Ok last week my XJ ran real smooth for 2 days didnt miss at all, then all of a sudden it has a rough idle again. Its almost like if I drive it normal for a few days it smooths out, then if I get on it or take it offroad or something like that is when it starts acting up again. So far I have replaced plug/wires, cap/rotor, cleaned pcv, cleaned throttle body, seafoam in brake booster vac/gas tank, removed catalytic converter. :banghead:
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Still have a rough idle
- Thread starter arsxj1
- Start date
magimerlin
NAXJA Forum User
- Location
- Flatonia, Tx
Year, motor, trans?
birchlakeXJ
NAXJA Forum User
- Location
- Melrose, MN
Any check engine light?
A rough idle can be related to dirty fuel injectors. A simple thing to try would be adding a bottle of quality fuel injector cleaner (Chevron/Techron, Lucas, etc) in about 3/4 of a tank of gas can sometimes help to optimize fuel injector spray pattern.
You should also perform a comprehensive search for a vacuum leaks. A vacuum leak is most noticeable at idle and can screw up your idle.
Verifying proper fuel pressure (with a fuel pressure gauge on the fuel rail) is never a bad idea as a matter of course.
A rough idle can be related to dirty fuel injectors. A simple thing to try would be adding a bottle of quality fuel injector cleaner (Chevron/Techron, Lucas, etc) in about 3/4 of a tank of gas can sometimes help to optimize fuel injector spray pattern.
You should also perform a comprehensive search for a vacuum leaks. A vacuum leak is most noticeable at idle and can screw up your idle.
Verifying proper fuel pressure (with a fuel pressure gauge on the fuel rail) is never a bad idea as a matter of course.
No check engine light. I have run 2 cans of seafoam and a bottle of stp injector cleaner through it added at 1/4 tank so it was strong and put 93 octane in it. I sprayed all the vac lines I could find with tb cleaner but never a change in idle. If it were a vac leak it wouldnt come and go right?
birchlakeXJ
NAXJA Forum User
- Location
- Melrose, MN
Expand your search for a vacuum issue. Hoses are always suspect but so are larger items like intake manifold, etc.
With things such as that, it can be heat related as heat causes expansion, so it can be symptomatic when cold, but then get better as the engine warms, which minimizes the loss of vacuum.
Finding a vacuum leak can sometimes be equated to finding the elusive "needle in a haystack". And if it is not a hose leaking vacuum but something else such as a gasket, worn throttle shaft, injector O-rings, etc., they can be difficult to isolate. That's where more comprehensive vacuum testing using vacuum gauges and exhaust gas analyzers can be helpful.
Last edited:
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Look--it only happens when you get on it or go off road.
Those activities have a couple things in common--things in the engine compartment are moving around. Torque and bouncing.
Look for poor ground contacts, look for burnt or bare wires making contact with metal.
Just for grins and giggles, what is the condition of your motor or trans mounts?
Those activities have a couple things in common--things in the engine compartment are moving around. Torque and bouncing.
Look for poor ground contacts, look for burnt or bare wires making contact with metal.
Just for grins and giggles, what is the condition of your motor or trans mounts?
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Electrical connections are buggers. Things can look good, be bad. Just go ahead and clean and re-tighten all of them.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Any electrical contact cleaner will work, but you want to disconnect those grounds and then make sure the metal of the connector and where it will attach is taken down to shiny metal--Dremel tool or sandpaper. Then use a corrosion inhibitor (any paint store) to keep things from, well, corroding, and then put it back together tight.
collkid
NAXJA Forum User
- Location
- Highlands Ranch, Colorado
Check to see if the wire from the TPS to the MAP is okay.
Mine was messed up had me Lost for about a year.
Mine was messed up had me Lost for about a year.
They seem ok. If I unplug the TPS it changes the way it runs and if I unplug the MAP it also changes the way it runs. That means there ok right?
