missfire?

[thedon809]

Ok i have an 86 t1 daytona and here is my problem. I will notice that sometimes when im cruising at like 65 my rpms will suddenly drop by about 500 and go back up. Also sometimes when the car is already warmed up and i turn the car off and then on it will seem to missfire and then clear up in about 15 seconds and the car will run perfectly fine. I think it has to do with something in my ignition system but i wanted to hear some of your ideas as to what it could be.

[85boostbox]

the hard to start when hot and misfire sounds like you have a hall effect sensor going out. either that or coolant temp sensor bit that would only cure th hard to start when hot issue. so try the hall effect first

[thedon809]

I put a new coolant temp sensor in a week ago or so with a new o2 sensor. It was doing it before the new one too.

[IROCNOROLL]

Quote:

Originally Posted by thedon809 Ok i have an 86 t1 daytona and here is my problem. I will notice that sometimes when im cruising at like 65 my rpms will suddenly drop by about 500 and go back up. Also sometimes when the car is already warmed up and i turn the car off and then on it will seem to missfire and then clear up in about 15 seconds and the car will run perfectly fine. I think it has to do with something in my ignition system but i wanted to hear some of your ideas as to what it could be.

HEP is a good suspect. This is also a classic symptom of a fuel pump starting to die / fuel delivery system issue. Hot restart and it is taking a little time for the pressure to build back to normal. Time to get a gauge on it and see what's up. If they both check out ok, then wiggle test the wire connectors behind the battery to the engine and the PM with the engine at idle. Common connector issues in this area can also contribute to the problems your experiencing. Stumble / stall while tweeking the harness here would show a connection issue. Green death, or just heat related connector expansion. The connectors are 22+ years old. HTH.

[thedon809]

Thanks for the suggestions. I shall put a fuel pressure gauge on it tommorow when i get to school. I hope its not the pump because i know as soon as i touch it im going to have to replace all of the lines. Also after a hot restart and it feels like its missing if i rev it up it will clear and then as soon as it hits 900 or so rpm it will start missing. Only 1 time has it stalled when i tried to put it in drive.

[crazymadbastard]

Check your fuel hoses- mine did that when I had a very slight gas leak at the fuel pressure regulator feed.

[thedon809]

I did have a little leak at the fpr but i tightend it down a few weeks ago. Its wierd because after it clears up and im driving the car runs good. I get about 30mpg and it has decent power for a stock t1.