aftermarket DME chip cures stumbling problem?!?
09-02-2002, 05:50 PM
#1
Drifting
Thread Starter
aftermarket DME chip cures stumbling problem?!?
Does this make sense, guys? The substitution of the Huntley chip in the DME of the '86 951 seems to have cured the mid-RPM stumbling problem?
This seems to indicate a defective factory DME chip, does it not? How common is this?
This seems to indicate a defective factory DME chip, does it not? How common is this?
09-02-2002, 08:32 PM
#2
Race Director
Stumbling can be caused by both lean and rich fuel-mixtures. From the path you've taken, it appears you may have been lean before since the Huntley chips add extra fuel in the mid-range. This is typically the case if you've got some sort of free-flow mods like air-cleaners and exhaust while still using the stock chips.
But that shouldn't throw things so out of whack like what happened with your car. I'd check for smooth operation of your AFM. You can measure resistance between the two inside pins on the AFM itself and check for continous changes as you open the flapper door. Or you can measure + voltage at pin#7 of the DME. It should read from 0.5-4.5v as your helper opens the flapper door slowly. You shouldn't see any sudden changes, dropouts or spikes.
But that shouldn't throw things so out of whack like what happened with your car. I'd check for smooth operation of your AFM. You can measure resistance between the two inside pins on the AFM itself and check for continous changes as you open the flapper door. Or you can measure + voltage at pin#7 of the DME. It should read from 0.5-4.5v as your helper opens the flapper door slowly. You shouldn't see any sudden changes, dropouts or spikes.
09-02-2002, 10:06 PM
#4
Drifting
Thread Starter
Gah! my meter is so slow it just ranges around for a while before it settles on anything, so I'll have to obtain a better one for any conclusive results on the AFM...
BTW, wouldn't the AFM problem show up with the car not moving? Like revving it while standing still? I suppose I should swp in a known good AFM to be sure (might swap in a known good factory DME chip also to find out something in that area...)
BTW, wouldn't the AFM problem show up with the car not moving? Like revving it while standing still? I suppose I should swp in a known good AFM to be sure (might swap in a known good factory DME chip also to find out something in that area...)
