vobs

Alright guys and ladies, need some more help with my idle. It is a 59 degree day here up in Wisconsin. After my car had been sitting all night I started it up at around 10:15 this morning. Here is what happens. After I start it, the rpm's go to 4000 and stay there until I put it in gear. After I put it in gear (don't like it iding at 4000) it will come down to 3000 rpms. I know it is supposed to do this to warm up the cats (well at least go to 3000, I don't know why mine is going to 4000). But my car will stay 3000 for approximately 3 minutes. Then the erratic idle kicks in.

It starts bouncing in about a 500 rpm range up and down. While it is doing this, the idle slowly starts to come down. About 1 minute later the idle will be down to about 1700 and still bouncing. Now I am even more late for work so I decide to leave with the idle still bouncing. After about the first three stop lights (1 more minute) I can finally get my idle to smooth out at about 1700 rpms. Now it gets hard to explain. As I am pulling up to a stoplight I always push the clutch in and take it out of gear and coast up to wherever. While doing this my idle is bouncing up and down in about a 500 rpm range. After I pull to a stop my idle smoothes out at about 1700.

You may be wondering why my idle is set at 1700? Well because this is the only way I can get it to stop bouncing. As long as my idle stays between 1450 and 1850 my idle will not bounce. I set it on the high side because pushing in and holding the brake pedal lowers it about 100 rpms, headlights lower it another 200 rpms, etc. So I'm trying to keep my idle from bouncing the majority of the time. If I try to lower my idle below 1450 (by adjusting the either idle screw) it starts bouncing again. Somehow it seems to me that my Control Unit is getting a message that the idle is to low at 1450 so it lets more air in and when it gets to 1850, it lets less air in, etc. causing the bouncing.

So I have no way of even lowering my idle at this point. First of all I think my car is taking way to long to warm up? Does everyone agree? Should I replace my thermowax? But thats is just my warm up problem. Heres what I have done to diagnose my idle. The tps checks out properly and is set to exactly one volt. My BAC valve is functioning properly and checks out O.K. I have also checked the voltages of each wire coming from the control unit as per the factory manual. The only bad voltages I got were from the Air flow meter at idle (1.77 when it supposed to be something like 3.5-4, was fine at key on postition) and the Intake air temp sensor (3.76 when it is supposed to be 1-2 volts). I took out he air temp sensor and the resistences checked out O.K.

I also took out the air flow meter and there was continuity on the leads and the door was not obstructed. Should I replace them? I have checked many other sensors, selenoids, valves, etc. I can't really remember them all now. All of those that I have checked were fine. There doesn't appear to be any air intake leaks. Another thing I did was took a vaccuum hose off to see what a leak sounded like. After doing this the three of us that were working on my car at the time could swear we all heard a hissing (like a leaking, unplugged vaccuum line). For the next hour we sprayed carb cleaner and listened with a small piece of hose to try and find a leak. We could find nothing. The hissing seems to be coming from the right side of the engine bay, but we couldn't find squat. All right, after all of this typing, I need some opinions/help/a kind word, anything. At this point I'm look for any help I can get. Thanks in advance. I am reall sorry about how long this was, everything just started flowing.
Matt

vobs

Just an update, Walking through the high idle speed at normal operating temps troubleshooting section in the manual.

1. Troubleshoot w/ self-diagnosis checker - No error codes.
2. Throttle valves are operating smoothly.
3. Fast idle cam is releasing from roller, it just takes like 4 minutes.
4. No air intake leaks that I can find.
5. Throttle sensor checked out O.K.
6. Check idle speed (Cannot adjust Control Unit won't let it get below 1450).
7. The only things I didn't check in the BAC system was the neutral switch and the clutch switch. Didn't think they would have much to do with my idle problems.
8. Air bypass solenoid checks out O.K.
9. Can't check ignition timing because the RPM's are to high. I think I would get a faulty reading.
10. I Have not checked the anti-afterburn valve
11. I Have not checked the dashpot
12. Air flow meter checked out O.K. Have not check the intake air temp sensor located on the air flow meter (I did check the other one, How do you check the one on the air flow meter?).
13. Control Unit - voltages were good except for the ones listed in previous post.

