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89 4.0 xj misfire/stutter

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Umm.. Where am I?
Location
West Jordan, UT
I have a 89 xj 4.0 that misfires/stutters with medium to light throttle, most noticable on the highway, just replaced the ECU for no #6 injector, igniton is new from the coil down to the plugs. Any one seen this or have any ideas?:confused:

Thanks
 
Kiel

Kiel

Formerly WJ ZUK
Everyone will say check the crank sensor, but we had a wrangler do the same thing, ended up being the coolant temp sensor
 
P

PREMIER.MOTORS

Member
CRANK POSITION SENSOR. MY 94 started doing that and it got so bad I couldn't pull out of the driveway. they aren't the cheapest part, about $90, but they are easy to change
 
Milner

Milner

formerly "rckcrlr"
Location
Hiding behind a camera
PREMIER.MOTORS said:
CRANK POSITION SENSOR. MY 94 started doing that and it got so bad I couldn't pull out of the driveway. they aren't the cheapest part, about $90, but they are easy to change
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89 is renix, cps should only be about $40 at the dealer. DO NOT use any aftermarket cps's....I got 3 bad ones in a row from AZ. Dealer only item!!

Yes, could be CPS, maybe and intake manifold leak? What sort of milage is on it? Have you check the compression? What does the spark plug from the cyl look like?
 
scramble this

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Umm.. Where am I?
Location
West Jordan, UT
168k-ish, checked for leaks in manifold and didnt find any, the #6 plug looked like sh--, but that was before the ECU replacement and spark plugs too, now the #6 misfire is gone, its more of a general misfire
 
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Umm.. Where am I?
Location
West Jordan, UT
activated the egr with a vacuum pump and it kills the engine pretty quick, so i assume its working properly, can also hear it clicking back and forth. Did the brakleen vacuum leak check and found nothin too
 
Brett

Brett

Meat-Hippy
Location
Salt Lake City Utah
scramble this said:
Im gonna scope the crank sensor and see how it looks. Any one know the resistance scale for the coolant temp sensor or where to find it?
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I know one sensor is on the radiator, left side, but I think that's only for the fan to kick on. The other......on the block or the intake manifold??? I can't remember for sure :(
 
gijohn40

gijohn40

too poor to wheel... :(
Location
Layton, Utah
same troubles..

my 91 did about the same thing... it would missfire and sputter until it got up to about 3500 rpm and they take off... I checked the fuel pressure and it was 35 psi but its suppose to be 40... and when you rev it up it will drop 10 psi if you take the fuel regulator vacuum off....

The trouble was diagnosed by Hickey.... bad fuel pump... replaced it and it ran fine as can be... I still don't know how it would missfire from low fuel pressure but it did...

The coolant sensor is on the intake manifold near the back...
 
scramble this

scramble this

Umm.. Where am I?
Location
West Jordan, UT
Brett said:
I know one sensor is on the radiator, left side, but I think that's only for the fan to kick on. The other......on the block or the intake manifold??? I can't remember for sure :(
Click to expand...

gijohn40 said:
The coolant sensor is on the intake manifold near the back...
Click to expand...

Sorry, let me phrase that a little better, I know where the sensor is i am looking for the resistance scale (certain resistance readings at certain temps)so i can check to see if its reading properly, wondering if anyone has that or knows where to find it

I hooked the crank sensor to a scope last night and it seemed to be just fine, other than the wires being spliced at one point with wire nuts
 
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