Okay, I have replaced the TPS and the car has improved a bit, it is reving higher and accelerating smoother. All the codes are gone now, however some problems still going on.

First somthing was jacked on the top screw on the TPS and was nearly striped out, I need to tap it and all that jazz.

After some time driving, and the car is suffecently warm and i come to a stop with the car in gear the idle will drop down and pick up the oil pressure and volt meter will jump around a bit. the longer it dose this the wores it will act when getting on it again.

In park and Neutral the idle is fine and dosent bounce at all. Ive gotten out and checked it the the diagnostice tools i have avalible. I cant get to it in drive because I dont trust anyone to keep there foot on the brake, besides it sounds dangerous.

One i put it in drive it it drops about 200 rpm and starts to drop more and bounce back. once it gets up 200 rpm ( approx from dash tach and ear ) it runs fine. from a dead stop letting the idle push the car ( auto tranny if you didnt figure it out ) it wants to stall and surges with the rpm jumps once it gets to the same rpm as it supposed to be in park and neutral it runs fine and normal.

Why dose the rpm drop when its in gear?

Why after it drops dose it drop more and bounce back?

Help me out please

 

Go take a run and have someone hand you a heavy box while you are running and see if you falter. That is what you are doing to the engine under load.

It drops low and may die out and the ECM tries to compensate which accounts for the hunting idle.

What diagnostic tools do you have?

 

i have a hand tach volt meter dwell meter paperclip stephscope, and fuel pressure gauge. I have access to compression tester.

While i understand there is a diference between load and on load, yet I know that it shouldnt be faultering like that.

My guess is that when the idle jumps back up the ECM is trying to get it there for a reason. Why dosent it keep it there? Even underload, shouldnt the ECM keep the same rpm level in drive? This is my first automatic ever. If this was a manual I think it would be a non-issue, but the shake and fear of stalling at a long light is iritating.

 

It tries to get into a certain RPM by advancing the timing and when it exceeds it, it drops the timing down then it needs to get it up again and so on and so forth. If you have a manual car, it would be the same thing as if you dropped it in gear and not give it gas. I had my IAC out of adjustment and it was always dying out at the stop lights.

Check that the fuel pressure is good and make sure the system holds pressure for a while after shutdown. Then if you can get a scanner, see what the idle counts are at. IF not, we have to go to plan B

 

my bro's trans am had this prob..we did the tps and nothing.....check ur headers/exhaust manifold....i dont know if this would help but his headers glowd red....we gutted the cat converter and that fixed it...so i dunno..check ur manifolds, if they r red gut the cc


dont ask y this worked, it just did

 

It probably glows read because the cat is plugged.

 

yeah, the cc was stuffed with carbon deposites....my poinst is that when we gutted it the idle prob went away as well

 

Well.

NO scanner, the neighbor is outa town for the week. Fuel pressure seems to be fine. The one thing i did notice is that the oil pressure drops at adle after the engine as gotten over 190 degrees.

when the engine is cool it runs fine. The oil pressure is at about 60psi on start up and for a while after. It seems after it gets up to opperating temp the oil pressure drops, unless im on the gas. Drops steadly down as tome goes on... at approxamatly 40psi it starts to have the idle problem . at 30psi is when the ECM will make the rpms jump back up. under acceleration it is a bit rough untill the oil pressure gets back up to about 40psi or so.


Thanks for your imput guys.

 

I was going to go new exhaust anyway, and i dont have emissions so no cats.

Any other ideas?