MeanYellowZ

k guys....had my 87 S10 for about 3 years now and it has always had a problem that sometimes gets worse and sometimes is not very noticeable. It has always ran pretty well for the amount of miles on it, except you could never push the gas over say 3/4s throttle most of the time, or it just kinda stops pulling, its like it freezes. This is how it is and has been for years and like I said, sometimes it gets worse, to were you can barely push the pedal more than half throttle or it just stops...feels just like I am just letting off of the pedal all together, it will stay running, but it just doesnt do anything. Anyway, since I have had it over the years I have replaced the plugs...the wires, the cap..rotor...the fuel filter....and just never thought muhc about it. Its juts a pain to drive sometimes because if you hit the throttle a hair to much the truck just falls on its face and makes driving really jerky

As I said its been this way forever and i just have not let it bother me. Well, the other day it got REAL bad...like were i literally couldnt press the pedal down more than 1/4" or it would do nothing. I could barely get the truck to 35 mph. I had to press the pedal just as much as i could without going over the "point" If i just hold the pedal down it will sit there and if i hold it long enough, it will actually backfire really loudly. I did this once with the air cleaner off and had quite a nice explosion. The wierd part is that if i shut it off and start it again it will be betetr for a bit, and if it still does liek it always has, I may go out and get in it and it will be just fine, it really goes through changes like that. Its about as close as it can be to not driveable at this point, because when its is being real bad it doesnt even want to cross and intersection...this is dangerous.

the vehicle is a 1987 S10 2.5/ 5 speed. The previous owner changed the fuel pump, and oddly enough he gave me the odl fuel pump with the truck. I wonder if it never quite acted right after he changed the pump out.

Any help would be appreciated.

thanks
Randy

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Currently own: 2001 Xtreme, 85 IROC, 87 S10
pics of my old 86Z:
Camaro1 Camaro2 Engine
More at: My Directory
Email: MeanYellowZ@hotmail.com Aol/IM: RCY1980

RARE-ROC-Z

sorry to hear it randy, wanna buy my S10. lol.
and hey you need to change your sig, it doesnt list the nova. and you dont have the IROC anymore!



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Jarrad
1990 IROC-Z L98 350 TPI
TH-700R4
G92- 9 Bolt Borg-Warner 3.27gears
Bright Red Hardtop/ Grey "Custom" Interior
NOT STOCK, NO WHERE CLOSE!
NEW RED PAINT and WELD PROSTARS.

DAILY DRIVER: 1991 GREY S10 2.5L/5SPD -FOR SALE. leaving for army.

Hulk0202

I had the same problem with my firebird. It did it off and on, but eventually it got real bad. Take off the air cleaner and give it full throttle. If you get air/fuel vapor coming out like I did, it might be your cat. I took mine off and it ran better then it has in years. I guess when it got to a certain point, it just couldnt remove anymore exhaust. Hope this helps.

Engineboy

As stated above, check the cat.

Also check fuel pressure while running.

Have you changed the fuel filter latley??

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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

R.I.P. #3
"He can see air"

coach

I second what Hulk said. I had a problem with my cat on an '84 Z28. On the freeway, the car wouldn't want to go past say 60mph; if I tried to push it the car would jerk and hesitate. Later, I couldn't go past 50mph, then 45, and so forth. The car finally quit moving all together. She wouldn't even crank, because all of the built-up backpressure(clogged cat). I cut the cat out and she fired right up.

Funny story: It took me about 7 hours to cut the cat out. The bolts were rusted on; the place where the cat slips onto the pipe was frozen solid; I didn't have a cutoff tool at the time. All I had was a hacksaw with a dull blade. To tell you the truth I was probably cutting more with the heat from friction more so than the teeth on the blade. I made a game out of it. Seeing how much of the pipe I could cut off from one hour to the next. (Anything to keep you sane when facing a pain-in-the-butt task). When one arm would get tired of cutting I would have to switch sides and use the other. I finally got the thing off. And it was all worth the time, to hear the sweet sound of a V8 exiting open pipe. I'm sure I annoyed some drivers on the freeway when I drove the car to the muffler shop.LOL

CAMARO82

Might be your fuel Pump.... Could be. LAters

AJ_92RS

Is the 87 4 banger a carb or EFI? I had an 81 GMC fullsize that was doing the exact same thing yours is. I was told by several places that the carb needed to be replaced. Well a replacement Q-Jet is about 450-500 bucks. I went and bought a rebuild kit ($35) and did it myself. Got done, put it back on, amazingly the truck ran again, (my first carb rebuild) and it still had the same prob. A mech. I worked with said, "Seems like the fuel pump is going and the float bowl is getting drained out." Well he was right. I replaced it and it ran fine ever since. That may be the reason the guy gave you the old fuel pump. Otherwise why would he do that? It's just another possibility. I guess it boiled down to fuel delivery. The fuel filter, like EngineBay said, could be it too.

