mats

I have been doing some reading and I am beginning to think there are two different problems. The code 33 is triggered because the MAP output voltage at idle (=TP sensor less than some 2-4 %) is too high. If the MAP output is correct, it means that vacuum is too low. This could be because the throttle plates do not close completely assuming there are no vacuum leaks. This I suspect because I have been adjusting the throttle plate opening to get them fully open at WOT. Maybe I tightened the throttle cable too much.......

The other problem is the stalling at midrange which most likely is ignition related. The tach drops faster than the rpm when it stalls.....

mats

insptech. What drives the tach? Is it the pulses on the primary side of the coil or is it something on the high tension side? I am trying to understand why the the tach drops faster than the rpm

GOODT

the tachworks off of the dist pulses at the - side( primary ) of the coil

GOODT

in most cases a mid to high rpm range stall is fuel related,

I think you are trying to over engineer the problem go back to basics, as Ted stated check fuel pressure ect

mats

Hi . Thanks for your input. Keep the ideas coming.

Fuel pressure is OK, rock steady through all the stalls. The tach drops faster than the rpm and if the tach is as you say GOODT driven by the primary side of the ignition that is where the problem must be. Somehow the squarewave on the primary side cuts out, taking away the input to the coil as well as the tach. I have checked the coil and the magnetic pick-up in the distributor. Most likely it is an open circuit or a short somewhere....

Dave_N

mats,
Have you checked or replaced the ignition module? It should be mounted with heat transfer compound and it needs a good ground to the distributor.

Have you cleaned and checked the connections at the back of the module (where the magnetic pick-up connects)? That is a real trouble spot, especially with the added moisture associated with MSD ignition. I can't remember if you have MSD or not.

What type of plug wires are you using? I have heard about some strange problems due to EMI on computer controlled engines with aftermarket plug wires.

Dave

mats

Hi Dave. well I have not checked the ignition module but the whole distributor assembly is new. Is there a way to check the ignition module or do you need an oscilloscope? The plugwires are stock. I have checked them with an ohmmeter and they seem to be OK. I have checked the connection on the back of the module and they were corroded but they seem to be OK now.

Question; if the tach wire(s) gets shorted to ground, can that bring down the whole primary squarewave?

GOODT

basicly yes and it will stall the mtr

Dave_N

They do sell inexpensive module testers, but I don't know if they will really tell you if you have an intermittant module failure. A scope would be a much better way to test it. A test bench where you can test the entire ignition system would be even better

Yes, it sure will.

Dave

Ted G

iTrader: (1)

I have seen similar problems with a failing module. It may be bad, even though the dist is new, especially if it wasn't installed with the heat transfer compound. There is also a possibility that the short wiring harness off the module has a broken wire. A good shaking on all the wires around the distributor might turn up something also.