Transmission Problems - '97 Chevy 1500

[Gearheadtom]

The truck took a turn for the worse over the weekend. Gradually lost power from friday night until saturday night. Now it will only rev from 3-4000 rpm with the pedal to the floor in neutral or park. Doesn't missfire or spudder, just won't make power. Driving it, it seems to make the most power and accelerate the best at 1/4 throttle. I tried another tps sensor and another coil, no difference.
I'm thinking fuel problem right now, I'm going to see if I can borrow a fuel pressure gauge from someone tomorrow, or buy one if I have to.

[belly]

It's very common for the fuel pumps to go out on those trucks. If it is the fuel pump, make sure you get the upgraded wire harness. They're prone to keep moisture inside and short out eventually. good luck!

[Larry T Moore]

take the radiator cap off....slide a new truck under it....

[Gearheadtom]

take the radiator cap off....slide a new truck under it....

That's my plan once I get the money saved up haha

I have heard about the fuel pumps in these trucks. They say the factory ones are the best until they die, and a lot of the aftermarket ones don't last long, but maybe the ones with the upgraded harness are better. I was planning on not getting the cheapest one if I buy one, I don't want to drop the tank in another year haha

[Mosh]

Not trying to be a jerk. Have you done anything other than plug and unplug sensors and just keep driving it? If you want to throw a 300$ fuel pump at it go ahead. But I strongly urge you to perform the tests I suggested last week first. I really feel your converter was partially clogged last week and now is fully clogged. You keep running it that way and you can add a 200$ egr valve to the parts list too once it melts down from the exhaust restriction.

[atc300r]

Speed control sencor could also be your trouble. Cats like mosh said could be your trouble a friend of mine had a plugged cat on his s10 he replaced it and the muffler says it runs like new.Im having trouble with my 97 s10 4.3 v6.Mine shifts good starts hard sometimes.

[Gearheadtom]

If I could just unbolt the y pipe and drop it I would. Unbolting my y pipe would include snapping off every stud, no amount of heat or oil will prevent this, then pulling the manifolds to replace the studs.
I put a fuel pressure gauge on it today, and got 50 psi at idle, and it got up to 60 when I reved it. I also swapped in a different coil and tps yesterday with no difference.

[briano]

Cut the cats off, that is going to solve your problems. Just put a piece of pipe in their place to try it.

[Gearheadtom]

That would actually be easier, and I might try that. I can't see why the cat would plug up tho, I've known many people with these trucks over 300,000 km's on them and not a problem. Would that cat plugged explain the surging I get at about 30 km/hr, if I'm just barely on the gas? It goes away if I get on the gas harder.
How well do these Vortec's run with the cat gutted long term? I know it'd probably trip some engine codes, but will it turn it into a fuel thirsty pig that runs like garbage?

[briano]

It should run fine, if not get high flow cats for it, they are universal and relatively cheap compared to the exact fit

[Dirtcrasher]

MOSH really knows this stuff inside and out. Keep him in the loop and he is always willing to help people; Just be nice!!

[Gearheadtom]

A plugged cat does make some sense, but the way the truck acts feels like a fuel problem, mainly because of the surging. The cat doesn't seem to get to overly hot, I figure if it was plugged bad enough to make the truck run as bad as it is, the cat would get pretty hot.
I'm going to see if I can borrow one of them infrared thermometers from someone to measure the the temp of the cat on each end, they say one end is supposed to be cooler that the other, I forget which end is supposed to be hot/cool tho.
I checked my fuel pressure again today, just key on it hit 60 psi until the pump stops, then it drops to 55 immediately, then leaks down to 50 in just a couple seconds. I've heard these trucks are sensitive to fuel pressure because of the popet vavle injectors.
I also forgot to mention before that I can hear it spark knocking a bit when I get hard on the gas, but from what I've read, a lean fuel mixture, or a clogged cat can cause that.

[Slingblade]

If the cats are clogged you should get a code for the downstream oxygen sensors. A clogged cat could cause your problems but so could many other things, or a combination of things.

Fuel Pressure Regulator, Bad injector(s), o2 sensors, spark plugs, wires, dist cap, bad ground wire, bad plug or bare wire in harness, map sensor, MAF sensor, How exactly did you deal with that?

When you drive with stuff unplugged (MAF) The PCM runs in open loop with a predetermined Air Fuel Ratio, usually really rich. This will in turn screw with your other stuff, o2 sensors, etc.

60 psi should be good for that Vortec. One more thing, when you unplug stuff and plug it back in this screws with the pcm, it has to go through a resetting process.

I would suggest plugging everything back up, remove the battery cable and let it sit a few mins. Drive it a few miles, let the pcm learn it's stuff and see what codes you get.

Or take it to someone with a good GM scanner and let them see what it's doing in real time. I know this stuff gets frustrating, Hang in there, You'll get it. Good Luck.

[Gearheadtom]

Everything's been plugged in since saturday. I did swap on another good cap I had, and no difference. It doesn't act like ignition, there's no spuddering or missfireing, except for the surging, but that feels like I'm on and off the pedal, like the motor loses and gains power.
When the maf code first came up (almost a month ago), I cleaned it, the code came back after a few days, and the same thing when I swaped in another one. The EGR code I had about a year ago was just because the valve stuck open just a hair because it was just gummed up. After cleaning, the code never came back until now.
After I had the maf code come up, the downstream O2 sensor code came up, then a week or two later, one of the other O2 sensor codes ( one of the two just before the cat) came up, along with the same egr code that I had a year ago.
I've pulled the EGR valve, and it was still clean, and not sticking at all.

[Slingblade]

If your getting o2 codes and egr codes, Theres a very good chance your cats are clogged.