Seriously need help, wierd Voltage issue

[Schmieder]

Well, I didn't get a chance to start it yet but....

I found a strong short in the upstream O2 sensor and confirmed it with the DVM.

BATTERY removed for this resistance test. Low resistance on a positive circuit shows a short.

UNPLUGGED O2 w/ KEY ON
F/INJ - 1.6k Ohms & 15m Ohms
ECM IGN - Infinite & 1.6k Ohms
ELEK IGN - 25m Ohms & Infinite

PLUGGED O2 w/ KEY ON
F/INJ - 1.6k Ohms & 3.9 Ohms
ECM IGN - 4 Ohms & 1.6k Ohms
ELEK IGN - 25m Ohms & 4 Ohms

4 Ohms is not much resistance at all, that is a huge discharge from the battery. And they all ground to the ground cable that had the burnt tips where it met the trans bellhousing. Ground G-113.

The O2 Heater element read about 4 Ohms. Far to low for any heater element.

[robertisaar]

~52 watts of heat.... i bet the O2 warms up quickly.

[Schmieder]

~52 watts of heat.... i bet the O2 warms up quickly.

So is that a normal reading? I do need to educate myself some more on general electronic principles.

[robertisaar]

if i had to guess, i'd say it was shorted internally, since normal O2 heaters are only around 5-10 watts, IIRC.

[Azrael]

My O2 sensor heater circuit reads 6.2 ohms which is about 30W.

[Schmieder]

My O2 sensor heater circuit reads 6.2 ohms which is about 30W.

Is that between the two heater circuit wires or is it the feed wire to the frame ground?

I have two and they read 3.4 Ohms and 4.3 Ohms. One is the original and the other is the new one on the DP. I did that to have an O2 on either side of the turbo to see what worked better while tuning.

[Azrael]

Between the two heater wires. I don't have a downstream O2 to compare against yours.

[Schmieder]

Between the two heater wires. I don't have a downstream O2 to compare against yours.

Downstream isn't necessary, mine is turned off but still plugged in. The car ran w/o a downstream.

My O2 reads 3.4 Ω from either heater element terminal to the frame. The car should still start w/o the O2 plugged in but I had no such luck.

Well, the engine STILL stumble barely to it's imminent stalling. At times it feels/sounds like it wants to fire backwards (strange I know). Like a REALLY bad erratic spark. And just as the engine makes it's last puff of combustion, it seems like it goes backwards at times. The spark degree also fluctuates from 0° to 19° like a square sin wave form coinciding w/ voltage drop to 5-7v while stumbling.

I'm about ready to start pulling hair!

I'm beginning to think the trans swap, 4t60e to getrag 282, has affected the grounding of the system somehow. But I had since tried jumping cables to quick ground the trans-ground spots w/o any improvement really.

Can an ICM and/or Coils rot sitting 8 months in a dry basement?

What about the sub-frame? Is that a critical structure requiring a proper ground? Thinking the 4t60e had a steel bracket to the sub-frame?? I know I have two new mounts.



Any more advise would be great. Like how to hunt down a voltage drop properly, I'm more Noob w/ electric engine function then mechanical function. My digital voltmeter can read to 0.1 Ω resolution and can measure AC volts as well.

[pocket-rocket]

I don't recall the 4t60-e having steel mounts or brackets to the sub-frame. No, ICM and/or coils should not go bad sitting in a dry basement. I think you may be on the right track with the CPS wiring that you mentioned earlier. CPS wires don't like to be modified and having sections untwisted (like crimp connections) will induce interference that the ICM does not like. The CPS wires are twisted to reject noise and interference like Cat5 cabling.

[robertisaar]

i know the later 4T60Es had a structural side pan, i believe that had a steel mount?

[pocket-rocket]

I know my 4t60-e's had a mount that was steel that went around the pan, but it bolted to a rubber isolating mount on the side to the sub-frame. You never see a solid steel mount between a drivetrain and structure in a domestic road going car.

[Schmieder]

Well, the CPS wire isn't the problem. I cleaned up the soder work, used heat shrink, maintained a very healthy and consistent twist, wrapped electrical tape around it, wrapped aluminum around that then electrical tape the aluminum nice and tight. I then spliced a ground wire tip for 6" of copper and braided that to the aluminum foil, finished wrapping it.

So the CPS wire is 100% shielded from sensor to ICM. At least I'll have a clean signal...lol

At this point, since the PCM fried way back in the beginning of these issues, I have to consider the CPS sensor and/or the ICM was damaged. I was so stubborn to believe the ICM could be bad as it worked perfectly (car ran great) before the trans swap and was stored dry and safe.

So, ugh, I'm going to replace the 3xCPS (or 7x, can't figure which one it is) and if that don't work, get a new ICM. The current CPS and ICM are factory so I don't feel to bad replacing it. I heard a new AC Delco ICM will provide a good strong spark.

As it goes so far, everything I end up replacing I used the higher quality option. ACDelco is a common name in my cars description now. I hope to make it last many years, once I am done building her up.

I just want to get her running so I can move on and repair body, repaint. I decided on a dark storm grey with metallic shimmer HIGH gloss polished over and over again. Acrylic Lacquer provides a really nice sheen.



jeese, what a run on......

Anyone know a good way to test the ICM for proper functioning? Already tested the ground and 12v feed, all wires are good (no open circuits)

[Schmieder]

My 7xCKP wire was wired backwards, lol. I had used the wrong pigtail by mistake of assumption. There were two pigtails available when I rewired the CKP sensor wire. One for the VSS and the other the CKP pigtail. Both are twisted Yel/Ppl wires, both are 2-pins, both have blue o-rings and both were cut the same length. BUT, the colored wires were reversed. The VSS had pin-A one color while the CKP had pin-A the other color wire.

So I had used the old VSS pigtail by mistake. The wires were soldered together according to wire color, which appears as proper. But clearly shows otherwise when it was figured out.

So, when a manual swap is done, keep the VSS pigtail FAR away from the CKP wires, lol.

[pocket-rocket]

One reason I didn't think of this, when we did the swap on the 91 the CPS wire never got unplugged, so the VSS hung by its lonesome.

[Schmieder]

One reason I didn't think of this, when we did the swap on the 91 the CPS wire never got unplugged, so the VSS hung by its lonesome.

This is a lesson in details and careless assumptions. From now on, under no circumstances will I ever loose track of a pigtail, or any part again.

I pulled the engine out so the CKP connector was disconnected. During my confusion finding which 2-pin ppl/yel pigtail was the CKP vs the VSS, they got swapped somehow. Later realizing the CKP was wired to the right device, the ICM, but the wrong way.

Oh man, such a confusing sensation of joy and shame...lol

I'm sure I'll get over it when I get to make that first hard pull in second boosting up.

What' funny is I kept replacing ignition parts, replaced battery cables, did the big 3 ground upgrade and they ALL had a positive effect on combustion. As the engines attempt to run was better but not proper. So in the course of all this my ignition system received a nice upgrade. AND I still have a 220 amp HO Alternator in transit.

On a positive outlook, I have lots of spare parts, lol. Spare ICM, spare plug wires, spare alternator, extra battery, a home made fuel injector cleaner, and more I know I'm forgeting.

Pocket Rocket deserves a big round of applause for all the help he has provide me over the weeks! He is a true Soldier of the Motor. General 60v6, lol. Robertisaar also provide some insightful knowledge along with others, even though I didn't mention names, I am grateful for your help.

In the coming weeks, I'll have some cool HD Videos to share. I happened to receive, as a gift, a REALLY nice HD Digital Camcorder. I also have an expensive professional microphone. I am going to build a steel cam mount that can be attached to the headliner frame for consitant, stable videos. What can I say? I love to build stuff.