Same Old Idle Problem
 

As mentioned in my second thread, our '94's idle just will not come down even after all the troubleshooting I've done. Probably the last item in the factory manual's list of possible causes of high idle (except for some unknown vacuum leak) is a fault with the Electrical Load ("EL" Unit), or with one of the inputs to it. So tomorrow I will warm up the car, let it idle, and disconnect the E/L unit connector to see if the idle drops down to the right value. If nothing is wrong with the unit, the idle will stay high. If it drops down, I will have to determine whether the problem is in the unit itself or whether one of the inputs it monitors is wrong.

have you sprayed carb cleaner around the intake manifold and throttle body rats nest etc to determine if its a vacuum leak??

You could also get a boost tester or make one to pressurize the intake tract and check for leaks. they are very easy to make with a tire valve and either exhaust tubing or probably somthing from a hardware store.

How high does it rev to? And does it rev straight to that when you start up the car?

you're sure it's not a thermal wax/fast idle cam issue?

Just proved it's not a thermowax/fast idle cam problem by pushing down on the throttle flange that bears against the thermowax rod to manually drop the linkage off the fast idle cam when the engine is warm. No change in the high idle.

As I've written in the two previous threads, the idle is at 1500 rpm or so when warm sometimes, and right where I set it at 720 rpm sometimes. But unfortunately it is usually at the higher of the two values.

Also as I wrote previously, I had the UIM off and checked all the rats nest hoses with my MityVac... no leaks. Also bought and installed new (metal) OEM gaskets for the LIM/UIM interface and the throttle body/UIM interface. New IAC gasket, AWS blocked off. If there is a vacuum leak, I can't find it at the top of the engine. And a vacuum leak doesn't explain the steady 1500 rpm changing to a steady 720 rpm and back again at the next stoplight.

Does having the clutch in or out effect anythiing? Or a/c on or off.. You should still pressurize the intake or use carb cleaner to see if there are any leaks found. For instance my injectors were leaking air past them and replacing gaskets wouldn't help me there. Somehow your engine is injesting more air at certain times. Does disconnecting the ics do anything to the idle?

Make sure the screw that's stick straight out from the throttle body plate isn't screwed in too much. Try adjusting it. You might have accidentally screwed it in or something. It should be right near the throttle cable. That also adjusts how much the throttle plates open or close.

I ran the E/L functional test (i.e. turning on headlights, rear window defroster, and HVAC knob to positions 3 & 4) to see if the idle increased as it should. In all three cases it decreased from its too-high value of 1500 rpm. So I think maybe the E/L (Electrical Load) Unit behind the PCME is bad. If its output voltage is varying with time (even though all those loads are off), that would account for the two stable idle speed states. Retail price of that unit is $209.45, so I'm going to disconnect it and see what happens. I would have done that sooner, except I have to unbolt the PCME to get at it, and wifey has been busy running around town doing Xmas stuff. Maybe I can fix it (I hope).

Has anyone had a bad experience with the E/L unit?

Been following your thread just out of curiousity. IF that ends up being your problem I gotta think that fritz flynn or somebody might be able to come up with a replacement. I've never heard of them going bad before, but then maybe some owners gave up before you did and it went undiagnosed.
FWIW..... :fingersx:

seems you could disable the ISC to get your idle to at least settle down. ANd if you still have a problem then you know its not the ISC or the E/L thing your referring to, as it would have to control the ISC in order to adjust the idle. The stock computer uses a combination of the ISC, Ignition timing, and fuel to adjust the idle speed. I'm running the PFC and datalogit and disabled the idle contro systeml and now run manual idle.

Today I disconnected the E/L unit connector and drove the car. Exact same symptoms... no change. I did find out that without the E/L unit connected, turning on the headlights, or the rear window defroster, or the heater fan to positions 3 or 4 did NOT reduce the idle speed, which was still at 1500 rpm. One side effect of the disconnect was loss of the MIL indicator, i.e. when I checked for stored faults with the "TEN" terminal in the Diagnostic Connector jumpered to the "GND" terminal, the lamp stayed off... no 2-3 second light-up and then going out as it usually does.

So the idle problem is still there.

Thanks for all your replies!

