Idle issues with surging.

[robert426]

My trucks idle surges while at a stand still and is driving me nuts! It’ll be fluctuating around it’s normal 650 rpm then drop down to around 450-500 and shoot back up to 1000-1200 rpm than return back to its “normal” idle. And then do it again in about 3-5 seconds repetitively. Any ideas?

 

[Ramitiner]

Year, engine, miles?

 

[robert426]

09 5.7 114500

 

[Fitz-0518]

Must scan the run condition. Will tell you what components should be checked for in spec or out of spec. We can all guess what part might be causing the run condition. But $100 of scan time with a pro scan by a tech who knows what they are looking at will save $1000 in "could be" parts cost.

 

[Nutshell]

My 2015 is doing the same thing. I’m lost on this.

 

[robert426]

It was after I put I bigger throttle body on. Put the stock back on did the same thing. Went back to the bigger oem throttle body reset the pcm like I was to do by the company I got the tb from. It seemed to be better but here I am 6 months later same issue.

 

[Ramitiner]

Ok, in my old car with this issue it was a maf sensor. Not sure what these hemis carry but that's where I'd be looking at. Also O2 sensors... Really is a guessing game unless you get it checked out

 

[Wild one]

It was after I put I bigger throttle body on. Put the stock back on did the same thing. Went back to the bigger oem throttle body reset the pcm like I was to do by the company I got the tb from. It seemed to be better but here I am 6 months later same issue.

Is it an SRP TB?

 

[robert426]

Srp?

 

[jasonw]

Ok, in my old car with this issue it was a maf sensor. Not sure what these hemis carry but that's where I'd be looking at. Also O2 sensors... Really is a guessing game unless you get it checked out

The 5.7 Hemi Rams don't have a MAF. I believe they are "old school" MAP sensors. I've read that the 3.6 and possibly 6.4 (2500/3500) have the MAF, and the Cummins definitely do, but not the 5.7.

I remembered having this issue on an older Ram of mine, and the below procedure resolved it. Granted, this was on my 2001 Ram 1500 with the 5.9 engine, and this procedure was found under the old Hemi (2003-2008) section, but its easy and free, no harm to try it.

In my case, and what this procedure is for, is my computer just had to learn the new throttle position sensor (TPS) that comes in the new throttle body. I'd ignore the "90 seconds" part and leave it disconnected for 15-30 minutes, but thats just me.


If the throttle body has been changed, the following
procedure must be performed:
(a) Disconnect negative battery cable from battery.
Leave cable disconnected for approximately 90
seconds.
(b) Reconnect cable to battery.
(c) Turn ignition switch ON, but do not crank
engine.
(d) Leave ignition switch ON for a minimum of
10 seconds. This will allow PCM to learn throttle
body electrical parameters.


If that doesn't work, +1 for the "get it checked out" part. I've played the "throw parts at it based on interwebs research" gamble before. I'm about 50/50, sometimes its perfect and saves you money, and other times it costs you double, triple, or worse.

I'd have a professional mechanic that you trust look at it, hook it up, and have him diagnose it. Then, based on that information (the best available), you can try to fix it yourself or pay him to fix it.

 

[robert426]

I’ve done all that multiple times. Still, same issue.

 

[jasonw]

Then you're left with having a pro hook it up and check it out. Sounds like your problem is a weird one, unfortunately.

 

[Wild one]

I’ve done all that multiple times. Still, same issue.

Idle issues with surging on an aftermarket throttle body usually go back to the fact the airgap between the throttle blade and the barrell wall has been opened up slightly.The bigger airgap lets slightly more air in at idle,which really screws up the idle air parameters with our MAP based systems.If the throttle body is clean and appears to be operating properly other then surging at idle,you might get away with slightly tweaking the blade so it closes the airgap up a wee bit when the blade is closed like at idle.It might or might not work,at curing the issue,but worth looking into.It doesn't take much more airgap to screw up your idle.