Hey guys ive searched and found some info on the topic but im not sure any of it is specific to mine. I just got my car back from the tranny shop fml. It set for two months. It idled great before hand and perhaps maybe this isn't that big of a deal and im just not back used to it? Anyways, So when you start the car it shudders for just a second then is okay. But if you are okay on idle and you kick on the head lights, the idle dips from about 850 to 600 and then goes back to normal. And its not just the drop in rpm because i know a little drop is common for a split second but it also sort of shutters when it happens and the idle is just rough all together. AFR is around 14.8 at idle also which is normal. No miss when you get into boost and no miss if you lug it into a load so i don't think it is a misfire. I've read things about the iac, egr, etc etc. I know it isn't always the case but i figured usually they would throw a CEL? I just changed the plugs and they were pretty black. The car is tuned and afr is spot on so im not sure why they seem fouled. We did a boost leak test the day the tranny tore up and it had no leaks, nothing has came off the turbo system since. I put some seafoam in the gas just in case it was bad from setting. Also we were doing an e85 tune when it tore up, i drained the tank, and put about 5 gallons of 93 back in. Is there anyway that there was trace e85 in there and maybe ate something up? Just a thought i feel like unlikely. And on top of everything ive never driven the car in the winter so maybe it is just adjusting? Hell idk any input or thoughts are appreciated thanks sorry for the ramble lol.

 

Any ideas? I was leaning towards the iac or the egr solenoid but i have read about people with the same issue and it seems alot of them have the CEL on?

 

Pull the IACV. Volt test it. Doesn't sound like an IAC issue but you never know.

 

okay ill do that. It is also getting cold as i drive but that isn't a new issue the themostat get here today and while im doing that i will check all the EGR lines, and the IAC ill get back tonight and go from there. Thanks for the info. Can i rule out the egr solenoid? Ive just read alot about that as well as the iac valve.

 

Not sure i would rule it out. I would also check for a boost leak. Might as well rule out everything. I found that my idle issue was due to the angle of my MAF. Go figure.

 

okay tonight im going to check every single vacuum line i can find. I dont have anything to do a boost leak test at my house but i will buy one. The car runs perfect just idles funny. it holds -15mmg vacuum and is ~14.6-15.2 afr at idle so it is something small or a sensor nothing is bad off it is just really annoying and mildly shakes the car and it definitely wasn't there before the tranny work so im thinking maybe a lose vacuum hose or something that isn't plugged in right or something small its just annoying. Ill post back up tonight thanks for the help.

 

mine does the same thing when its first started but im also running a aem and its getting colder out and harder to start so ehh gonna be parked all winter anyways

 

Is there anyway tb seals being bad would cause a shudder?

 

you know what after i changed my clutch i started having the same problem got a cel for egr i thought it was a leak but i checked all my lines and everything seem fine. So i went ahead and bought a new oem egr hopefully that'll fix the problem.

 

That was going to be my next suggestion rebuild the TB.

 

Yeah i just had the ACT installed also. the car has no issues other than this "shudder" maybe i can make a video of it but im not sure how much it will convey the issue but it is worth a shot. I have checked every single line on the car and i cannot find a loose line every vacuum line is see is zip tied on both ends. IC pipes are tight. I still don't think it is a boost or vacuum leak.

I have been thinking. At first i wanted to rule out the IAC and the EGR because of no CEL. But is it possible the IAC teeth have failed like many have had and the electronic motor is functioning correctly and the ECU doesn't know it is broken? If so can someone send me a how to to test the IAC or tell me how to check? I know to leave it plugged in and take the off the bolt up but do i just turn the key on and see if it is working or do i have to use an ohm meter?

 

To check pull the iac. Leave it connected. Have someone turn the car to the on position. Not started. See if it moves in and out. Then I would also check with a volt meter. Pull the connector and test the pins. I am on my phone but search my threads there is a DIY in the idle issue one.

 

Ive also seen where people unplug it from the car to test it is that true? What should the car do if you unplug in while its running and the iac is good? This is so annoying i have been without the car for 2 months and now this..... fml

 

okay i took the iac off the mount. I left it plugged into the connector and had my buddy turn the key over as i held the iac in my hand. I felt a vibration for about half a second in the iac and it moved once just a little bit when he turned it off. Other than that it didnt move back and forth or anything and it was just one vibration and one very tiny movement and thats it no clicking or anything. Is that my issue or is that how it is supposed to act?

 

I had a similar issue. I unplugged the negative terminal from the battery and let it sit for 10 mins. Then hooked it back up. Then try the IAC again. I would go for the volt test. Its pretty straight forward.