Along Dudemaaan's line, you may have the ISC hung open. Sometimes debris will get in there and actually lodge it open. It will affect the idle like a vacuum leak.

are your throttle bodies fully closing?

u might want to take off the elbow and check...

as suggested by JD.. your ISC may require cleaning..

if all else fails.. u can do a boost leak test

jd, I had the throttle body off, had removed the ISC valve, and cleaned it very thoroughly with WD-40. I also tested it with a variable power supply and it worked fine with no stickiness. When I re-installed it, I used a new OEM gasket. The throttle butterflies are completely closed, both the primary and secondary. The AWS valve is removed and blocked, also with a new gasket. The EGR manifold tap is blind-capped.

If there truly is a vacuum leak, it is randomly sealing and then opening, and it would have to be below the LIM, since I just put new OEM gaskets between the LIM and the UIM, and also between the throttle body and the UIM. Maybe a leak in the brake booster diaphragm? But why open and then sealed from stoplight to stoplight?

Extra air is getting in somehow. Thats what creates a higher idle. I still suggest you either pressure test or use carb cleaner to find where the extra air is getting in

Thermal expansion is sealing it perhaps?
it could be the gasket between your LIM and block..(if it a gasket)


it could be a leak in a vacuume hose,

it could be a worn/cracked coupler..

A cracked coupler wouldn't effect the idle since the car is map based. It has to be something from the throttle body back. To the op go buy some carb cleaner, start the car and start spraying all around the uim, throttle body etc. The carb cleaner will cause the car to bog down when you find the leak. You have air leaking into your engine from somewhere and its best to pin point it instead of blindly replacing things.

he has already sprayed carb cleaner.

I have recommended it before and I'll recommend it again: physically pressurize the entire system with an air compressor:

this one for a 300zx might work, the "dual pop" one on www.boostpro.net/prodtester.html . I have never used one on a car with twins but I'm sure you can make it work.

http://www.boostpro.net/images/dualpop5.jpg

I'd like to believe I haven't been "blindly replacing things." I have meticulously gone through the "high idle" row of the 1994 FWM's "Troubleshooting Guide" on pages 178 and 179, and have now addressed every one of the circled causes except "air conditioning sensor," and "intake air leakage" (since I cannot see anything below the top of the LIM without tearing the entire engine apart). There is also an alternate cause... something is telling the PCME to increase the idle speed, or there is a fault in the PCME itself. Although I tend to agree the problem is air leakage, I cannot see how that explains the varying idle speed while the engine is warm, in a random pattern that changes so slowly.

I will be gone until 12/18, but would still appreciate any other ideas you folks might have. As for now, I have reconnected the E/L unit, since that wasn't the source of the problem.

At times, my car's idle would tend to remain at a higher idle at the 1300 or 1500 RPMs that the Power FC is set to regulate the idle to when revs drop. I only noticed this when I was stuck in traffic for extended periods of time going light to light (or bumper to bumper). In this scenario, the car was quite warm from a coolant and air temp perspective. In some instances, the idle would remain at the elevated 1300 RPM level for the duration of the stop light - in other words it would take longer than a few seconds to normalize back to the standard idle (850 RPM as configured in my PFC).

While I am not as adept as you with electronics, I did clean the idle control valve at the rear of the UIM and readjusted the throttle body mechanical settings. I remember readjusting the throttle body mechanical settings decreased the issue for me - meaning the car would drop down from the higher idle sooner. Its been ages since I've been stuck in extreme traffic and the temps got as hot as they did when I was having the problem so I can't offer any other input at this point.

I'd be interested in seeing a video of your scenario to better view timing of the events and how they manifest themselves.

What is the air bleed screw under the TB set at currently? Have you tried the 1/4 - 1/2 turn that most people run with a power FC? I know in your very first thread you mentioned jumpering one of the diagnostic connectors and adjusting it that way. Try just setting it to 1/4 turn and see what it does.

Still looking for vacuum leaks, I used the MityVac to pull a vacuum on the brake booster line. Odd result... although the MityVac is capable of about 25 in. Hg vacuum, I could only pull about 18 in. on the brake booster. It did not leak down at all, but could not get it to pass 18 no matter how fast I pumped the MityVac. Same sort of thing under pressure... the MityVac will do about 18 psi, but on the brake booster it wouldn't go over 15. Again, no leak down at all.

Is this normal behavior of the brake booster?

