Idle speed increase

"Been trying to "fix"

"Been trying to "fix" a rough idle issue for some time in one of my 8.2 MPI Crusaders, posted numerous times here, got great suggestions. Crusader has been very helpful, Mark Schneider in their warranty/technical department has been great. The last thing I did was have the ECMs recalibrated and while it sure helped the engines start up better I still had the rough idle. The rough idle/rattle/vibration goes away right above idle, Marks suggestion is to send the ECMs back to him and he will reprogram them to a higher idle. The idle now is 600-650 rpm. The suggestion was to bump them up to 700-750 rpm. Does this seem like a good idea? Mark commented that these engines do not have the smoothest idle anyways and by bumping up the rpms a little it may smooth right out..."

"Scott,

Mark is the authori

"Scott,

Mark is the authority on these guys but I have a suggestion as well. He is right about the idle not being the smoothest and if he suggests raising the idle it can be done without reprogramming the ECM.

There is a hidden idle stop adjustment on the bottom of the throttle lever. It is a small allen head set screw and is usually painted so heavily you don't know it is an adjustment. Turn that guy in a half a turn or so and you will raise the idle.

Hopefully it's as simple as that.

Good luck,
Rick"

"Rick,
Thanks for the input,

"Rick,
Thanks for the input, but I have one concern, if I manually adjust the idle what is the ECM going to do? Do those things have Type A personalities where it is going to be sending signals to the IAC valve and who knows what in order to get the engine to idle at ITS programed RPMs? Or are they more laid back and once it tries to get it to conform to its programing it gives up? Kinda like the "California surfer dude" personality? I am just concerned if I do it the "old fashioned" way that it will confuse the ECM???
Scott"

"Why would ECM recalibration b

"Why would ECM recalibration be the solution? If one engine runs well, then the existing calibration is fine. Thats treating a symptom and not correcting the actual problem. Are you sure you don't have an IAC failure?

I also wouldn't recommend messing with the throttle plate stop screw unless you know what your doing (and are monitoring the engine data with a scan tool). Again, this is treating a symptom and not the problem."

"Dave,
New IAC valve was inst

"Dave,
New IAC valve was installed. New plug wires, tune up, timing, injectors removed and bench cleaned, new fuel pressure regulator, PVC valve ok, valve job done last year (low compression in #5 cyl.) ECMs sent in and reprogrammed by Crusader this April. After the ECMs were reprogrammed the Crusader tech asked me to see what I could get at WOT, engines spun up to a little over rated WOT at 4500 RPMs. After I spoke with tech with WOT info, he suggested to double check the compression to be sure valve job did the trick and if compression checked out to reprogram the ECMs. I asked the tech if I should have the injector harness checked out or do a check on the injectors to see if I had a bad one, he felt that since the engine ran fine a little above idle and I was getting full rated RPMs that I did not need to. Any suggestions where to go from here???"

The IAC is normally closed at

The IAC is normally closed at idle. All the air feeding the engine is coming through the bypass circuit. The ECM recognizes that and is content it is doing everything needed to maintain the idle. I have had adjust the linkage stop (as per Crusader) in the past on brand new 8.2s.

There is no problem making this adjustment.

"Scott,
I don't know what

"Scott,
I don't know what to suggest other than try to find someone with better understanding of computer controlled engines and some better diagnostic equipment.

First you have to determine if the ECM is in control of the idle speed, and how hard it's having to work at it. Using a scan tool (or better yet a laptop with diagnostic software), you would compare actual idle speed vs desired idle speed, and observe IAC position and ignition advance.

Next you would check individual cylinder performance using an ignition scope and performing a cylinder balance test. This should give you a good idea of what the problem is and what further tests need to be performed, or what repairs need to be made."

"Rick,
Just to be sure, the

"Rick,
Just to be sure, the allen screw I found was on the bottom of the throttle assembly, it is the only one I could find, is that the correct one?"

"Yep, it's not easy to fin

"Yep, it's not easy to find, especially if you don't know it's there."