[PonchoV8]

I think my truck has either jumped time, gotten sugar in the tank or bad gas has caused a major problem.

Sunday, I filled completely up at a gas station--all gas was $2.99. The truck immediately ran poorly. Today, it has lost power. It won't accelerate at all. If you try, it just bucks badly and the temps start rising. It will idle and motivate itself up to about 30 mph on flat land--and stay at about 200 degrees. But it will not climb a hill or accelerate. I can hear an unusual noise from under the hood. Judging by the heating up and the sound, it sounds as though it's starving for fuel. The oil just smells a little overheated. The coolant is not low and I think looks okay. It's a 5 spd with 154K miles--well maintained.

How does a contaminant (like sugar) in the tank behave?
How does bad gas behave? (we just filled it up with premium Exxon and no change).
How does a jump in timing behave? I haven't noticed popping from the exhaust or intake, but there is a sound eminating from the intake (I think).

[dreamingmuscle]

Sounds like a plugged catalytic converter to me. Pull the O'2 sensor and drive it with it out. If the power is better then change the catalytic converter.

[PonchoV8]

There are 4 O2 sensors on this truck though. Ouch. Is that so the exhaust has somewhere else to go other than through the pipe?

[mzbk2l]

Sounds more like fuel to me. It is possible to get gas so dirty that it will clog up your fuel filter within one tank full.

I would start with a new fuel filter and fresh gas. If you have or can borrow a fuel injection pressure gauge, hook that up to the rail; you'll know right away if it's a fuel problem.

[PonchoV8]

I'll get a fuel pressure gage--there should be a Schraeder(sp) valve to quick disconnect right?
Is it a vacuum gage that will indicate a restricted exhaust? I've seen one in action before, but I don't remember what it was called.

[jjscerbo]

Hook up a vacuum gauge and rev up the engine to about 2500 rpm and watch the gauge. Normal reaction should be a momentary dip from idle vacuum while accelerating then the reading should return to normal while at 2500. IF the vacuum remains low, there is an exhust restriction that is more than likely the converter.

These engines also had a problem with leaky fuel regulators. The regulator is inside the intake plenum and is part of the injector module that is also inside of the plenum. To check it, you will have to remove the upper plenum. if the regulator is leaking, you will see it drip when you activate the electric pump. You will also see that the lower plenum will be cleaner near the regulator location. If this is the case, the fix is easy by replacing the injector unit. It comes complete with regulator and the six flex liines that attach to each port.

[Hitman]

I had a 1992 GMC Jimmy 4 door 4X4. On my way to Florida I stopped somewhere for something but when I got back onto I-75 it had the same symptoms as you described. When they pull the catalytic converter off it was plugged up. New one on and it ran like a champ, got a little better mpg after that as well.

[dreamingmuscle]

Originally Posted by PonchoV8

There are 4 O2 sensors on this truck though. Ouch. Is that so the exhaust has somewhere else to go other than through the pipe?

Yeah thats the idea. It's a easy cheap way to check for a plugged cat. You should only have to remove one maybe two to know if it is the cat.

Could be the fuel filter. I had a old van with a rusty tank that would plug the filter pretty quick. It would act like yours except for the heating up part. Before you buy a fuel pressure guage. If you have never changed the fuel filter. It's due anyway so try that first.

Glen

[cuz68]

Doug you have worn that gmc out, Time for a new one my friend.

[PonchoV8]

It's still a decent, tight truck--and has been retired to merely driving to work and back. It's replacement is a diesel Sierra 2500. It's light, has 4wd, will go about anywhere and won't tear up the grass when I drive around to move engine parts and equipment.

I'll start with the fuel filter anyway since that's the only thing I haven't serviced in its history. Autozone probably has the pressure gage for loan.

[hectore3]

Had the same problem some time ago. Found out it was water in the gasoline. Don't discount bad gas from that station.

[PonchoV8]

I haven't done anything yet, but I did just start the truck and drove it down the street. It was fine other than a just a little lower performance than normal. It may be water too--since it really started getting bad when the truck had 1/3 of a tank of gas. I'll change the filter--the catalytic converter has been rattling for a long while too.

My neighbor across the street owns a gas station. He said cut rate gas is not certified. They can buy anything off the market. Major name brand gas has to be certified. Now the reality is that all of our gas here in our town comes from one of two pipes. Two competing companies own a pipe. But during the change over of shipment from blend to blend is where you get variations. They also put the additives in during loading for each name specific brand gas (Techron, etc). Same gas, different additives. Cut rates commonly use changeover fuel.

[se428bandit]

is it a 2.2 izuzu or a 4.3 gm

[PonchoV8]

It's the 4.3.
I just drove it to the store and it did it again--loss of power, and immediately heated up to about 210 degrees then dropped back to normal range right away. The power was still diminished some, but actually started accelerating where it wouldn't when it was having a spell.

[PonchoV8]

Changed the filter, but it's still the same. I'm gonna have it checked at the dealer I believe.

[pontiacmark]

Doug, I don't know if the 1997 is the same, but I had a 93 Sonoma 4.3 Vortec that the catalytic converter crapped out at 20,000 miles. The Vortec fuel injection is good for about 100,000 then it goes.

[mzbk2l]

Glad I wasn't a betting man - it sure sounded like fuel to me. We used to get a lot of clogged filters here when the EPA forced us to have that MTBE crap in the gas in the winter. It really managed to knock loose the crud in your tank and clog filters in a hurry. (Not to mention pollute the ground water and cause cancer or whatever else it does. Thanks, EPA.) The symptoms were usually very close to what you described.

[PonchoV8]

100K?! That's not good news. We've got 154K on the thing and I've just been putting off trading it off for something newer. It's been a reliable truck.

I'm not so sure it isn't a fuel pump or something. I think a lean condition is causing it to heat up when it's having a spell. The filter really wasn't that dirty appearing when I dumped the gas out of it.

My choices were to buy a fuel pressure gage and try that, then pull the O2 sensors for that, but I think the diagnostic for 30 or 40 dollars will be time saved. I already have two cars in my driveway unused.

[Tin Injun Tom]

Did you take her in for diagnosis yet? I still wouldn't be surprised if they find water in the tank.
I had that problem (as a result of vandals) on my '75 Ventura twenty-three years ago. The car ran OK with a full tank, then started having 'spells' as you described. Seemed to be more frequent when the fuel load was down to 1/3-1/4 tank. And it really didn't like to climb grades.
Before I found out it was water, I would pull off the road, shut it off and raise the hood to let it cool down. I had no temperature gage, but I reasoned that cooling was good for it, whatever it was, because it always seemed to be OK when I finally would get going again.
How I found the culprit was; a local private mechanic took the fuel line off at the carb & ran some gas into a clear glass bottle. Water settled down to the bottom of the bottle, BINGO.
You might be able to disconnect the line underneath somewhere, maybe before the filter inlet, and do the same test.
Anyways, keep us posted.

[PonchoV8]

I haven't taken it down yet. I called a guy I know that works in the service dept where I bought one of my trucks. He said to check the EGR first and call back--since it does the trick when it warms up. I'll look into that and if that's not it, I'll take it to him to check out. I figured out that it does this after warming up right about the time I changed the filter.

What I didn't mention was that I called the Dept of Agriculture weights and measures dept to have them test the pump I was on. I called the next morning first thing. They said I'd get a report, but it hasn't come yet.

Also, when the mileage go to 200 miles of the 300 the truck gets per tank, I filled it up with Premium Shell. That was before my first post, but it made no difference so I didn't mention it.
I'll check the EGR now.