Off fast idle, with the dashpot pushed partway in:
The whole thing (note: I took the accelerator cable off its mount, and that other cable too):
And with fast idle off:
Here's the fast idle arm at the lower right side of the screen, and that little roller connected to the throttle lever. Again, engine cold and sitting normally:
And here it is with fast idle off:
Just for kicks, I tested the TPS again. This time, I didn't have a second person handy, so I checked resistance by gradually pushing in the button on the back of the TPS. I got 0.2k ohms at idle and about 4.5k ohms at full throttle, consistently. Not what it should be, but closer. Don't know what to make of that. And then I reconnected the TPS, and I hooked two multimeters up to the green connector and switched them to 20V DC, and put the key to ACC. I got an erratic 10-20V+ on both, so I backed off the TPS adjustment screw counterclockwise just the slightest amount, and I got 0V on both. I turned it clockwise again to try to get one multimeter to register, but neither would register any voltage from that point. Then somewhere in the engine bay starting furiously clicking/ticking, like something was shorting out. Bad ground or wiring, maybe? I took the key out, took the multimeters out, and reset the screw to what it was before (I'd taken a pic of the position of the screw beforehand). It's odd; I go out at different times, do the same thing, and get crazy different results, and I've been testing TPSes and other sensors for many a year. So something is causing that massive steady high idle, and I'm thinking a (potentially?) separate electrical issue could be causing (or exacerbating) that unpredictable bucking and surging while driving.
Is the throttle shaft tab resting on throttle stop stud,like in this pic after engine warmed,fast idle cam off step in base idle position?
Something doesn't look right with your throttle linkage, will compare with a throttle body i have at home later.
Ok, like mentioned in previous post...if engine is cold,flip fast idle cam to off position and check to make sure throttle shaft tab is resting on throttle stop stud as in pic in above post where i'm holding a penlight to highlight what you should be looking at. It should be. Don't adjust if not,very rarely if ever does this adjustment need to be altered. Now look at pic in this post where screw is highlighted with penlight. This is from my SE. Look at the next pic with the throttle opened nearly wot, see how the screw is threaded into another lever arm with spring in middle to hold tension? Look back at one of your shots that show the same view and look at the same screw adjuster, see how yours is backed out-been like that long enough to make witness marks where it's been moving around. Open throttle about 90 degrees like you see in my second pic so you can see the screw thread/spring and lever arm it's supposed to be screwed into,pretty certain it's barely screwed in at all.
Your comment about idle position tps reading of 0.2k got me thinking about linkage again. No reason for this adjustment to be changed either,suppose someone twiddling screws trying to lower idle speed... make sure adjusting screw threads are not effed up and tighten screw til duplicates what you see in my pic. Close throttle,flip idle cam down and look at throttle stop tab/adjusting stud. Are they touching each other now,is throttle plate open now to about 15 degrees=closed more than it was? If so recheck your tps idle speed ohm reading,should be close to around 1k ohms-close enough to start and warm car to adjust tps properly.
Really hard to see this stuff thru pics,kept scrolling back and forth thru all pics you've taken before i saw that,lot easier when car is in front of you. Put this right and see if this doesn't get you closer to where you need to be. Post back results so others may learn from this thread in future. Will look in on thread later.
All right, finally got a break from the rain to go out there last night. That fast idle adjusting screw was pretty loose; that was a good catch. I checked resistance on the TPS again after tightening it up, and the three pics show, in order:
- 1k ohms, engine cold, didn't touch fast idle
- 0.3k ohms, engine cold, flipped fast idle off
- 4.15k ohms, engine cold, throttle completely open. The throttle linkage was not touching the button on the back of the TPS at this point, so there seems to be no way to raise it by fiddling with any of the screws on the throttle arm. That's as far as the TPS button goes out. Does that matter, or is that considered close enough to the 5k specified in the FSM?
And then the last picture was the end result of adjusting the TPS afterward. That took care of the ticking I mentioned in my last thread. It seemed that fast idle adjusting screw was so loose before that it was causing the TPS to go rapidly in and out of spec, and that was the ticking sound. Once the screw was tightened, I could set the TPS.
Having trouble following what you're saying regarding your measurements. The most important thing with ohm testing tps is to note min/max ohm readings and then sweep tps thru its range from idle to wot and look for steady ascending/descending resistance values with no glitches or dropouts.The actual specific numbers are not as important as smooth operation of tps.
ANY adjusting of tps should be on a warm just shut down engine. Critical here is the throttle shaft tab resting on throttle stop stud in warm idle position? Is primary throttle plate closed except for about a 15 degree opening-at warm idle position? If they're not as described,you need to find out why. Removal,disassembly and thorough inspection/cleaning of everything involved should be done first if this is not the case. Lastly,all the tps adjusting is meaningless if the throttle shaft/stop is not in closed warm idle position. This is how ecu knows engine is in idle position and calculates everything for operation in off idle position.
I was sorely hoping my next post here would be "Hurray! Mission accomplished!," because I was 95% of the way there, but I'm back with a last call. I tightened up that fast idle adjusting screw and started the car, and it idled much better. Low and steady 1ks until the engine warmed up, but then it sank to a steady 700 RPM, which is admittedly pretty close. But I'm having a hell of a time getting it to 800 RPM.
