Here's the situation can't drive my TPI motor anywhere w/out hearing backfires and watching the tach jump. It does it both cold and warm. So far in the last week I've replaced Distributor, module, cap, rotor, and wires. Just to make sure wires where straight checked resistance 8-14 on all. Plugs have been pulled and checked (have about 1k miles on em). Timing chain has 1k miles on it. She runs fine at idle w/ no problems. as soon as a load gets put on the motor tach starts jumping (looks like someone shut the motor off then it jumps back up) and the backfiring begins. The SES light comes on every once and a while, but mainly when the rpms drop down between 0 and 500 (no hard faults when I check for codes). Other sensors/parts that might effect it and that have been replaced within the last 4 months are Knock Sensor, MAF, and ESC. Double checked timing when I installed the distributor (6 deg). Fuel pressure is right at 40 and there's no vacuum leaks that I can tell. Do have a small exhaust leak but nothing that should effect the operation of the motor. It will sit and idle all day long at any RPM only acts up when load is put on the motor. Any help would be greatly appreciated.
BOB

I'm thinking pickup coil

I was thinking the same thing so thats why I replaced the complete distributor with one that I bought from Autozone. There was no change when I replaced it.
BOB

I just recently went through this with another member's TPI. He had exactly the same symptoms, and replaced all that - distributor cap, HEI module, rotor, and wires, plus the plugs, ESC module, pickup coil, an entire distributor, and the ECM. I found a problem with the primary power feed to the distributor. Check the ignition switch, fuse and power distribution panel wiring, and power wire to the distributor.

That jumpy tach is a good hint.

how hard was it to change the distributor? Because I have the same type issues with my car, except mine runs like crap even at idle.........

There is only one 3/8-16 bolt holding it in. There are three electrical connectors with a factory tach setup, two if there's no tach. As long as you install the replacement with the rotor pointing in the exact same position, then set the base timing after installation. there should be no problems.

checked all the connections but all where good, then I double checked the main ground at the battery. It was a little loose then I tightened it and the problems went away. Something so simple, go figure.
BOB

with the right tools (a crows foot works very well to get in under the distributor..). It should only take about 10 minutes max to take a distributor out.

took me about 10min to change it and 1hour to make sure I got it lined up exactly where the old one was. My pickup coil actually blew up for some reason LOL...literally cracked to shreds while the car was idling in my driveway. That was 3 years ago and no problems since...

i had a stock in cap coil actually catch on fire. it had a crack i did not see and it started the platic cover on fire when it arced arcross... one of those. sometimes it starts sometimes it doesn't ones...

Vader,

Can you give me a little detail on diagnois of the Distributor power wire problem. What wire do I start with and what voltage readings should I except to see. I already replaced my ign. switch. Do you have some step by step Instructions I could run through to verify I am getting good power to the distributor system.

Power distribution panel wiring? Where is this panel?

K this kinds sounds like what my car is doing. One questions though did your cars run fine for a little bit cause my runs strong after i warm it up but then when i get on the high way if i floor it my tach starts bouncing then it drops to zero then starts backfiring?

i dont know much but i had that problem once and it ended up my computer ground was faulty

I have been chasing a problem with my 86 z28 tpi since I bought it over a year ago. Intermittently running bad, or slightly backfiring, and other times it would run ok. It would especially run bad when it rained and I went to drive it. I have given up on replacing parts, cause there really is nothing else left for me to do. I have replaced ALL ignition componets, ALL sesnors, EVERY power relay, The MAF sensor, ALL the injectors have been rebuilt by Cruzin Performance, and the fuel rail has been rebuilt. I have replaced the EGR valve, repaird all vacuum, lines, replaced intake air temp sensor. I finally took a good look at what my gut instinct has been for quite sometime. The wiring harness. I found a exposed section of my orange power wire by the oil pressure switch. Arcing on the block and blowing the fuse. I also found FINGER TIGHT grounds on the cylinder heads. I have sent off my wiring harness to TPI parts.net to have the harness reconditioned, and any repairs it needs to be done. I suspect my car is gonna run like never before after I get the harness back in.