HT4100 4.1, 4.5, 4.9 Discussion, HT4100 Misfire Question in Cadillac Engine Technical Discussion; Hi everyone--
So my car (85 Deville with 32,000 miles) runs perfectly now for the most part except an issue ...
So my car (85 Deville with 32,000 miles) runs perfectly now for the most part except an issue that still continues to plague it that I've finally been able to rule out a few issues as the culprit:
Basically, my car runs just fine now around town and at anything up to about 3/4 throttle and 3500 rpms. After that, if I really lay into it, I'll get popping in the intake, like an exhaust valve is sticking or not sealing. There's no ticking ever, so I don't think it's a lifter...but what do you think? Bad valve spring? Rocker arm pivot? Bent pushrod? Flat cam?
I have an early 85 model with the more flimsy rocker arm pivots so I was wondering what the symptoms are of a car with such a problem.
As I said, the car has good power up to about 3500 rpms, but the compression is low on one particular cylinder (#7).
Timing is spot on (jumps around a bit because of the low compression, but not much), all new ignition system (the entire thing--distributor, plugs, wires, etc.).
Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
Re: HT4100 Misfire Question
I agree, the fuel filter is probably original! if an engine runs lean, it will pop thru the air intake. Change the filter. You can verify if the filter was plugged by simply blowing thru it once removed.