- No further slight adjustment of that fast idle adjusting screw, clockwise or counterclockwise, has any more effect on the RPM; it doesn't raise or lower it from 700 RPM.
- I unplugged the vent/vac solenoid connector and then tried to adjust the air adjust screw, but that had no effect on the RPM either, which shouldn't be the case.
I feel like I'm overlooking something minor and obvious. I'm going to look at this with fresh eyes tomorrow when I'm not exhausted and mentally spent.
Ok...1st need to put that "cam"screw adjuster back to the duplicate of the pic i previously posted. Start car and let run to operating temp=temp gauge at normal position. Leave this screw alone at this point until final adjustments are made,it has nothing to do with idle speed. It is used to adjust reference point for tps at base idle speed.
With car running at base idle speed,all accessories off,note idle speed. Air bypass idle screw on top of throttle housing.. turn clockwise to lower idle speed,ccw to raise it. Keep in mind this is a fine adjustment with an optimistic range of 150 rpm approximately. If there is NO change up or down on idle speed,idle air bypass circuit may be plugged,not common but happens. Fix is thorough cleaning of throttle body. Of mention here,this is a delicate adjustment and screw should turn smoothly. It has a stopping point when screwed in all the way,don't force any further. Likewise turning ccw to raise idle speed shouldn't be turned past point where idle speed raises no more. This is the 150rpm window referred to above.
Put a timing light on leading/trailing pointer and be sure ignition timing is correct while car is running at warm idle. With light on #1 leading plug wire,raise engine rpm to around 3k rpm and note smooth advance of ignition timing,release throttle and watch for timing to go back to base timing position. Do same for trailing. Anything not proper here can have an effect on consistent idle speed. If the base timing is incorrect for leading and trailing ignition,correct it now. ALL the adjustments for tps reference,tps adjustment are dependent on correct final idle speed and there is a sequence that needs to be followed for proper adjustment. Any mechanical change in throttle shaft(from adjusting idle) invalidates all adjustments made concerning tps reference and tps adjustment prior.
Do these checks and post back results,especially idle air bypass adjustment.
Ok, finally got an update. As an aside before I get started, I noticed I was calling the fast idle screw the cam adjusting screw, so I went back and made the edits so I don't throw any future visitors off. Long story short, the car now idles at 800 RPM. For those who find this thread in the future, here's what happened, chronologically:
- Previous owner fiddled with all the idle and TPS adjustment screws, throwing them wildly off and giving me a 4-5K cold idle.
- I went through the adjustment sequence, but I didn't see the fast idle screw. It's kind of hidden when the throttle isn't open at least partly. Unfortunately for me, each successive adjustment - TPS, AAS - is thrown off when you adjust this screw, so at this point, my adjustments were pointless.
- GSLSEforme pointed out my fast idle screw was loose. High five for that.
- In the order given by the FSM, I went through the entire idle system adjustment. In order:
- Cam adjusting screw. This is the screw whose thread rests on the rod coming out of the wax pellet. The FSM goes into the adjustment procedure. The diagram is on its side, 90 degrees turned.
- Fast idle adjustment screw. Rotates with the throttle arm, near the throttle chamber letters. As you turn the screw, the primary throttle plate at idle closes or opens slightly. The FSM calls for a .16-.20" gap between the primary throttle plate and throttle wall. That's why I had such a big gap in those earlier pictures. FYI, getting any kind of blade feeler gauge in there is a pain. You can use pliers to crush a wire or paper clip end to the width of the feeler gauge blade.
- TPS adjustment. This page is a good reference for this and the next step. I used two multimeters; Harbor Freight's worked as well as my Actron, so if you need a $7 multimeter, there's a good one.
- Air adjust screw. This meant fine-tuning to 800 RPM.
Fiddling with one step affects the one underneath it, so try them in order. If I have two lingering issues, it's these:
- My brand-new Optima Red Top measures 13.2V fully charged with my multimeter, but when hooked up to the car, the car's voltmeter only shows 10.5-11V. At this point, the key is in "On" but the car is not running. The battery cables had just been cleaned with CRC battery cleaner, so it's not that. When the engine is running, I register 12.5V (b/c of the alternator). It's a bit hard-starting.
- The car idles at a relatively steady 800-ish RPM, but when I press the brake pedal, it drops 50 RPM. Issue?
50ish rpm drop is normal,system load/draw of brake lamps. Alternator should be charging 13.8-@14.2-at battery. Bit normal for dash gauge to read slightly less than system voltage at battery,car 30+years old,resistance in wiring could be responsible for this.
Suggest having complete starting/charging system tested. Battery/starter/alternator can be performance tested with an adjustable carbon pile tester like a Sun VAT40 to test each component individually and together as a system. Tell the technician what your concerns are. No the toaster type clamp on battery alternator testers most parts stores use to check these things are not accurate enough,nor is taking alternator into one of these places to test on their machine for a pass/fail result. The low 12.5 charging voltage makes me suspect a bad diode(s) which would take away 1/3rd of alternator output-still charges but barely. Turn any accessories on and surely car will be running essentially on battery.
05-28-17, 04:48 PM
Poltergeist Causes Surging, High Idle
