I am at a loss with my car. It is a 95 850 n/a motronic 4.3. The other day I pull it into the shop put a new fuel filter and balljoint in it. Start it up to check for leaks and runs ok. Went to leave and go home and will not start. Has 45psi of fuel pressure and good spark and good compression. work on it for 2 hours give up and drive my other car home. Go in the next day after changing the rpm and cam sensor after it starts and let it run for 3 hours in the shop and seems ok. Take it for a drive seems ok until it wont start again. Finally it starts and stalls on the highway arrow blinking and cel on. Swap out tps and all seems well for a few days then it stalls again on the highway will not start sit for about 15 mins and it starts right up and drives ok. get home next day starts then after a few mins will stall checked all the wiring from ecm to tps and all ohmed out ok along with the grounds off of the tcm. Also just changed the pnp switch and now it started and stalled again and will not start. After clearing codes the only one coming back is p0120 ecm 223 tp position too low. Any advice would be greatly appreciated.

 

Shot in the dark but I'd pull the ecm and clean the prongs.

 

Thanks but already did that.

 

What about harness grounds in the engine compartment and positive connections at starter, alternator and battery?

 

Next time its not wanting to start try bypassing the fuel pump relay, i.e. pop it out and replace with a piece of wire so the pump is hot all the time.

I had a fuel pump relay that went out on me but didn't fail completely, it would prime so I'd see fuel pressure but it would come back on to keep the motor running.

Just another thought for you.

 

I just went through the same thing. After replacing just about every ignition part on the car, it turned out to be a bad wire at the battery that powered the fuel pump. Whenever it happened, I still had fuel pressure also.