502RJ Dips below idle at stop

[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]

Originally Posted by 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

could be a couple of things. Throttle blade too far closed, or the dashpot or throttle follower settings in the tuning need tweaking. The dashpot (may be called throttle follower 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

[projectile]

Originally Posted by 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

I had the same problem. Jody is 100% right.As jody said, reset tps voltage after each adjustment to throttle blade. If you don't, ecu may not be in idle mode. Hope this helps.

[pushrod243]

this is common ith the ramjet 502. I talked to few GM engineers at SEMA who admited they are working on a cure. They claim the servo in the ISC does not react fast enough as the motor returns to idle. Mine is better since I switched to the fast xfi system but still is annoying. I havent look harder into a fix since.

[camcojb]

Originally Posted by pushrod243

this is common ith the ramjet 502. I talked to few GM engineers at SEMA who admited they are working on a cure. They claim the servo in the ISC does not react fast enough as the motor returns to idle. Mine is better since I switched to the fast xfi system but still is annoying. I havent look harder into a fix since.

look at the throttle follower, and ramp it up higher to slow the return to idle.

Jody

[tomspo04]

Originally Posted by pushrod243

this is common ith the ramjet 502. I talked to few GM engineers at SEMA who admited they are working on a cure. They claim the servo in the ISC does not react fast enough as the motor returns to idle. Mine is better since I switched to the fast xfi system but still is annoying. I havent look harder into a fix since.

Pushrod, How do you like the fast? How much of a differance did it make on the RJ? Is it worth it? Thanks...

Tom

[rockdogz]

I don't think this is happening to me, but then if the engine doesn't stall I'm wondering what the problem is.

[pushrod243]

I like the fast system but I cant say its the best since it is the only system I have worked with. With some help we improved drivabilty and increased performance over my stock mefi4 system. The car ran 12.66 with the stock ecm and in a few hours at the track with the fast system I ran a traction limited 11.72 and picked up 8mph in the quarter. The engine sounds totally different much crisper. Best $ I have spent on the motor by far. I am experimenting with a big stuff3 on my race car and it seems a bit more user friendly so far.