View Full Version : 1991 Chevy Pickup with 5.7 V8.

06-21-2007, 02:38 PM
I hope their are some good mechanics out there.

My truck is starting and running smoothly except for one problem.

It is having a tough time climbing even moderate hills and accelleration is poor.

I have replaced the distributor, cap, rotor, wires, plugs, coil, air filter and fuel filter.

Someone suggested it might be a plugged catalytic convertor or muffler. I tried a vacuum test that is supposed to indicate if those devices are plugged and the test did not seem to indicate that was the problem. I suppose they could still be the problem. But if the problem is not there, where is it?

Frustrated amateur mechanic.

p.s., I have tried car repair web sites and the information I get from fellow boat builders is always more to the point and more accurate!


06-21-2007, 02:50 PM
Alan, I have a 92, 5.7. I had the same issue. It would idle and do just fine on flat ground. Under load it would start to buck and stutter. $128 installed for a generic cat from a muffler shop and now all is good. I did the same thing you did, plugs, wires, coil, cap, rotor, all the normal stuff.

I am not saying it will fix yours, but it sure fixed mine..;)


Kim Whitmyre
06-21-2007, 02:58 PM
A muffler shop can test it for you: they drill a small hole, insert a sensor and read the pressure, then weld the hole up.

John B
06-21-2007, 04:33 PM
Given what you've already done and assuming you'll do the cat thing first, I'm thinking fuel pressure or perhaps fuel contamination ie water in the tank through condensation etc.

I've had similar issues on various cars over the years and a litre of what we call methylated spirits in the tank has fixed them. Meths absorbs the water and allows it to pass through the fuel system.
I think you call it something else ?( you need to check out whatever the equivalent is.) Maybe there's a proprietry product that achieves the same thing you could research. Small investment to eliminate it anyway.

This says you call it denatured alchohol if I read it correctly.

here's proprietry version. I've used their water wetter but not this product.

06-21-2007, 05:02 PM

It's commonly referred to as 'Heet' over here.

John B
06-21-2007, 05:54 PM
I was at my local station a few months ago and a guy with a shopping cart pulled up to gas up, I kid you not, with premium petrol( gas). after he bought his 2 litres and 'drove off',I asked the question and the attendant ( who I know well after 10 years of business here) told me he bought it for grog and he drank it.:eek: Been doing it for 10 years She reckoned.

06-21-2007, 08:42 PM
Thanks for the replys. Sounds like the convertor is a prime suspect. Glad to hear there is a reasonable way to have it tested.