My 305 doesnt idle correctly and it stumbles when i give it some gas.


Asked by Apr 26, 2015 at 03:43 AM about the 1988 Chevrolet Caprice Classic

Question type: Maintenance & Repair

I changed the spark plugs less than 20 km ago and they are really black. It also has broken valve stem seals....making it smokey on cold starts. im guessing its running rich. could anyone help?

7 Answers


I would suggest pulling the codes, see what is stored. MAP sensors can get out specs and not set off the light, so check all of the codes. The other problem is the seals, if they are leaking like that then it is a good possibility that it has fouled the O2 sensors, the catalytic converters will be next as they can only handle small amounts of oil in the exhaust before they start plugging up.

1 out of 1 people think this is helpful.

If you are certain that the valve stem seals are "broken" then you have oil from the cylinder head getting into the combustion chamber which will create smoke and seriously foul the plugs.


is it posible that codes be stored without a check engine light. I dont have a check engine light on, and my car is carburated. The cat converter is clogged but i made a big hole in it.... i didnt run the car for a year, i let it idle today for a good 20 mins, it seemed to get better.


Yes I have seen the old OBD 1 do that. A stumble can be a bad accelerator pump in the carb, or worn throttle shaft bushings, even severely worn timing chains can do that. Make sure the base timing is correct and the computer changes the advance when you reconnect the spout connector.

1 out of 1 people think this is helpful.
Best Answer

You might consider a carb overhaul if it hasn't been updated with the new E10 resistant componets. Or find some station that still sells actual gasoline not E10 and run it.


Thanks, il try a new O2 sensor and later get my carb overhauled. i heard to stay away from remans. my original has only 152,000km on it.


Yes if at all possible have your carb overhauled, the remains over the counter are terrible and a new one any more are getting expensive.

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