Anybody. Thanks in advance.
Matt

SpeedRacer

I'm guessing your thermostat might be stuck open. This will cause your car to warm up slowly. As for the crazy idle...most likely thermowax.

vobs

I just replaced the thermostat last month with a new one from the mazda dealer. Can you be more specific about the thermowax. From my understanding of the thermowax is that it is part of the system that warms up the cats. In other words doesn't it slowly close the throttle valves while it extends (while the wax melts), letting less air in, therefore lowering the RPM's. Or are you trying to get at that maybe my thermowax isn't extending all of the way, therefore the throttle valves are not being closed as far as they should be? This would kind of make sense in the fact that my control unit is trying to keep my idle between 1450 and 1850. So if the thermowax isn't extending all of the way, the rpm's will never come down to the 750 that they are supposed to. Since the Control Unit has nothing to do with the thermowax, does it just assume that the thermowax is doing its job and closing the throttle valves as far as it should? Let me know if this what you were getting at? Or am I way off on the thermowax's job? Thanks for the reply.
Matt

HAILERS

I do not see it being the thermowax. You just said the fast idle cam came off the roller. the roller is controlled by the thermowax. If its off the roller the thermowax is out of the picture. I think you need to pull the plug off hte bac. Insert the initial set jumper and see what the idle is. If its still outrageous like 1700 then make sure that the screw on top of the dynamic chamber is screwed in. If it still is way too high make sure that idle screw that is near the front of the throttle shaft is backed all the way off. If it is still too high press the throttle shaft with your fingers in the close direction to see if it lowers the idle. If it still is too high look again for the vaccum leak. Also is it possible that the timing got fooled with? If you can get the idle down below 800rpm throw a timing lite on it to make sure its not too advanced. Has this car ever run proper? When did it go bad? Has someone messed with the fast idle screw lately? You might check the throttle body valves for the proper clearance( see section 4a of the manual, free at http://www.iluvmyrx7.com Not to worry about the voltages on the airflow or intake sensor. Need answers to the above to make further wild *** guess.

vobs

Hailers, the reason I said the roller is coming off the cam is that eventually my fast idle process stops. Doesn't this only stop when the roller comes off of the cam? My fast idle process just lasts like 5 minutes instead of 17 seconds or whatever it is supposed to. Is there a way to visually check and see if the roller is coming off. You can't really see it back there with it on the car, and thats the only way to test it, correct? Yes the car did used to run proper. A couple monthes b4 I put into storage for a year and a half it started bouncing, did nothing with it at the time. Now I have been driving it for about 2 monthes or so, with it idling goofy. Another thing I just tried was starting it up and waiting for it to warm up, 5 minutes later, I pushed the clutch and the brake down and put it into 5th gear. I slowly let off the clutch and as soon as the rpm's got to 1450 it just started bouncing. Shouldn't it stall? The fast Idle screw has been messed with, but the problems were there way before we ever did that. Last time I had the throttle body off and was trying to line up the cam and roller I checked one set of the throttle valves and set them to spec, I think they were the ones that are adjusted with the fast idle screw. When we were futzing with it this weekend, we turned the fast idle screw a little bit (while on car, so I'm not sure what that did to the linkages). Also we cranked that front idle screw all of the way down practically. This is how we got the idle to stabalize a lot of the time in the first place. The timing has never been adjusted since I have owned the car. I don't remember the specific circumstances of when the idle started to be erratic, but I do remember it just started doing it when day, out of the blue. No gradually getting worse, it just started doing it. I'll try and do what you said to do and check all of the things you said to check as soon as I can. I don't know if I will have time to do it tonight tho. Thanks for the help, I'll get back to you.
Matt

