Topic: Jeep Idle question..

[somthinwicked]

This question probably will seem short because i really don't know much about what I am asking, so if you do know any things that can help me please don't be shy.

When I brake my jeep doesn't always idle... most of the time the tac goes up to 2000rpm. Just curious but is this a bad thing? And if it is what should I have done?



Much thanks, Ian Pline

[flyingbrick]

OK i think we'll need more info then that, first what does you jeep idle at in Park or neutral? Does it fast idle up to 2000 when you press the breaks or all the time? From the information you gave I'm thinking vacuum leak in the booster.

[jrollings]

vacuum leak was first thing that jumped into my mind as well. hook up a guage and you want a reading b/w 15-22.

[somthinwicked]

I'm glad people are willing to help me, I am going to gather more info. thanks.

I searched for this vacumm booster issues for wrangler...

came up with this...


""
Recall Summary
VEHICLE DESCRIPTION: MULTI-PURPOSE PASSENGER VEHICLES. THE POWER BRAKE BOOSTER VACUUM RESERVOIR DIAPHRAGM CAN SPLIT OR TEAR.

 
Consequence
THIS CAN CAUSE AN INCREASE IN ENGINE IDLE SPEED AND A LOSS OF POWER ASSIST DURING BRAKE APPLICATION WITHOUT PRIOR WARNING.

 
Remedy
DEALERS WILL INSPECT THE BRAKE BOOSTER DATE CODE AND ANY BOOSTERS WITH THE SUSPECT MANUFACTURING DATE RANGE WILL BE REPLACED.

 
Notes
CHRYSLER CORPORATION  ""

[flyingbrick]

I'm glad people are willing to help me, I am going to gather more info. thanks.
I searched for this vacumm booster issues for wrangler...
came up with this...
""
Recall Summary
VEHICLE DESCRIPTION: MULTI-PURPOSE PASSENGER VEHICLES. THE POWER BRAKE BOOSTER VACUUM RESERVOIR DIAPHRAGM CAN SPLIT OR TEAR.
Consequence
THIS CAN CAUSE AN INCREASE IN ENGINE IDLE SPEED AND A LOSS OF POWER ASSIST DURING BRAKE APPLICATION WITHOUT PRIOR WARNING.
Remedy
DEALERS WILL INSPECT THE BRAKE BOOSTER DATE CODE AND ANY BOOSTERS WITH THE SUSPECT MANUFACTURING DATE RANGE WILL BE REPLACED.
Notes
CHRYSLER CORPORATION  ""

Most everyone likes to help out round here, but there you go call up a dealership tomorrow and see if they'll look at it for free. Hope it all works out for ya.

[jfrabat]

Before you go around hunting for vacuum leaks, let me ask you something; is this idle issue happening after you drive in the highway, and then levels off all by itself?  In my case, when I am driving in the highway for some time, and I get off on the exit ramp and come to a stop on the stop light, my idle is a little high (not as much as you, but around 1,500 rpm's), and it takes the Jeep a couple of seconds to come back down to normal (ussually about 10 to 15 seconds).  I have heard that this is normal...

[somthinwicked]

Before you go around hunting for vacuum leaks, let me ask you something; is this idle issue happening after you drive in the highway, and then levels off all by itself?  In my case, when I am driving in the highway for some time, and I get off on the exit ramp and come to a stop on the stop light, my idle is a little high (not as much as you, but around 1,500 rpm's), and it takes the Jeep a couple of seconds to come back down to normal (ussually about 10 to 15 seconds).  I have heard that this is normal...

I do get on the highway to go to school, but barely on it for more than a few minutes as the school i go to is just on the other side of the highway. I reach a speed of 70 for about a minute then back down to the speeds of 40-45 for the rest of the drive. When I stop in the parking lot my engine roars up to 2000rpms.. somtimes for more than 10 seconds... I remember going through a burgerking and it was still in the 2000rpm range when i was trying to make my order.

