Ignition module rewire

syclownz

syclownz

New member
Here's to a shot in the dark.

I read on here somewhere someone rewired their ignition module to ecm and it turned out to be a great idea. Well, I thought I'd give it a try since I keep on getting tach surge or flutter and est code from time to time. Idle will be at 800 or so rpms and then it will drop to 500 then jump up to 1500 rpms. You would barely notice it if you weren't looking at the tach.

I bought the new 4 pin connector from the chevy dealership and rewired the whole thing. took it on a test drive and it was a beautiful thing. No glitches or anything. I start to pull in and the truck dies on me. No warning-just dies. I try and start it but nothing. Has full cranking power just no start. I notice the tach isn't moving while cranking so I go to 2 different autozones and they both tell me the ignition module is good. Wtf! Once again I thought if there is no tach signal then the ign. module is at fault.

I get home and put the ign. module back on and try some stuff before cranking again. Check to make sure I'm getting spark from msd coil >yes and check #6 plug wire (because it is the closest) for spark>yes. While checking for spark on the #6 while cranking the truck fires right up before I could even turn the key back.

Put everything back and try to start truck and everything is fine again for now. I'm affraid to drive it because what if it turns off on me in the middle of the street again? I got lucky my neighbor was home to help me push it UP my driveway.

Did I miss anything when I rewired the 4 wires at the ignition module to the ecm or has this happened to someone before? I did> white wire to pin 8 #423 D
purple/white to pin 8 #430 C
tan/black to pin 7 #424 B
black/red to pin 9 #453 A as per "vault" ecm schematics.
 
wildphil

wildphil

I Love My Ty's
Re: Ignition module rewire

I had one of the wire from the distributor to the coil going open under the insulation. Easy to check. Just wiggle the wires while the truck is running.
 
syclownz

syclownz

New member
Re: Ignition module rewire

wildphil said:
I had one of the wire from the distributor to the coil going open under the insulation. Easy to check. Just wiggle the wires while the truck is running.
Click to expand...

Tried wiggling all the wires at ecm, the computer itself, main wire harness, at the fuse panel and at all the sensors them selves while truck is in idle and no luck. Thanks.
 
syclownz

syclownz

New member
Re: Ignition module rewire

Quadrajet72 said:
EST code is 42, yes? If so this can be set by an intermittent set-timing connector above the passenger's feet. (The tan wire). If this code sets, or is set while running, it will affect idle speed because timing retards a LOT.BUT. 42 won't cause a no-start.



Did you check the pick-up coil in the distributor? The green and white wires going into the module. Should be 500-1500 ohms, and not change while wiggling wires.

I've had intermittent pick-up coils drive me nuts. They're hard to find. The symptoms you describe that I quote are identical to what I had on my first encounter. Sometimes it wouldn't act up for weeks. Then it might stall 5 times getting off my street. It finally quit for good about 10 miles from home. I had to be towed. But I found it. It was the pick up coil.
DaveP
Click to expand...

I made sure I had a good connection with the connector on the tan/black wire every time the code would flash. Code never really sets only flashes. Had a scanner on at the time. I re-did that wire with a new connector.

I replaced the pick-up coil about 2 years ago because of the easy to break wire connectors to the ign. module. They always break when I have to mess with the ign. module. I have the msd pro-billet and I couldn't find the right pick-up coil. no one had it in town so I ordered it through Az. They sent me the wrong one. I had to trim the wires to length but the coil itself was basically the same. Been using it ever since. Gets rust build-up all the time.

Is it possible to get the 2 wires at the pick-up coil to ign. module backwards? Only 2 wires but does the connection order matter?
 
syclownz

syclownz

New member
Re: Ignition module rewire

Quadrajet72 said:
No.

I didn't know this was an MSD system. My ESP wasn't working. Based on all the trouble peeps have with MSD on here, I'd never use their stuff. Good Luck. I don't know shit about MSD. Except that I'll never use it.
Click to expand...

I'm laughing out loud! Sorry, I guess I should have stated that in the 1st post. Seems like a touchy subject.

Have been contemplating getting another dist. but wasn't sure which one. Do you recommend one? I've gathered a lot of people do not like the msd pro-billet.
 
Ty 1885

Ty 1885

Member
Re: Ignition module rewire

syclownz said:
I'm laughing out loud! Sorry, I guess I should have stated that in the 1st post. Seems like a touchy subject.

Have been contemplating getting another dist. but wasn't sure which one. Do you recommend one? I've gathered a lot of people do not like the msd pro-billet.
Click to expand...

Bought mine on ebay, BRAND NEW ( Distributor King ) I belive with cap and rotor (Brass terminals) for under $100. Works great.
 
qbnkiller

qbnkiller

Conflaguration Specialist
Re: Ignition module rewire

I wanted to add something to this thread for history's sake.

I run the stock distributor (Autozone replacement) with my Bigstuff3. Earlier this year, I started having issues that I couldnt put my finger directly on. Truck started running hotter than normal (water temp, oil temp) and was not as crisp a throttle response as before. When I would go out and check timing through the BS3, at idle it was absolutely perfect. This went on for a week until one day when I decided to check the timing for the thousandth time. I blipped the throttle while watching the timing and it did not change (advance/retard). The BS3 timing map would show the ellipse move around, the desired timing would change, but the timing light did not show these changes. I tested for +5VDC onthe EST BYPASS wire to the module (right at the connector at distributor) and it tested good. I pulled the cap off and looked for anything wrong. I found nothing so I suspected the ignition module.

I pulled it out and took it to NAPA and AUTOZONE for testing. Through multiple tests, it always passed. The store manager at AUTOZONE told me (after testing my module 8 times in a row) that sometimes the modules fail when they get hot, and the test bench does not replicate conditions under-hood. He gave me a new replacement module, I went home, and threw it in. Timing control came back and all was well.

I thought this info might help someone in the future diagnose potential issues.
 
syclownz

syclownz

New member
Re: Ignition module rewire

I knew it! That's worth it's weight in gold right there my friend. They test them but under cold conditions and not like you said under-hood conditions. One guy there at AZ was trying to run multiple tests to see if it would heat up for a more proper test but fail he did.

So it is possible I may have a bad module. Thank you!
 
B

bonesdmz

In Mother Russia Typhoon drives You!
Re: Ignition module rewire

Interesting. My truck runs good when its cold, and starts to misfire a bit when its very hot outside, or after long runs.
Maybe I have simular issue.
 
syclownz

syclownz

New member
Re: Ignition module rewire

Just a heads up after doing this rewire and replacing the ignition module and relocating it to the firewall. Truck runs great now. Jumpy tach needle is gone and idle is good.
 
syclownz

syclownz

New member
Re: Ignition module rewire

syclownz said:
Just a heads up after doing this rewire and replacing the ignition module and relocating it to the firewall. Truck runs great now. Jumpy tach needle is gone and idle is good.
Click to expand...

Scratch that, truck still has that jumpy needle from 800ish at idle then drops to 500 then up to 1500 then back down to 800ish rpm's in the blink of an eye.

Don't know what it is or what to do. This needle is really pissing me off.

Anyone have any thoughts?

p.s. It's not just the gauge because if you listen to the exhaust there is a small burp.
 
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