synergy58

So, I have buttoned up the AC issue with the replacement of the electric fan, (Freon is good) replaced the belt and almost got the little chirp completely out with numerous turns on the idler adjusting bolt (still has a slight start-up squeak for a second or two).

I made several short runs around the house, shut it off, turned it on, ran it in place with AC on, about 10-15 minutes. Everything seamed good, no ruff idle. Hm?

Time for the real test, taking wife out for a Mother's Day run. We ran to a few different stores, out for a meal, drove around town, and then back home. Put on about 100 miles with several start and stops. AC on almost the entire time.

Not once did it have that previous ruff idle issue, not once! It ran perfectly!

There must be gremlins hiding in there just waiting for my wife to drive the Jeep by herself, thats when they'll appear and scare the heck out of her again.

Why does this thing have an intermittent ruff idle issue, with momentary loss of power, generally only after reaching operating temps?

I have wrapped injector #3 with that cotton swab tube thing, and wrapped aluminum tape (HVAC tape) around it to make sure it stays in place. I have peeked into every crevasse around the engine to see if anything looks out of place, but nothing (except some irritating oil leaks - working on this part).

Just can't figure it, but it sure was nice to have a great Mother's Day run!

Any ideas how to figure this out?

El_Guapo

Could very well have been an electrical gremlin hiding in there. On our later models they decided to save a few ounces of copper by underwiring things. Your electric fan amping up because of the bad bearing could have been causing a downstream effect in one of the engine management sensors.

Mine gave us fits for a couple of weeks without throwing a CEL, we eventually gave up and hooked it up to the Modis and found a microvoltage loss to the TPS. We ended up curing it by adding a new ground cable.

synergy58

Wow, a microvoltage loss could cause this? Not very reassuring considering that that could happen most anywhere. I just ran around for about 50 miles, stopped and started 6 times. It runs great, with a minor ruff idle at stop lights, nothing like the other day, and not at every stop. Someone recommended running a can of Sea Foam through the system, just to clean it up a bit. Not sure if thats a good idea or not.

I ran by a shop and they scanned it for me (FREE!) and came up with a code that refers to a vacuum line leak, which we saw nothing broken , lose, or out of place, can't find anything wrong; it could be just about anything. There was no CEL though.

What do you think of this Sea Foam, ever used it?

El_Guapo

Seafoam is one of the few "mechanic in a can" fixes that actually works. I usually just put it in the gas and don't bother with running it through the booster hose.

You can usually trace down a vacuum leak with a propane torch (unlit). Just turn the gas on and run along the vac lines and listen for a bump in RPM's (a tach is better, but less fun). A few good places to start are the brake booster grommet/elbow, the little ball gizmo behind the front bumper, and the pcv hard line/connector.

synergy58

Ok on the Sea Foam, going to run this through tomorrow. Now, as for the propane torch, you mean that the flow of propane along the lines will cause a bumping sound? Like what, a miss in the engine idle like sound? Hmm? ok, I can do this too. I have one of those yellow canned, electric ignition type propane torches I can use, if that counts.

As for the ball gizmo behind the bumper, I don;t see anything like that. I must be missing something?

Cheddarnut

He's saying that the propane will cause the engine rpms to go up when it gets sucked into the engine. I haven't done that before, so no actual experience personally. Also, FYI, yellow bottles are MAPP gas not propane. Burns hotter.

El_Guapo

The propane (or MAPP gas) will cause the rpm's to increase by 50-100 normally when you are in an area that has a leak.

The ball thing is a vacuum reservoir - on most late model XJ's it is a little bit right of center near the horns. There's molded rubber connectors on it that tend to degrade after 10 years or so. I've found that a little RTV tends to seal them right up with no ill effect.

synergy58

Ok, thanks. I use propane.

synergy58

Cool! I'll get a regular bottle of propane and use it. Search the lines for any leaks. Hope I don't hit something while the engines running. That always scares the crap out of me!

Going to service tranny and transfer case this afternoon. First time doing this.