HAILERS

The initial fast idle at 3000 lasts for 17 seconds. Then the idle will be around 1200 and gradually come down when the fast idle cam comes off the roller. You can with some difficulty see this with a mirror(the cam and thermowax.`Hey here is an idea about the hissing sound around the right hand side of the engine. Could it be the Water Thermo Valve that actuates the Double Throttle Diaphram? Its at the right rear of the throttle body. Has two vaccum lines going to it. One of these goes to a diaphram at the front of the throttle body. Sometimes one of these comes off or there is a crack in the plastic body of the thermos sensor, or one of the **** gets broken off. You might have to end up taking the dynamic chamber off to correct the fast idle cam. Have fun.

Brian P

You should be able to temporarily fix this buy unplugging the air by-pass solenoid, If its sticking on after the thermowax opens then it will do the bouncy idle thing.

The car I'm working on right now has a screwed up BAC and the idle doesn't drop below 1500rpm. I would check the bac circuit

vobs

Well, here's the latest. I jumpered the int. set conector, unplugged the BAC, played with both idle screws, and pressed on the throttle shaft with my fingers. I can physically make my idle go down to 1450 by adjusting those things, but then something kicks on and makes the idle bounce up. I am very confused, when the int. set plug is jumpered isn't the contol unit supposed to be bypassed, what is causing my idle to bounce up. Also, unplugging the air-bypass selenoid does nothing. The warm up the cat system still operates, what the hell. I have some crazy stuff going on here. Help!!!
Matt

HAILERS

While we are scratching our collective heads, try starting it up again and disconnect the tps plug while its running and see what the results are. Or you might , while its running reach in there and depress the tps plunger and see what happens. Wish there was some way to check the timing, but you can not do that with the engine reving so high. It would be a false reading. Need to somehow bring it down to around 700 to check the timing. I think its broke(humor). A part of me says there is something askew with the timing. No real good reason. Just a feeling. Brian P had I thought the answer but you did that. Say, you know that about one inch hose that comes off the inlet duct about half a foot before the inlet duct attaches to the throttle body? Plug both ends with something and start the car. That line connects to a metal line that runs around the back of the throttle body and feeds the air bypass solenoid. Just a thought. Strange car. Its kinda like the ECU is advancing the timing too far.

vobs

Hey Hailers, you said that the initial fast idle lasts for 17 seconds, correct. What causes it to go down to 1200 rpms after that, because whatever that is, is not working correctly on my car and fixing that may be a start. Then you also said that it is supposed to slowly go down from 1200 to 750 as the fast idle cam comes off of the roller. Is that the thermowax's job? Just thought of something else, if the whole BAC system is supposed to keep the idle rock solid, why is it that if I have my idle set to just below 1850, I can lower it to just above 1450 by turning my headlights on and pressing the brake in. And if I'm doing both of those and I turn the steering wheel, hello bouncy idle. Seems to me my BAC system isn't really doing its job, thats over a 400 rpm drop. Yet everything in my BAC system checks out O.K. on the components side and the Control Units side. Scratch, Scratch, Scratch. Oh, tonight I'm going to try your latest ideas Hailers, and what I don't get to tonight I'll try and check this weekend. Why did school have to start so early this year. Oh wait it starts at the same time every year.
Matt
P.S. Now I just need to go by a mirror, did you mean one of those dentist type mirrors, small round mirror on the end of a little stick?

