Andy

My car seems to run fine when cold but once it warms up, the idle gets really rough, almost like it's running on only one rotor and the other is misfiring. If I give it throttle it smooths out at about 2000-2500 rpm and power is normal. After I first noticed it the first thing I did was put new plugs in because it wouldn't start the next day and the old ones were full of carbon.
Then I checked the TPS but the checker light I made wasn't working so I swapped the TPS for a spare I had which then adjusted fine. After I take it for a test drive, same idle problem and the TPS checker won't work again and now I've got a fluctuating idle that goes from 500-1100 rpm, which I'm pretty sure is a TPS adjustment problem.
Any thoughts would be greatly appreciated.

Andy
87 TII, RB turbo back exhaust, HKS intake, FCD

Keith

Hey Andy,
I would adjust the TPS using a Digital meter on the middle pin of the TPS plug to ground. It should read 1.00 volts ignition on, engine off on a warm engine. Get it as close as you can. If you cannot adjust it, bad TPS. This is the only sure fire method, since the method you used simply tells you that the Switching Valve and Relief Valve solenoids are correctly energized, which means that the TPS is somewhere close to idle, assuming the ECU is working ok and you have no other sensor problems. While you have the meter on the connector, I would make sure that the voltage varies smoothly from 1 volt to about 4.5 volts over the TPS range. Check complete. Hope this helps!

Irv, Keith's dad

Andy

Thanks I didn't know that, I'll definitely try that on Monday.
I don't really think that the TPS is the primary problem though.
I'll post again and let you know how it goes then.

Andy

Andy

Nothing wrong with the TPS. But it still runs rough when its hot and will not start once its been running and I shut it off.
Another thing I noticed the other day was that with the ignition on and the IC removed I could here a constant clicking coming from the BAC. Today it wasn't doing that though.
Another thought I'm having is I noticed that there's a bulb about 3 inches round between two 1 1/2 inch hoses (under the AFM) It had popped one of the hoses off, I reconnected that 2 days before this all happened. The manual calls it the air chamber. The hoses lead to the air control valve on the intake and the relief silcener at the front of the car. I think I'll pull that and see if anything's wrong with it, maybe it sucked some dirt in when it was disconnected.
So far I've checked
AFM
pressure regulator control solenoid
TPS
Intake air leaks
All are OK
Anybody have some thoughts on this, anything is OK just give me something to tinker with.

Andy

Keith

Hey Andy, its me again. I would do a fuel pressure check, just to eliminate this possibility. Should be 28 psi with vacuum, 39 psi without. If this is ok, I would check the primary injectors, one of them might have a bad spray pattern. Also, check injector o-rings for leaks. Also, check for corroded/loose connectors on the injectors. Hope something turns up!

Irv, Keith's dad

Andy

The gasket on the ACV was blowing through. After fixing that it idles a lot smoother but still won't start hot. So now I've got the upper intake manifold off and the plug on the rear primary injector was loose, just fell right off when I unbolted the rail.
Guess this is it, gonna put it back together after lunch and take it for a spin.
Thanks (again) Irv

Andy

HAILERS

*TPS checker won't work again* caught my eye. I'm on a one track mind right now about adjusting the tps and thought it worthwhile to say that if the tps setting is jumping around on you, take a mirror and check and make sure that when your setting the tps, that the thermowax is or has released the fast idle cam, prior to setting or checking the tps. Just a thought. Loose injector plug probably fixed your prob though. Still would not explain a tps setting that varies from day to day. By the way, I've heard that clicking of the bac before. If I remember right, with the engine off but the key on, I could with my finger play with the plunger on the tps and hear the bac click. I supposed it was responding to an input from the tps saying the throttle is open and now its time for the bac to supply enough air to idle at 750. Just made that up. Not real sure if that is what is really happening . After work I'll see if I can duplicate that clicking.

