K guys... so i've been monitoring this bitch quite a bit lately... here's what i noticed:.

When starting the car early in the morning, it will do it's whole 3000 drop to 2000 routine... then slowly goes down to about 1300rpm and idles ROCK SOLID. No backfires, no misfires, just pure rotary bliss. Then all of a sudden, the rpm jumps back up to about 2000RPM, and the misfiring begins again.

So it looks like the car runs perfectly for the first 30 seconds of the cold startup... then the rpm climbs back up, and starts misfiring.

What would cause it to do that? Some sort of valve/solenoid that I haven't checked yet? I checked the BAC and the AWS systems already, and they're perfect. So what the hell is left that would affect idle so gayly? ECU? *shudder*

 

Whenever it goes up to 2000 and it stays that way (im assuming thats what its idleing at when warm) Try to adjust the idle down, and then re adjust the TPS. I know it sounds like something stupid, but i dunno. You probably already have tried this. Id look for a vacume leak that might throw something off.

 

how does it idle when the engine is fully warmed up? My idle feels like it has a tiny misfire when fully warm. Do you think it might just be that the rotary doesn't like to idle absolutely perfectly?

 

Wrong.

TPS and idle have been set about a zillion times. different methods... everything.

It is NOT a vacuum leak, i've tested for it with propane. It is something either electronic or mechanical that's doing this because it happens within a snap of the fingers. Goes from normal to **** instantly. Something is making it do it. Something that happens in THAT very moment. a vacuum leak will not develop instantly, and every time the car is cold, and only for the first 30 seconds lol

 

When warmed up, at 750, it idles perfectly but if i raise the rpm to 1000-2000, it misfires randomly. if i raise it past 2000, it's fine.

 

How do you know it's misfiring. Did you see it on an asciliscope or dyno? If it doesn't do it under load at 5k or 7k I don't see why only at 1000-2000rpm. Are you revving it in nuetral? Get new wires and plugs!

 

You guys aren't listening. It's something that happens instantaneously. Goes from perfect to ****. Idle speed changes when it happens too.

It's NOT the plugs, NOT the wires, both have been replaced.

How do i know? i can hear it and I can see the RPM change when it happens.

 

i dont have any problems like your describing, but my check valve leaks air after the car warms up.

im a novice on the air system components and functionality, but when the car is warmed up, you hear the air being sucked/blown out the check valve near the TB..

check valve, delay valve, bah whatever its proper name is

here it is

 

Oh yes, it does NOT happen under load, or in any other RPM range. Having some starting difficulties under REALLY hot conditions when its BOILING outside, and the engine has been driven "spiritedly". Similar to the misfire issue.

 

relax man..

not everyone has read all 17 threads you have about this problem..

j/k..

 

Nope. no vacuum leaks. checked when the car was very warmed up. Did so extensively. Its a series 5 T2

I appreciate the help guys!!

 

LMFAO!!! sorry that must have came out wrong.

I really didnt mean any offense... i do appreciate the help i'm getting from every board member. But I am CERTAIN that it is not a vacuum leak, and its not my plugs, wires, tps, bac, aws, or anything like that.

I'm thinking ecu/afm/something electronic like a solenoid, valve... ?

 

Then it's your one of the other 10+ items under the hood. BAC, TPS, Coils, Wiring, etc. If you think it's your ECU, seloind, or a valve then replace them. One at a time.

 

Well naturally, but which one?

Not the bac, checked and triple checked... not the tps... not the aws... not the coils... (tried another leading coil that i had. trailing is for emissions only anyway)... not the wires, not the plugs... not a vacuum leak. These are all things i've tested REPEATEDLY and/or replaced.

Short of a data logger for every single bloody sensor, i'm screwed. I've been trying to solve this gremlin for the past two months i've owned the damn car.

 

when my mx6 would do crap like this it had to do with the air system there was something called an idle control solenoid that let more air in for a higher idle when cold and would screw up all the time. is there anything like this on a T2?

 

Yup, there's one on my gf's talon, and that has given us countless problems. Fortunately, rx7's weren't blessed with a peice of **** system such as an idle servo.

 

Hmmm... maybe its the timing... last time i checked the timing was set to spec... but then again, i didnt do the jumper... so it might have been in cold mode.

does anyone know if the timing changes within 30 seconds of warmup?

 

ever thought it was a bad signal getting to the ECU or something?

do you know anyone else with a S5 TII?

maybe you can swap ECUs for a day and see what happens..

isnt TOO difficult to remove and install one..

but im a bit of a novice - i may be overlooking something as im sure someone will correct me that temporarily swapping an ECU might be a bad idea..

 

no other s5 tii's within MILES

 

My T2 has a little idle misfire too. like a little coughing sound is the only way to describe it. It only does it during the higher rpm idle while warming up. Once you drive around a little and it settles in at 700-750, it's fine.

 

If you take the bac plug off....does it do it?

How many seconds after starting does it happen?

Happens even after the car has reached operating temperature? How many seconds after startup when fully warmed up?

 

Based on what your saying that during warmup it smoothly drops down then jumps to 2000 I'de say you have some unmetered air entering the engine, likely through a solenoid since you've checked for vac leaks.\

Don't know how applicable this is to S5's but on S4's there are three timers in the ECU that affect cold start. The AWS (17s) and two related to fuel enrichment (60s and 120s). The PRCV valve is affected by the AWS timer so I'de try checking/swapping the PRCV solenoid. The valve that Black13b has pics of could be a candidate too although it doesn't change until several minutes of operation (it affects the secondary throttle plate opening).

Henrik
87TII

 

Yes, unfortunately.

Quote:

How many seconds after starting does it happen?

About 30 seconds. ONLY after a cold cold start. Like in the morning. You watch it go down from 3000 to about 1100... ROCK SOLID (hell you can even rev it between 1100 and 2000 and you wont hear a single misfire). Then something changes and the idle jumps to about 1800 and then starts to do the whole misfire bit.

Quote:

Happens even after the car has reached operating temperature? How many seconds after startup when fully warmed up?

The car misfires between 1000-2000RPM, in neutral only, but not within the first 30 seconds of the initial cold startup... anytime after that. Whether warm, lukewarm, or otherwise.


Thats the best i can describe it. Lemme know if you need to know more, HAILERS. I know you've seen it all lol

 

Thank you Henrik. It's about 30 seconds to 60 seconds during the initial cold startup. I will time it more precisely next time as i'm not exactly sure. But during that time, it runs PERRRRRRRRRFECTLY.

I'd also like to stress that this does not happen under load, or in any other RPM range.

Unmetered air? Don't think so. Although i wish it was that easy. My mechanic spent a good 10 minutes with a propane tank and a length of hose poking around everywhere to see if the idle changed. NOTHING. Not a single freaking thing.

 

Could it be your MAF sticking, or maybe changing resistance a little as it warms up?