So my problems all started one night when my car wouldn’t turn over and start. I had the car towed to a chain auto repair place and they found that my valve cover gasket was leaking oil into the where the spark plugs are. (They checked the fuel pressure and said that was fine). They replaced the spark plugs, valve cover gasket, tubes and o-ring.
The car ran fine for a couple of days, then started skipping while I was driving and idling rough.
1. I changed the distributor cap, rotor button, and put in fuel injector cleaner. Car ran fine, but a couple of days later it started skipping and idling rough again.
2. I replaced the fuel filter. Car ran fine, but a couple of days later it started skipping and idling rough again.
3. Took it to another chain auto repair place and they found that the first auto place put the wrong spark plugs in my car. They replaced the plugs and put on new plug wires. They also checked the fuel injectors and said they were fine.
The car stopped skipping, but still idled a little rough.
I noticed that the car started to skip or idle rough after I filled my tank up full with gas. So I thought I might have gotten a bad tank of gas. I tried a bottle of water remover in my tank. This time the car ran fine for a couple of weeks, but still idled a little rough.
At this point I’m thinking it might be a bad tank of gas w/ a contaminant in it, so the next step would be having a shop drain the fuel tank and clean it out. Any other ideas of what the problem could be? Between myself and the auto shops we’ve basically assembled most of a new fuel system. (The car has 270,000 miles on it and I recently started a new job that requires me to put about 620 miles a week on the car)
A number of things may be “close”, but, that may not be good enough. Several things being “off” may be enough to cause the “rough idle” (misfire).
It’s impossible to know what has been checked, and how well they have been checked; so, a repairer has to start over “from the get-go”.
Check the fuel pressure (yes, “again”). Check the fuel pressure at idle, and at 2000 rpm with the transmission in DRIVE. If it’s a manual transmission drive the car with the fuel pressure gauge attached, and observed the fuel pressure.
Change the air filter, and the fuel filter. Make sure that the spark plug wires “snap” onto the spark plugs and into the distributor cap. Clean the air intake tract and throttle body with Throttle Body Cleaner.
Perform a compression test, and/or cylinder leakdown test, to see how well the cylinders are sealing.
A good mechanic will know additional things to tweak, and tune.