Hi, I am chasing a " Jerking" gremlin at low rpm's lately. Thought it was the EGR valve, but I tested it and it was fine. So I went to set the timing (with the EST connector off) and noticed the timing cruising up and down about 2-4 deg. I don't think it's my timing chain- I just put a new one on. What else could cause this? could it be the dist. module? could this timing problem be what's causing the jerking?
Thanks, Jeff

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88 Trans Am 305 Auto Red/Silver, MSD coil,wires, ported plenum, gutted airbox, TB bypass, comp cams 08-408-8, everything else stock

 

88,

It could be the HEI module, ESC, ECM, coil, a loose timing chain or worn distributor shaft, or just your timing light. Inductive pickup timing lights are prone to a little of this, which is why the clamp should be connected as near the distributor cap as possible.

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Later,
Vader
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Justice and Freedom will Prevail

 

Thanks, Vader. Just curious (I'm learning), with the esc bypass disconnected, does the computer still control the timing? my car has a new coil, maybe it is the timing light. Also, how does the computer control the timing? is there something mechanical in the distributor that the computer controls? What could be causing this jerkiness at low rpm cruising (1500 RPM)? there are no vac leaks, replaced the intake manifold gaskets, etc, EGR works, new pickup coil, wires, cap, rotor, O2 sensor, maf power relay. This problem follows a new cam (in sig), but it idles great, and runs great except for this one prob. HELP!
Thanks, Jeff

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88 Trans Am 305 Auto Red/Silver, MSD coil,wires, ported plenum, gutted airbox, TB bypass, comp cams 08-408-8, everything else stock

 

UPDATE!!!! OK now this is really strange. Went out to check the timing again, and with the EST wire disconnected, the timing STILL ADVANCES ITSELF according to RPM. when the engine is idling, it stays at about 6 ( or close to) and when I rev it ( to about 3000), the timing advances to 12 deg or so. What is going on here? HELP
Thanks, Jeff

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88 Trans Am 305 Auto Red/Silver, MSD coil,wires, ported plenum, gutted airbox, TB bypass, comp cams 08-408-8, everything else stock

 

Anyone? I'm stumped

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88 Trans Am 305 Auto Red/Silver, MSD coil,wires, ported plenum, gutted airbox, TB bypass, comp cams 08-408-8, everything else stock

 

There is some advance in the "limp home" mode, which is what you're doing basically when the wire is disconnected. Follow Vader's trail for the jumping around part.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).