n3squ1ck

Hey guys,
here a small list i made so youll get a better understanding of what i did and what is the issue.


What is the issue:

• Engine is stumbling if you hit the throttle a bit harder in P at around 1500-2000 rpm it stutters, stumbles and cracks (misfires).
  
• If im driving it drives like **** (same as above, stutter, misfires, at around 1000-1500)
  
• If i accelerate i can mitigate the issues mostly and it runs “fine” until i start to glide again, then it runs like **** again.
  
• Hitting full throttle mostly works as well
  

Known other issues:

• The silencer has a hole and needs changing
  

What did i do:

• Cruisers tips 1-5 8 11
  
• I redid all the grounds, cleaned them and added new ones
  
• I redid all the power cables
  
• New batt terminals (to get rid of the chinese car audio bs ones)
  
• Changed the (potentially broken) original GM MAP for a new Walker one
  
• Changed the Valve Cover Seal for a Fel Pro one
  
• Changed the EGR valve seal for a Fel Pro one (and figured out it got deleted beforehand)
  
• Closed down the vac line to the EGR since PO just deleted it and left the vac line hanging
  
• New Champion Spark Plugs
  
• New IG Cap, Finger and Cables
  
• Set the TPS correctly (was .53 is .85 now)
  
• Measured the fuel pressure, don't remember exactly, but it was in line with what was written online
  
• Since im vaping i took the chance and blew out the TB with vapor to check for any Vac leaks (went in through the fuel pressure regulator connection) and couldn't see any leaks
  
• Changed the front vac harness since it was broken
  
• Couldn't change the rear harness because the new one doesnt have the line to the CC Module (can i delete the Cruise Control?)
  
• Resistance Harness near the Valve cover 0.9
  
• Resistance DiPstick 0.4
  
• Cleaned the relay contacts of every relay i could find
  
• Cleaned the IAC
  
• Cleaned the TB without taking it out
  
• Cleaned the TB Air Temp Sensor
  
• Cleaned every electrical connection i could find that needed cleaning
  
• Welded rusty spots
  

What did i test:

• MAP with vac disconnected runs better then it does now, no misfire, cracking or stumbling, accelerates perfectly fine but dies sometimes at a standstill, sometimes doesn't start or just starts while hitting the accelerator pedal, was able to drive for around 30-40 minutes perfectly fine
  
• Map with vac connected, O2 Sensor disconnected doesn't change anything obvious
  
  
  I found this btw. looks quiet fishy, but it ran like that obviously the last years...
  
  
  

cruiser54

I hate throwing parts at things, but I wonder if your coil/ICM is bad.

At idle wiggle the engine bay harnesses and see what happens.

n3squ1ck

Hey Cruiser,
i do so too but if it helps i can try, i didnt change the coil yet, have to order one in the states since here in germany you cant pay them...
You're talking about the harness at the valve cover? I'll try!

€: I did wiggle it while in idle, it didnt get rougher then it was before, it felt like nothing changed, then again it wasnt a smooth idle before.

cruiser54

That coil/ICM is a European part.

n3squ1ck

That meassurement looks fishy to me, if i meassure - and + its pretty jumpy and as far as i know it should be at around .5 shouldnt it?
Also i cleaned the ICM and the Coil contacts, can i meassure the ICM before i put it back?
If that wont help im going to order both, still in the US, since its cheaper and i trust rockauto more then german partsstores

cruiser54

I found this in my archives. FWIW.

Three wire connector:
A = +bat voltage (from latch relay)
B = Ground....
C = Tach

Two wire connector:
only wire hooked up = spark pulse from ECM (5v square wave)

So, as I figured above, the ICM is just another version of the Duraspark II ICM (or more accurately, ignition amplifier, since all it does is take a TTL pulse and amplify it into ignition coil drive).
This one just gets the pulse from the PCM instead of directly from a hall effect sensor in the dizzy....

So, I rechecked the ground wire to the ICM (unplugged the 3 wire connector, measured from the B pin in the connector to the - battery pole. 0.1 ohms. Then I rechecked the +voltage. Battery voltage present when key is on..

So, I hooked up my scope to the 5 volt pulse line (back probed, both plugs connected to ICM) and grounded its ground clip

The ECM provides a nice pretty pulse both when the engine will run (it was nice enough to run for 30 seconds while I did this test) and when it has no spark.
When the engine died, the pulses continued until the engine stopped spinning (as one would expect with the key in the on position).

At this point, it is my opinion that if I can send a pulse into the amplifier (ICM) and not get a spark out, then the amplifier (ICM) must be bad....