Stalls after warms up

I hv been battling with my 2000 3.4L for 2 yrs now. I hv swapped out everything I can think of, some parts twice. What happens is when the engine is cold, I can crank it up and drive it all day long with no problem. The minute I shut the thing off, It gives me a system too Lean code and runs like total shit until I get it rolling down the road and it corrects itself. I am stumped as to what it could be. Please Advise!

 

List the parts you have swapped.

List what you have swapped them with (used/aftermarket/oem).

What codes exactly are you getting?

What modifications from stock have been done?

 

I hv swapped, plugs, plug wires, coil packs, TPS, coolant temp sensor, injectors, intake, timing belt, belt tention pulley, water pump, thermostat, radiator, IACV, hoses, belts, Oxygen sensors...Not all those parts were a direct result of the problem but all has been done within the last 2 yrs. I am getting a "System too Lean" code and a "multiple cylinder misfire". The motor is bone stock
There is no water in my oil and it doesnt blow smoke either. I am really leaning twards it being the wiring harness is shorting out somewhere. The vehicle is over 20 yrs old and has 400,000 miles on it and I hv already had to repair some brittle wires myself. Your thoughts

 

Yeah, but what codes EXACTLY. What are the code numbers? These are important. Usually a cylinder misfire code tells which cylinder. Code combinations also can indicate specific troubleshooting.

One thing I haven't seen you change is the fuel pump. If the cylinder misfire is indeed across ALL cylinders and low fuel pressure is causing a lean condition then it's probably the fuel pump.

I would test fuel pressure when car is warm. If you have low pressure, then replace the pump with a DENSO along with the evap gaskets and valves in the tank. Replace the sending unit too as those burn out at 200k miles or so.

 

Could also be the fuel filter causing low pressure, I think. How long has it been since that got replaced?

Might be something to consider if you have low pressure. Easier to replace than the pump, and much less expensive. No promises, but it's something to consider.

Good luck!
Pat☺

 

I just forgot to list that, (suprised I forgot bc it was a mf to change out) Yes i HV REPLACED the fuel pump and fuel filter.I am not sure the exact codes but will let u know.

 

Well, on-line searching shows that lean condition culprits seem to be vacuum leaks, MAF, PCV and O2 sensors.

I see the MAF was not in your list. Has it been tested/replaced? PCV valve?

Have you tried the starter fluid/cigar smoke/propane spray test for vacuum leaks?

 

I hv several times and yes I hv tested or changed every part u listed. To be honest with you, the wiring harness and the
ECM is the only thing I havent changed on it. Which it very well could be either one of the two. I was leaning twards the wireing harness at first, but I just drove the vehicle 30 min ago, and it ran like complete shit, but it never threw a code!! Soo IDK....Its crazy

 

Kinda sounds like the ECU going south to me, but I may well be wrong.

The wiring in these, over time has a problem with the insulation getting brittle, and cracking, exposing the bare metal of the wire's strands. Especially anywhere it might rub against metal, or goes around a corner.

Finally, check the grounds. There's not that many, and a bad, corroded/dirty ground can cause all kinds of odd problems. There's one for the ECU right near to it. May be worth taking a look at. Or a quick look at any other ground that might be related to the problem, no matter how remotely related they might seem to be.

Good luck, and let us know what you find, if you don't mind...
Pat☺

 

thts exactly what I was thinking..Ill let u know