I have a 1987 z28 with a 305. for the last few weeks it has been dieseling kinda sporadically. it happens mostly when it is cold and idling fast, but it has happened when it was cold a few times too. i found that shutting it off in reverse seems to keep it from happening most of the time. any help or advice would be much appreciated!

i also have another little problem. occasionally when i try to accelerate the car it wont accelerate at first then it all of a sudden accelerates very quickly. i am thinking it might be a fuel pump problem, but i just want to make sure. again any help or advice is greatly appreciated!



yes the car is completely stock as of now :]

thankyou everyone! you definitaly kicked the **** out of my manual troubleshooting lol XD

 

Its probably your timing or a vacuum leak or both. I have a boat that runs 10 degrees of inital timing and I have to run 93 just to keep it from doing that. It calls for it though. Have you done any mods? Is it stock? Check for vacuum leaks in your hoses etc. Spray some carb cleaner on your vacuum hoses/connections and see where it stumbles. If you have a vacuum leak, and let it idle for a bit and then mash the gas it should choke it out. Thats my two cents. Had this happen before not on a 3rd gen, but it sucks and I feel your pain. There is nothing like pulling up to a fancy resturant and getting out and making it to the door before the car shuts off lol.

 

the acceleration problem is due to a dirty O2 sensor i almsot GARUNTEE it lol

 

Yeah it could be the 02 sensor on the accelleration. If you have a fuel pump problem it wouldn't have enough fuel to accellerate over like 3grand and then the ecu would be retarding the timing like crazy to keep you from being way lean. It would be like having a 3grand rev limiter. Been there. Done that. I still think you have a vacuum leak too.

 

Welcome to TGO. Most likely a vacuum leak. Shutting it down in reverse puts drag on the motor and is only masking the problem. Hunt down that leak.

 

Carb Cleaner. Spray it. You will find that leak(s)!