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Low idle and very hot exhaust gas?

K

KaiserMan

NAXJA Forum User
Location
Huntington MA
See this thread for some back info.

http://www.naxja.org/forum/showthread.php?t=991708

I got the Jeep to run fairly decent, it was idling better (around the third mark on the tach which I'm guessing is 750). I just got back from a quick 4 mile or so trip (that involved a couple stops) and on teh way back it started to idle at the first mark (that I'm assumingis 250). It almost died facing downhill at a stop sign.

I opened the hood when I got home and check thigs out, nothing I could notice amiss, just the rough low idle. I stuck my hand at the end of the pipe (thought my intermittent miss might have been back) and the exhaust gas is so hot that I could not hold my hand there for more then a couple of seconds.

I've got no clue as to what is wrong with this thing. I can't figure out what could casue the ilde to be so low, it's not adjustable right?
 
I'm wondering, could the idle problem be the IAC? It starts ou finr at 750 or so then drops. Seems like the same peoblems IAC have caused in some of the posts I've been reading. I don't want to just start throwing money at it though.
 
So it only seems to be an issue when it's hot. I just moved the Jeep and it fired right up. RMPs revved to 1500, came back down to around 800. I'm letting it run to see if it drops once it warms up.
 
Okay, by the time the temp hit arond 160 (just over the first mark on the gauge) the idel was down to around 300RPM, but it was smoother then the last time. Gases out of the tail pipe where not burning hot either.
 
Can you just bypass it? I've read a ton of threads and it sounds loke it may be the IAC. I'm going to clean it tomorrow and see if it makes a differance.

I'll poke around at the EGR as well. Can it be taken apart or would it just have to be replaced?
 
I would start by checking the most obvious things. Basic electrical is a good place to start. Check your grounds. Mainly engine and computer grounds. I know, I thought the same thing too when I heard that. The grounds are more important than one might think. Jeeps are not very tolerant of lousy grounds.

Could be a bad CPS. They often go bad with little or no warning.

Check your Dist cap and rotor. If they have lousy connections you wont get as good of spark. Might check the coil too. Not exactly sure what it should read but grab a voltmeter thingy.

As for sticking your hand behind the exhaust pipe....:dunce:

When it gets properly heated up or stays running for a while the exhaust is probably gonna be hot regardless. Seeing how hot exhaust gas is with your hand is almost never a good idea. I bet I know your reaction the first time you stuck your hand behind it.... :soapbox:
 
I dont' know, I've never felt exhaust gases ge that hot, but then again I've never owned anything with a cat. Maybe that has something to do with it?

Is everything grounded off one or two spots, or am I going to be chasing 10 or 20 individual grounds?

Rotor and cap are new, coil is old. I have a spare somewhere that is suppsoed to be new I could toss in.
 
KaiserMan said:
Is everything grounded off one or two spots, or am I going to be chasing 10 or 20 individual grounds?

Rotor and cap are new, coil is old. I have a spare somewhere that is suppsoed to be new I could toss in.
Click to expand...


I believe there just grounded once. I know the engine and battery cable is.

I would throw in that other coil before spending a load of green.
 
There is a "base idle" screw adjustment, takes a 3/32 allen.
 
actually my renix jeep does similar but its directly related to octane.

on 93 it just purrs and idles at about 400 rpm
on 91 it idles a bit higher but is acceptable
on 87 it idles at 1400 rpm and really is annnoying.
 
99_XJ_ said:
As for sticking your hand behind the exhaust pipe....:dunce:
Click to expand...
My exhaust isnt that hot....

Disconnect the vacuum line from EGR...make sure to plug up the open end with something. If that fixes your problem, get a new EGR or make a block off plate and get rid of it.
 
KaiserMan said:
Okay, by the time the temp hit arond 160 (just over the first mark on the gauge) the idel was down to around 300RPM, but it was smoother then the last time. Gases out of the tail pipe where not burning hot either.
Click to expand...
A clogged cat will continue to heat up as the Jeep is on...How long did you let it warm up?? I have seen clogged cats glowing red under cars before and yes the exaust gas was very hot...
 
jeepman121 said:
A clogged cat will continue to heat up as the Jeep is on...How long did you let it warm up?? I have seen clogged cats glowing red under cars before and yes the exaust gas was very hot...
Click to expand...

Only aobut 15 minutes, I was more concerened about figureing out my idle issue. I plan on cutting my cat out since I don't need emissions, so if that is the issue I'll find out pretty quickly.

It looks like someone has been at my idle adjusting scew before, it's kind of buggered. I snapped a clip (ine lue of posssibly snapping the adjusting scew) onto the throttle cable tab (that rides agaist the adjusting screw) and new it idles around 780 even when hot, but idles at 1200 in park or reverse.

I'll be cleaning teh IAC and EGR today.
 
Well I cleaned the IAC up. It was caked in a good 1/16" layer of carbon all teh way around. Used about 10 q-tips cleaning the it's port in the TB. And I put in the new coil. The old one was pretty ratty looking, and the plastic on the bottom (loks like the back side of a circuit board maybe?) was cracked in a few places. The Jeep fired right up, idle went to about 1800, then dropped to 1000, then dropped to around 750 and has been hovering there for the last 10 minutes. It dips down to around 700 in reverse.

I'm going to let it warm up for bit and see what happens.

I forgot that I had let my friend borrow my torx bit sockets and I can't get a srew driver in there, so I didn't take the EGR out. I'll try disconnecting the line if my idle drops when the Jeep is good and warm.
 
up to about 180 and it's back down to around 450 RPMS. Seems to idel fine at that though, and it has not dipped lower. Tried pinching the vac. line for the EGR and nothing changed. I', going to try leaving it like this. I'll keep my clip with me in case I need it.
 
Okay, one last poet for now. I found a better clip to put on the tab that sits against the throttle stop. Now it idles just uner 1000rpms in park or revearse and just a hair over 750rpms in all other gears. It does shoot to 2K rpms when first started. I can live with this.
 
KaiserMan said:
Okay, one last poet for now. I found a better clip to put on the tab that sits against the throttle stop. Now it idles just uner 1000rpms in park or revearse and just a hair over 750rpms in all other gears. It does shoot to 2K rpms when first started. I can live with this.
Click to expand...

I think the best idle for an auto is about 700 to 750 RPM in Drive. You need to have a second person sit in the driver's seat and hold their foot on the brake with the vehicle in Drive while you adjust.

DO NOT TRUST THE PARK BRAKE OR WHEEL CHOCKS. To many people injure themselves doing it that way--they usually forget and give the throttle a good twist with their hand and run themselves over.
 
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