Topic: 1999 TJ SE Bucks, bogs and bangs when cold

[DaveNC]

I was wondering if anyone can help me diagnose an issue I am having with my 99 Jeep TJ SE. I have been troubleshooting when the engine is still not completely warmed up the vehicle Bucks, bogs and bangs. P.O. rebuilt the Trans, I have given it a full tune up with quality parts, added a clean 4.0 throttle body, changed out the TPS and cleaned and replace some of the ground wires. Before I jump in the fuel system does anyone have any suggestions? Thanks - Dave

[Jeffy]

Are there any codes recorded on the PCM?

[DaveNC]

No codes. Been going a little nuts with this issue. Started with the cheapest fixes first. Installed new battery cable ends, cleaned all the ground wires, tested both the upstream and downstream O2 sensors, checked all the plug wires, adjusted throttle valve cable. So far no change. I ordered a new ignition coil. Thinking it may also be a problem with the crankcase positioning sensor or maybe valve spring sticking.

[Jeffy]

No codes. Been going a little nuts with this issue. Started with the cheapest fixes first. Installed new battery cable ends, cleaned all the ground wires, tested both the upstream and downstream O2 sensors, checked all the plug wires, adjusted throttle valve cable. So far no change. I ordered a new ignition coil. Thinking it may also be a problem with the crankcase positioning sensor or maybe valve spring sticking.

I'd put a fuel pressure gauge on it and see if it's holding pressure.  Could be something as simple as a clogged fuel filter or a weak pump.  I don't think fuel related stuff other than the injectors firing have any CEL codes.  The Crank Position Sensor can do some weird things when they start to go bad.  Though not wanting to start is usually a big one.