Yet ANOTHER rough idle - 2002 P5
- Thread starter sslavik
- Start date
I don't know... I couldn't find anything in the FSM about the vacuum pressure for the IAC..
Hey man, could be your intake manifold p0660. Not sure if you're getting codes or not but I just ordered the part off ebay to replace my VICS Solenoid and I think that hopefully will bring my idle back to 1k steady. I'm not idling rough, but this could be your issue. It's a $20 part that takes 5 minutes max to install, try it and see if it works. It is right under the strut bar and on the left and green; the right plug is white and noticeable and is your VTCS solenoid which you dont need to worry about. PM me if this helps.
Finally had some more time to work on it. 2 mechanics suggested fuel filter or pump. Replaced screen & filter (fuel pump "body"), no change. New fuel pump, no change, grrr. [anybody wanna buy a fuel pump assy?]
008's comment on MAF jarred my memory of an erratic MAF on a Mitsu pickup I had years ago. That was a $180 part, ugh. So, unplug MAF, test idle, still bumpy. Until I turned the a/c off. Suddenly no bumps. Huh? [If you've kept up, it's always been WORSE with a/c on, but still bumpy with it off. First eureka: stop using the a/c, it's adding another variable. But dang it's hot right now...] So plug MAF back in. Still no bumps, no way. Test drive, no bumps! Even with a/c on!?! WTH??? It drives great. For 2 days, then back to the bumps, with or without a/c, sigh. The last thing I did before it temporarily cleared up was idle with MAF disconnected. Try that again, still bumpy. Maybe MAF is schizo. Buy a new one (only $30 this time thank goodness). Just put it on. Drum roll...........no change. [anybody wanna buy a MAF sensor?] I'd kill this car if I didn't love it so much.
bbbalace1 thanks for the VICS tip. I'm not getting any codes other than the random misfire when it does a super-stumble. I've read up on VICS and VTCS and it doesn't seem either of those could cause this problem, buy hey, I think I'm out of reasonable conclusions, so need to investigate.
pcb, you listed the components that the ECU uses to control idle. I'm most suspicious of the two temperature sensors, only because I never get the bumps within the first minute of running. Will be investigating those too.
008's comment on MAF jarred my memory of an erratic MAF on a Mitsu pickup I had years ago. That was a $180 part, ugh. So, unplug MAF, test idle, still bumpy. Until I turned the a/c off. Suddenly no bumps. Huh? [If you've kept up, it's always been WORSE with a/c on, but still bumpy with it off. First eureka: stop using the a/c, it's adding another variable. But dang it's hot right now...] So plug MAF back in. Still no bumps, no way. Test drive, no bumps! Even with a/c on!?! WTH??? It drives great. For 2 days, then back to the bumps, with or without a/c, sigh. The last thing I did before it temporarily cleared up was idle with MAF disconnected. Try that again, still bumpy. Maybe MAF is schizo. Buy a new one (only $30 this time thank goodness). Just put it on. Drum roll...........no change. [anybody wanna buy a MAF sensor?] I'd kill this car if I didn't love it so much.
bbbalace1 thanks for the VICS tip. I'm not getting any codes other than the random misfire when it does a super-stumble. I've read up on VICS and VTCS and it doesn't seem either of those could cause this problem, buy hey, I think I'm out of reasonable conclusions, so need to investigate.
pcb, you listed the components that the ECU uses to control idle. I'm most suspicious of the two temperature sensors, only because I never get the bumps within the first minute of running. Will be investigating those too.
Control isn't handed over to the IAC until the car warms up.
I think you should replace your IAC valve...
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You could get an Elm 327 code reader ($10) and the Torque app and use your cellphone to record the temperature sensor data to see if it seems to be working.
Your ECU maybe getting bad data and be instructing the IAC improperly...
(our ECU should know if its getting bad data... but it is running Windows 95...)
Your ECU maybe getting bad data and be instructing the IAC improperly...
(our ECU should know if its getting bad data... but it is running Windows 95...)
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I don't have the car for a couple days, but I'll start with the IAC tests. Previously, I disconnected the IAC and held it at idle with the gas pedal, still got the bumps, so doesn't seem it's giving bad info. I also put a blocking plate below the IAC, and with it hooked up still got the bumps, so doesn't seem to be creating the bumps. I'll still do the formal tests. Any bets?... thanks for the help pcb, greatly appreciated.
Would you rule it out after those functional tests? No matter, I'm going to do the formal tests.
It's brand new. With both the old and new I wiggled the connector like crazy (both old and new one) while it was running and it had no effect. It runs like total crap when unplugged, so seems to be doing something.
If I can't get my P5 back I don't want to live.!
Almost but I'm not 100℅ sure.
As far as I know, you need to to have zero throttle position and either the clutch in or be in neutral to have the ECU give control to the IAC.
Another thing that comes to mind is slightly fouled or sticky injectors so that's why I suggested more seafoam.
Putting it in the gas runs it through the injectors.
Here's the big list in case there's something you haven't considered...
You've been holding out on me! Just kidding. Just measured IAC resistance. 9.8, supposed to be 7.2 - 9.2, so just outside. Regarding my IAC functional tests, if it were giving no feedback to the ECU, the ECU might not tell it to operate. My tests wouldn't catch this "zero operation" condition. OTOH, the IAC is supposed to energize when the a/c operates to maintain idle, and that indeed happens, grrrr. Still, being out of spec and having a notorious reputation, I think replacement is in order. Big price range on that thing: $20-$300! I'm gonna order one and push some Seafoam thru in the meantime.
