Ignition ? breakup

[87OmniT2]

My car is studdering under boost. It cuts in and out. Not overboosting, just studdering, like a miss. Its an 87 T2 set up with a stage 2 mopar logic module. I thought it was running out of fuel because the air/fuel ratio gauge would flutter into the "stoich" range as the studder would occur. I checked the fuel pressure and it was good. I am getting about 70 PSI under full boost. I know that it could still be a fuel problem, but im leaning more towards ignition now. I have changed the wires (nothing special though), and regapped the spark plugs to .030". Plugs look pretty good. Shudder wheel in the distributor is solid. I've tried two different coils. The car runs good otherwise. I only have the trouble under boost. Anyone ever run into this before?

[87OmniT2]

bump

[lametec]

Try gapping the plugs even tighter, like .025".

I had a power module go bad once. Caused a no start in my case, but when I measured the voltage at the coil, it pulsed like it's supposed to. Point is, the power module could have a bad driver transistor, causing a weak signal to reach the coil, which in turn causes a weak spark.

[87OmniT2]

OK, I pulled up the pinout for the power module. According to the diagram, the 1st wire in the 10 way connector, which is black and yellow is the feed for the coil. I am only getting 9-10 volts there when the car is running. Im guessing that this should this be a 12 volt feed? Now, if the voltage is too low - why? Power module issue? THe battery feed TO the power module is reading 12-13 volts when it is running......can anyone help?

[86Shelby]

How does the cap and rotor look? No burning, pitting, track marks, anything like that? Also check the underside of the rotor. sometimes they will burn through and allow the spark to jump through the rotor to the distributor shaft only under high loads(boost).

Is the terminal end of the coil clean? If it's all nasty clean it off, I've seen dirt&buildup there cause high load misfires.

Do you have any vacuum leaks? A leak could cause the MAP to read a bit low which would give the engine less fuel, which could cause a misfire.

[87OmniT2]

Quote:

Originally Posted by 86Shelby How does the cap and rotor look? No burning, pitting, track marks, anything like that? Also check the underside of the rotor. sometimes they will burn through and allow the spark to jump through the rotor to the distributor shaft only under high loads(boost). Is the terminal end of the coil clean? If it's all nasty clean it off, I've seen dirt&buildup there cause high load misfires. Do you have any vacuum leaks? A leak could cause the MAP to read a bit low which would give the engine less fuel, which could cause a misfire.

Ive tried switching all of that basic ignition stuff....and I checked the vacuum lines too. Thanks though....keep it coming.

I would really like some insight into the power module voltage issues I mentioned above....

[87OmniT2]

scratch that. the black with yellow is the ground side of the coil......the coil is fed through the ASD.

[igotaneed4speed]

try using a msd coil not a stock version of the coil. Mine used to break up with the stock computer like that at 18 + lbs of boost with the stock coil..

i just put a msd coil on it and it clean right up...


it would help even more if you put a msd box on it with the coil

[87OmniT2]

I fixed it...I think. I am not sure how, but it is. I did some little things like clean up the contacts on the distibutor and some grounds and stuff and the problem went away.

[fusiondaytona]

I have the same prob Ill be trying some of those too