HAILERS

On a cold engine start the Air Bypass Solenoid Valve opens for 17seconds and gives you that 3000 rpm speed. After 17 sec it shuts off. Then the idle will still remain high, around 1100 or so because the thermowax in conjunction with the fast idle cam are holding the throttle plates cracked open . As the thermowax heats up it lets the fast idle cam slowly come off the cam roller until it compleyly comes off. At that point the throttle plates should be at their initial setting and the idle should be around 750.....There's something that we have not been looking at. Its the dashpot. Its on the right rear of the throttle body. Look in the factory manual in section 4a to get a view of it. It is possible that it has been screwed in too far. I think you should loosen its jam nut and rotate it until it does not make contact with the throttle linkage and see what happens. Its just a damper type device. Its got a spring tit that keeps the throttle from slaming shut when you let off the gas. It lets the throttle slowly come to its off position(relativly)sp. You can on a normal, good car, make it idle faster by turning this dashpot towards the linkage, making it act as a throttle stop i.e. keeping the throttle plates open further than they should be. Factory manual free download at http://www.iluvmyrx7.com Dashpot sounds promising. Oh the mirror. Needs to be about 2 in dia. Do not spend a lot on one. Break a cheap larger one if you have to. Its the devil to see the fast idle cam. Need light to see it.

vobs

Since the air-bypass solenoid valve is only supposed to open for 17 seconds, there is either a problem with that valve (don't think so, since it checked out O.K., although I think I might recheck it know) or what is supposed to cause it to close. What causes the valve to close? How fast is the valve supposed to close, does it take just a few seconds, or does it take a while. One of my problems is there, because it does not close until after about 3 min. on a cold car. If I remember right on a cold car it takes about 30-60 seconds for the rpm's to come down to 1500, but on a somewhat warm car it falls fairly quickly. Is there anything there? It sounds to me like the air-bypass solenoid has to be on a timed schedule, if it closes after exactly 17 seconds. After mine does finally close it drops to 1500 or so and stays there. So I am also wondering if my fast idle cam is actually releasing from the roller, I'll try to check after work. Another weird thing that I just thought about. After my idle does finally drop to 1500 it will not steady itself right away. It takes a few minutes before it will actually steady itself, even thought it is in the 1450 to 1850 rpm range. It almost seems during that time the thermowax heating to allow the cam to release from the roller (if this is actually working) my idle will not be stable, but after the cam releases from the roller (again, if it is actually happening) my idle becomes stable, unless it goes outside of the 1450-1850 range. Am I on to anything here? What cause the air-bypass solenoid valve to close? Thanks.
Matt
P.S. I feel like I am learning so much about my car, yet I am getting nowhere!

HAILERS

That solenoid is controled by a relay in front of the air flow meter and filter assy. Just below I believe. It, the solenoid shuts off in a heartbeat after the 17 seconds. To prove it is not the solenoid go here http://www.rhichome.bnl.gov/People/shrey/images/bac.jpg see the screwdriver? Parallel with it to your right is a metal air pipe that has two air hose connected to it in the picture. Short one goes to the BAC. The other goes down. Take it off and plug the pipe and the hose. Use duct tape, or a large bolt in the hose, whatever it takes to seal both open holes. Now start the car. If the problem with the high idle continues it ain't the solenoid. Have you checked the dashpot yet? Oh yes. I don't think it can be the air bypass solenoid if you have disconnected the plug to it and it acted the same as before. I'm stuck on the thought that the throttle plate is being held open by SOMETHING, such as the dashpot. Can you pull the inlet duct where it hooks on the throttle body and look at the butterflies and see if they are being held open. The gap should'nt be more that I think .020 or so. http://www.iluvmyrx7.com section 4a, free download.

vobs

You weren't kidding about the thermowax being hard to see with a mirror, practically flippin impossible. Got any recomendations on angles? Which side of the car do you start on to give you the best chance, pasenger or driver? I just found some pictures and it seems even more impossible that I would be able to see that with a mirror, but I'll keep trying. Hey if I can't find it I was wondering since I was going to take my throttle body off anyway couldn't I just put some heat on the thermowax and see if it extends? I don't have a torch, but would a hair dryer work? Here are my plans for checks and other things to do for this weekend.