HAILERS

Ref to my above post....nope, could'nt dupe the click, but I know what you refer to. Heard it before. Bac. Click, click, click, click etc

Andy

Well I was wrong afterall. The rough idle just came right back again after the test drive BUT when I give it throttle and it drops down to idle it hangs at 1100 nice and smooth for about 3 or 4 seconds then falls to 700 and runs rough but not quite as rough as before and the idle mixure and idle speed adjustments do nothing. I feel like I'm so close. Haven't got the tools to check fuel pressure, checked it this summer at a shop down here and it was OK. Oh yeah one more thing the air bypass solenoid valve(right near the BAC on top of the intake) the resistance is 20.5 ohm the manual says 16.2-19.8 could this cause my problem? I don't have the cash to throw at it right now unless I know it will fix the problem.
I'll have to check the thermowax tomorrow. I'm gonna try swapping the air intake temp and water thermo sensors with spares I have. (Also potential culprits) And Irv's TPS adjustment was way easier, didn't like the lights anyway (not enough hands)
Thanks again, keep it coming I don't want to park a car for the winter when it isn't gonna start in the spring.

Keith

Sorry, I haven't got anything further for you. However, don't worry about the Air Bypass Solenoid valve. It is only energized for the first 17 seconds after you start your engine. From then on, it's a paperweight, so the resistance doesn't really matter.

Irv, Keith's dad

HAILERS

Rough idle is a subjective thing. On my 87turbo I have three acv available. All of which have some function broken. The one acv that has a bad switching diaphram, gives me a rough idle. At throttle above idle alls well. Just at idle. At startup alls well until the car warms up and idles. I found this by pulling the vacuum hose off the switching nipple on the acv. Its the only one sticking straight up, and if I remember right, on a turbo, the only one that has a vaccum.Pulled it off and plugged it. Car idles ok, not rough. The number two acv I put on does good at idle, but the anti-afterburn fails and gives me backfiring when I let off the throttle. The third has a bad switching diaphram but a good antiafterburn. I leave it on and plug the vac line for the switching diaphram. If that does not do it take the vac line off the egr valve and see if the diaphram is broken on it. Just plug the vac line to see if things get better. NO WORK? Spray engine parts and TID at turbo w/start fluid.Just gotta be a air leak.

HAILERS

Also read this article.Somewhere down on the post there is a reference to the 20 ohm's and a don't worry about it. Its a good article. I used it to repair my spare N332. Had a bad transistor for the bac. Cost about three bucks to fix. Just threw that in there for folk who think their bac is not getting a signal from the ECU. Guy that did the article is Paul Stoaks. http://www.teamfc3s.org/info/articles/idle.html I've had two *rough idles* with my new used car. One was the TID where it attaches to the turbo. Had a crack where the coupling clamps down. Found that by getting under the car and spraying ether up at it. I had failed to see the crack when I had it off earlier(cracks happen only to other people, not me, attitude). The other rough idle was the acv switching diaphram described earlier. I swear, yours sounds like a vac leak, but where?

Andy

Took the intake apart right back to the turbo, no leaks there.
Took the upper intake manifold off again, injectors have a good spray pattern and no leaks there. The little screw in the pulsation dampener was sitting in the cover though.
Still the same problem, but I noticed the idle slows with the lights on or if I hit the brakes. So I'm thinking BAC is the problem, when is swap a spare ECU in the problem doesn't go away. I may just change it on blind faith if I can find one cheap. Any donations?

rxse7en

I agree with Hailers—TRY THE ECU TRANSISTOR FIX. The transistor is a Darlington Tip120 available at Radio Shack. I had a short in my BAC connector and it kept blowing the transistor. I fried my ECU after replacing the transistor 3 times. Finally rebuilt the BAC connector first, replaced the ECU with a used one, and still found that the BAC wasn't kicking in at load. Replaced the transistor in the "new" ECU and everything works correctly now. Don't be intimidated about working on the ECU. Just go slowly, use a deslodering strip to get that nasty Mazda solder off first, and make sure your BAC connector is not shorting out! I believe that if the two leads in the BAC connector ever touch—they are so close together(!)—they will short out and fry that transistor. Seriously, if there's anyone in my area with this problem, message me and I will do the fix for you! I am a firm believer in the ECU TRANSISTOR FIX!

Brian

Andy

A tech at the dealership sugested it could be the intake gasket or possibly the ignitors. The intake gasket turned out to be ok(not something I care to repeat) and the ignitors seem ok too. I'm seriously considering taking it to the dealer. At least I'm sure it's not an air leak now.
Brian, I know it's now the ECU because the spare did the same thing and the BAC plug is in good shape.Anyone have any other thoughts?
Thanks
Andy