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Old 02-04-2007, 08:29 AM
tomspo04 tomspo04 is offline
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Default 502RJ Dips below idle at stop

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
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1970 SS (L-34) Protouring Camaro, 502 RJ, TKO 600 W/aluminum drive shaft, 3.42 rear, C5 ZO6 brakes front & rear, Hotchkis TVS, Boze Mesh; (17X9.5 275-40) & (17X11 315-35), Rick SS fuel tank W/pump, March Ultra serpentine setup, Hiedts/GW UCA's & LCA's, MagnaFlo 3" SS exhaust w'Xpipe.
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Old 02-04-2007, 10:57 AM
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Quote:
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
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Last edited by camcojb; 02-04-2007 at 06:53 PM.
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Old 02-05-2007, 12:34 AM
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Quote:
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.
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Old 02-06-2007, 09:09 PM
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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.
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Old 02-06-2007, 09:16 PM
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Quote:
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
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SPECIAL THANKS TO:
Jacob Ehlers and Amsoil for the lubricants and degreasers for my 70 Chevelle project
Shannon at Modo Innovations for the cool billet DBW bracket
Roadster Shop for their Chevelle SPEC Chassis
Dakota Digital for their Chevelle HDX Gauge Package
Painless Performance for their wiring harness

Ron Davis Radiators for their radiator and fan assembly.
Baer Brakes for their front and rear brakes

Texas Speed and Performance for their 427 LS Stroker
American Powertrain for their ProFit Magnum T56 kit
Currie Enterprises for their 9" Third Member
Forgeline for their GF3 Wheels
McLeod Racing for their RXT street twin clutch
Ididit for their steering column
Holley for their EFI and engine parts
Lokar and Clayton Machine for their pedals and door and window handles
Morris Classic Concepts for their 3 point belts and side mirrors
Thermotec for their heat sleeve and sound deadening products
Restomod Air for their Tru Mod A/C kit
Mightymouse Solutions for their catch can
Magnaflow for their 3" exhaust system
Aeromotive for their dual Phantom fuel system
Vintage Air for their new Mid Mount LS front drive
Hydratech Braking for their hydroboost system
Borgeson for their stainless steering shaft and u joints
Eddie Motorsports for their hood and trunk hinges and misc parts
TMI Products for their seats, door panels, and dash pad
Rock Valley Antique Auto Parts for their stainless fuel tank
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Old 02-07-2007, 11:02 AM
tomspo04 tomspo04 is offline
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Quote:
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
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1970 SS (L-34) Protouring Camaro, 502 RJ, TKO 600 W/aluminum drive shaft, 3.42 rear, C5 ZO6 brakes front & rear, Hotchkis TVS, Boze Mesh; (17X9.5 275-40) & (17X11 315-35), Rick SS fuel tank W/pump, March Ultra serpentine setup, Hiedts/GW UCA's & LCA's, MagnaFlo 3" SS exhaust w'Xpipe.
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Old 02-07-2007, 03:33 PM
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I don't think this is happening to me, but then if the engine doesn't stall I'm wondering what the problem is.
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  #8  
Old 02-07-2007, 08:19 PM
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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.
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Old 02-21-2007, 06:28 PM
undertaker undertaker is offline
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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

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.


Last edited by undertaker; 02-21-2007 at 06:30 PM.
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