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]

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]

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]

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]

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.

[undertaker]

I have more of a surge at idle and recovery with my ramjet (in my 2000 tahoe tow rig) and its pretty much always been there, I've just grown use to it. The one thing I'd say is check over the manifold bolts and the 8 bolts that torque the plenum to the base the base to the heads wasn't torqued right from the factory or within the first few run cycles loosened so those had to be retorqued, and the bolts from teh plenum into the base manifold were always slightly leaky.

You really have me wondering if throwing an aftermarket efi system on the motor would clean it up a bit, I'm on the first generation with no O2 sensor (came out a month after I ordered it and wasn't upgradeable just replaceable) The truck never performed the way I wanted on the track, I just attributed it to all the accessories, and a truck driveline's parasitic loss (4l80, 14 bolt semi floater etc) sucking up the power, darn thing only dyno'd around 350-370 rwhp. but hell its been alive for 27K miles now at least 30-40 bottles worth of 200 shots, and towing 8K lbs. Love the motor and tranny more than teh truck so I'm keeping them after the tahoe and finding a lightweight donor/bracket car so maybe I can keep it efi and get the thoughts of carbing it to get it more effective outta my head :lol:

but hell if it can lift the front wheel of a 5850 lb truck with a 2500 stall on motor I can only imagine in a 'normal' weight car.

http://james.jaguar.net/y2klimited/etown2281.jpg