Perpetual Diagnostic Black Hole of a vehicle

[Witsend]

Got a 94 Camaro 3.4 V-6 I fixed a bunch of service engine soon codes, timing cover gasket coolant leak, and blown rusted brake line. Car had a long crank , hard start/ no start condition. Code 82 was fixed for a 3X cam sensor signal . Circuit was verified pigtail connector was replaced at ignition module and a new AC Delco 3X crank sensor installed and even a new Cam position sensor( because the wire insulation was failing I broke plastic retainer and flange trying to free it and pull it out of block) Glad I decided to mess with the cam sensor while the timing cover was off, because I had to literally push it out of block from the inside outwards with Cam gear off with a radiator hose removal tool. The Timing chain damper was missing pieces, so the chain, gears and damper got changed out while doing timing cover gasket.Put all together, there is now no service engine codes , but the long crank hard start or crank no start persists. Repeated start attempts usually gets it running and when it starts on all 6 it runs great until you turn it off and have to restart.
Fuel pressure is 42psi , all injectors ohmed out about 13ohms. Once in awhile while cranking it seems to resist cranking like having an over advanced timing. The passkey security light does go out within 5 seconds turning key on engine off . The pass key circuit has already been bypassed with a resistor loop of the same resistance of the pass key pellet. Hit or miss starting and often have to tip in the gas pedal and pump it to keep it going. Sometimes it starts and runs on half the cylinders, sometimes starts up fine and runs perfectly. I'm thinking a quad driver for half the injectors isn't being turned on. I had it running on some cylinders and had good spark coming out of a coil for 2 and 5 and no change in rpm (stall out ) when pulling cable off either tower and letting the spark arc to a jumper wire to ground .
Even though this seems like a pcm quad driver issue to me , I'm inclined to slam the ICM:

[greasybob]

As I remember weren't quad drivers on GM used to supply voltage to various sensors or actuators and not ground them ? I'm probably wrong about that, cars don't last long enough around here to see this old stuff much. Do you have good battery voltage on both fuse 9 and 10 ?
All this talk about black holes got me to wondering, aren't they all perpetual ? What happens if you starve one ? Will it break up ? Can it consume all the time that's been available since the beginning of time ?

[Witsend]

Power probe registered power on both 7.5A fuse 9 and 10 KOEO and removed the fuses and fuse box terminals appeared ok. I should still check voltage at the 2 power feeds to 10 pin connector for the fuel rail feed while cranking engine though.

[Witsend]

Very Low running KV a tip off to check the spark plugs

Got all the codes fixed but long Crank hard start persists . Verified all fuel injector traces ok . When it starts up and run on all 6 , it runs and drives out fine without hesitation or miss till you turn it off and the whole process occurs again. Tried a new IAC valve because it seemed to help tipping in the gas pedal , but new IAC valve made no difference. Hooked up the ole Counselor in secondary menu and the KV requirements look way too low.
Decided to look at the plugs. Anyone think a new set of plugs might make a difference for this hard start problem?

[Crusty]

First thing, what's with the one old rusty different plug-??

Second, all those plugs are fuel fouled----why-??

Third, if a "tip-in" part throttle opening helps a start up, the throttle body is probably "coked up". The older term of "Minimum Air Rate" should be setup after the throttle body is cleaned. Setting minimum air rates has always helped the vehicles that need just a wee bit more air on startup, regardless of manufacturer (as long as it stays within ECM control)
The IAC is only part of what allows the air to enter for initial startup.

[Witsend]

When this thing is running it seems to run just fine and at first glance the spark plug shells look rust free like they were replaced not too long ago , so I didn't proceed to inspect any from the beginning, and went after the codes first.
I repaired the intake air temp circuit that at times read minus 40 degrees , there was no thermostat making things run cooler and richer for longer periods of time. I repaired a vacuum leak that restored some HVAC functions that also may have also messed with the MAP sensor. I repaired a 3x crank sensor code too.
The different plug was hard to get at under EGR pedestal, so some one obviously let it go without the newer one.
There was no fuel pressure bleed down but obviously some past contributors to causes for rich running condition.
I cleaned out the throttle body and Iac passages which might have got the plugs even more sooty.
I would da got fired if I was working for anyone else but myself.

[Crusty]

HaHa...not the first time a six cylinder got a five cylinder "tune up"-!!

Coolant sensor open circuit at -40 and no thermostat would explain the soot on the plugs..... too much fuel at -40 and too much fuel with no thermostat either. OK, there is a good explanation for the sooty plugs.

