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RJCapt
August 10, 2011, 20:56
Looking for some help here. I have an 03 TL-S with 140k on it. Completely stock.

Here's the problem. After the car warms up completely (15 mins or so) and it idles for several minutes (in traffic, closely spaced lights, drive-thru, whatever) the idle increases. If the car is in gear (automatic) it will pull against the converter to about 3k. If left in neutral, it will actually bounce off the rev limiter.

If I drive it away for a few minutes it will clear itself up (not using the IAC valve), but if left alone, it will slowly hit the rev limiter and then work it's way back down in 100-200 rpm increments until it reaches a normal idle.

I have so far replaced the IAC and the TPS. Neither had any effect. There is no binding in any of the cables (including the cruise control) and if you watch the TB while it's doing it's thing, the throttle plate doesn't move at all. I am assuming it's in the IAC but I really don't know. It is throwing zero codes.

The last thing I have to change is the ECM but I would rather not change that unless it really is to blame ($$$$).

Any ideas?

Thanks

Pete

SWOHFAL
August 10, 2011, 21:06
I believe that it may have something to do with the ECU relearning the system after adjusting the idle on the TB - you may have to jump through hoops to keep the ECU from trying to compensate against a baseline that started out at normal idle speed. Best to go somewhere like Acurazine.com and ask there.

evan price
August 11, 2011, 01:17
My wife's Toyota had the exact same problem and it wound up being the coolant temp sensor (the one for the ECM, not the guage). It had a bad spot in it, when it hit operating temperature it would start throwing bad values and the ECM thought the temperature was subzero outside and started increasing the injector pulsewidth (and richening the mixture) which increased the idle speed.

I would say you need to hook it up to an OBD-II scanner with live datastream monitoring and see what value is out of spec and causing it. My money is on either the coolant temp sensor or perhaps a vacuum leak of some kind. If a vacuum leak the ECM will notice a lean condition in the exhaust O2 and richen the mixture, but at the level of problem you are describing I am surprised it is not throwing a code even for high idle speed.

Brett
August 11, 2011, 01:24
Not an Acura mechanic...but I would check for a vacuum leak on the intake plenum between the TB and manifold.

RJCapt
August 11, 2011, 09:51
Thanks for the input.

I spent 4 hours searching acurazine.com last night. I found several posts with similar issues but no answers. I did however find all the info I have been looking for on a 6MT swap! But first things first...

My next plan is to change the ECT, I just need to figure out where it is and if it sisters with the sensor for the guage. If it does, I don't think it's the problem because the guage is spot on. The other reason, I'm not leaning that way is because the rpm increase is very smooth and clean. I have a good deal of experience tuning the fuel map on the FI system I have on my camaro. If I just increase pulsewidth, the idle will increase but not to redline without introducing more air from someplace (IAC or TB). It should also only be able to compensate for the change by adding only the temp compensation amount (which is usually only 20% give or take. It can't actually change the PW at that point in the map. Unless of course it's an exremely sophisticated system and it may be.) But it's worth a shot.

My first thought was a vacuum leak. But it's very controlled and it will fix itself. Never had a vacuum leak (except for a bad IAC valve) do that. But once again, I'm looking at everything, so that's worth some investgation as well.

Yes, if I had a scanner that could tell me real time FI data that would be awesome. I'm not quite in that league. I think I will do the stoneage version of that and tap into my sensors to see where they are when it happens. That of course sounds like as much fun as a root canal...

Thanks again. The search continues...

Pete

RJCapt
August 11, 2011, 10:05
Ok more random thoughts to add...

The FI ECT should control the fan cut on/off points. If it uses the same temp value, the fans should turn off when it senses a "subzero" temp. They still run normally. It doesn't matter, it gets changed regardless....

If I can find the IAC valve entrance point (the place it actually draws it's air from) and it should be somewhere in the intake tract ahead of the TB, I will try to smother that and see if it either loads up (trying to add too much iPW) or stops, (IAC getting false signal from ECU).

Anyone wanna buy an Acura.....

Pete

SWOHFAL
August 11, 2011, 12:41
I'd try to search eBay or acurazine for factory service manuals to buy.

steve3320
August 11, 2011, 21:24
not sure on that exact Acura, but check the IAT -- intake air temperature sensor -- if it is thinking the intake air is super-cold, that is what would be giving that signal.
Also, I assume you took off the TB and cleaned out the 8 years of gunk when you replaced the IAC? If not, do that -- I have had several vehicles with idle surging (though not to your extent) that smoothed out after some time on the bench with some pipe cleaners and solvent.
Last thing, and again I don't know if this is possible on this exact model, but is check to make sure the IAC will not fit on the throttle shaft more than one way ---- most likely not, but hey worth a look before spending money.
Hope you find it -- nothing more frustrating than a "good" cat going bad on you!

adam762
August 12, 2011, 00:53
I'd say limit yourself to airplanes, but every man has to have his hobby. Sounds like you're enjoying yours.

Hope they're treating you well these days.

RJCapt
August 12, 2011, 09:44
Adam, how are you brother?

Things are good, hope things are well with you. We will have to get together sometime btw I finished that short gas FAL and it runs great thanks for the advice. Doesn't look anywhere near as pretty as the ones you turn out but it's good for me.

Back to my pos acura.

Yesterday while driving it, I lost a coil so as soon as I get that changed out I will be back to my search for the problem.

I did clean out the TB when I replaced the IAC (and it's in correctly, fortunately for me it can only go in one way...). After some reading I found that there are egr ports in the intake that should be cleaned, so I guess I'll pull that and clean them too.

I think it's heat related. It was 75 yesterday and it only happened once on a very mild scale. I think my PCM may need replaced if that's the case. I think I will temporarily isolate it from the engine compartment heat and see if that makes any difference.

Thanks again for all the help guys

Pete