Misfire problem with 88 YJ (Long/detailed)
I have been searching all over the net for a resolution to a misfire problem. Here's the problem:
When cold, the Jeep starts and idles for about 2 seconds then starts missing/misfiring at idle. If I try to drive, it doesn't want to take full throttle and starts missing and popping/banging out the intake, and won't pull over 2000 to 2500 rpm.
It also misses/misfires at idle after about 2+ miles of driving into the wind. It runs great however once it's warmed up, and pulls hard and smooth. Just throws a fit at idle unless I let it sit there for about 4-5 minutes.
If I start it cold, and I drive for 1-2 miles only, it misses BAD at idle and sounds like a clanking sync'ed with the misses, and that clanking is coming from under the jeep and not the engine. This totally goes away if I let it sit for 5 minutes then start it, then I only get the 2+miles in wind problem.
I am getting spark on all cylinders.
I have not done a compression check.
88 Jeep Wrangler 4.2L I-6
8' Before Top Dead Center Timing
New ignition module
New Distributor Cap, rotor, and magnetic pickup
I started with Carter BBD Carb and removed the emissions and did a "Nutter" bypass. Ran rich, but fine.
Took a trip from Florida to Oklahoma, then when I got to Oklahoma I realized that I made the entire trip at about 10' AFTER Top dead Center timing. (The vacuum canister on the distributor was hitting the motor mount and turned the distributor to fix that problem, rewired and replaced plugs, and retimed to 8'.)
It ran fine from there to California.
It started giving me fits on starting, so I decided to get the TBI to resolve that problem (thinking it was the carb) and to pass emissions.
I replaced the ignition module, got a HD coil for it and replaced the plugs again and regapped to .040-inch, and got new distributor innards.
I still have this problem, and it is MUCH worse when it is below 40-50 degrees outside. If it is warm, then it almost goes away, but not fully, and I still get the "2+miles into the wind" problem, and it still gives me the problem if I drive only 1-2 miles (bad missing and popping/banging from intake.
I have heard that a catalytic converter meltdown could cause too much backpressure on the engine, and that might also be the clanking from under.
I also found something about the timing chain jumping which would affect idle.
Thanks for any help you could provide to save money on replacing good parts. [img]images/graemlins/laugh.gif[/img]