Have you run a compression test yet?

This problems is sounding more and more like a mechanical issue within the engine...

 

I have not got that done yet. with the snow in taxachusetts I've been plowing or fixing something. Finding a shop that can do it after a snow is tough.

 

You can check the fuel your using for ethanol content. I wouldn't be surprised if the fuel you are getting has over 10% ethanol. Fuel Testers -Ethanol Fuel Test Kits -Protect your engines from E10 alcohol blend gasolines.

 

Ain't that the truth. It never seems to fail that something goes wrong at the worst possible time to do anything about it.

Hang in there!

 

update.

I changed from the 93 perf. tune to 87 econo tune, the truck kept stalling, bucking and surging. went back to stock ran ok. still getting 4-5 mpgs. going to try to check the plugs and get a cam cover off today.

 

got the plugs 6-10 out all looked the same brownish rust color pulled #1 for comparison looked the same. ran out of time to get the cam cover off, my 8 &5 year old demanded my attention. tried my econo tune, bucked surged and stalled. going to try my 87 tow tune.

 

Stay with the stock tune until you get this figured out. Something is definitely wrong if the 87 tune caused such problems.

 

update
got the cam cover off. not that I know what I'm looking for, but everything looked the same. no metal shavings, chunks etc. everything tight including the chain. put a wrench on the cam gear nut eased it back and forth no rotation.

Krewat, I know I should stay with stock tune, but I can't leave well enough alone. I put my 87 tow tune in, ran better but still pinged a little. took 2*global, 2* 0-2000 out. power is up economy is up, not where it should be but better.

while changing the tunes, I heard my fuel pump running (dumba$$) quickly pulled the fuse. I don't remember pulling the fuse the last couple of times I've changed or adjusted the tune. could I have hurt something, exacerbating my problems????

 

They say to pull the fuel pump fuse just in case it comes on when you are uploading/flashing the tune. In case there is not enough battery power, you could ruin the PCM because the tune doesn't fully upload and after that the computer crashes.

If it runs, I'd think it's fine. Just reupload the tune again to be sure, with the fuel pump fuse out.

Funny that retarding the timing 2-4 degrees made an increase in power.

I'd start wondering if the crank/cam sensors are flakey and firing off at the wrong time.

 

I'm guessing it's not pinging with the 4* pulled out so it's running better??????
I did get 6.5 mpgs on my last fill up. is it possible the pcm is screwed up? would a reflash of the pcm fix it??

 

Its beginning to sound like a pcm problem, but I'm not sure a factory reflash will fix it. It might take a new pcm to get it right.

 

well, in the midst of another snow storm I got the pcm reflashed with the latest and greatest factory version. see what happens.

what should my cylinder head temp readings be? datalogging shows it to be 200-210*, I do have a 195* in it, and that seems right to my logic, but...

 

another update

after the the pcm reflash the next fillup I got 10.2 mpgs. power isn't any better. put the 87 ecno tune in for s&g's. didn't run right, much less dramatic surging and stalling. put 87 tow tune in runs good! power is better only have about 100 miles in this tank but it's looking like my mpgs are up from 5 to possibly double digits. now if it would grow some gonads I would be a happy camper!

datalogging shows the same as before except my long term fuel trims stay closer and fluctuate less. if I start another slow decent in economy, my opinion would be a faulty pcm. arguments for or against that?????

 

If you had the PCM reflashed, the calibration is certainly going to be different, and you have to go back to the tuner (Mike?) and get new tunes based on the calibration code.

 

Wow is Mike fast! called him up, explained what was going on, he told me he would revise my tunes and fix my 87 econo tune and email them to me. strapped on the plow, scraped up some ice and cleared the town plow leavings from the road widening and they were done! uploaded them to the sct put the econo tune in the truck so far runs better than it has in while. only been about 35 miles since I put the revised tune in, cautiously optimistic.

thanks Mike you rock!