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sprinkles08
sprinkles08, Chrysler/Dodge/Jeep master tech
Category: Dodge
Satisfied Customers: 22394
Experience:  ASE Master and Advanced Certified, Chrysler/Dodge/Jeep Master Certified, Trans and Hybrid Specialist
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I have a 1999 Dodge 2500 Diesel. Intermittently when I come

Customer Question

I have a 1999 Dodge 2500 Diesel. Intermittently when I come to a stop it idles down to normal idle speed then it will up surge approx. 200 rpm for a few seconds then down to normal rpm. The next time I come to a stop it will idle down and remain constant. As I said it is very intermittent - several stops no problem then maybe one up surge then several good then maybe 2 or three up surges. REALLY annoying.
All fuel lines, lift pumps checked - all okay. Fuel filter replaced.
Whats up?
Submitted: 11 months ago.
Category: Dodge
Expert:  Chad Farhat replied 11 months ago.

Hi, I' m Chad. Welcome to JustAnswer. I' m reviewing your question now, and I will be post back with your reply ASAP

Expert:  Chad Farhat replied 11 months ago.

Do you have a check engine light on at this time ?

Has a Diagnostic scan been performed to retrieve any fault codes from the vehicle?

Customer: replied 11 months ago.
No check engine light and Diagnostic scan reveals NO codes
Expert:  Chad Farhat replied 11 months ago.

how many miles

Expert:  Chad Farhat replied 11 months ago.

if all that checked out okay and no codes

i would be looking into a vacuum leak

a good scanner can pull up live data for fuel trims , long term and short terms fuel trims , is it possible to get those values at idle , engine running

and let me know , you can post them back here and i will see them

Thank You ***** ( aka - Jhook1398 )

ASE Certified Tech

Customer: replied 11 months ago.
126,000 Km = approx. 78,000 miles
Also injection pump was replaced at approx. 50,000 miles as the lift pump had failed at that time the left pump was replaced and also an additional lift pump was added into the circuit with a pressure monitor - everything worked absolutely perfect until just recently
Customer: replied 11 months ago.
Firstly, where could there be a vacuum leak - I was not aware that there is any vacuum functions on the dieselSecondly I do not have a scanner that can pull live data - will try arrange this in a few days and get back to you
Expert:  Chad Farhat replied 11 months ago.

sorry my bad you do have a diesel , i had another 99 dodge truck gas got u mixed up .

I will opt out for a diesel expert for you .

Customer: replied 11 months ago.
Thanks
Expert:  sprinkles08 replied 11 months ago.

Hello and welcome to JustAnswer!

What you'll want to look at is the accelerator pedal position sensor. Voltage fluctuation can sometimes be too fast to see on a scan tool and is visible on a labscope, but if idle stays high for a few seconds then hopefully you'll be able to see it. I expect the APPS signal voltage is jumping up with the throttle closed either due to electrical noise on the circuit or (most likely) the sensor itself.

Customer: replied 11 months ago.
I have been doing alot of web searching for a solution and it appears that there may have also been a recall for my truck which I never received but the recall indicates the up idle surges may require a ECM flash.
I will try to confirm the recall with a dealer and give that a try first.
Will let you know of the outcome in a week or so - hard to get into a dealership easyily
Expert:  sprinkles08 replied 11 months ago.

There weren't any driveability related recalls but there were a handful of software updates over the years. It wouldn't be a bad idea to make sure the ECM and PCM software is up to date but it's not likely that a software issue would just start to present itself on a 17-18 year old vehicle.

Customer: replied 11 months ago.
Thanks
Expert:  sprinkles08 replied 11 months ago.

You're welcome!

Customer: replied 11 months ago.
Will keep you posted once I get the problem solved
Expert:  sprinkles08 replied 11 months ago.

Great!