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Update 7/8/17: Well it's been like 3 months and I recently had the time to work on this. I took the throttle body off and clean it, it was a bit dirty but nothing crazy. Also cleaned the MAF and air filter too. Took it for a drive and everything was good until I got out of the neighborhood of course. Although it wasn't as bad as before, I think. When I throw it into neutral it seems to be fine, it's when I start braking it seems to start. I still need to check all the vacuum lines.
I don't really know how to describe the problem but when I drive around like a normal person everything is fine for the most part. But when I drive around heavy on the gas and come to a stop the rpms kinda of fluctuate up and down anywhere from 400 to 900. Sometimes, it sounds like it almost dies. Any ideas what the issue could be? My vette has a cai, cam, borla exhaust, and it is tuned. I haven't played with it too much but it may be only when I shift to neutral at about 25 mph and lightly brake to a stop. I will be adding headers next month so I will be getting it re-tuned if it is a tuning issue. I read something about the throttle body building up carbon. Maybe I should just take it apart and clean it? It only has 13.1k miles so I am hesitant to waste my effort on that lol.
Last edited by JZB1887; Jul 8, 2017 at 10:44 AM.
Reason: UPDATE
Second, make sure your connections from the air filter to intake are good. My car likes to have the bellows work loose about once every 20k miles. It makes my car idle a little rougher. Especially after an extended drive.
Alright so it's been a few months, and I still have this problem lol. So, I have checked all the vacuum lines to my knowledge, they all seems good except for one. From my understanding it is the PCV valve that goes from the front of the intake manifold to somewhere. But it was loose and could have been leaking from here. I zip tied it down, but I am not sure if I put it back on the correct way, I may have reverse it... also from looking online it seems it could be possible that it's bad and/or should I install a oil catch there as well? Also I couldn't really find anything with the specific one that I have.
Lower hose is going from valley cover (where air is metered under the cover) to the intake manifold. Other hose is the filtered air intake to the PCV system, i.e., its the clean air feeding the PCV.
Lower hose is going from valley cover (where air is metered under the cover) to the intake manifold. Other hose is the filtered air intake to the PCV system, i.e., its the clean air feeding the PCV.
Alright thanks for the info. I did some googling and found a picture that shows that it is indeed connected the right way. Before it was swapped around. Hopefully everything will work now, I hope to get it off jack stands this weekend and take it for a drive.
You can check for sneaky hard to find vacuum leaks by using some carb cleaner while the engine is idling. Spray carb cleaner around ALL the top engine air passages. Intake manifold to head joints, Air ducting joints and bands, vacuum lines, and around the TB. See if the engine idle changes when you spray an area.
You can also PINCH vacuum lines to see if that changes the idle. There have been BRAKE BOOSTERS that have caused weird engine idle issues. Pinch off or disconnect and plug the vacuum line going to the booster and see if that changes things.
Make sure that your intake manifold bolts are the correct tightness. (inch/pounds). I've seen the intake manifold seals fail to seal. Give a good spray to check that out.
When you pop the vacuum nipple off the booster, there should be a lot of residual vacuum stored inside the booster.
02 Z06 "Surging"
