1991 1500 z71 serious problems help!



This problem has been CONSISTANT: it revs up and down then dies. It dies even when he revs the engine. All the following has been done:

Rebuilt 350/700R4 engine and trans

New M.A.P sensor

new I.A.C valve

cleaned E.G.R

new 02 sensor

new exhaust w/out cat

new cap, rotor, wires

new coil

upper half of TBI unit

new fly wheel


new prom chip for computer (fast chip from ed wright)

new T.P.S sensor

new temp. sending unit and thermostat

new fuel filter and fuel line from filter to back of throttle body

new battery


You name it its been replaced or rebuilt. Please, Please, Please someone help us. We’ve had this truck for over 2yrs and only ran for 1. It’s been undergoing work for this long. We’ve spent well over 5k trying to fix it and cant even get it paid off due to it. We can?t sell it or trade it in. We are in it deep. We are down to one car, mine.<o:p></o:p>

We have had a professional try to work on it, each time anyone works on it and it runs for 5minutes to 2days.


Well, the fuel pump has not been named.

It’s near impossible to say on this; especially if some of those things have been done in an attempt to cure the consistent problem you have.

Things like a rotor, cap, plug wires, performance chip, O2 sensor, flywheel, exhaust, etc. have nothing to do with your problem.

Are you sure someone is just not repeatedly guessing and talking you into various widgets in an futile attempt to fix this problem? (as in performance chip, cat-less exhaust, etc.)

Should I ask what the reason for the “engine rebuild” was and how many miles on this truck at the time?


I wonder if anybody has done any real troubleshooting. What you need is a shop/mechanic who can, and will, use the OBD scanner, engine analyser, multimeter, and the technical data, and his own expertise on this truck. Ask around for such a person/shop. Even ask mechanics. They know who is good.


The first step in a situation like this should have been to check the car’s computer to see if it has noticed any problems. Many auto parts stores will do this service for free. Right now I would guess you could use something that was free. Try AAuto zone or Advanced Auto Parts.

Get the actual code like P0123 not just the English translations and post them back to this tread.


The rebuild of the engine is due to its own problems. The headers froze and other problems. In which were all remedied by the rebuild.
Thank you very much for all of you whom responded. We welcome any and all responces on this to continue.


Since this all still murky, I’m sticking with the fuel pump being at fault.

I would sure to love to hear an interpretation of that “headers froze” in regards to the engine rebuild. ???


How about something as simple as a vacuum leak.

Maybe during the rebuild someone installed the intake manifold gasket incorrectly.

TBI gasket improperly installed.


Joe! Again this is an OBDI vehicle. Not OBDII. So the codes won’t be of the P0XXX variety. As a matter of fact, these people can pull the codes themselves by inserting a jumper between the A and B terminals on the ALDL connector under the dash, and then turning the ignition switch to the ON position. The Check Engine light will then begin to flash out the codes.



Willey? That’s what I would look for. A vacuum leak.



This has been done. We have done so much we cannot remember right off hand what all has been done. Matter of fact we had a list of all things at one time but was on the pc and then it got hacked and upon gettin it fixed we didn’t think to get a back up.


this has been replaced. it was one of the problems.


Forgive me, the wife i am, i was incorrect to say the “headers froze” the problem was a spun main bearing.


The computer chip, at an insane amount of money, has been replaced, no vacuum leak, gaskets are in place, all and any codes have been checked and nothing comes up.
We welcome, still, anyone and everyone whom think they may add somthing to this. May be takin it to the junk yard.
We have done so much we cannot remember right off hand what all has been done. Matter of fact we had a list of all things at one time but was on the pc and then it got hacked and upon gettin it fixed we didn’t think to get a back up.


Did I miss it or was the ignition system thoroughly examined?


Don’t junk the truck yet.
The idle moving up and down can be caused by an air leak. You state there is no vacuum leak. How have you determined this?
You do realize a vacuum leak can occur nowhere near an engine and may be in the canister hoses, brake booster, the vacuum resevoir, or even inside the dashboard?
The only way of removing all doubt is by using a vacuum gauge.

As to the engine dying even when revved, this could still fall back on the fuel pump as I mentioned earlier.
A fuel pump pressure test AND a volume test should be performed.

Thanks for clarifying the “frozen header” comment. A spun main is definitely a major problem.


Not that this helps, but if you are trying to sell the truck the “new exhaust w/out cat” will need to be fixed. That is a federal offense to remove and if you are selling it someone might notice.