[jfrabat]

I do get on the highway to go to school, but barely on it for more than a few minutes as the school i go to is just on the other side of the highway. I reach a speed of 70 for about a minute then back down to the speeds of 40-45 for the rest of the drive. When I stop in the parking lot my engine roars up to 2000rpms.. somtimes for more than 10 seconds... I remember going through a burgerking and it was still in the 2000rpm range when i was trying to make my order.

In that case, I would take a look at your vacuum lines and connectors.  In my case, I replaced all of them because they looked like they were about to crack at any moment, so even though my vacuum was good, I decided to replace the lines anyway as a preventive measure.  But measuring the vacuum is also easy, and I recommend you start there...

[Mr_Random]

Mine is so screwy, it does something similar, but it's all over the place! I'm thinking the ECU is shot, I can't begin to explain how weird it is... or maybe I will begin, but won't say everything...

First off, sorry if I hijack your thread. When cool, my idle can either be low and stumbly (800 RPM's), or super high (2000), when I disengage the clutch, it can either idle to 2000, or sit around 1500. The most common place, it seems, is 1500, but it's still all over the place!

Would it be sensors, or the ECU? The MAP and O2 sensors work for sure, which one's should I check, and how can I check them? I'm pretty sure I don't have any vac leaks, I replaced quite a few of the lines, but I'm still unsure about the vac canister itself... hum...

This may also be relevant to other people with high idle problems.

[jfrabat]

The only real way to be sure you do not have a vacuum leak (and I recommend this before going out and buying a bunch of sensors) is to do a vacuum test.  The gauge you can get at any auto parts store, and they ussually come with the instructions.  Hook it up, and check the vacuum at idle, and with the engine running at higher RPMs.  I dont remember what the readings needed to be, but I am sure you can find them online...

As far as sensors (and, again, I would check the vacuum first!), you could have a problem with the IAS, but it sounds more like a vacuum problem (or maybe a loose TB) than a problem with a sensor to me.

[somthinwicked]

Well, I wen't to AutoZone to get them to hook up the Diagnostic Code reader thingy. Here's how it went:

"
Advance Auto Parts


Vehicle Scanned
1998 Wrangler
P=2.5L SFI



Codes



ENG:  33/-----
Low Engine Temp



ENG:  40/-----
IGN Reference
Signal



ENG:  138/P1294
Idle Speed
Performance



Temporary Codes



System Pass:
No Faults Detected."



---------------------------------------

I hope this will help.

[Bounty Hunter]

33* An open or shorted condition detected in the A/C clutch relay circuit.

P1294 (M)  Target Idle Not Reached
 Target RPM not achieved during drive idle condition. Possible vacuum leak or IAC (AIS) lost steps.
 

Didn't see anything on 40, but from what you posted that could be as simple as the battery being disconnected recently.

33 is normal for a non-AC vehicle.

As for the P1294, either a vacuum leak or a bad IAC (idle air control) motor.  It's mounted to the side of the throttle body.

[somthinwicked]

33* An open or shorted condition detected in the A/C clutch relay circuit.

P1294 (M)  Target Idle Not Reached
 Target RPM not achieved during drive idle condition. Possible vacuum leak or IAC (AIS) lost steps.
 

Didn't see anything on 40, but from what you posted that could be as simple as the battery being disconnected recently.

33 is normal for a non-AC vehicle.

As for the P1294, either a vacuum leak or a bad IAC (idle air control) motor.  It's mounted to the side of the throttle body.




Thankyou, any other suggestions?

[aw12345]

Idle goes up when hitting the brakes means vacuum leak in booster. Pinch the vacuum hose going to the big round can behind the brake master cylinder while its idling use vise grips or hose pinchers. step on the brakes idle doesn't go up any more booster is bad. Preferably do not try this driving.

[somthinwicked]

I do not currently have a mechanic, And I really don't know how to go about finding a jeep mechanic..