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92 RS w/t-tops 305 TBI Auto.
170K miles and don't burn a drop o'oil
-K&N Truck filter #1500 w, open ele.
air cleaner
-Dynomax 2 1/2" cat-back
-B&M TransPak
-Jet Stage2 Chip
-180* T-Stat w/ 185* Fan Switch
-JVC CD--Alpine speakers & 4ch. amp
Rockford 2ch. to 2 MTX 12" subs

MeanYellowZ

as I said in my first post, I've replaced the fuel filter already. Second, the truck has no cat, and its EFI with TBI

thanks
Randy

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Currently own: 2001 Xtreme, 85 IROC, 87 S10
pics of my old 86Z:
Camaro1 Camaro2 Engine
More at: My Directory
Email: MeanYellowZ@hotmail.com Aol/IM: RCY1980

Vader

MYZ,

How's the fuel pressure? I just had a bout with one of the roller skates - TBI and occasionally low fuel pressure made me one frustrated puppy. If you don't have the test adapter you can purchase or fabricate one. I found a failing fuel pump pulsation damper that caused a lot of variability in pressure. Same problems - idle was actually RICH and mileage was suffering, but anything about part-throttle was way lean. If the replacement fuel pump wasn't done correctly, you might still have problems there. You should also make sure the PROM is correct for your engine. If the fuel map is skewed a bit lean, not much will compensate.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

MeanYellowZ

hey Vad, Im gonna be honest here, I know nothing about checking fuel pressure on an FI motor. There is a port just for this correct? if i beg, borrow, rent a testing guage what should I look for? Any idea what the psi should be on this truck? Will it fluctuate with RPM, or should it generally stay the same through the full range of RPM?

thanks
Randy

Needs to learn Fuel Injection Racing

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Currently own: 2001 Xtreme, 85 IROC, 87 S10
pics of my old 86Z:
Camaro1 Camaro2 Engine
More at: My Directory
Email: MeanYellowZ@hotmail.com Aol/IM: RCY1980

MeanYellowZ

Vader??

Vader

MYZ,

Sorry, there is no port installed at the factory that can be used to test fuel pressure on most TBI engines. I guess the TPI engines are just lucky. I fabricated an adapter from the end fittings on an old fuel filter (tapped them to 1/4" NPT, installed a 'T' & nipples, and Schrader valve from a refrigeration kit) to break into the line to test pressure. Some guys just take the easy way out and run out to buy an adapter, but I need an excuse to have all the equipment and junk stored in the corral.

You could also fashion an adapter from hose and a 'T' fitting I suppose. In any event, you need to break into the fuel line ahead of the TBI unit, since the pressure regulator is integrated into the injector mounting pod. If you have a means to measure the fuel pressure, you should get between 13-15 PSIG with a stock regulator.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

Vader

BTW - since there is no vacuum control of the regulator, the pressure should remain a constant 13-15 PSIG at any RPM or load. I've had to modify the FPR unit to enable me to adjust the pressure up to 18 PSIG to feed my roller skate engine correctly, but that's because I screwed with the heads, valves, and cam.

And even if the pump was replaced, if the clamps were not securely installed at the pump mount, you could have had this kind of thing happen:



If you decide you have a pressure issue and want to adjust your regulator, let me know. I need an excuse to finish the article on the conversion (complete with photos, of course).

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

MeanYellowZ

wow...ummm.....I'm gonna be honest with ya here...I think I'm just gonna replace the fuel pump and see if that fixes the problem....that actually sounds easier to me....

I REALLY need to learn fuel injection crap

Vader

MYZ,

I just couldn't stand it. I had to finish the TBI AFPR sheet, so if you are interested, here it is:

TBI AFPR.pdf

You should have Adobe Acrobat Reader by now, but if not check the link below for the free software.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader