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07 hemi wont hold steady idle rpm

13K views 60 replies 6 participants last post by  hotbird 
#1 · (Edited)
I working on my brother in laws 07 5.7 hemi charger it wont hold a steady idle speed. it run up and down and up and down .....

I am fairly good at wrenching on cars but this has me baffled.

Any ideas on where to start trouble shooting?

No engine light or codes.

I will try to post a video tomorrow. Thanks for your help!
 
#6 ·
How many miles, when was the last spark plug change? Copper plugs only right?
Maybe bad gas? Idk anything about our egrs
 
#12 · (Edited)
That is the first [place I would look on a older car.

But this car is drive by wire. No TPS

Just has a Accelerator position sensor and the throttle body internals.

Any one have a code scanner that shows data (pids) willing to look at something for me?

I need a 5.7 hemi drive by wire owner to look at a few pids for me to see if what I have is normal or if my Pedal sensor is bad..
The pedal has 2 sensors one reads say 14.6 at idle and the other reads about half of the first say 7.3 but the second sensor reads 0 then 7.3 then 0 this is with out pressing the pedal at all.

Im thinking this reading might be why my the idle goes up and down, because the sensor it reading up and down.

But I cant find anywhere how to test the pedal or if this is normal or not.

If it was a cheap part I would get it just to see but its like $150-250
 
#14 ·
Hmmm... Have you tried any type of cleaner just in case? What RPMs does it idle at when in drive. Can you adjust the throttle control thingy like on older cars? When my cars egr made me start stalling out my dad would adjust something with the screwdriver and it would send more fuel in and idle higher...
Check the coil packs are working correctly.
 
#16 ·
No holes just the plastic melted some. not sure why.
It makes me wonder about the history of this car.

I cleaned the throttle body spot less front and back and it made no change.

I guess I could block off the egr just to rule it out.

I see no adjustments on the throttle body.

I am going to try a new Accelerator pedal assembly to rule that out also.
 
#26 ·
Where is the sensor that goes on the end of the intake right before the throttle body???
 
#22 ·
#24 ·
Just watched your video and you have either a major vacuum leak, or that engine has an aftermarket camshaft and needs a custom tune...Can you please hook up a vacuum gauge and post of a video of the gauge...I could tell you ASAP which one is going on
 
#32 · (Edited)
at the auction yard they use big front end loaders with long forks to move the cars around.

Looks to me like the forks hit the small flexible area just after the converters and made small holes.

I will fix this but I'm looking into how to do it without replacing the converters as that's a very pricy way to do it.

If I can find aftermarket flex joints I can weld them in to repair the damage.

I was hoping to fix the idle issue before sinking any more funds into it

I am uploading new video with vacuum gauge now.
 
#34 ·
Wow, that is one wild dance on the gauge!!! let me listen to the idle, watch the tach and the gauge and I will give you my opinion on the situation
 
#35 ·
I am betting you have a vaccum leak..or a slightly larger camshaft that needs more fuel at idle. I am confident that the motor is healthy, just need to determine if the intake and vaccum lines are sealed, if so time to look at the possibility of a camshaft and missing custom tune. Best guess is a leak
 
#37 ·
Every once in a while it will idle normally then give the accelerator a jab and its back to doing its up down thing.

I have sprayed carb cleaner all over the top of the engine looking for a leak when it was holding steady idle and found nothing.

Whats the best way to look for leaks?

How can I check for a bigger cam? (without pulling cam?)
 
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