Before take throttle body off:
Disconnect TPS while running, see what happens
Depress TPS plunger while running, see what happens
Disconnect one in. hose coming off of disconnect pipe, plug both ends, see what happens
Adjust dashpot as per factory manual, loosen nut and turn dashpot towards linkage, see if car idles faster
Disconnect hose on air-bypass solenoid & plug both ends, then start the car and see what happens
Check Water Thermo Valve for cracks or broken ****,

When throttle body is off:
Check and adjust linkages
Check throttle valves for proper clearance
Check dashpot and verify that its good
Check water thermo valve
Check thermowax assembly

Oh, by the way, I beleive I checked the relay in front of the air flow meter, etc. and it checked out fine. For disconnecting the water hoses that are attached to the throttl body. Last time I had the throttle body half way off I didn't remove them because they were kind of melted on. Here's what I was thinking of doing, crimping each hose shut (what would work best, I don't have and c clamps or anything) and cutting them off of the throttle body. And if they are long enough just cutting the old hose off and putting back on? Good/Bad idea? And if you can think of anything else that I should check while the throttle body is off let me know. Thanks for all of your help. I'll get this damn thing fixed eventually.
Matt

HAILERS

I'm fixated on the dash pot, so maybe you could check that first. Convinced there's something keeping the butterflies from closing. And usually I remove the Dynamic chamber with the throttle body attached. Can't say I remember removing the throttle body by itself. Just a habit I picked up I guess. I forgot about that water hose on the rear. Nasty piece of work there. Poor design. Then again if you remove the whole kit and cabootle you have to make sure not to drop things in the intake holes. That water hose. The guy who designed that was a loser. Brother in law of the guy who did the logicon and wiper switch. Uncle of the guy who did the cheap **** door handles. Grrrrrrr

kliftin

My idle jumps up and down from 500 to. It also raised to 1500 when I turn on the head lights and its because thiers a leak in my acv plate I made. I striped two bolts on it but sealed it with gasket maker. Its still their but cant hear it. Also my actuators were leaking slightly. I also got eratic idle when a hidden vac line was disconected. Use carb cleaner on everything except for the exahust manifold.

Brian P

Ok, here's something to try, take off the BAC valve, take a square piece of gasket material, I used Mr Gasket exhaust material, and put it over the hole left by the BAC. Now put the BAC back on and tighten it down. Now the BAC is blocked off. This fixed my idle problems, so I know I need to replace this. Give it try.

khoney

I had a similar problem (high initial idle, bouncy idle after warmup) during the continuing saga of my own search for idle solutions. I am racking my brain right now to determine the sequence of events that caused the problem to appear (the high idle was not my initial problem, but started after making some other adjustments). However, the SOLUTION to my high and bouncy idle problem was an adjustment to the screw underneath the intercooler against the firewall (I think it is called the throttle stop screw). After adjusting this screw followed by the TPS, my idle is pretty much back to normal. I went back just now and reread the "Solving GSL-LE Idle Problems" and based on that, I think I still need some fine adjustment of it. I have a very limited understanding of how everything interacts, and that document helped a lot (and so did Hailers). Hailers, does this sound like something for vobs to check?

vobs

Well fellow forumers, I did absuletly nothing on my car this weekend, no time, grrrrr!!!!! So hopefully next weekend I will start on my previous list.

Hailers - I will definately check out the dashpot first. After reading about what you said the dashpot's function was I noticed something about my car. When I am driving down the road, say at 30 mph, and I am just keeping it steady at 30. Every once in a while my car starts to jerk after I ever so slightly let off the gas. I am barely moving my foot and all of a sudden I almost get whiplash, not actually that bad, but... . Could this also be related to a sticky/bad dashpot? Let me know what you think.

Brian P. - I tried totally removing the BAC valve and plugging up all of the respective hoses. I then blocked off the BAC valve opening and started the car. This did absolutely nothing. Which made sense because after completely testing the BAC valve and system it checked out O.K.

khoney - I found that article.

I'll keep everyone up to date as soon as I get a chance to work on it.
Matt

jrussell

Vobs,

What condition is the engine in? How many miles are on it? Rebuilt recently?

