Misfire

[Triballee8up]

I have a 91 Sho+. Had a clutch installed in the spring and after about two weeks the car stopped running. I thought the 60k maintenance had been done from the paperwork I had from when I bought the car but it had not. There was oil in the spark plug holes. I replaced the plugs, plug wires and intake gaskets. I sent it to a mechanic to do the water pump, cam positioning sensor and seals, crankshaft positioning sensor and timing belt. They had it running with a slight misfire and suggested driving it for 400-plus miles with a cleaner called BG. This has not solved anything and car is still misfiring and it is worse I believe. I checked the codes and two popped up. One is 91 and the other is 25. Any suggestions or thoughts are appreciated.

 

[luigisho]

https://shoforum.com/index.php?threads/ran-codes-have-a-few-questions.7755/
It sounds like vacuum leak and/or faulty o2 sensor. Was the car misfiring before you had the 60k done or only after? These people familiar with this model of car? These are uncommon cars. Anyone can work on them but people with alot of reps know where to avoid mistakes during reassembly and such.

 

[rubydist]

I would also double check the plug wire routing - a lot of the published plug wiring diagrams are incorrect, so you may have followed a bad one.

 

[Triballee8up]

https://shoforum.com/index.php?threads/ran-codes-have-a-few-questions.7755/
It sounds like vacuum leak and/or faulty o2 sensor. Was the car misfiring before you had the 60k done or only after? These people familiar with this model of car? These are uncommon cars. Anyone can work on them but people with alot of reps know where to avoid mistakes during reassembly and such.

 

[Triballee8up]

After the clutch was done it died a few times which I was able to get it started and run again to make it home. It ran off and on for 2 weeks and then wouldn't start at all. That's when I started doing these 60k maintenance. Once it was started and running that's when it had the misfire.

 

[rubydist]

Then there is a good chance its something simple like a plug wire not attached all the way, or a weak ground in the ignition system or that type of thing.

 

[luigisho]

If it wasn't misfiring before the 60k then something went wrong there. I would retrace everything. First thing I would do is triple check the spark plug wires and make sure they are routed correctly as they have had bad info diagrams in circulation from a long time ago. Check the plugs and wires, crawl under the car near the clutch job and check the wiring at the starter. Check the braided ground strap on the firewall to the intake. Check for vacuum leaks up top https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

 

[pjtoledo]

is it a steady or random misfire?
if it is steady you can get an extra plug & wire, clamp the plug onto the engine, substitute it for each wire at the coil pack and see if that isolates the problem. 5 will get worse, the bad one won't. that will only tell you which cylinder, not what's wrong with that cylinder.

these engines use a waste spark system, 2 cylinders fire at once from the same coil module. so simply pulling one wire actually kills 2 cylinders.