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I need all the help I can get here. Quick run down,1990 trooper 2.8L auto 185k miles. I was told the motor was replaced when I got the truck with a 50k motor? My problem now is that I have major loss of power problem that started a few months ago. Now I can't get the rpms over 2800. I cleaned the injectors best I could seem to be spraying fine, timed the motor, pulled a #34 code and replaced the map sensor. New plugs.new pcv checked for vacume leaks, newer wires,cap and rotor (3months). Now what.....? Any help Please?
 

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Another vote for a clogged cat.

Jim
 

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don't kill me (I'm new here, but not to the game...)

-- The approach for diagnosing a clogged cat is a bit pricey and labor intensive unless you're properly equipped...

The 5-10 minute approach around here involves a wide muffler clamp (cheap & sold near the "gun putty" muffler repair products) -- I'll just cut a sizeable hole (3-sided rectangle works) in a straight section of pipe somewhere up-stream of the offending cat (best if you can get the hole right at the front of the cat for subsequent repairs)...

With the hole open - see if you can get your RPMs back... Then cover the hole with the fat-clamp until you've got time to weld it shut and/or replace what's clogged.

It's a little Cro-magnon, but can be done with a variety of cutting devices (plasma here) and provides real-time results for just a few minutes of under-car.

Best of luck -- I'd offer to help if you were closer...
 

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Clogged cat is certainly a possibility (ain't gonna fall for a banana in the tailpipe! :wink: ), but IMHO rarely turns out to actually be the problem.

Go the roots - fuel, air, spark. Make sure they are all working. Lotta possibilities here.

Fuel - Maybe a bad tank of gas? Fuel filter plugged? Fuel pump underachieving? You already checked the injectors...

Air - How old is the O2 sensor? Clogged cat, as previously mentioned? Mouse nest in the intake (it happens!)? Throttle plate opening properly? Does that vintage engine computer have a "limp" mode? Leaking intake gaskets affecting vacuum and computer controls?

Spark - even though the cap is new, they can still go bad almost out of the box. Recheck. Check under the hood in the dark for arcing while someone revs the engine. Is the spark advance working right (I don't know if what system that vintage uses)?

That's just what I come up with off the top of my head, not the end of the list. Good luck!
 

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I would replace the fuel filter. I know on the older pickups like i run almost evertime someone complains of loss of power its been a fuel filter. On the older guys its a $3.50 part. I wouldnt think it would be more than $10 for a newer truck.
 

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in other rigs i have had fuel filter plug up in 1 or 2 months. Thats just a quick easy way to make shure your getting fuel. I always go there whith most of my driveability issues.
 
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