I'm pretty much committed to setting idle speed per the manual, i.e. so that jumper in vs. jumper out gives no change in idle speed with no electrical accessories on and engine fully warm. That occurs at around 720 rpm. Any adjustment "offset" would restrict the ability of the IAC system to control idle speed over the full range of the PCME's voltage capability.

Once again I re-confirmed that the E/L - PCME idle speed compensation system is not working. Neither turning on the rear defroster, nor setting blower fan speed to #3 or #4, nor turning on the headlights speeds up the idle, as it should per the manual. However, disconnecting the E/L unit doesn't cause the idle speed to fall, either. It's like the E/L unit just isn't there, or the PCME is not recognizing its signals. The CEL, which is powered by the E/L unit, does work, however, so at least the E/L unit is doing something.

Just visually inspected the PCME PC boards. All 4 sides looked good; no leaking or bulging electrolytic capacitors. (Maybe idle doesn't rise in response to E/L unit inputs because the idle speed is already higher than the correct value.)

Idle is now permanently high...
 

Yesterday I replaced the air filter element (35000 miles old), and now the idle speed is permanently high at about 1400 rpm either with jumper between "TEN" and "GND" or jumper out, no change. I backed off both the primary and secondary throttle butterfly adjust screws until they weren't touching anything, AND screwed in the Air Bypass screw fully CW. No effect. Pressed down on the fast idle butterfly flange... no effect. I have never checked the timing... looks like it is set by the Crankshaft Angle Sensor locations, which are fixed. The idle has a lot of putt...putts in it, which sounds like a piston engine's idle if ignition timing is advanced too far, but I cannot see how the timing could ever have been changed on this car since new. Is there a way to adjust it? The FWM does not address it other than to say essentially "don't do it." I guess I could measure it... have never done so.

What elements or units below the UIM/LIM interface could be leaking air into the intake manifold volume besides the LIM-to-housing gasket?

Wife is gone to visit grandkids, and took the Fusion, so I used this opportunity to remove our '94's Air Adjust Screw and clean it and its passageway. Had to extract it using my Mityvac in vacuum mode with a klugey adapter setup, but it finally popped out. The tapered cone area was really oily, not surprising since the intake air track is oily too, no doubt from the turbos. I got everything clean, turned the screw back in until it was about 1/2 turn out from fully CW. Then I discovered wife had taken all the RX-7 keys with her, and she won't be back until tomorrow. So whether the cleaning operation has changed anything, I don't yet know.

It sounds like you have a vacuum leak somewhere. I don't think cleaning the idle screw will since you screwed it all the way in with no change. Have you tried spraying carb cleaner around the intake with the engine idling? this is the easiest way to get a general idea of where its leaking from. Just listen for the idle to change once the cleaner is sprayed towards the leak. Once you have an idea of where it is, the pressure test with soapy water will find it in no time.

Thanks for your reply, Dude! Yes, I agree it's a vacuum leak. I thought it might be something in the AAS passage blocking the screw from going fully closed... don't know yet. Everything in the vacuum volume of the intake path has been checked downstream of the throttle butterflies, to and including the UIM-to-LIM manifold gasket. New gaskets between throttle body and UIM, UIM-to-LIM, under IAC valve, and under the block-off plate for the AWS valve, as well as all hose connections to the UIM leading to the solenoid rack, the PCV valve, and others. So if it isn't that the screw was faking me out when I thought it was closed, the leak has to be the LIM-to-housing gasket, which was replaced by a Mazda dealer long ago. I realize I'm looking under the street lamp for a problem that is probably in the dark; I'm just reporting as I go along.

It's not aways gaskets that leak, the injectors can have leaks around them too. Or vacuum hoses. Thats why its best to pinpoint at least the area of the leak. Saves time and money. Its no fun going in and replacing random gaskets just to find your problem is still there. The method i listed below should give you a general area of the leak in 3 mins or less, and pinpoint the leak in about 20 mins time. There is really no reason to do things the hard way unless working on the car is more fun then fixing it. Thanks for keeping us posted. I Hope cleaning the screw worked, sucks you have no keys to test it.

Yep, I know... don't even want to think about fuel injector O-ring leaks; I replaced those when I had to replace the FPD; used silicone grease on them to keep from damaging them when installing. I have no reason to think they are leaking, and with the UIM and solenoid rack on, no way to spray anything near them. Vacuum lines I have already tested, as I indicated above. I'll test/adjust the idle tomorrow, then I'll know if that was a problem.

