My car
1991 Z28 5.7 TPI
3 speed auto with OD

This has been an ongoing problem that has been the biggest roadblock since owning this car. I have searched through many threads with this problem and nobody ever got it fixed.....

Anyway, I have already replaced air filters, fuel filter, plugs, cap and rotor, and took off the cats to see if they were junked up and it still tries to die out when you floor the pedal or put more than half throttle on it. Taking it easy it will drive around at 60 mph all day long.

Any other suggestions?
I was thinking possibly
fuel pump
distributor
fuel injector
sensor somewhere
ECU

 

Anybody have suggestions? Im stuck in a beat up Ford Explorer otherwise...

 

Do you have nay stored codes?
Check fuel pressure and engine timing. Also check the operation of your TPS voltage and its operation. These would be the places I would start.

 

I stuck a paper clip in 5 and 6 of the diagnostic module under the steering wheel beside the fuse box but it only repeated code 12 over and over again. I know it is supposed to do it three times and then give any codes. Is it normal to just repeat over and over? It seems that it was of no help to me. So my next step is to check the TPS voltage as you said, but woulden't I get an engine code for the TPS if it wasn't operating correctly? Also, my second guess after TPS would be the MAF sensor. Does this seem logical to you guys?

 

If you have a 91, you do not have a MAF sensor. You have a MAP sensor, located on the passenger side of the intake manifold plenum. You may not necessarily get a trouble code from the TPS if it has not failed completely. The TPS is pretty much a variable resistor. The TPS on your car is not adjustable. It shoult read somewhere between .7 and 1 volt when the throttle is closed, and over 5 volts at WOT. The thing to look for is that as you move the little arm that hooks into the throttle body, the numbers increase and decrease linearly, that you don't have any points where it sticks or jumps in voltage.
Also check your fuel pressure at the fuel rail. You could have a fuel delivery issue where FP drops when you give the car some gas. You can get a FP gauge fairly cheeply at autozone. It is about $37 and is a good tool to have.
Also, check the resistance of your fuel injectors. It an easy and straightforward thing to do and will help you rule out the possibility of any injectors being shorted out.

 

I'm have almost the same problem, just posted mine above you, I'll let you know what I find please let me know about yours if you get it fixed thanks , George

 

did you happen to test drive it without the cats on? sounds like a plugged up cat or cats. im also kind of curious how you took the cats off so easily, they should be welded in front and back.

 

I never said it was easy to take off the cats lol. Now I have an extremely loud exhaust if you know what I mean. Even when I know it's coming I still jump out of suprise when I start it cause it's soo effin' loud lol. We just took a hack saw and started sawing in front of the cat. So pretty much all that is left is a few feet of piping past the headers. I plan on getting a cat back system soon so for now im just going to get a Y fitting and merge the two pipes into one and run it along the passenger side skirt, stick a glass pack in the middle and then put a turnout right before the rear wheel. Just a temp fix, live and learn....

I have a feeling it could be the fuel pump as well. For awhile in the begining when the probelm started it would just jerk back at a regular interval while driving. So I think I can credit that to a slowly failing fuel pump? Luckily my buddy works at a garage close by and can get me one for $80. He took it this mourning to work with him to do some testing and get some opinions from the guys at the shop, a couple of them have owned 3rd gens in the past.

Sacula: thanks alot man, thats the kind of information I was looking for. I'm still new to 3rd gens so im slowly learning more and more about them, like the fact that I was stupid in thinking it has a MAF...
Could the MAP sensor cause this problem as well? I have seen many threads about this same problem with the same symptoms, but nobody ever ends the thread with "I figured it out".

Quickstyle: Just out of curiosity, was the Super Ram worth the money and hassle?

So what i'm left with is:
Fuel pump
Injectors
TPS
MAP

Thanks a TON everybody, This is why I love this website.
you can check out this thread if you wanna see a pic of my sick baby
https://www.thirdgen.org/forums/orga...und-right.html

 

You could check the vacuum lines that plug into the MAP sensor and the fuel pressure regulator to make sure you have no vacuum leaks. Also turn the key to the ON position with the vacuum port to the FPR disconnected and make sure there is no fuel coming out of the port.
If you had problems with the MAP sensor, I think you will get a trouble code, code 32 I think, but don't quote me on it because I am not sure.
I would start with the basics: fuel pressure at the rail, injectors, TPS. If they check out good, then you can start looking for other issues. Chances are it is one of these issues. Fuel pumps and injectors are common trouble points on these cars.

 

upgrade the fuel pump mine was doing the same thing until i got one to pump the shiat out of some fuel lol

 

i only paid like $350 for my super ram, upper and lower used from the classifieds on here. most people think it is a hassle, but once you have it off more than once, you get to know it and its fairly easy to take off and on. but the first time was a bit harder. its the only intake option i had to remain smog legal, even if i could have used the mini ram or stealth ram, i would still stick with the super ram, its matched to my cam, and it still has alot of bottom end.

 

Just a little bit of an update:
Fuel pump checked out OK, so that's not the issue. I have a good inclination that it's the injectors. It's pretty much the only thing that makes sense to me now. As you guys said the TPS system usually screws with the injectors and fuel pump. The senior mechanic at the shop suggested that it was probably the injectors as well. Its a good thing I know people, this would start to get expensive lol.

We did put it on the lift and give it a thorough look around and blueberry deffinately is requiring a bit more restoration after I get this problem solved.

One of my wheel bearings is shot, thanks to the hell hole dirt road I just moved away from. Im leaking differential fluid, so I need a new seal for it. Lastly the rotors are swiss cheesed in the rear and I am pretty sure the calipers and pads are as good as mummified too...

Thank god I got to this car in time, it was headed in a downward spiral with the last moeron that had it...

I know that eventually when I get my Mazda MX-6 back from the rebuild (gonna come out as a low 14, high 13 car hopefully) I can put up blueberry for awhile and focus on getting a new intake system. Anybody have any suggestions? Ive done a pretty decent amount of research but i'd like to hear from some of you guys on personal experience. I know there is the option of new runners and base from holley or SLP. How does that compare to a mini, super, or stealth ram? Is it worth spending a little extra to get the ram systems or just be frugal and upgrade the existing base and runners?
Feel free to PM me if you want to chime in on that.

Once again guys, thanks a TON.

 

just a little bit of an update:
Finally got to check the TPS and it read fine... The timing is off so I am adjusting that as well.
I am awaiting some injectors I won on ebay right now. Hopefully that will be the fix.

 

okay everybody problem solved. Ended up being a bad fuel injector