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sprinkles08
sprinkles08, ASE Certified Technician
Category: Jeep
Satisfied Customers: 21572
Experience:  Chrysler/Dodge/Jeep Master Certified, ASE Master and Advanced Certified, Trans and Hybrid Specialist
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Tj: I have an 06 jeep tj that runs fine but after warmed up

Customer Question

I have an 06 jeep tj that runs fine but after warmed up when you stop at a light it reves up high the almost quits ....I've changes the cps and tps..and put a new aic in it
Submitted: 7 months ago.
Category: Jeep
Expert:  sprinkles08 replied 7 months ago.
Hello and welcome to JustAnswer!An idle fluctuation as you've described is very often caused by erratic throttle position sensor signal voltage. You may have a connection issue at the sensor or a wiring issue causing voltage fluctuation.The first step in diagnosing the problem is to see if any fault codes are setting. Have you checked for codes?
Customer: replied 7 months ago.
Yeah there are no codes and I changed the tps about 3 months ago when it started doing it and the cps
Expert:  sprinkles08 replied 7 months ago.
If you wiggle test the connector with the engine running does idle speed change?
Customer: replied 7 months ago.
I will check that when I get off work in the morning
Expert:  sprinkles08 replied 7 months ago.
Ok.
Customer: replied 7 months ago.
I wiggled the connector while running but no change in idle
Expert:  sprinkles08 replied 7 months ago.
Did the problem start after any work was done?
Customer: replied 7 months ago.
It did start around the time the alternator was changed
Expert:  sprinkles08 replied 7 months ago.
It's probably not related but can you try unplugging the alternator field connector and see if the problem goes away?
Customer: replied 7 months ago.
Where's that located
Expert:  sprinkles08 replied 7 months ago.
On the back of the alternator.
Customer: replied 7 months ago.
There's that one plug ...I'll unplug it and when I drive it to work I'll see if it still does it....it only does after warming up then only when stopped
Expert:  sprinkles08 replied 7 months ago.
That's the correct connector. As long as the battery is good you'll have some time to run it with the alternator unplugged.
Customer: replied 7 months ago.
Someone said if the battery is bad it would do that too with the idling
Expert:  sprinkles08 replied 7 months ago.
There is very little chance of the battery causing an idle fluctuation.
Customer: replied 7 months ago.
I drove it to work with that unplugged and let it idle and it was still doing it
Expert:  sprinkles08 replied 7 months ago.
How high is it fluctuating?
Customer: replied 7 months ago.
It normally idles a little below 1000 and then jumps to about 2000 when your stopped then drops to almost dying after it jumps
Expert:  sprinkles08 replied 7 months ago.
How did you check for codes?
Customer: replied 7 months ago.
A friend of mine has a code reader and I took it to a local shop just to see and they said nothing was showing up ...the put a new cps in after I put a new one in a few weeks earlier
Expert:  sprinkles08 replied 7 months ago.
Do you have a voltmeter?
Customer: replied 7 months ago.
Yes I do
Expert:  sprinkles08 replied 7 months ago.
Can you monitor the voltage on the orange/dark blue wire while idle is fluctuating and see if the voltage is steady or moving?
Customer: replied 7 months ago.
On the tps or alternator
Expert:  sprinkles08 replied 7 months ago.
The TPS.
Customer: replied 7 months ago.
I'll try that out soon as I get home
Expert:  sprinkles08 replied 7 months ago.
Great!
Customer: replied 7 months ago.
Hey sorry my mom got put in the hospital yesterday and I was there all day....I'm going to test it in the morning after work
Expert:  sprinkles08 replied 7 months ago.
No problem. I hope everything goes well with your mom, respond whenever you're able to.
Customer: replied 7 months ago.
I've tried testing it but it only does while driving then stopping....if I let it idle just sitting it doesn't do i t
Expert:  sprinkles08 replied 7 months ago.
The alternative is going to be a scan tool to monitor data.
Customer: replied 7 months ago.
Like at a shop type scan tool
Expert:  sprinkles08 replied 7 months ago.
You may be able to borrow or rent one at a big chain parts store such as AutoZone. You may not be able to effectively diagnose the problem without the ability to monitor data if no fault codes are setting.
Do you have a manual or automatic transmission?
Customer: replied 7 months ago.
It's a manual transmission.. Is it the same thing as a code reader ?
Expert:  sprinkles08 replied 7 months ago.
A scan tool is a multi thousand dollar tool capable of monitoring data and performing actuator tests. A code reader is just capable of reading fault codes.
Customer: replied 7 months ago.
That should identify the problem or what should I look for
Expert:  sprinkles08 replied 7 months ago.
It's still up to the user to analyze the data seen.The first thing that I would look at is throttle position sensor voltage and see if it is fluctuating when this happens.
Customer: replied 7 months ago.
If this is the case what will have to be replaced...I'm heading to advanced auto now to have it checked
Expert:  sprinkles08 replied 7 months ago.
What needs to be replaced will depend on testing results. If the TPS voltage is erratic then you have a sensor or wiring issue and testing of the sensor and wiring will be necessary.
Customer: replied 7 months ago.
The guy yesterday hooked it up and was basically guessing he said it could be a fuel pressure sensor or reflash my computer or another sensor that controls when the engine is over load
Expert:  sprinkles08 replied 7 months ago.
You don't have a fuel pressure sensor and it's quite unlikely for a software issue to present itself at this age.Was the TPS signal monitored while the idle was fluctuating?
Customer: replied 7 months ago.
Yeah he said it wasn't fluctuating while the idle was that's when he started guessing
Expert:  sprinkles08 replied 7 months ago.
Was the IAC step count raising when the idle was?
Customer: replied 7 months ago.
He didn't say if it was raising but said the IAC was normal and the cps was fine both I've had changed recently
Expert:  sprinkles08 replied 7 months ago.
If the IAC step count wasn't raising but the idle was then a vacuum leak is very likely, if the air wasn't coming through the IAC and the TPS was showing the throttle closed and steady it had to be running off unaccounted for air.
Customer: replied 7 months ago.
How would be the best way to look for a vacuum leak
Expert:  sprinkles08 replied 7 months ago.
The easiest way would be to spray suspected leak areas with carb cleaner with the engine running and cold. If the idle changes when spraying an area then youve found a leakm

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