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1994 Cherokee Country 4.0 poor engine performance

redwolf698

NAXJA Forum User
OK, I bought a 94 Cherokee from a guy. It's a Country, with aircon and the AW4 automatic transmission.

Motor swapped with a salvage yard unit (old block was cracked) the salvage yard unit was labeled as a reman unit, and when I pulled the water pump off it was cherry, all the champion plugs that came off were in great condition, but still replaced.

Trans rebuilt.

Catalytic converter has previously been blown out (empty shell). The muffler, tailpipe have been replaced.

AEM cold air intake, throttle body spacer installed. All new plugs, wires, rotor, distributor, rotor button, cap.

We have adjusted the detent cable. Just replaced fuel pump. 1994, no signs of a ballast resistor.

It acts like a bad cat, when it warm up, performance trails off to horrible, as in everyone is flying by me and I am barely making it up this hill. Max RPM is 3400, and she pops, crackles and screams the whole time she's there.

Vacuum lines all are good. No trouble codes. Veh has been timing checked, even though it's computer controlled.

I have regeared it to 4.56, and replaced every component in the air conditioning, engine cooling, and breathing.

I have replaced MAP, TPS, and oxygen sensors. I have reset all parameters with a scan tool.

I am just at a loss, there's no way this critter should be this sluggish.
 
I see you've replaced the fuel pump, but there's no
mention of the fuel filter...?

Might be worthwhile to blow out the fuel line with
compressed air.

Only other possibility I can think of is the ignition coil.
 
I see you've replaced the fuel pump, but there's no
mention of the fuel filter...?

Might be worthwhile to blow out the fuel line with
compressed air.

Only other possibility I can think of is the ignition coil.

Sorry for not mentioning it, yes, the fuel filter was replaced during the engine swap. I'm 100% in agreement that blowing the lines out is a good idea. will get it into the shop today and try that.

Fuel pressure regulator was replaced as well, during the swap... it sits at 51psig at idle, dips as low as 40 (spec 39) during command.

hastas
 
You are pushing 3,400 RPMs and wondering why everyone is blowing past you? 4.56 gears is your problem. Not your engine. Stop driving it at 3,400 RPMs.
If you're at 3,400 RPMs with 4.56 gears something is not right. You should be cruising on some 38s or larger for that RPM range. Stop driving it at 3,400 RPMs and you'll stop hearing the loud popping, crackle and scream.


www.speednik.com-xj-cherokee-gear-ratiotire-guide-gearratiochartxjcherokee.jpg


Gear-Ration-Chart.png
 
yeah, I am not 12 years old on my first time driving or working on a car.

I reached out to a knowledge base with an issue that incudes the fact that the vehicle will climb to 3400 rpm in 2nd or 3rd gear, but will not get any higher with or without a load.

I appreciate your point, and I hear you about driving around with it in that condition. Again, I am not that guy, though, I was simply giving a point of detail to aid in the diagnosis of the condition.

Other than assuming I am driving around with the vehicle hung up in gear, do you have any suggestions in troubleshooting the condition?
 
Since this engine was "reman" I would suspect the camshaft was not degreed properly. If you can't degree a camshaft, I suggest you have someone degree it for you.

Best regards,

CJR
 
Just a thought, do you know what year the engine came out of? If you didn't re use your original flex plate you could have the wrong one, different years had different counter patterns; although I would be inclined to think it wouldn't run at all if you had the wrong flex plate.
 
yeah, I am not 12 years old on my first time driving or working on a car.

I reached out to a knowledge base with an issue that incudes the fact that the vehicle will climb to 3400 rpm in 2nd or 3rd gear, but will not get any higher with or without a load.

I appreciate your point, and I hear you about driving around with it in that condition. Again, I am not that guy, though, I was simply giving a point of detail to aid in the diagnosis of the condition.

Other than assuming I am driving around with the vehicle hung up in gear, do you have any suggestions in troubleshooting the condition?


Change the distributor to a 93 instead of a 94 since you said the engine came from a 94.
 
Change the distributor to a 93 instead of a 94 since you said the engine came from a 94.

Did you read post 11? :roflmao:
 
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