Once it gets up to full temperature, with all accessories OFF, pull it into drive and let it sit for about 2 minutes running. Look at the IAC "counts". 10-counts, 15-counts, 20-counts is a good minimum air rate.
"0" counts is the ECM command to bottom out the IAC valve and 255-counts is the command to back the IAC valve all the way out.
Then put it into an A/C mode (or defrost) and the counts should come up a bit. (maybe 5, probably not more than 15)
If you see an engine with 45 or 70 or more IAC counts, the throttle body is badly coked up and the IAC opening on a cold start isn't enough for the engine to "breath" on initial startup.

[Witsend]

not out of the woods yet . Put a new set of 6 new R43TSK in it and it still has same long crank hard start, but when it does start and runs on all 6 it runs ok and the KV looks a lot better but still see a minimum KV of only 1k, so before I slam the new $56 Air tex Wells Rock auto ignition module on Tuesday I might try some injector cleaner fuel conditioner mixed in a 5 gallons of fresh gas and see what happens.

[Witsend]

At operating temperature in gear with my foot on brake I have a IAC count of 13. I do not like what my Baro in hg and Baro voltage reads at and Map actually reads about 10.7 hg in gear and about 12.0 hg in park at idle. Strange. I did a cranking amperage check twice and cylinder 5 and 6 refused to register on the test , so I'm still thinking it's going to be an ICM and a coil or two that's going to finally resolve the hard starting.

[Crusty]

As I remember weren't quad drivers on GM used to supply voltage to various sensors or actuators and not ground them ? I'm probably wrong about that, cars don't last long enough around here to see this old stuff much. Do you have good battery voltage on both fuse 9 and 10 ?
All this talk about black holes got me to wondering, aren't they all perpetual ? What happens if you starve one ? Will it break up ? Can it consume all the time that's been available since the beginning of time ?

No, the quad drivers controlled the grounding of a circuit (4). Sometimes a solenoid wouldn't have enough resistance and yet it would still work, but, it would overcurrent the "quad" driver and another circuit wouldn't function.
THAT was why it was important to verify the pinout resistances of any ECM controlled solenoid device so it wouldn't take out the new ECM.
Later on they current protected the quad drivers so they would simply shut down and not burn out.

[Crusty]

not out of the woods yet . Put a new set of 6 new R43TSK in it and it still has same long crank hard start, but when it does start and runs on all 6 it runs ok and the KV looks a lot better but still see a minimum KV of only 1k, so before I slam the new $56 Air tex Wells Rock auto ignition module on Tuesday I might try some injector cleaner fuel conditioner mixed in a 5 gallons of fresh gas and see what happens.

At operating temperature in gear with my foot on brake I have a IAC count of 13. I do not like what my Baro in hg and Baro voltage reads at and Map actually reads about 10.7 hg in gear and about 12.0 hg in park at idle. Strange. I did a cranking amperage check twice and cylinder 5 and 6 refused to register on the test , so I'm still thinking it's going to be an ICM and a coil or two that's going to finally resolve the hard starting.

Definitely clean the injectors.

Check the resistance from one paired coil tower to the other with an ohmmeter. Should be between 5,000 ohms and 7,000 ohms (some specs say 5 to 8)
After that check each plug wire for the capability of firing the ST-125 spark tester. Very often when one plug wire won't jump the tester gap, the problem is the opposite paired plug and ignition wire (or the coil)
Coils are paired 1/4, 2/5, 3/6

[Witsend]

This PCM appears to have 6 individual ground switching injector drivers, so pretty sure it is higher up on the tech chain than GM's Quadzimoto ones. I think I'm going to pull the PCM connectors and individually load test the ground wires and power supplies with a halogen headlamp bulb.

As far as the Cranking amp test only showing results for only 4 cylinders. I don't know if I'm loosing spark on a coil or not , because Cylinder 5 and 6 are not paired cylinders on a single coil. I did have the DIS adapter hooked up , but I'm not sure if the Byzantine technology of the Counselor can handle and make sense of the cranking true and waste spark of DIS ignition system to display correctly or not.

[greasybob]

Tipped in throttle and it starts ?
Fouled plugs ?
Extended crank ?
Where are your fuel trims ? ? You got a leaking injector or pressure regulator ?

[Crusty]

Tipped in throttle and it starts ?
Fouled plugs ?
Extended crank ?
Where are your fuel trims ? ? You got a leaking injector or pressure regulator ?

Bob, the coolant sensor showing -40 degrees and no thermostat would make it run colder than it should ALL the time, thus increasing fuel delivery, thus the fouled plugs.

Checking the integrator and block learn for fuel trims is a good idea but only after the secondary ignition has been verified that it can deliver consistent spark in the shop.

[greasybob]

Sorry, I must have read over (skipped) that part.