rough idle and CEL, coil packs and plugs are good

[ultrasport69022]

So today my car started to idle rough, the CEL came on and only making 5 pounds of boost (stock ecu). I checked all of my coil packs and plugs and they were all good. I also checked some of the hoses to see if there was a vacuum or any other kind of leak but nothing. what could this be!?!

[shane.trammell]

what did you find out you checked the codes?

[ultrasport69022]

i dont have a scan tool but im waiting for my friend to get off work to use his. is that the only way to find out whats wrong?

[Stubek]

Check 02 sensors, also, if you are high miles, you might have a leaky valve cover gasket

[texasboy21]

Could be the MAF, but since your only seeing 5psi that means limp mode. Unplug your MAF and see if the idle improves, if it does that means in bad.

What your gauge read at idle? You can either wait for the scanner to pull the code, or reset the ECU by disconnecting the battery for 5 minutes. That will take you out of limp mode, but you will have to wait and see what codes come back.

[ultrasport69022]

thanks for the fast replys everyone! well i changed my valve cover gasket last weekend actually and i just recently changed my MAF. Is there any way to check the O2 sensors?

[ultrasport69022]

o and my gauge reads at about 15 vacuum when its normally around 25

[PDX04a4]

uhh, vacuum/boost leak anyone? do a leak test and check, it could cause all your symptoms. there are a lot of areas/hoses that could be the source of the leak, not all are visible with the hood popped.

[ultrasport69022]

Is the easiest way to find a boost/ vacuum leak the diy on a4 mods? or is there an easier way?

[texasboy21]

^probably the easyiest unless you can visually find the leak.

-15inHg at idle is too low and -23inHg is too high, should be around -20-22inHg at idle. You probably have a boost leak

For the o2 sensors, log with VagCom

[ultrasport69022]

would a boost leak cause this problem? I reset the ECU so i am no longer in limp mode and i am now making 8 pds of boost.

[ultrasport69022]

UPDATE: found out that my PCV valve was bad. going to pick up the part tomorrow hopefully that is all thats wrong

[starfriend]

how did you figure the PCV valve was bad?

[texasboy21]

UPDATE: found out that my PCV valve was bad. going to pick up the part tomorrow hopefully that is all thats wrong

Good 8 psi is normal, and a leak can cause limp, let us know if thats what was up

[deltaforcehall]

UPDATE: found out that my PCV valve was bad. going to pick up the part tomorrow hopefully that is all thats wrong

i doubt this is the problem, if it turns out not to fix your car, check the check valves around the top of the motor, they break in half and cause leaks which have the same problems you're describing and have pissed me off a couple times over the years

[ultrasport69022]

it was the pcv valve it now runs great. i found out that was it by clamping the hose that goes into the valve.