1988 S-10 2.8 rough idle/surging at idle

MRAUSCH82

MEMBER
1988 CHEVROLET S-10

I have a 1988 S10 we bought brand new. It has 236K, 70K on reman motor. When you first start it, it idles rough and surges like crazy on idle. Sometimes it will stall. When accelerating and shifting from 1st to 2nd, or most any other gear, it'll "miss" and do a momentary "buck" when releasing the clutch and giving it gas. It'll do the same thing if you give it half throttle very quickly when idling. It runs fine down the road and once warm, it seems to idle better, without the surging. I have replaced the idle valve (that WAS bad), the O2 sensor, wires, cap, rotor, plugs, fuel filter, air filter and it still does it. I just replaced the fuel pump with a new AC/Delco pump and that did not help. I am told it is running lean but the sensors seems to be working according to the scan gauge. I tried a different MAP sensor and that did not help and the timing is also correct.

1 Reply

4BANGERJIM

MEMBER
3 POSTS

My 88 S10 with 2.5 engine does the same thing and will also flood when a hot start is attempted in about 20 minutes after a hot shut down. I did get a message that there is carbon build up and cleaning the throtle body of carbon did nothing. I started to read the service manual I have for the S10 and found an interesting affect if the vapor canister is failed, it will cause same problem. Hope this helps.