alright i need help with my friends 94 auto z28.not sure of the exact motor code but this is the proplem,the car starts and drives fine but it idles iratic(sp) it acts like the tps sensor is bad.it jumps from 1000 rpm to 17-18 hundred then back down and then back up so on and so on.when u beat the shit outta it one time it stops for a minitue then just continues to do it again.he just replaced the map sensor,idle air control sensor and the throttle posesiong sensor less then 3 weeks ago and its still doing it.never stoped but when he first put the sensors in it stoped for like 1 minute and then started back up and hasent stoped since.i'm stumped with it.if anybody has any suggestions i would appreciate it if u would post them up so i can get this solved A.S.A.P.thanks

 

Vacuum leak?

 

optispark?

 

a vacuum leak would make the idle high all the time no?

 

whats that?

 

Well, maybe there is a crack in one of the vacuum elbows and it is not allowing for a full 100% of the time vacuum leak. The motor might be producing enough vacuum to seal the problem for a second, then the air gets in or something. Seen it on a different car, that's why I thought that first. Your post makes it seem like it has a weird idle all the time, except for the one minute sometimes, correct?

I also thought the Opti, as stated above, but I'm not sure. Every opti I have heard going bad has been a misfire, not an erratic idle. Not that I am an expert or anything though.

To me, erratic idle means air problem somewhere. I would think mass air flow meter before the opti personally.

How many miles are on the car?

 

The opti is the distributor on the LT1 cars. They have a bad reputation for causing problems, more a misfire though. I'm sure there are a 1,000 symptoms that have been linked to a bad opti though.

 

i'll check the vacuum but the idle fluters exactly at 1000 then back up to 2 then back down to 1 then back up to 2.the change seems to exact to be vacuum if u get what i'm saying.the mass flow sensor could do that no?thats about the only thing that he hasent replaced.

 

I didn't realize it was so exact like that.

I cleaned my mass air flow meter with a q-tip and alcohol. Might want to try that. Or, you can find someone locally that will let you borrow theirs for a second.

Does he have any mods done by chance? Some people have K&N filters, over oil them, then the oil gets on the MAF.

 

i dont think he has a filter but i'll check and i do know he has a chip in it.but i'll try the q tip thing and the other stuff now and i'll let u know man.thanks