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Misfire after acceleration...

JBurian

NAXJA Forum User
Location
Moscow, PA
This seems like a weird problem. I have a 94 Cherokee Sport with 4.0L HO, currently has 248,000 miles and for the most part runs great. If I drive normally and keep my foot "off the gas", everything is fine, but if I accelerate hard pulling out into traffic or off-road, I get a misfire that has the engine shaking side to side and a very distinct exhaust note like a stutter. I have to heavy foot it again, sometimes more than once to get it back to normal, then it runs fine again. Coil, plugs, plug wires, distributor cap and rotor all changed. It seems like it may be the #1 cylinder, when I pull the plug wire to that cylinder there is no change in the way the engine runs, but there is spark. Could getting on the gas cause a problem with fuel delivery through the injectors. I remember reading on a forum a while back that #1 injector has a tendency to clog. Does anyone have any experience with this type of problem and possible solutions? I run Seafoam through it on a fairly regular basis and this seems to help keep it running well. I should mention that the misfire has happens since I got the Jeep and before I started treating the engine with Seaform. Thanks guys. I figure if anyone can help, it's the members of NAXJA.

Jeff
 
A long shot is a clogged fuel filter causing a drop in fuel pressure when you try and use a larger amount of fuel. You can verify this with a fuel pressure gauge.

For cleaning injectors, I prefer BG44K. I think it runs circles around Seafoam.
 
Thanks for the info. I did change the fuel filter several months ago, but changing it again may be worth while. The acceleration is great, the misfire is only really apparent at or near idle. I'll give the BG44K a try. Thanks again.

Jeff
 
Last edited:
The first thing I would do is to check the compression on all the cylinders. You DO have a few miles on this faithful beast. #1 may have low compression from valves, rings, or head gasket. No point in wasting time and money on external parts if this is your problem. Reportedly, XJ's have run on as low as 80PSI, the the standard is 120-150PSI.

Next step would be to swap the #1 injector with a different one (like switch between 1 and 3 or 1 and 4 and see if the problem moves with the injector. Hopefully this is the case.
 
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