Just put a new fuel pressure regulator in her yesterday and it didn't solve the problem. She still runs great on COLD START and only until the truck reaches normal running temp. Then it runs like crap, skipping, and missing. It seems better with the O2 sensor off but still like crap. I have an O2 sensor waiting at Sanels, as well as a thermo sensor but at which point do I stop buying all these sensors? I could literally spend hundreds of dollars replacing one at a time.

I know this is an old truck and hard to diagnose but here's a list of what's already been done.

compression test
leakdown test
vacuum test
heat test
valve adjustment
exhaust gas analyzer
fuel pressure test
replaced the fuel pressure regulator
disconnected the O2 sensor (got better/lower O2 readings on exhaust gas analyser by doing this)
fuel injector cleaner using fuel pressure guage kit

Seems to be sensor related. If it's not sensor related it's seems wierd that it runs good till it warms up. I'd say it's got something to do with the temp sensor that goes to the computer, or possibly the thermal valve is bad.

I'd check the thermal sensor first. There are two thermal sensors, one for your dash gauge and one for the ECU.

By the way I am assuming this is a 2.6, 4 popper?

Yep, it's a 2.6, 4 banger....I am gonna go ahead and change the thermo sensor this afternoon and maybe even the O2 sensor as well. I figure...what the heck, the parts are right there, $50.00 would cover it, and maybe solve the problem.

Gotta have my truck back!!! Not only my daily driver but also my best friend.....:(

Runs great until warm...? Did you check the air thermal valves? Both under the intake manifold. The big tube one off the throttle body (throttle air control valve?) should close (like a choke) in a few minutes when the engine heats up to block excess air. It's electric (heating element) so if the wire or element is bad it'll stay open The teeny plastic/brass one with two small pneumatic tubes (one to throttle body and one to the transducer that provides vacuum to the EGR valve) is supposed to open when the engine's warm to allow the EGR to work. You can trouble shoot them by plugging the ACV ports when the engine is warm to see if it makes a difference. The other you can just by-pass for a test by hooking the transducer direct to the throttle chamber at any handy port and plugging the tube to the valve. There's that third thermal valve on top of the thermostat housing but that shouldn't do anything unless the engine is overheating or you have AC. I mention it because the lower
port on mine cracked letting excess air into the throttle chamber with resulting bad idle and poor acceleration.

Changed the O2 sensor today with no change....ARRRGGGGGHHHHH. Have a new Coolant Temp Sensor to put in but DANG IT, the darn thing is 'feelable' but not 'seeable'. And I'm not even sure that would do the trick either. This has got me feeling defeated big time. After all I've been through with this truck I can't and won't just give up but everyone's got their limit and I'm reaching mine. Course it doesn't help that the temps have gone below freezing here and I don't always have the luxury of working at school where it's nice and toasty. Where to go from here?

I tried running the truck with the coolant temp sensor detached today and it wouldn't start so that should tell me it's working right? Sure, I could do an OHM test on it but lets be real, is it really worth me wrestling with this thing to change it? Come on, there's gotta be someting I'm missing here....HELP ME......!!! I feel like I'm letting the friggin' thing down by feeling like I've reached the end. It can't be that damn difficult...

Remember there are two temp senders, the one for the gauge isn't what sends info to the ECU. You don't need to change that one unless your gauge isn't working. Just cause you took the temp sender out shouldn't give you a no start?? Even if you took the correct one out.

Yes, I'm aware that there are two temp sensors. One is fairly small and easily visible, just under the intake manifold and it goes to the dash. The coolant temp sensor that sends to the ECM is located directly under....(on the underside) of the intake manifold where you can feel it but not see it.

If unplugged, the truck will not run because you've got an incomplete circuit and the ECM will not allow ignition. The sensor itself could still be bad but it needs to be plugged in regardless in order to be able to run the truck....it just won't be doing its job.

I'll go ahead and test the harness with my multimeter but the new sensor only cost me $25.00 and I'm just gonna replace the darn thing but I'll say a little prayer before I do.

Of all the things I've been through with this truck, this most definitely feels SNAFU. Gotta love it right???

Thanks for the input....and wish me luck...

dawn...

Dawn...is the access easier if you remove the front passenger-side wheel and go in through the wheel well? Or is that what you're already doing when you say you can feel it but not see it?

I'm sure you know this but when you install that sensor don't put any thread tape on it.

Read these posts and the last ones concerning skippy and got to thinking, mine got to doing some hairy things after warm up. Cold, perfect. Warm, well...it was trying to do the hokey pokey. I exhausted several efforts. I finally took the fast idle solenoid off the fender and took it apart and there was some carbon build-up in there. Cleaned it up and put it back on and so far (knocking on wood right now) good idle warm and cold, well no more trying to put its right hub in and shake it all a...well you know. It may or may not fix it but if you haven`t already done that, hell it`s free, give it shot. Couldn`t hoyt eh?Good luck,A.T.