TBI high rpm problem

[smashingchuck]

Background:
1991 TBI 350, 700r4. 125,00 miles on the engine. The plugs have about 5000 miles on them, the cap and rotor about 10,000 miles, and the plug wires about 40,000.

I have a problem with my truck that is progressively getting worse. It idles fine, and accelerates fine, but anything past about 1/2 to 3/4 throttle that damn thing just spits, sputters, and goes NOWHERE. It used to only do it at WOT, but has also progressively worked its way down to 1/2 throttle. Today when I started it (very cold) it almost did it right off idle. It does seem to be worse when the weather is cold out. I ran a bottle of Lucas fuel condition through it the other day, it didn't change a thing. I tried higher octane fuel as well, and that had little effect on it. I'm thinking this is somehow fuel delivery related, but also think it could be ignition. I really hate to just start throwing parts at it... anyone have any ideas?

thanks
chuck

[78 Chevyrado]

Try replacing your fuel filter. if it's blocked, it will deliver enough fuel for low rpm use but not enough for higher rpm usage.

[smashingchuck]

I've considered that.... where is it?

[HarrisonTX]

should be passenger side of the frame, maybe drivers side. On the inside of the frame, just about right below the front seats. Its a cylinder, smaller than a coke can, but similar in shape. Very easy job

[pig rig]

yea I'd look at the fuel filter but with that many miles I'd also look at the fuel pump if your filter dosn't cure it

[Rob73-87]

Don`t forget to check all TBi - related sensors and the vacuum lines...
A friend of mine owns a `92 C1500 with TBi engine and had similar issues...


Rob

[James McClure]

Chuck, If it isn't blowing a code aand the CE light isn't on, it probably is the filter\pump. Be careful changing the filter if the lines are rusty. Srray them up good with WD40 beforehand then heres a trick. Using 2 ball peen hammers place 1 hammer on one filter side nut flat and use the other to whack the filter nut from 180 degrees away. Don't try to kill it, just a few good whacks before you try to remove it. Once it's off make sure you anti seize everything before reassembly. jim

[Damien]

Be prepaired to replace your fuel pump. I have had trucks that will drive in, you replace the fuel filter and the truck will not start. The pump is weak and loses its prime and will not restart. Have it somewhere you can replace the pump if needed.

[smashingchuck]

Originally Posted by Damien

Be prepaired to replace your fuel pump. I have had trucks that will drive in, you replace the fuel filter and the truck will not start. The pump is weak and loses its prime and will not restart. Have it somewhere you can replace the pump if needed.

Good advise. I guess I'll put it off until the week end. I suspect my fuel pump is weak anyway (seems to loose it's prime when it sits for longer than a few hours).

Here's what I know so far.... first off, the muffler shop put my flowmaster about two inches away from the filter, and if that wasn't enough, the few Michigan winters that my truck have been through have really taken their toll on the fittings and filter. I did knock it with the wrench a few times after I figured out that this wasn't going to be a "quick before work fix" (I work 2nd shift) but just those few wacks have got it running a little better already.

chuck