502RJ Dips below Idle, Then Comes Back

[tomspo04]

Can anyone help? I'm running a 502RJ/TKO600 combo. As I'm slowing down to a stop and take the car out of gear engine rpm drops to an almost stall, then comes back to idle. I ran it for codes and come up with none. Any help? Thanks...

Tom

[camcojb]

could be a couple of things. Throttle blade too far closed, or the dashpot settings in the tuning need tweaking. The dashpot (may be called something else in your system) controls how fast the rpms drop when you close the throttle. Too low of a setting can allow the engine to die or almost die as the IAC catches it; too high can hang the idle up, or make it return too slowly to idle speed. Throttle blade too far closed can do the same thing. I don't think you can adjust the second item yourself unless you've converted it so you can tune it yourself. I do not know how they said to adjust the throttle body minimum spec, but with the aftermarket tuning systems I've used I get the engine fully warmed, turn off all idle timing control, command a very low idle speed (so the IAC will fully close) and then set my lowest idle with the throttle blade itself. That way you have full range of the IAC to work. Reset TPS afterwards to correct setting.

However, I do not know how much of that you'll be able to do with your non-adjustable system. At that point I'd likely try slight turns opening the tb, keeping track of exactly how far I turned it so you can return it to where it was if it doesn't help. Also check tps voltage first so you can adjust that back to where it was after tweaking the tb.

Jody

[fotoboy]

if you have a cold air kit, try blocking it. Also check for vaccuum leaks, prob in the tune though

[andrewb70]

What Jody is describing is sometimes also called the IAC follower parameter on other systems. I had this issue on my GTO and was able to tune it out by setting the IAC to follow the throttle more closely and keeping the IAC open just a little longer after the throttle blades are slammed shut. With a non adjustable system try cracking the throttle blades just a little bit more, as Jody suggested.

Andrew

[camcojb]

What Jody is describing is sometimes also called the IAC follower parameter on other systems. I had this issue on my GTO and was able to tune it out by setting the IAC to follow the throttle more closely and keeping the IAC open just a little longer after the throttle blades are slammed shut. With a non adjustable system try cracking the throttle blades just a little bit more, as Jody suggested.

Andrew

thanks Andrew, knew there was another name for it and blanked........... throttle follower.

Jody

[andrewb70]

thanks Andrew, knew there was another name for it and blanked........... throttle follower.

Jody

That's it! Throttle follower. I didn't have it right either. LOL

Andrew

[tomspo04]

Thanks, guys... I'll try cracking the throttle a little. There's also a slight chance that I do have a vacuum leak. I cut the runners down 7/8" and had new base mounts welded on. It all seemed true, but you never know. I have another question. It runs like crap when it's cold, and runs way too lean on two cylinders. As for the running lean, I think it's got some crap in a couple of the injectors. I called AZ Speed to get a price on cleaning the injectors… they quoted me $15 bucks a piece. That comes out to about half the price of a new set of injectors. Would it be better to just buy a new set? If so, what injectors should I buy i.e. brand, type, size?

As for the running like crap during cold start up. What would cause this? Could this ALL be attributed to a vacuum leak? I'm new to FI...any and all help is greatly appreciated. Thanks, in advance.