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Old April 5th, 2019, 17:37
Jradkins Jradkins is offline
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Acceleration problem

I have an 89 xj sport and have just recently replaced the head gasket and got a valve job. I also have performed a complete tuneup and service including fuel filter. I had a rough idle problem to start with before the head gasket was replaced and now Iím having a problem while driving. When accelerating it starts at low end fine and when the throttle is half open starts to hesitate and skip but when I put it to the floor it clears out and runs seamingly well. I have put a new map sensor, iac valve, cleaned throttle body and put all new plugs ,wires, rotor button ,cap , fuel filter and air filter. Even added Lucas to the oil and gas and still have the same problem. Also all the vacuum lines and pcv valve have been cleaned or replaced. Any ideas?
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Old April 6th, 2019, 05:35
CJR CJR is offline
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Re: Acceleration problem

I'd look for an intake manifold leak; i.e. a cracked intake manifold, a poor sealing intake manifold gasket, etc. It appears to be "loading up" with too much fuel because the computer is seeing a lean condition(i.e. too much air into the engine). When you floor the pedal, it clears out the excess fuel and then runs properly for awhile until it loads up with fuel again.

Best regards,

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Old April 6th, 2019, 08:50
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8Mud 8Mud is offline
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Re: Acceleration problem

On my 89 (I bought used) somebody had replaced the water pump and routed the harness that comes up from the O2 sensor, knock sensor and engine temp. sensor too close to the exhaust manifold and it was melting. It was really hard to see in there, the melted section was really hard to spot.

A year or so later mine developed what I call a 2000 rpm buck, it bucked when slowly accelerating at or around 2000-2200 RPM, ran fine at lower RPM's or higher RPM's (or more pedal). Turned out to be the O2 sensor.
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Old April 6th, 2019, 09:03
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jbeintherockies jbeintherockies is offline
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Re: Acceleration problem

Not to be a smart ass, but what Jeep Cherokee doesn't have an acceleration problem?

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Old April 7th, 2019, 09:27
JeepNoob JeepNoob is offline
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Re: Acceleration problem

Originally Posted by jbeintherockies View Post
Not to be a smart ass, but what Jeep Cherokee doesn't have an acceleration problem?

You're new here, aren't you?

Saw a buddy of mine at the store one day, we get to s***ing the bull about his ride (old-school Pontiac Grand Prix with a factory 3.1 turbo V6, VERY rare and pretty cool) and mine (P.O.S. XJ with a 4.0 and a slush-box AW4) I comment that the thing's pretty fast for a 4x4 SUV. He calls shenanigans and wants a race. Now I don't condone or recommend shenanigans like this on public roadways, but hey, I'm an XJ-guy.

Rolling start, I let my buddy catch up until we're about even and doing I dunno, 20, 25 MPH. Then we both give 'er. Damned if we both weren't even all the way to 55 or 60. After that, aerodynamics seemed to kick in, and he pulled away from me. But to quote Enzo Ferrari "Aerodynamics are for people who don't know how to build an engine." Plenty of engine options out there to make an XJ go faster- stroker kits, blowers, turbos, LS-swaps, sometimes a combination there-of.
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Old April 8th, 2019, 12:09
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Rob Mayercik Rob Mayercik is offline
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Re: Acceleration problem

Don't forget, Enzo also said "Jeep is America's only real sports car"...
1992 Cherokee Laredo: "A wonderful balance of grace and rust"
1984 Dodge Omni
2002 Volkswagen Jetta GLS TDI
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Old April 12th, 2019, 18:21
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old_man old_man is offline
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Re: Acceleration problem

What you describe could be a ton of things. A cracked header could be screwing with the O2 or the O2 could be bad.

You could have a slightly clogged CAT.

You could have a flakey CPS. I had one that limited the rpms to only 2000.

I have even had a coil that could not handle load or rpms over 2500

Have you done a plug reading? Post up pix.

How old are your plug wires?

Double check the distributer wiring/firing order.

Long shot, clogged fuel filter (monitor fuel pressure with gauge)
Tom Houston - Former Colorado Chapter President, current Treasurer , Terminal Adrenaline Junkie, and Rocket Scientist
Loveland, Colorado My teardrop build
You're just jealous because the voices don't talk to you.
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