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Sputtering XJ

A

argalaviz

NAXJA Member #1248
Location
Centralia, WA
While wheeling yesterday my XJ started running like crap. Sputtering and hesitating. I'm getting a gasoline smell at the exhaust pipe.

I changed the cap, rotor, plugs and wires today and there is no change in the behavior.

Could I have an injector stuck open? Does that even happen?

It's idling fine.

1990 XJ 4.0
 
Sounds like you're getting spark. Could you fuel pump be the problem? Check the pressure at the fuel rail. Fuel filter old/clogged?
 
I checked the air filter yesterday too, and it was soaked in oil. Is it possible it sucked oil into the intake to the point the fuel injectors are affected?

The MAP sensor tested out within range and the vacuum hoses are firmly attached.

Thanks for the tips so far.
 
Spray some carb cleaner or other type of spray around all the vac connections and listen for an engine pitch change, that should locate any other vac leaks.
Check the O2 sensor to make sure it did not get unplugged or broken while wheeling.
Check your gas tank and make sure you did not land on something, seen them get punched up in the center where the pickup is and do some weird things not to mention they take 3 gallons less fuel.
If your air filter is full of oil then you need to clean/replace the vac lines that go from the back of the valve cover CCV to the air box and the one in the front too. You can clean them but the dealer has a kit for doing this. You are going to have to pull your valve cover and clean that out too.
 
I think the oil soaked air filter could be the blame for running rich too. If you plug the filter, the engine will suck a lot of fuel.
 
I checked the compression and it was 149, 150, 149.5, 150, 150, and 120.

So one lower reading that is still in spec.

I bought some Mustang injectors off Ebay and will try those.

Thanks for all the help guys!
 
You might try replacing the fuel pressure regulator, you can check to see if you have a leaky injector with a fuel pressure gauge. fuel pressure should be around 35# when you turn the key on (turns on the fuel pump). when you turn the key back off, pressure should stay for at least 5 min. if it drops before then, you have a leakey injector. pull your spark plugs, the one with the most carbon build-up is the culprit.
 
logdog said:
You might try replacing the fuel pressure regulator, you can check to see if you have a leaky injector with a fuel pressure gauge. fuel pressure should be around 35# when you turn the key on (turns on the fuel pump). when you turn the key back off, pressure should stay for at least 5 min. if it drops before then, you have a leakey injector. pull your spark plugs, the one with the most carbon build-up is the culprit.
Click to expand...


4 of the 6 plugs are covered in carbon. I'll rent a fuel presure guage and check tomorrow.

Hopefully this is it!
 
Was just reading your post about your XJ sputtering, my wifes is doing the same thing, did you get it fixed ? What was it ?


Thanks
 
JCWjeeper said:
Was just reading your post about your XJ sputtering, my wifes is doing the same thing, did you get it fixed ? What was it ?


Thanks
Click to expand...
Dude... you shouldnt talk about your wife that way...err...I mean her jeep. Mine was doing the same thing, I replaced two leaky fuel injectors, bye bye problem.
 
the oil in your air filter has nothing ti do with your sputtering, it is caused by blow by and guess what.... we all have that problem, so don't wory about that.
 
It's beyond mere sputtering. It acts like the timing is off. Is there a test for the camshaft position sensor? Or is a buy one and put it in to see if that was the issue kind of deal?
 
My money is on low fuel pressure, because your symptoms sounds similar to
a very recent experience I had.

2 days ago, I swapped out a leaky fuel pump on my 4.0L XJ for one that I got
from a local wrecker.

Once installed, I tested the fuel pressure from the new (used) pump and it
read below spec. 24-26 psi (vs 31 psi).

Disconnecting the vacuum hose from the Fuel Pressure Regulator did not
show an increase in pressure. Ordinarily, this would indicate a bad regulator
but since this happened just after swapping the fuel pump I dismissed this.

The car idled great and I could roll it out of the driveway - but once I tried
to get under way the engine would sputter, stall, and pop out the exhaust.

I ended up fixing the leaks on the original pump and reinstalled it.
Pressure is back up to spec. Pressure Regulator is OK. No leaks.
Car runs great again.

After drying things off, I took the new (used) pump and clamped it on a vise,
then gave it a couple of short bursts of 12V DC. The motor whirred ever-so
slowly and sluggishly. Lesson learned.
 
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