High idle when check engine is on, runs lean and stumbles when off

JMarion89 · Jun 29, 2011

I have an odd situation going on, Just picked up my first dsm. It was already modded (probably a mistake) but the car ran ok when i got it. First off, cold starts are bad, have to start the car 5-6 times before i can give it any gas to keep it running (as soon as you hit the pedal it dies but if you dont give it gas it will die). Recently the check engine light came on and the car would idle at 15-17 and jump up to 20-21. the car still ran fine just acted goofy at idle. I went to drive my car to work, planning on checking the code at lunch and but on my way to work the light went off. Car went into a "limp mode", it idles at about 800. Theres an a/f gauge in the car and it said it was running lean, the car stutters and has no power. I have no idea how it acts under boost i just tried to baby it home. Tried to check the code but its just continuous blinks . Not sure where to start, I feel like im chasing a few different problems. Thanks

thector1 · Jun 29, 2011

I had a similar problem and it was TB leak. Do a boost leak test first before you start buying stuff. Good luck!

obryantms · Jun 29, 2011

Blt!!

GsxMan98 · Jun 29, 2011

If not a boost leak, could also be a pre turbo exhaust leak like a cracked exhaust manifold.

zdravko_k2002 · Jun 29, 2011

Ive had the same problem with my car in the past and I checked everything from plugs wires fuel pump injectors blah blah blah everythign was fine. It happened to be my ECU had leaking caps and a blown driver or two so the first thing I would do if I was you is take out your ECU and inspect is visually for any damage. If it is damaged send it off to ECMLink and they can repair it for you for about $60. Hopefully I just saved you lots of headaches....keep me updated on the issue!

JMarion89 · Jun 29, 2011

Thanks for the imput, first thought was ecu. i thought obd1 was supposed to store codes but when i checked, there was nothing. GSXman, explain why you say manifold.

I just drove the car and the ce light came on, the factory boost gauge stops working when the light comes on. it also started reving up on its own at a stop sign, slowly till it hit about 2500 then tappered back down, not sure if that helps anyone

GsxMan98 · Jun 30, 2011

I had that happen to me with running lean but i didnt see the part about the idle surge. It could be your maf or ecu if your boost gauge stops working and you go lean.

obryantms · Jun 30, 2011

yea if the factory boost gauge stops working i would check out the ecu.

JMarion89 · Jun 30, 2011

Always has to be the most expensive part.. when i open the ecu it says to check caps and something else. what exactly am i looking for?

obryantms · Jun 30, 2011

Burnt up capacitors. You should be able to smell it if they're bad

AlaskanDsm · Jun 30, 2011

Ok. My first question I will ask you is that you know that the OBD1 in our car stores codes but do you know how to read the voltage sweeps coming from the port? If not:

ECU Code Checking

To check the ECU for any damaged components, remove the ECU from the center console area and open the case. Examples of damages to look for are:

corrosion01 [ECMTuning - wiki]
corrosion03 [ECMTuning - wiki]
corrosion04 [ECMTuning - wiki]
driver01 [ECMTuning - wiki]
voltage01 [ECMTuning - wiki]

IF everything looks ok with the ECU, then I would say that it would be time to consider performing the BLT like said above as even the smallest leak in the intake system can through these cars all wacky.

IC Pipe Tester
(basic idea for the BLT)

One thing that sounds similar to a problem I have had is the cold start problem. For me it was because the wires on the Coolant temp sensor were busted off at the thermostat housing. Check to make sure you have all sensors plugged in. If you are also able to pull any codes from the ECU, it may make life easier for yah and point you in a better direction.

JMarion89 · Jul 3, 2011

thanks for the links, i'll pop it open and take a look. the coolant temp looks like it could be a problem. or looks like it was messed with.

92AWDHX40 · Jul 3, 2011

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

JMarion89 · Jul 3, 2011

I did check for codes and i know how to. when i checked its just a consistant blink which means it has no codes correct? The check engine will pop on every once in a while and then go off but the ecu still says it has no codes stored

92AWDHX40 · Jul 3, 2011

Problem could be with the ecu, something is throwing codes, simple as thate figure out what they are fix them and clear the codes, do you have a logger, dsmlink. Sounds like a ecu problem i would have it looked at. Did you check anything with a tuning device other wise you can have a problem until you solve your codes.

JMarion89 · Jul 5, 2011

well found my boost leak, right between the bov and ic piping. now i have a dtc code! 25-barrometric pressure sensor. how do i know if i have a maft and how do i check it? still have an issue with the stock boost gauge not working with check engine light on

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High idle when check engine is on, runs lean and stumbles when off

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JMarion89

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