98 Z28--idle Trouble Again!!!!!!wtf!!!!

[LETHALxLS1]

I have a 98 z28 that I bought about 6 months ago. I recently got back surgery so I havent driven the car much at all. When I got the car it idled smooth as hell. About a month ago I noticed the car started to idle rough and surge a lil bit. The car runs fine other than the idle. So I bought new plugs/wires and a fuel filter and got them installed and got the MAF cleaned. I picked the car up and it idled great. By the time I got home in my driveway the idle was rough again!!! SONOFA!!!! When I just barely push the gas I feel a little shake also(ever so little). But give it more pedal and its fine. I noticed that one screw is missing from the part of the stock airbox and this allows the airbox to shift left to right ever so slightly when I push/pull on it.Could this be causing the rough idle??? The screw hole is wallowed out and it is supposed to have a plastic screw in it.The radiator is directly below this hole so too long of a metal screw and a hole in the radiator.Any ideas fellas?? The hole is stripped out. Could this be causing my problem or is it something else? Why did it idle so good when I first picked it up??? Thanks for any help-----mike
--I also run the best gas and tried fuel injector cleaner as well.

[2001NBMZ28]

I'd think if the idle was surging bad, or if you have a misfire, etc. you'd be throwing an SES light. Not sure what screw in the airbox you're talking about - doubt that's it though, any unmetered air would throw a code too, but would be behind the stock airbox. Is it only doing it when hot? Might explain why it was fine when you picked it up. Sorry no help, sounds like you need to put a scanner on it to see what's going on.

[LETHALxLS1]

Yes it does it when its hot or cold. They said at the shop they could put it on the computer but would the computer tell them anything even if the check engine light isnt on? I hope so. It was so weird that when I picked it up it idled great.Thw screw I am refering to holds the plastice stock air tanks on the left and right of the airfilter cover. I go nuts over stuff like this(hate rough idle) even though its not terrible it bugs me. I guess only time/money will tell.

[2001NBMZ28]

Yes, a scanner that can read real time data will display any issues, regardless if the SES is on or not.

[LETHALxLS1]

Yes, a scanner that can read real time data will display any issues, regardless if the SES is on or not.

Thanks I appreciate your time/input.

[barnat]

How did the plugs look when you pulled them? any wet ones or funky colered ones ??IF so and you remeber which plug and cylinder,pull and check!plugs can tell you ALOT!! COIL ? VALVE SEAL ? STUCK INJECTOR ETC And i know some of em are a bitch,Im talking last resort here

[LETHALxLS1]

How did the plugs look when you pulled them? any wet ones or funky colered ones ??IF so and you remeber which plug and cylinder,pull and check!plugs can tell you ALOT!! COIL ? VALVE SEAL ? STUCK INJECTOR ETC And i know some of em are a bitch,Im talking last resort here

I got it done at a shop that only works on vettes and f bodies because I just got spine surgery. I didnt get to look at the old plugs but they acted like everything was normal. I am taking the car back and will ask. I am talking to the guy tomorrow morning and I will ask about the old plugs. That idea makes alot of sense.Thank you!!!!
---dont get me wrong its not terrible as far as wanting to die but it bugs the shit out of me cause it idled so smooth when I bought it 6 months back. I have let the car sit alot due to surgery and wonder if that has anything to do with it.Maybe not i dunno. I will let you know how it turns out.

[socmninja]

if there is a hole in your air lid it shouldn't cause any problems because it's in 'front' of your MAF. it's just unfiltered air getting in. my advice is to check for vaccuum leaks. Since the car had sat for a while, a vaccuum line may have dry rotted or cracked. I'd say you had a vaccuum leak.

[LETHALxLS1]

if there is a hole in your air lid it shouldn't cause any problems because it's in 'front' of your MAF. it's just unfiltered air getting in. my advice is to check for vaccuum leaks. Since the car had sat for a while, a vaccuum line may have dry rotted or cracked. I'd say you had a vaccuum leak.
No --the hole I am refering to is not in the air lid its a mounting hole that a plastic screw goes in on the side of stock airbox..The mounting hole is stripped so the air box can shift side to side ever so slightly. I agree though I dont think thats causing this problem with the rough idle. Its just weird as hell to me that when I first picked up the car from the shop it idled puuuuuurfect. I even had to stop at a few pretty long traffic lights on the way home and it idled excellent.When I pulled in my driveway I sat for a minute and bam!! it was idling rough again.Wahhhhhhhhhhhhh!!!!!! I started my car today and it is still rough cold or hot engine.
I hope it isnt one of those weird things that is hard as hell to figure out and winds up costing a chunk.