Slant Six Forum :: Idle/acceleration

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Idle/acceleration https://www.slantsix.org/forum/viewtopic.php?t=62983	Page 1 of 1

Author:	Fraser67ValVc [ Wed Nov 07, 2018 3:16 am ]
Post subject:	Idle/acceleration
Hey everyone I have a 67 Valiant Safari Wagon VC Automatic It has an Atomic MSD EFI installed (https://www.holley.com/products/fuel_sy ... parts/2900) It was installed prior to me purchasing the car. She starts first go every time On a cold start it stalls if you don't keep the accelerator on a little. Once the car is warmed up it will idle fine. Occasionally, after its been idling for 10/15 minutes maybe, it will randomly increase rpm and then drop and stall. an anyone help with this? The accelerator also stumbles a bit when you step on it. it definitely should be a lot more responsive that what it is. any help is great, i just want to see if i can resolve the issues before taking it to someone which may cost me an arm and leg Cheers

Author:	NextGenSlant [ Sat Nov 10, 2018 9:08 pm ]
Post subject:	Re: Idle/acceleration
Fraser67ValVc, Cold start... does the choke function properly? Have you observed the throttle plate in the carb while cold starting? The after warm-up issues sounds like it could be a few things, have you checked for vacuum leaks? Do you get the same results with the air filter off and the carb plate propped open (air flow)? Next up on the lineup would be check the air filter and air delivery system, then EGR valve, then distributor, then coil, plugs and wires, etc. Timing could also be sligtly off (stretched chain?). Checking chain stretch is relatively painless if you trust your ability to verify TDC#1 and have a distributor that allows you to see the rotor move. With Piston #1 at TDC according to the engine timing mark and compression verification (shop towel stuffed in spark plug hole works in a pinch), back off the #1 piston about 30 degrees before TDC. Remove distributor cap and turn crank slowly by hand until reaching TDC (rotor should be pointing to #1 or very close). Mark the exact position of the dizzy rotor and note where the engine timing mark is, then turn the crank VERY slowly the opposite direction until the slightest movement is noted on the rotor away from your mark. Look at the timing marks on the harmonic balancer / timing tab and see how many degrees of difference you have from initial measurement. This indicates your degrees of stretch, compare to your specifications for tolerances and replacement recommendations. Hope that helps. NGS

Author:	sixinthehead [ Sun Nov 11, 2018 7:35 pm ]
Post subject:	Re: Idle/acceleration
Since you are dealing with EFI, it should have some kind of diagnostic mode that will give you some information about possible sensor failures or the like. Since it is supposed to be self-tuning, it should take care of itself as far as driveability unless there is something wrong with the installation (vacuum leaks, as mentioned) or the system itself. I am reading up on that Holley system to see what it is capable of. Since it seems to run well otherwise, I wouldn't expect any serious mechanical issues. You mention that the flare and stall happens after an extended idle period, so you may have a heat-soak related issue. Combine that with poor cold start performance and I would suggest you look at the temperature sensors, especially the coolant sensor. If it is faulty (or perhaps installed incorrectly?), the computer won't be able to calculate the proper mixture.

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