Idle problem still..

[Baddmove]

so, i bought this 86 XJ a month ago and after a couple of days it started to rev up to 2000-2500 rpm every time i started it, sometimes up past 3000 rpm. so i just installed a new IAC and no changes, i have looked all over for a vacuum leak and can't find one. i also put on a new TPS and had the Jeep guys here in town set it to factory settings...it does it every time, not just sometimes but every time, any ideas guys and gals what i can do or should look for? it is making me crazier than i already am....Thanks...BM:banghead:

[4.3LXJ]

I'm confused. The 4.oL did not come in an 86. Is this a conversion?

[Baddmove]

yes, the Jeep guys said a 4.0 was installed at some time. The tag under the hood says it has a 4 cylinder. It started just fine when i bought it, then BAM! it started to do this high rev at start up..

[Mudderoy]

yes, the Jeep guys said a 4.0 was installed at some time. The tag under the hood says it has a 4 cylinder. It started just fine when i bought it, then BAM! it started to do this high rev at start up..

TPS would be one possible sensor issue. I'm assuming all the 4.0 engines have them, I only have ever worked on 97+ models.

[Baddmove]

New TPS also, i edited my post...

[Mudderoy]

New TPS also, i edited my post...

There is a common issue with 97+ 4.0's where the harness rubs on the fuel rail near the firewall. It randomly grounds out a wire (after rubbing through the insulation) and causes the same issue as a bad TPS.

This happened to me, so I pulled the harness up and off the fuel rail with a nylon tie wrap.

[4.3LXJ]

What year engine? Renix or OBDI? Surely not OBDII.

[bigbuk29]

almost sounds like it could be a hidden vacum leak. I know this is gonna sound crazy, but I was having all kinds of idle issues with mine, finally gave in and took it to a shop. It ended up being a hole in my brake booster. That was the last thing i would have thought to check cause the brakes were working okay.

[Baddmove]

OK..i went out this morning and started my jeep up..same problem but this time i was looking at the brake booster, then i noticed a small black hose going into the throttle body, so i poked at it with my finger and the idle dropped hard and fast..i looked at the MAP sensor and that little black hose has an adapter on it which looks like it is kinked...so i poked at that little hose again and idle dropped again...could that be my problem? something wrong with that little hose? if so, where do i get another piece of hose like that? it also just goes into the throttle body with no adapter, just looks like it goes in...i will take some pics so you all can see what i am talking about...

[Baddmove]

you can see the kink in the hose in the first pic..

http://i269.photobucket.com/albums/jj55/baddmove/jeep123.gif

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232

that is the little black hose and a pic of my motor, cause it is not the 4 cyclinder, it is a 4.0l..
sorry i don't know how to make pics easier to see..maybe a mod can fix them???

[bigbuk29]

If you are talking about the hose going into the booster in the picture, that could be it not supposed to be kinked like that

[4.3LXJ]

Bob, an easy way to manage pics is to use an image hosting service like photobucket. This works well especially if you are on more than one forum. One of the nice things about it is that you can set preferences to screen size. Most of us use the 15" screen size, meaning it will fill most of a 15" screen which is a nice size. And it is free

[Baddmove]

thanks, i will figure out photo bucket..lol.. anyway, so i went out and took the little black hose off and cleaned out where it goes into the TB, there was a hole/split in it at the TB..I took off the part where it was kinked and shortened it about 1 inch, seem to fit better and not so stressed, idle is a bit better, makes me wonder if i need a new MAP sensor, wife says it's a money pit and should just push it off a cliff...

[4.3LXJ]

So what do wives know anyway? :D

[bigbuk29]

thanks, i will figure out photo bucket..lol.. anyway, so i went out and took the little black hose off and cleaned out where it goes into the TB, there was a hole/split in it at the TB..I took off the part where it was kinked and shortened it about 1 inch, seem to fit better and not so stressed, idle is a bit better, makes me wonder if i need a new MAP sensor, wife says it's a money pit and should just push it off a cliff...

My girlfriend used to say mine was a money pit, until I did a tuneup on Lincoln Navigator and spent almost as much as I did on my intial lift kit. She stopped saying that after I showed her 400.00 dollars in receipts for a tuneup:smiley-laughing021:

[defibvt]

When I bought my 93 I had the same issue. I will be looking into it as soon as the temp drops below 90 consistently. I figure a year putting up with it is long enough. LOL.

[Baddmove]

yea well, i still have the rev up problem at start up, there must be something i am missing...c'mon guys, i need help here, my idle fluctuates so badd and still jumps up real high at start up..

[4.3LXJ]

How high at start?

[Baddmove]

How high at start?

anywhere from 2000-3000 rpm, mostly between 2000-2500

[4.3LXJ]

That can be normal. The IAC is all the way open at startup and then closes down afterwards to reduce the rpms to idle speed. The problem is if it stays that high.

[Baddmove]

Nah. that aint normal...lol.. it also surges a lot when idling, it never just purrs at idle, always fluctuates, I just can't seem to figure it out. I might have to take it to a shop and that sux...

[bgreed]

So did you ever take your jeep to the dealer? Did they come up with an answer?

[Showtime3492]

being that its an older jeep could it be a fuel pressure problem?

[Baddmove]

Actually, it was my brake booster all this time. It had a vacuum leak inside of it..go figure.

[oderdene]

Actually, it was my brake booster all this time. It had a vacuum leak inside of it..go figure.

mine too, hissing if brake pedal pressed. what is your mpg? I got 8.7mpg :(

[4.3LXJ]

What are you doing Od, dumping fuel down the manifold? Or is the gas different in Mongolia?

[oderdene]

What are you doing Od, dumping fuel down the manifold? Or is the gas different in Mongolia?

:D I had this since I got the jeep, last 3 years gas became worse, everybody claims about it. even 2.5 toyota engine drinks ~20-25l per 100km :(. Winter is very cold here, sometimes temp drops down to -40F night, -22F daytime. We start engine this cold and need a long idling till warm up. Even after coolant temp increase I still have cold and almost frozen ATF, diff fluid etc :D

I've replaced exhaust manifold (it was cracked), installed remanufactured 4 hole injector, air filter (mitsubishi delica 2.8 TD), fuel filter, spark plugs, wires, rotor, cap, installed oil catch can, O2 sensor, replaced PCM capacitors, valve cover gasket etc. Everything seems good except brake pedal activated hissing sound and too lean O2 reading.

Summer I got 11mpg city, 15mpg highway (const 80-90 kmph)

just above 320k km (200k mile) my beauty is still doing good, sometimes i felt a bit of lack of power.

she drinks 92 octane gas, tried 95 octane & euro 4 92 octane, no difference.

[4.3LXJ]

I don't know what to say Od. And we complain here about ethanol in our gas. :D

[ALS XJ]

Well, if we're still talking idle issues...My '92 has a real issue lately. Starts up just fine, then...after about 1-2 minutes into idle, she revs to 1200-1500rpm, then down to about 500rpms. I've removed, cleaned the TB, istalled a new gasket, tried to clean, then replaced the IAC...still no improvement. When I take it out on the road, I can feel the idle doing the same thing. :banghead: Anybody else run into this problem...tired of throwing parts at it, without any real direction....Some help...anybody??????:sign0181:

[4.3LXJ]

Just for giggles, pull your battery cables touch them together, reinstall and start it up and see what happens