Urgent: Recently my truck has started to have an idle issue, every time I would start slowing down to a stop it would bog down, the rpm’s decrease to 250-300 and when I would give it gas it would sputter and back fire…a lot, and feel like it’s about to stall. It could be so many different issues so I just need some advice, anything is appreciated.

 

What type of maintenance has been done already on your motor recently? After reading your symptoms, the first thing I'd suggest is removing your Idle Air Control (IAC) unit from the rear of your throttle body and cleaning out the rear passage the IAC plugs into, as it tends to accumulate carbon deposits in that well. Once that's cleaned up really well, re-install the IAC and see if it runs better. If unsure of this process, there are plenty of YouTube videos that show how this process is done.

 

Believe it or not I’ve already replaced that, and maintenance work I keep it in tip top shape, I like to take care of. Alternator, water pump, front main seal, A/C pump, battery, i clean out the throttle body because it seems to like it. I also run it with 15-40 oil because it has well over 260,000 miles. I just can’t seem to figure this problem out.

 

If it's sputtering or backfiring, has it turned on the check engine light? Have you scanned the engine with an OBD2 scanner to determine if there are any pending or stored codes that may provide some clues regarding your issue(s)?

At that mileage, has the timing chain and gears been changed and has the plenum gasket been changed? When looking down the intake with the throttle blades fully open, do you see any oil puddled down at the bottom of the intake? Might also want to perform a compression check to see what the overall health of the motor is.

 

there are 4 codes being thrown, 3 of which are for oxygen sensors, the last one is a P1494, which is “Leak Detection Pump Switch Or Mechanical Malfunction.” And if I’m being honest I have no idea what that one would be. And about your second question, no I have not changed out the timing gears/chain, but the only reason for that is because when I had the water pump and and replacing the front main seal I had a look at the timing gears/chain looked just fine. The truck does not burn/leak oil so I’m just assuming the engine itself is in “okay” shape. And I could go ahead and check down the intake, it won’t be any trouble.

 

Based on your codes, check your vacuum hoses for any breaks or looseness. With the engine running, spray carb cleaner around the base of the throttle body and intake to see if you notice the idle change - if so, you're near an area where the is a likely leak. Also, check for any vacuum leaks around the intake or throttle body - see this video for an example -

 

Also, if your O2 sensors haven't been changed in quite some time, now may be a good time to do so. Please be sure to use either a Denso or NTK brand of O2 sensor, as others are known to cause issue with these engines/trucks. Once the sensor is changed, be sure to reset the PCM by disconnecting the battery, let the connections remain off the battery for a few minutes, then re-connect the battery connections.

 

Thank you a lot man for your advice, as well as time. Hopefully it’s just a vacuum leak and I’ll be on my way. Once again thank you.

 

If you put an aftermarket IAC valve in there, swap it out for a genuine Mopar unit. The aftermarket fellers don't react as well/quickly as the mopar units, so, they tend to introduce issues, rather than solve them.

 

No problem. Please let us all know what you find to be the issue, along with a photo, if possible.