Our Community is 940,000 Strong. Join Us.


Misfire


sassee
10-01-2013, 07:59 AM
I have an 85 K-10 with a misfire. The vacuum check had a fluttering needle around 18 Inches Mercury so vacuum is ok, just the flutter indicating the misfire. Compression aint that great (avg 125) but it will do until we can put another engine in (it's my 16 year old sons' truck). Put new cap, wires and plugs in it a few months ago and new plugs again a couple weeks ago but now the skip is back. He pulled some plugs out and they look to be slightly carbon fowled and they don't appear to have a good burn. I'm thinking either an ignition module or a bad coil. I'll check the coil tonight if i can find my multimeter. Any other suggestions while I'm looking???

Schurkey
10-01-2013, 07:42 PM
When was the last time you adjusted the idle mixture screws?

You've done a compression test; time for a cylinder balance test. A leakdown test would be helpful as well.

I'm thinking that an '85 pickup still uses vacuum and centrifugal advance. Does the vacuum and centrifugal advance work PROPERLY? Have you ever checked the centrifugal advance pins and weights? Is the timing set correctly?

Any broken valve springs?

sassee
10-02-2013, 09:23 AM
This is an intermittent thing. It stopped for no reason when we checked the compression. Last night my son told me it ran fine when he left school but started skipping when he was leaving the house of a friend that rides to school with him. I asked him if it had had times when it ran fine and then skipped before and he said yes..........apparently he didn't understand the importance of that information. The times it was running fine was from a cold start and THEN started the skip. I am slightly more convinced it is a coil breaking down but, as with any teenager, i can't check the truck while he is driving it! Hopefully he will leave it home tonight.

Add your comment to this topic!