Sounds like your BIGGEST problem is that it is somehow possible for your wife to take ALL of your FD keys!!! How can that happen??? Good luck finding the problem.

LOL! Um, it's her car... and one of the keys got tweaked somehow, so she had the spare in her purse and forgot to leave it with me.

BTW, the AAS was not the problem... idle is still at 1300 - 1400 rpm warm with screw fully CW. And now I know it is really fully closed.

I told you a year ago to pressure test for air/vacuum leaks and you still haven't listened. Why are people so stubborn about this?

The recommendations involved equipment that I do not have and have no idea how to make or buy. I have a tire air compressor and a MityVac, period. I have no idea how to pressurize the entire volume of the throttle body, UIM, LIM, turbo compressors, and rotor chambers simultaneously. If you have a link to a step-by-step for a DIY'er, or can recommend a shop in the So. CA. area where I can have that done, I will do that.

Hi wstrohm,

Did you figure out this issue yet? Any ideas? I have a similar problem and am wondering what I should be looking for. I'll go by all of the suggestions posted in this thread in the meantime.

daem0n,

Nope, haven't had time to do anything yet... still living with the high idle. My best guess at this point is that my LIM-to-housing manifold gasket is leaking air into the rotor chamber(s). Changing that gasket requires more than what I am willing to do at the moment. If I finally decide to bite that bullet and tear into the engine, I will update this thread.

Stop just arbitrarily replacing parts, it's a waste of time. The required equipment is so easy to make, and cheap to purchase if you're either retarded or don't own a drill. It drives me nuts watching people struggle with something for no good reason! If your idle is high it's not some major mystery of the universe! You're getting air in somewhere other then your throttle body! or the throttle body is adjusted to let too much air in! It's that simple. 2 very simple ways of pinpointing exactly where the air is getting in is (1) go buy a $1 can of carb cleaner and spray around until you find an area where the idle changes. And (2) pressure test the intake manifold and get some soapy water handy. Here are some links to make your life even simpler. It took me 20 secs to find these. (google search "boost pipe pressure tester") The next post I want to see in this thread is "I followed that simple advice and found the leak in less then a minute!"

Make your own: http://www.stealth316.com/2-pressuretester.htm
http://www.audizine.com/forum/showthread.php?t=190404

BUY your own :

http://cgi.ebay.com/ebaymotors/TURBO...61210004r26724

I have never done that in my entire life. Does not appear so to me; none of the referenced links refer to anything made for an FD, and all seem to require a tank-type air compressor to generate enough volume to pressurize the FD's entire intake system.I guess you really meant "unless you're either retarded or don't own a drill." Anyway, the e-bay link is irrelevant to my issue.No kidding! Well, the throttle body is completely closed to all normal entry paths for intake air. Butterflies, IAC valve, AWS valve (blocked off) and AAS are all closed. All solenoid hoses into manifold and the PCV valve hose have been checked with the vacuum mode of my MityVac.Unneccesary above the engine since I have done all the mentioned checks, and not possible on the passenger side of the engine below the level of the UIM, due to all the stuff in the way of the intake manifold. Plus, I'm not enthusiastic about spraying a flammable substance in the area of the turbos and the exhaust manifold while the engine is running, and removing anything in those areas prohibits the engine from running at all. This is NOT a simple problem, or I would have found it already and fixed it.

It IS a simple problem you just haven't followed the advice of others. I had a vac leak at my secondary injectors. Guess how I found it? With the advice I and others have posted many times. I also fixed one at my boost pipe about a week ago using the pressure testing method. Took about a minute.

You do NOT need a specific tester for an FD, the concept is exactly the same. Since the problem is after the throttle body all you need is something, ANYTHING to plug the end of the throttle body elbow with a fitting to put air in there. I prefer a tire valve. If you don't have an air compressor maybe you have a friend or gas station with one.

The equipment is very, very basic and common sense. Take a plastic or metal fitting, shove it into a coupler, drill a hole, put a tire valve in and stick the thing on the end of the plastic elbow and tighten it down like an intercooler pipe. Fill up with air, and listen.

And I meant it how I wrote it, basically if your retarded maybe making the thing isn't for you, or if you don't own a drill. because you will need one of those, and a drill bit. So there is the option of purchasing one. The one on ebay will work, but you will have to push the 2.5" coupling over the 2.75" elbow. I'm sure if you spend 5 mins you could find a 2.75" one with a tire valve fitting instead of the direct air coupler.

