How to diagnose bad cam sensor wire ( all things related to timing/ignition replaced)

[that_Z69]

Hello everyone my 1999 k1500 suburban 5.7, was driving perfectly fine until one day It had a hickup sitting at a light, like it just missed a little maybe once or twice but went back to being perfectly fine. Drove 20more miles towards home and then everything went down hill. It started breaking up, had little power almost like it was running out of gas. Went home. Replaced cam and crank sensors, knock sensor, map sensor, cleaned MAF sensor, new distributor, new injectors, fuel filter, ac Delco fuel pump, most recent was new timing chain hoping that would solve it...no dice.
I checked my timing a million times with my scanner and zerod out the CMP retard to exactly 0, blipped to make sure it held reading, supposedly at zero. I think that the culprit may be old wires leading to the cam sensor on the distributor. My question is, how do you isolate a wire break in that? Can I set my multimeter to ohms and check for a break with he battery disconnected, or do I have to check with it powered up? I don't want to fry anything that's why I'm asking before I do anything. Didn't see anything online besides a post of like fixit.com or fixya.com... one of those websites where the original poster at the end talked about it being a bad ground by the firewall. I wish I could contact the original poster but I can't unfortunately. Was wondering if anyone had some insight. My car has been sitting for months due to this issue.

Starts right up, smells a little rich, idles fine, can rev to redline in park fine. Once I'm moving at a certain speed it like keeps misfiring/falling on its face off and on. Like it wants to go but it stops itself, then want to go again, then stops. Fuel pressure is good, have the updated injectors too.

I think it may be an intermittent loss of signal from the cam sensor and is throwing the whole thing off. But I'm no expert

 

[Schurkey]

If the ECM wasn't getting a signal from the cam sensor, you wouldn't be able to synch the cam and crank sensor signals within "0" degrees.

What is the fuel pressure when the engine is misfiring? "Good" is not a pressure.

Use that scan tool, look at the data stream. Verify EVERY sensor, verify short- and long-term fuel trims. See what goes wonky when the engine misfires.

Check spark power with a spark tester that has a spark-gap calibrated for HEI. (Avoid spark testers that have a flashing light-bulb.) Perhaps the ignition coil is weak. How old are the spark plugs and plug wires? Have they been inspected?

When you installed the timing chain, did you degree the camshaft? Or merely install the chain "dot-to-dot"? What is the cranking compression pressure? Is it reasonable for your altitude?

 

[that_Z69]

I did multiple continuity tests....turns out my Innova multimeter is a POS, buddy let me borrow his craftsman and it worked. Found out the middle wire (ground I believe) on the cam sensor wire had no continuity, other 2 wires did. Getting to the harness where that sensor wire ties into is a pain in the a$$. Could I bypass that wire and ground to the body or something, or should I use the probe and find where the actual wire break is and fix that? The harness is hard to pull up to work on that's why I'm asking

 

[Schurkey]

Look at the actual schematic, find out what the "middle wire" does for sure. You're almost certainly going to have to fix that wire so you don't create a ground-loop (if in fact it's a ground wire.)

 

[that_Z69]

Look at the actual schematic, find out what the "middle wire" does for sure. You're almost certainly going to have to fix that wire so you don't create a ground-loop (if in fact it's a ground wire.)

I just ordered a Chilton manual right now. So I'll update this when I get this

 

[Schurkey]

Chilton--and Haynes, and Clymer, and even Motor's manuals make great emergency toilet paper.

Download the REAL manuals from the links in this thread:
www.gmt400.com/threads/88-98-service-manuals.43575/

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

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