I'm helping my friend with his 03 AP1 which is having an idle problem.

Throttle response and pull are all fine when the car is moving, the issue is when the car goes from moving to a stop.

Now as I understand the only 2 things that actually can adjust idle are the IAC valve and the ECU, but the ecu takes readings from MAP and 02 sensors.

The car currently has:
fresh OEM plugs
cleaned IAC valve body
IAC prop appears to be uninhibited in terms of spinning ability
replaced 02 upstream sensor
MAP has been cleaned
Throttle body has been cleaned
Air Filter is cleaned
Valves have been adjusted

The service manual states the idle needs to be 850 +/- 50 rpm i believe.

Now originally it had a really low idle (500-550 I believe), after doing the service manual ECU reset and idle learn procedure, the idle eventually improved to the service manual specs. However, after moving and coming to a stop, the idle will stumble to 2-3 bars and then recovers to 1 bar below 1k.

I have tried swapping positions of coil packs and I have checked the plug condition. I don't believe it's a spark issue as all 4 plugs show similar deposits and condition. It looks like the plugs have significant carbon build up and aren't the same cocoa colored that I'm used to seeing on my friend's AP2. Since the plugs exhibit similar conditions, I believe the problem is not with 1 particular cylinder but that something in the system is running the car too rich.

Any thoughts?

Pictures attached are cylinders #1-4, photo 1 = cylinder 1; photo 4 = cylinder 4

http://www.youtube.com/watch?v=OUWiVJJxmp0

 

I'm having the same problem! I almost died at a stop light. I did everything you guys did as well plus a valve adjustment. I can't figure it out!

 

What are the conditions of your plugs and o2 sensors?

Can you make a video of your problem?

When did you first notice your issue?


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I didnt check the o2 but I believe its ok, I have a test pipe. I noticed it about a week ago and its progressively getting worse.

Don't know if you can click this or not but here's a video. And the my plugs looked just like yours, lots of carbon around the top.


http://www.youtube.com/watch?v=DlYDoDNQ2us

 

Oh that's too much throttle slack you need to adjust the play in your throttle cable


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I did since then doesn't help. I get tightening it little by little until it was idling to high. It wont find an easy medium, even when I leave it it just falls back down again.

 

Ha I just made a similar post with the same particular problem. Ive been told I may have to "burp" her to fix that problem.

BTW does this only happen to you on cold engine/first starts?

 

From the thread I just created... Did you replace both O2 sensors or just one?
"
My AP1 with 110k miles developed rough idle and stalling. Once the car was warmed up, revving up in neutral and letting go of the gas pedal would result in RPMs going to 500, shaking and the car either recovering back to idle 850 rpm or stalling. It would almost always stall out while driving when stopping at the light.

Battery connection was good, had new spark plugs, new TCT. Because I recently replaced my battery, I followed the idle re-learning process as seen on the 00-03 maintenance manual page 11-100 - car would still behave the same

Then my check engine light came on and reading was bank 1 oxygen sensor voltage low. I replaced both sensors and cleared the CEL - car still had idle issues. Performed the idle re-learning process and car started running like new. Haven't had any idling issues or RPM drops.

I wonder if oxygen sensors that are about to die cause rough idling and stalling in other s2ks on this forum. I used TORQUE app for RPM reading during idle re-learning process (keeping RPMS at 3000) ... Cluster would show 3100 while torque would show 3000 - not sure if that makes a difference.
"

 

Replaced just the upstream one. Do you think both should be replaced?


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Chances are if one goes, so will the second one shortly
Rock auto parts got DENSO o2 downstream for $30 shipped

Once you replace it, rest the ECU by pulling #6 and #25 fuses out(unsure if that's correct) and repeat the idle learn procedure
Use 3100 as your mark if using cluster or 3000 if using software