I'm sorry but there is no reason to go a year with the same simple problem and still not know the source of the air leak, especially after the solution is repeated to you. The time it spent you to get the idle adjustment screw out and cleaned you could have made 10 of those testers and figured out where the real leak is.

Use a straw that's taped to the carb cleaner can, and don't spray the exhaust. Do it when it's first started when everything is cool. A little common sense goes a long way when working on cars.

EDIT: oh wait, what does it say on that ebay link?? "* I now have ALL sizes available for any turbo inlet: 2.0", 2.25", 2.5", 2.75" & 3.0" !!"
Holly sh*T he has one that fits, now there is no need for a 5 min search.

You need to pressure check the motor. I just made a quick and easy setup for less than $10. You need qty 2 2" pvc plugs from Home Depot and one press in rubber valve stem from your favorite parts store.
Drill a hole small enough in one of the caps so the valve stem presses in. Remove airbox and leave the top relief valve hooked up to the y-pipe. Put one 2" cap in each turbo inlet tube and use existing clamps to hold them in. Supply air from some sort of compressor, doesnt need to be really big but if it's loud find some way to quiet it down so you can hear the air.
I almost guarantee it's a lower intake gasket. Have someone pressurize the fitting and stick your hand right underneath the airpump and you'll feel air blowing out at you. You shouldnt hear or feel any air and your boost gauge should rise and hold if you have no leaks. I just took delivery of my first FD yesterday. It had a high idle when I bought it. I have never touched an FD before today but it took all of 2hrs to find the problem. No brag just trying to give you an idea how easy the process really is. Post back with questions or problems.
I'm starting my LIM replacement today. :)

Please tell me exactly how you found it. OK, you had a spray can of carb cleaner. What, you started the engine, and somehow managed to isolate the secondary injector with the engine running? On MY FD, the secondary, and primary, injectors, are completely buried behind wire harnesses, which are buried behind the rat's nest, which is buried underneath the UIM. Not only would I NOT be able to thread a long tube from a spray can under all that mess, even if I did, I would never know what was leaking, even if I heard the engine begin running differently.Fine, but as you know, my problem is not before the throttle body, so no point in testing anything prior to it.When it's first started, it runs on its fast idle cam, and is already idling at or above the too-fast warm idle speed. That test condition will not allow detecting anything. Plus, you must be kidding about "don't spray the exhaust." It's not just the exhaust, it's the entire lower section of the passenger side of the engine that is VERY hot. The LIM and turbo/exhaust manifolds are intimately intertwined... impossible to spray selectively in that area. I would think the pressure system would be the way to go to detect a leak, IF I had access to an air compressor other than my wimpy tire compressor and MityVac, neither of which would do the job.Well written, but I don't have an air compressorl I also, at this point in my troubleshooting, would "almost guarantee it's a lower intake gasket." What that means is that no matter where air would blow out from the passenger side of the engine during a pressure test, whether under the air pump or anywhere else, I would have to tear out all the components on the passenger side of the engine, including the turbos, to get to it. And that is the same thing I would have to do if I did NOT pressure test. In short, I do not think that a pressure test would alter anything I would need to do from this point forward. So far (for the past three years) we have been living with the issue, since it is not damaging to the engine. Maybe one of these days I will decide that reducing the idle speed when warm is worth the misery, cost, and risk of doing the work.

You act like it's this huge struggle but its not. And if it's not the lower gasket then you end up doing all that work for nothing. And will still be no closer to fixing your problem. You apparently want it fixed or you wouldn't have gone to that waste of time pulling the air screw. I really don't care if you fix it or not, but for the benefit of others i'm saying it is not difficult to find your problem, your just making it harder then it should be.

If the LIM is leaking it is damaging to the engine. Pulling unfiltered air into the engine less than 6" from the apex seal is a bad thing. Anytime your engine is under vacuum that's whats happening. If you check it before you tear into it you might find it's something simple and save yourself some trouble. Good luck.

n2o4fun,

Good point; I hadn't thought of the air leak as a possible source of damage. Don't know how to "check it," though. Will consider doing the job to prevent further damage... in the near future.

"check it" = pressure test. Sorry, but that's the only way to find it that I know of.