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My 85 olds delta 88 has 117,300 miles & it passed smog today. I put in premium gas prior to the smog. I went to a test only station & it didnt idle rough until after the smog test. The smog tech didnt disconnect or touch anything. All vacume hoses are good. My car has never idled rough before. It idled good at the smog station. Do you think i put in dirty gas or whats going on here ? The car still idles rough & has cooled down ( 3 hrs). The engine is a 307, v-8, 4 barrel carb. The cars idles rough in both park & drive.
Could be that you got a load of bad gas, could also be something unrelated. Check that all your spark plug wires are attached, IIRC your engine is really a small block Chevy, these are notorious for valve cover oil leaks, these sometimes get oil on the plug and under the spark plug cap, from there thermal expansion pushes the plug wire cap loose/off.
How old are your plugs?
Depending on what the tech did to perform the smog test, it's possible he idled the car long enough to foul a spark plug - although this is more typical of hi-po engines like the S14 in the original M3.
If you can find an uncluttered road where you can pretty much go whatever speed you want from say 35 to 60, if the car will run smoothly at say 35, run 35 a while, then slowly creep up on speed ("Italian tuneup") till you are up to 60. Sometimes this will burn the deposits off a plug that's dirty and sometimes it won't.
The smog tech told me it could be dirt in the carb. Ill get a can of carb cleaner & see what happens. The spark plug wires are attached & good & the spark plugs are ok. If the spark plugs are fouled i doubt it if i would of passed the tough ca emissions test. This is just confusing.
Good point - check to see if the nitwits damaged some vacuum hose. A damaged vacuum hose, either plugged or cracked, which is not too hard to imageine happening on a 1985 car, could be your problem.
If this is the problem, probably the car will run fine, only acting up at very low engine speed/loads.
Another reason I would never consider living in CA...
The vacume hoses are fine. I may have a clogged fuel filter. I started the car today after sitting for 10 hours & it still idles very rough. It nearly stalled out again.
My old 307 powered Delta 88 ran rough, chugged, etc....turned out the carb needed rebuilt. Have you ran a dianostic check on the ALDL port to see if there's any codes?
My old 307 powered Delta 88 ran rough, chugged, etc....turned out the carb needed rebuilt. Have you ran a dianostic check on the ALDL port to see if there's any codes?
No i havent. My check engine light works & doesnt come on when its not suppose to. My car has not gotten as hot as it has or driven over 10 mph in 5 yrs. The smog tech station is 3 miles away & the smog tech said the cat was not hot enough so he got it hot. My test results were overall good. The smog tests in ca are the toughest in the nation & i didnt really expect to pass. NO work or adjustments were performed on the car. Test only stations are not permitted to do that. I watched him & he went by the book. He even did a vacume hoses test, evaporative canister test & gas cap test. The tests sure have changed over the yrs & they are getting tougher & tougher. Maybe i have fouled spark plugs. This is annoying. My mpg is going to be really bad. The spark plugs, wires, cap & rotor have 16,492 miles on them (2-98/100,812 miles). Since i got the car in 5-96 i have written everything i have had done or done myself to the car. I can do basic bare min mechanic work. Just wish i knew more. I was told it might be a clogged fuel filter. The last time the fuel filter was replaced the person who did it stripped the housing & resulted in him jb welding it shut. Ill have to break the jb weld to get to the filter. Thats going to be a hassle.
I'd be suspicious of the ignition system. I know you don't have many miles on it, but your plugs, wires, cap & rotor are over 10 years old.
Go out after dark, open the hood, start the engine and - with a trigger spray bottle - spray misty water on the engine, especially the area of your distributor, the plug wires, and down into the spark plug recesses.
The darker the better. You might see spark somewhere, and that'll be your culprit. The engine might bog down a bit, and that's a sign.
Also, pull your distributor cap & clean the rotor & contact points. That can have some bearing. Check for minuscule, hairline cracks in the cap. All that can contribute to rough idling.
And check your plugs. You can pull plug wires, one at a time, and see if the car runs any rougher. You'll have to start & stop the engine before & after you test each plug, but this might isolate your problem.
By the way, changing your fuel filter is extremely easy on that car. I'd suggest you do it anyway. Even if it's not the culprit, it's a good preventative measure.
Good luck!
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