Quick question. Car has been idling funny like it's "chugging" since being pulled out a few months storage last month. It's like she ain't running on all cylinders. At low rpm as when comming to a stop she feels like she's gonna stall, and at mid range cruising along she occasionally feels like spark is cutting and stumbling / hesitating.

Recently replaced the cap, rotor, wires, plugs (NGK) with AC Delco products. The MSD coil is firing but it looks like a weak spark (any way to check the coil?) and spark is getting to all 8 cylinders. The distributor shaft looks good and so does the pick-up coil reading a reistance of .930 or so. Currently running off an MSD 6A.

The fuel pressure is steady at @ 41 psi.

However there seems to be good film of black carbon on the plug in the #8 cylinder. The resistance on injectors #1 and #8 are reading 16.3, while #3,4,5,6,7 is @ 7 and #2 is at 4.7.

Could my rough idle and hesitation be bad injectors? Shouldn't the resistance readings be fairly close across all of the resistors?

 

My reman'd gm 22# injectors were all around 17.5 ohms or so. Id also check the terminal on the coil for corrosion. There is a way to check the coil and its outlined in haynes/chilton.

 

anything under 12 ohms is junk, according to gm

 

Thanks guys.

Ya, the pick-up coil seems to be slightly corroded at the connectors, but it is still functional and really doesn't look all that bad.

I believe my worst fears are confirmed, being, the GM service manuals for Camaro's and Firebirds I have been looking up here at the GM dealership (I'm a parts counter rep) all list resistance at a minimum of 11.7 or higher (ohms).
A couple of mechanics had pointed out the same. I've got at least 6 hovering at around 7.

I'm considering replacing all 8, and even with my discount a set of new GM injector kits from the GM warehouse for a '91 5.7 tpi will cost me @ $900 (Canadian).

I hear the GM's flow pretty good and I am really just thinking about sticking with them. I'm not sure if I should go aftermarket though.

Anyone got any suggestions?

 

Common failure mode of the Multec injectors.

Most folks go with the SVO F*rd/Bosch injectors for replacements.

RBob.