93 FZJ 80 losing power on highway above 2000 RPM (2 Viewers)

Joined
Mar 13, 2018
Messages
107
Location
Philadelphia
Hello fellas
93 FZJ 80 losing power on HWY when accelerating since 2000 RPM. RPM going up and down and vehicle jerking . When applying gas slowly below 2000 RPM it rubs fine between 30-50 mph. On idle if I try to bring RPM above 2000 it goes right back down. No CEL. No starting issues. Any ideas would be appreciated. Thanks.
 

Squash

SILVER Star
Joined
Dec 8, 2006
Messages
1,525
Location
Sudbury, Ont. CA
How is it in reverse?
If she runs better in R check the wiring harness.
Obviously you've looked at vaccum lines and haven't screwed with the airbox, or just changed out the air filter.
Does the issue go away once the engine is warmed up?
Just asking because my 97 would do this till it reached 192 degrees.
Luckily with OBii I was able to see this trend and on a hunch replaced the ECU temperature sensor.
This is the one closest to the driver.
The other temp sensor is for your gauge.
 
Joined
Mar 20, 2007
Messages
69
I went through a long process trying to diagnose intermittent loss of power on hills. Felt like it was running on 5 cylinders, and it was. Only happened at higher RPMs. Ultimately it was a bad fuel injector, though having them bench tested did not find any of them to be bad. After eliminating other options, I finally replaced the one fuel injector that with a different looking spark plug and, bingo! problem solved.

Your problems sound different, though. Personally, I would suspect the distributor--if you could borrow a known good one that would be an easy diagnosis.
 
Joined
Sep 25, 2014
Messages
1,147
Location
Gilbert, AZ
My 94 did something similar. I would double-check your wire harness to assure it has not melted and shorted out. While you are in there have the injectors cleaned. I would also recommend cleaning your TB and make sure the hole that runs over to the EGR is not plugged neither.
 
Joined
Feb 23, 2015
Messages
255
Also might check the fuel filter. Low or loss of power at higher rpm under load is something this could cause and may be on your PM list anyway. I replaced one with a cheap aftermarket filter as PM in an old RX7 and shortly after developed similar problems that had me throwing other parts at it until I pulled the new filter to find it had failed and couldn't blow through it like a good filter. I would also monitor fuel pressure when the issue occurs before throwing other parts at it.
 
Joined
Apr 24, 2021
Messages
1
Location
Houston
When you say it "goes right back down" going above 2000 RPMs at idle, do you mean it dies?
Seems like fuel/air/spark issue.

Could be a plugged cat like others have said. That also comes with sometimes backfiring, bad fuel economy, engine codes. The engine cant breathe if exhaust cant get out. You can loosen the bolts from the exhaust manifold and the precat exhaust to let some exhaust escape. If that fixes your problem then thats the issue.
Could be spark. When did you last change your plugs? Also, if you pull some plugs and look at them they can reveal other problems (fouling, running lean, etc).
Is your air filter clean or full of garbage?
Do you have a fuel pressure gauge? You can check running fuel pressure and see if thats an issue as well.
 

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