91 80 running issues (1 Viewer)

Joined
Sep 13, 2020
Messages
6
Location
north texas
My 91 80 has a running issue that had progressively got worse. It is a trail rig/truggy but drive line is 100%

so last year took it on a run on the last day was going up a trail and it started stumbling and losing power. Never had done this before and kinda assumed it was low on gas and brushed it off. Then I took it out at the beginning of the year and it randomly started stumbling every once in while and knew I had a problem at this point. Got back home did a basic tune up plugs, wires, cap, rotor, and fuel filter. It ran and idle much smoother. So loaded it back and went out again. It ran good for about 6 hours then stumbling and no power. This time though it stayed that way, it runs all the time, idles and starts great

so started digging into it first thoughtwas TPS sensor, ordered a new one. Put it on it is set at .9v at at idle. Still started and run great but has no power and still stumbles. Was suggested to check the cat out. It was clogged and bad. 600 degree difference from the front to rear of the cat. So I just took it out and re did the exhaust since there are no down stream o2s. Now it runs better smoother way way way more power until it starts getting a little warmed then back to stumbling and running bad. Next place I go is the coolant temp sensor, it’s broken. Put a new in it since I figured that’s it. Stumble is gone butttt it won’t rev well now. So check fuel pressure, like 54 at the fuel filter. But I check it behind the regulator and it still like 54. So the regulator is straight by passing and there is no real rail pressure. So put a new one of those on and it seemed to help it rev more. Ohmed and voltages check the AFM it shows perfect also

So where am at now. With the truck warm and in park if you give full throttle it revs very slowly. If you give like half throttle it revs like a top. If give just a touch supplement fuel while rev the motor (carb cleaner) for full throttle it rev up perfect like it should. So this tells me it’s a fuel delivery issue and it’s lean.

I’m really hoping someone can help because I don’t know what to check

sorry for the long lost just trying
To give and much info about the problem as I can. This is my first post but I have fixed and built mine reading this forum

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Joined
Aug 26, 2007
Messages
158
Location
Baton Rouge, LA
 
 
How old are the o2 sensors? Also I tend to preach this but check all of your ground connections. A bad ground can do weird things and it is free to check and free or cheap to fix.
 
Joined
Sep 13, 2020
Messages
6
Location
north texas
Did check the AFM
The o2 is new because I cut the wire wheeling and replaced a couple years ago
Will have to check the grounds out, haven’t go through those
 
Joined
Sep 13, 2020
Messages
6
Location
north texas
After reading some info on here AFM still might be the problem. I went head ordered the camery afm
 
Joined
Sep 19, 2020
Messages
10
Location
USA
Im having a similar loss of power on my 92 80series did basic tune up and head gasket and it seems there is a fuel sending issue possibly do you have any trouble shooting updates or progress? Best of luck
 
Joined
Sep 13, 2020
Messages
6
Location
north texas
Nope, new mass AFM didn’t fix it. It’s a lean condition under heavy load or throttle still. Nothing has seemed to change it
 
Joined
Sep 13, 2020
Messages
6
Location
north texas
So I had it out last weekend...
It’s def a fuel delivery problem
Coolant temp sensor has been changed
I had the tank out a while back and the fuel sock seemed ok. Will this affect fuel pressure or just volume?
I’ve never done valves? Do I need to adjust them? I didn’t know about this.
It def runs better but still not correct. No more stumble just bogs on heavy load and throttle
 

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