any ideas? idle/stalls but drives fine

VAC leak VAC leak Vac Leak
Ive had lots of experiences with this issue.

i had the same issue after i deleted the manifold butterflies. Bouncing idle and near stalling. I could not find find the vac leak. I took it over to a friend of mine and he found it right away. I had connected the vacuum line for the MAP sensor to one of the studs that used to hold the the actuator. So the port for the line was open and caused a big vac leak. A silly mistake because i was trying to go fast. Followed by me being frustrated and not checking properly.

I work at a parts store, customer came in and bought a MAF sensor for his Ford Taurus, told me its stalling and the idle bouncing. I asked him if he had checked all the vac lines he said yes. Came in a few minutes later (he changed it in the parking lot) continued to have the issue. I went outside with him and i found his breather tube grommet was ripped in half. 4 dollar part ran normal after.

Did a h22 swap into my friends civic. Again bouncing idle. Did everything you can think of; cleaning out the idle control valve, fast idle valve and bleeding the coolant system(part of the trouble shoot from honda idle control valve has coolant like flowing through it) and checking every vac line. We decided to take out the manifold to change the gaskets. gaskets where fine, but i started to look at the manifold and the previous owner had tried to do a port and polish. he cut so far into the metal that he cut into the idle control valve port which was the cause of the vac leak. Had the manifold repaired. and wala not more bouncing.
 
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I just had a friend come over and he brought his smoke test machine and didnt find any vac leaks. I just dont what else to do besides bringing it to a shop to ripped off.
 
if the harness is bad you should get a code for something like MAF circuit malfunction its P0100.

Just curious how did he connect the smoke machine?
 
We ran it through the brake booster and the intake and also through The top of the valve cover where the pcv valve goes. Im wondering if it might be fuel related i just dont have a way to check unless i take to shop
 
Sometimes it runs fine...Once im driving it runs just like it always did. When i come to a stop i have to feather the gas.

Pretty classic for a vacuum leak or sticky EGR valve. You can disconnect the electric connector to the EGR... the CEL will turn on, but if the intermittent rough idle goes away, you have a diagnosis. Cleaning the EGR has mixed results (it lasted 50 miles when I cleaned it), it's best to replace it for ~$100.
 
+1 on the sticking or clogged egr valve.
and +1 on the maf wiring maybe having a short( if you have a check engine light)
check your air intake boot for rips as well, look real close, they can be hard to see, mine had one kind of on the sode near the throttle body and it was hard to see. caused me similar issues,
 
hello also consider that maf sensors fail or act up due to cai filter oils and etc. placement of the sensor can also be a factor brittle wiring or just a down right faulty sensor as not all maf act up due to a cai.
 
Also consider the IAC valve... disconnect it with the engine at idle. The engine should stall, if it doesn't, the IAC should be inspected further.
 
Hey guys heres an update... so after replacing the MAF sensor and thought it was fixed, i went ahead and bought some seafoam. I put half in tank and half through break booster vac line. And while doing this i noticed alot of smoke coming from the engine bay. I had a friend rev it so i could see where it was coming from exactly and it was my exhaust manifold/ header. It was missing a bolt and three others were very lose. Put a new one in and tighten the rest. Drove it around a few days and now alls good. Im not sure if that was my main problem but it did contribute to it. I think the ecu was just relearning/ resetting a new MAF sensor. But its running good now. I really want to thank everyone for helping me in my time of need and i will definitely give back my input and knowledge to try and help out the next person. Thanks again guys!
 
just fyi for all, DO NOT PULL YOUR MAF (MASS AIR FLOW SENSOR) PLUG WHILE THE ENGINE IS RUNNING!!! on obd2 cars(1996 and newer) doing so could fry the computer, just like pulling the battery cables while running could fry computer and alternator as well.

if you need to test that the sensor is working correctly turn car off, unplug and re fire, if its running worse, or wont stay running while unplugged then sensor should be good. if no change then sensor could be bad
 
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