TheDullahan

So after the car warms up, it seems to want to stall out as if running out of gas at idle. It has not stalled yet. It drops to 300-500 rpm and starts missing about 2-3 times a second. When I go to accelerate, it jerks and misses like a slipping transmission for 1 second then its normal power again. When driving or cruising it has no problems. It is not low on power and has no problem starting. It has new plugs, air filter, and fuel pump all within the last 2 months. Is it possible that it is fuel pump related or could i be missing something simple.

02GTSharkin

Could be a vacuum leak. Check all of your vacuum lines.
Throwing any codes?

TheDullahan

Only code is for a bad cat, checked all vacume lines and they seem good. I will do another look through in the morning, could have missed one.

JJ Glo

How does a vacuum leak cause low idle? From my understanding, a vacuum leak means that the engine is pulling in extra air aside from the air being pulled in from the throttle body and the IAC. More air = the engine using for fuel = engine revs up.

I don't know much about cars, but if I'm mistaken, please someone correct me.

A low idle would be the opposite of a vacuum leak, which would be that the engine is not getting enough air or fuel.

TheDullahan

If the engine is getting unmetered air from a vacume leak you now have a lean condition as there is more air than fuel because the motor can't add more fuel since it doesn't see the extra air. This can cause a miss or for it to stall out.

GT210

I have the same problem going on right now as we speak. Check for codes and see if anything is popping up and have you tried to clean your IAC or MAF yet?

dawson1112

Generally a vacuum leak would cause idle to go up, the computer would see the lean condition in the upstream 02 sensors and adjust fuel trim. I would also expect to see drivability issues while cruising and hunting idle while cold as well as the pcm tries to maintain engine rpm by opening and closing the iac.


Since it only does this after it gets warmed up I would suspect that the idle air control valve has some crud on it .

Is the new air filter an after market cold air intake or is it an oem stock filter?

The after market cai filters have oil in them to help trap debris , if it was over coated in oil that oil can make its way to the maf and cause idle problems.

Also you could have a failing engine coolant temp sensor, as the ect reaches a certain temp the resistance could either be way to high making the computer thing the engine is much colder than it actually is increasing fuel to the point that it is killing ignition, or the resistance drops of to 0 making the computer think the engine is extremely hot. Either way this will affect the fuel trim to the point of stalling, almost stalling , or missing/ popping .

NTO_GUY

I agree about the IAC and the Coolant temp sensor.
I had two separate occasions on two separate cars. Same issues except one would die even if not warmed up. The first issue missed and after heated up would die once every time. It was the coolant temp sensor and my car was reading -40degrees. Replaced it and no more problems. The second same issues but died all the time almost had to throttle it to keep it alive. I had a bad seal in my turbo. The oil cause the IAC to get carboned up and it was stuck.
So I could see either of those two being and issue. Here is the kicker though. There were no codes for the coolant temp sensor or temp related on the first issue. So be aware.

CalBoy101

I don't think anybody else mentioned this but I'm waking up slow today so sorry if its a repeat-

One other thing to check in this case is a dirty and sticky EGR valve. It can be not fully closing and letting exhaust gas thru during idle, with a bad leak the engine will totally stall and it can give you the poor light throttle performance you are seeing.

TheDullahan

So it's definitely running rich. I noticed under hard acceleration it studers and has a hard time building rpms. It also has an awful exhaust smell.