My engine had similar problems. It wouldn't idle for crap. I had the whiplash while maintaining speed too. I tested all the electronics, everything on the Throttle Body was working fine. I ended up blowing a seal later that week, and I'm in the process of installing a newly rebuilt ported engine, but I figure a lot of the idle problem was actually internal to the engine. Weak seals, low compression... I'm going through all the vaccum lines and replacing them. They are very tough and brittle from being so old. My lower intake gasket was leaking pretty bad too. An air leak anywhere in the intake system can cause idle problems. Check for that if possible.

Hopefully it is in the dashpot though. It does make sense that that would be part of your problem.

vobs

Alright I have been working on my car finally this weekend. The dashpot plunger pushes in slowly and comes back out quickly. After I loosened the nut, I turned the dashpot in and it did nothing. The engine did not speed up. After that I took the throttle body off (just the throttle body) and I noticed that on the seal btwn the throttle body by the primary valve and the primary valve opening on the throttle body and the dynamic chamber had water/liquid on it. Is this normal? Also I just noticed that inside the dynamic chamber, where the secondary openings are is all rust colored inside, but inside by the primary valve opening is nice and metal colored. Is this normal?

The backside of the secondary throttle vavles are all dirty and rust colored, but they move freely. The back of the primary throttle valve is nice and shiny. One other thing, in the manual in the throttle body section, under #2 in inspection, it says to "Ceck the clearance btwn the primary throttle valve and the wall oth the throttle bore whent eh No. 1 secondary throttle vavle starts to open." The clearance is supposed to be .02-.03 inches. Mine is nowhere near this, infact is well over a 1/16 of an inch. The solution is to bend the tab they show in the picture.

Can I bend it that far? How could mine have gotten this far out of whack? Also the water thermo valve does not appear to have any cracks in it, but I have not tested to see if it is functioning properly. jrussell, my engine, as far as I know, is in fairly good condition. My car runs fine, except for the goofy idle, and I have been driving it like this for a long time. The engine has about 126,000 miles on it, never rebuilt. I also have never had a compression test done. Anybody know whats up with my throttle body? Thanks for everyones help.
Matt

vobs

^bump
Hailers, where are you?

HAILERS

Hello. Say, what is the clearance of the primary throttle valve with it full closed? I have been using a strand of wire out of a harness that I sanded down to b/t .016-.020(never said I was high tech). If that gap is b/t 016/.020 then one of my ideas of something holding the butterflys open is all wet. One thing you might do after you rig the throttle is to pour some boiling water over the thermowax to see if it will extend and then retract when you pour some cold water on it. I never had to adjust the tab for the secondaries. I've got a spare throttle body that I'll do that to but its going to have to wait until the US Grandprix is won by Michael Schumacher today. About 3pm Central. Thinking about your car during the race. Really odd.

vobs

Hey, I'm just as high tech, a staple is about .02 in. And, yes I adjusted the screw so the valves are at the proper clearance. My thermowax is extending and retracting but I don't know if it is extending all of the way. I have visually (by the mirror) seen that the thermowax is extended when the car warms up, and when the car is could it is retracted. I heard sometimes that the coolant passages can get clogged so that it takes longer for the thermowax to extend (sounds like my problem), or may not extend all of the way? How would I check to see if the passage is clogged, since the hoses are "welded" on, I'll probably have to cut them off and replace them. Is it worth the effort? Another thing I did was to pull the 1 in. hose off of the inlet duct and plugged both ends, like you said to try about a million posts back. Now my car runs funny. When I start it up cold now, the idle goes right to 1500 and starts bouncing immediately. And then if I start to drive my idle will jump up to 3000 like it was before, still bouncing (when the clutch is pushed in), and slowly come down like it was. Since that hose that I plugged goes to the air bypass selenoid, it seems like there is something wrong with mine, like it is getting stuck on or off, but sometimes it works? But it passed all of the tests that the manual said to do on it, WTF? Should I replace it anyway and see what happends? Anyway, thats where it stands now, let me know what you think.
Matt