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Odd power delivery problems

1K views 8 replies 5 participants last post by  bigblockbob 
#1 · (Edited)
1987 Turbo 100% stock except for updated muffler and cone air filter.


Items replaced: CHTS, timing kit, BA fuel pressure regulator with sensor built in, W255 fuel pump.


Symptoms: About 50% of the time full throttle does not provide normal turbo acceleration. It seems that there is a sweet spot in the gas pedal that the car likes, somewhere in the 1/4 to 1/2 pedal travel range. If I push full throttle, a lot of the time it will not pull hard even though the boost gauge shows normal boost. When this happens, letting off the throttle to find the sweet spot will make the car achieve full acceleration. Keep in mind the boost gauge shows full boost whether the car is accelerating normal or not, so its not like the turbo is not working 1/2 the time.


Furthermore, the car is very "wheezy" after 4300 rpms+/- and does not really do much. The power band is 2800-4000 +/-.


Any ideas? My first thought is TPS, but after reading many posts here the Zcar TPS does not do much unlike other TPS's in other cars.


Thanks for any ideas.


EDIT: After replacing the CHTS and fuel pressure regulator, there are no codes in the ECU.
 
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#4 ·
you can buy a pressure gage for like $5 why rent. put a boost gage on the system the stock unit is unreliable. Check your waste gate operation. not the tps. be sure your carpet isn't bunched up under the gas pedal altho that usually is on a s130.

boiler plate may or may not help on the immediate problem but will over time:
Get your battery load tested. Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen. Usually on a rainy night around Oh Dark Thirty.

Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion. DON'T USE DIELECTRIC GREASE.
 
#6 ·
If you have a stock exhaust and your car was at any point running rich for a while, it could be a clogging catalytic converter. I cut mine off due to sluggish takeoff and bogging at lower RPM's.

That being said, listen to the guys helping you out on here about fuel pressure. They know their stuff, and it's good to diagnose before replacing part after part.
 
#7 ·
Fuel pressure was the problem! Turns out that when I replaced the fuel pump, a bunch of tank sediment was stirred up and then clogged up the fuel filter. When I removed the old filter, a bunch of nasty muddy red-ish silt ran out of it. With a new filter, it now runs good again. Thanks!
 
#9 ·
That's good news for sure. But I would still put a gauge on it and see what your fuel pressure is. You may or may not be within specs. Its easy enough to do.
 
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