Troubleshooting a 1988 TPI 350, car starts, runs, but does not want to accelerate hard or maintain speed under load at freeway speeds (>50mph), especially up a hill. New distributor cap/rotor, ICM tested good, new plugs, good coil (checked windings), timed car to 6 degrees with brown wire disconnected. In the process of changing the spark plug wires as I found one that had wear spot through loom so I'm sure that doesn't help, but I'm also looking at the pickup coil. The GM manual states leads on pickup coil should be open to ground/infinity, and they are, but when I check across both leads on the pickup and wiggle the wires, it's open/infinity, not the recommended 500-1500 ohms that move with wiggling the cable that connects to ICM. Manual states replace the pickup coil if this is the cause, but usually bad pickup coils are cause of no starts, and this starts fine. Could this be enough of an issue to cause drop of power at higher rpm or under load?

 

I wish I could recall, but GM states something like 600-1100 ohms? That said, it should be like 500/600 when wiggle the wires.

Does it have a greenish spooge <tech term> on it?

All that's needed to replace is to knock the roll pin out of the distributor gear, slide it off and pull the shaft out.

FWIW when my PU coil was going south, I was missing at higher RPMs.

 

One small correction before we start , your thread title says "0 ohms across" , which means a dead short (0 ohms is a nice heavy piece of copper wire , for instance) , but then in your post you say "open infinity" (no connection whatsoever) , which has no value assigned to it in the Ohms scale (since the better the connection the smaller the number and the number 0 is already taken to mean a perfect connection) , so if your meter is reading "INF" or "OL" it's saying "Open Line" , indicating no path for our happy electrons .

With that said , if your meter is reading "OL" or "INF" (infinity) on the pickup coil , and the car runs at all , my bet would be that your not making a proper contact with the meter's probes on the coil's connector , a pickup coil that was truly electrically open wouldn't be sending any pulses to the ICM , resulting in no zappity zap from the big coil whatsoever

 

Shoot, now I'm confused and have to go measure again. I know it was infinity/1 on the coil to ground. Was it that across the terminals? Thanks for pointing that out. I'm still leaning towards faulty coil based on 8Mike9's comment, and the basis that I'm missing/loss in power/misfiring/whatever at higher RPMs. Idle and lower RPMs to around 1200 or so are fine but when RPMs go higher perhaps the coil is shorting out, causing misfire/loss of power, and not completely broken (more common, causing a no-start).

One of the only posts on the net I could find that partially describes the symptoms I'm having - I think the coil is occasionally shorting internally:
https://chevytalk.org/fusionbb/showp...p?post/566016/

I decided to replace the coil a few days ago just haven't had the time to pull the distributor yet. We'll find out and I'll update this thread and fix the title when I remeasure the old coil and replace it with a new one.

 

To clear up and answer this, replaced pickup coil and that took care of 95% of tach jumping. Then replaced the ignition coil with a Blue Streak Standard from Oreillys and that cleaned up the last little bit of the tach jumping. Still doesn’t take care of acceleration but I have another thread about that.

And old pickup was 0 ohms across terminals like my title and not open like I said in the post.