Rough Idle

You know its interesting that i have had a similar overheating issues through out this problem. My idle never casues the engine to actually die out like your does "themj", but it casues a small surge during idle especially when the engine becomes up to temp. The surge is felt when at a stop light or something every 3-5 sec i get a small little noise/vibe. This issue doesnt cause any issues when i am up to speed just idle regardless of gear. THe vacuum lines have been tested with a gauge and fixed (canister was cracked and replaced), with no improvement in idle.

Pete
 
I know this is gonna sound lame....but if I run anything other than Mobile Preminum gasoline my XJ runs like crap...Had a similar situation except mine would only do it if my tank would go below the quarter mark....not run outta gas but just below the mark...gofigger
 
jeepsrock said:
You know its interesting that i have had a similar overheating issues through out this problem. My idle never casues the engine to actually die out like your does "themj", but it casues a small surge during idle especially when the engine becomes up to temp. The surge is felt when at a stop light or something every 3-5 sec i get a small little noise/vibe. This issue doesnt cause any issues when i am up to speed just idle regardless of gear. THe vacuum lines have been tested with a gauge and fixed (canister was cracked and replaced), with no improvement in idle.

Pete
Click to expand...
Check your fuel pressure, borderline low fuel pressure or a defective regulator will cause those symptoms.
 
old_man said:
The absolute best fuel system cleaner is BG44K. It runs around $20 a can. The other stuff can't hold a candle to it.
Click to expand...

Where could I find BG44K on Sunday? Just called Autozone and they don't carry it. Napa is closed on Sundays. :( Doubtful if Wal-mart has it either.
 
There is a schrader valve on the front of the fuel rail. I've read the best way to test it is a set of gauges from an AC hose. I tested mine using a cheap dial tire pressure guage. It was like $4 at advance auto. I figure the seals are probably shot how, but it served it's purpose.
 
langer1 said:
I would be careful with that, carb cleaner's so flammable and the hot exhaust is right there too.
Click to expand...
I just read in a magazine today about a cool way to check for vacuum leaks.You use an unlit propane torch near a vac line and if it's leaky it will inhale the propane and cause the engine to rev up slightly.
 
I havnt had time to test the fuel pressure with a test gauge yet but i guess i should say an observation i made over the last few days. When i stop at a stop sign or signal and i feel the rough idle kinda toward the back of the jeep if i look real close at the tach i can see it fluctuate in really really small amounts is this normal ?

pete
 
I'd say to do the Seafoam treatment through the throttle bottle twice. The 1st time I did it, it didn't smoke. The 2nd time it put on a great show, and made a huge difference in running smoother. Pour a 1/2 bottle in the gas with only a few gallons to clean the injectors too. This was the only thing that improved my idle. After going through all the tune-up steps you did, aside from a few sensors. Don't remember if you mentioned cleaning out the TB and pull out the 2 sensors and clean them too. I notice that the Jeep is very sensitive to where you get your gas. It runs better on some tanks than others. Replace the fuel filter AFTER you do the Seafoam too. Otherwise it could clog the filter.
 
My rough idle problem turned out to be a bad fuel pump. My pressure was around 38-39, and it should have been 51 +- 2, according to the service manual. A new fuel pump put the pressure up to 52 or 53, IIRC, and it only cost me another $550.00 or so, for the second time in less than 2 years. :( Also, the faulty fuel pump was pumping air bubbles into the fuel rail.
 
My idle isnt rough, but it isnt constant either, moves slightly up and down, but smoothly and doesnt jerk... Variations is as much as 250 rpm between stoplights though, can idle low (around 550-600) at one stop, then next time I stop it can be as high as 850.

Bothers me a little, but I cant seem to find the culprit.
 
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