rangerrick63

I have a 454 mag that has a surging problem between 1000 - 2000 rpms. I'm wondering if I have an IAC problem, & if cleaning it will help, or should I just replace it? If I remove it, is there an adjustment I need to do when I reinstall it?
A second problem is that the throttle is extremely sensitive, if I move the throttle just a click, it jumps up to 2000 rpm, & starts to surge. I can play with it, to get it to throttle down, while still surging, but it just seems quite sensitive. So, I'm wondering if I also have a TPS issue, or is one thing causing both issues? It clears up above 2000 & seems to run just fine, just looking for a direction to go.

29scarab

Dude,

Need to hook a scan tool up on it and test both to see if they are working properly. I tried for months to guess without the tool and wasted my time. There are guys here on the board that may be close to ya that might be able to let you borrow it or have them hook up for a few minutes and check things out for ya.


That scan tool only takes a couple of minutes to hook up and to run through diagnostics and let you know whats up.

Not sure if this helps, but been there done that...

rangerrick63

I appreciate the input, I'll check around to find someone with a tool. I pretty much figured that's the direction I would end up having to go, but was hoping for a short-cut on troubleshooting these issues, thanks again.

TylerCrockett

If you have a volt meter take a paper clip and stick it along side of the blue wire in the plug on the throttle pos sencor. When the throttle is closed and the key on (engine not running) it should read .500 volts.

rangerrick63

If the voltage is not at .500, is there an adjustment, or do I just replace the TPS?

Dave_N

If you havn't changed them already, I would start with plugs, wires, cap and rotor. Sometimes a surging problem can be caused a simple misfire, one cylinder starts to drop out, the computer opens the IAC to compensate, the cylinder starts to fire and the engine surges.

Dave

rangerrick63

Actually, no I've not changed them, that sounds like a rather simple place to start, just a good ole fashioned tune-up. Thanks for the input.

mats

You would be surprised how often the problems with fuel injected engines are "classical" ones but then they are effectively disguised by the electronics trying to compensate making troubleshooting a PITA.