2007 Equinox 3.4 U0131 No Comm to Pwr Steering

Doc n2mx wrote: Hi…
I would look at all connections pcm etc. This vehicle is known for bad connections. I have found issues just an inch or two in the harness. I also found bad body Grounds the same way. I also found that the person before me opened one of the pins on the PCM thus not making good contact…


Good luck.

Doc n2mx

I have been through all of the grounds, Ben advised me to do that, I found the one in the RH kick panel had a little more resistance than I liked, I got it down to 0 and the one under the driver's seat was also nearly 2 ohms, it is now at 0. I had the ECM out once and looked at the ECM pins, I am probably gonna pull it out again tomorrow and do an old school injector balance test from the ECM connector because 1) the stinkin car won't allow the scan tool to run an injector balance test and 2) the injectors are buried beneath the intake. I will look at the connector with a magnifying glass and see it anything look bad. I am trying to get my hands on some DeOxit D100. it is said to be spectacularly good at curing oxidized connections.

Gary

Gary B wrote: It was bad first thing this morning, probably a dead miss on Cylinder 2 for a while, it counted up 388 misfires in about 30 seconds. Got better pretty quick and as soon as I got it in drive and started down the road it was fine. It almost never misfires when it is not idling.

OK cool, got a pattern to follow. Love it. I don't suppose you caught a secondary waveform during this period?

#2 is on the front bank, right? I hesitate to say it, but a head gasket leaking coolant into the cylinder while hot soaking matches your symptoms. You could check for this by doing the hot soak, then pull the spark plug and bring that cylinder to TDC. Or, do a clear flood crank and look for coolant to spit out of the cylinder during cranking.

Tyler wrote:

Gary B wrote: You could check for this by doing the hot soak, then pull the spark plug and bring that cylinder to TDC. Or, do a clear flood crank and look for coolant to spit out of the cylinder during cranking.

I tried this Saturday morning with the engine cold and then again last night after getting home, neither time did I see or smell any coolant. I pulled the spark plug and unplugged the ICM, stuffed a while paper towel down into the well where the spark plug goes and cranked it.

Here is a shot of part of the data I collected, the upstream O2 is on top, the waveform does not look right to me, the frequency is too high, I am used to seeing about a one second sweep but this thing is jumping all over the place and it doesn't go from 100 to 800 ish, often it runs in a tight band of a few mV.

I have the whole file of course, it is 4000 frames, or 71kB if anyone is interested in seeing it.



Also I did run an injector balance test with the OTC buzzbox, I started at 50psi each cylinder, I used the setting in the middle, 50 pulses @ 10ms, and they all ran down to 34, dead even.

One more thing, I discovered that the ground for the ECM is not the one I thought it was, once again, it is not even near the ECM but there are two ground within 12" of it. I checked the actual ECM ground and it is dead zero.

Gary

Zoomed all the way out gives a better perspective on it... this is different file, it is about 20 minutes earlier than the first one...

Was this taken at idle or driving or part revving? It's not uncommon to see 02s readings lag with missfires

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Also is the engine fully warmed up when this is taken?

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Ben wrote: Was this taken at idle or driving or part revving? It's not uncommon to see 02s readings lag with missfires

Hi Ben,

This was on the Interstate at a pretty steady 65mph and the engine was fully warmed up. One capture was started about 20 minutes into the trip the other was about started about 5 minutes in.

It doesn't look horrible to me for driving was you experiencing any misfires during your drive?

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Ben wrote: It doesn't look horrible to me for driving was you experiencing any misfires during your drive?

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Hi Ben,

No, it only misfires at idle. If I even crack the throttle the misfires stop, I put a lot of water on that engine looking for vacuum leaks but did not find any and the fuel trims are pretty good even at idle so I am not convinced that it is a vacuum leak. As soon as I crack the throttle the fuel cell changes and the misfires stop. At idle, iirc, the fuel cell is 14 for what it's worth.

One thing I have noticed since I am driving it more is that it is getting terrible fuel economy. I was at first thinking that the trip odometer was resetting when I disconnect the battery but that does not seem to be the case. Although it's reporting over 23mpg it's actually getting 13mpg. I will use the odometer next time instead of the trip odometer in case I have to disconnect the battery again so I can be certain. I can smell that it is running rich yet the LTFT is positive, STFT is 0 and the O2 sensor is showing a rich condition most of the time. That doesn't make sense to me.

Gary

I don't remember did we test the 02 sensor by providing a vacuum leak and propane to see how it responds ? If not let's do this now

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Ben wrote: I don't remember did we test the 02 sensor by providing a vacuum leak and propane to see how it responds ? If not let's do this now

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I don't remember either, here is a screenshot of normal, then I start adding propane around frame 700 to about 1200, then pull a vacuum leak around 1500 to 1600.




here is another with a few more pids




I saw Tyler or Noah use a PID sharing service but I don't know how to do that yet, I can email the full files if you want them. But, what I see is the STFT reacts to both the propane and the vacuum but the LTFT never reacts to the propane. I'm going to do another test with propane and vacuum and watch the misfires.

Gary

That'd be www.scanshare.io/ . ;) Free to sign up and share data.

Also, that data looks good for the propane test.

Tyler wrote: That'd be www.scanshare.io/ . ;) Free to sign up and share data.

Also, that data looks good for the propane test.

Thanks Tyler,

Why doesn't the LTFT ever adjust during the propane test? I see it start adjust almost immediately for the vacuum leak, once the STFT hits 22 the LTFT starts adjusting but during the propane test it never does even though the STFT seems to max out at 32.

Propane Test

Propane and Vacuum Leak Test

Gary

Gary B wrote: Thanks Tyler,

Why doesn't the LTFT ever adjust during the propane test? I see it start adjust almost immediately for the vacuum leak, once the STFT hits 22 the LTFT starts adjusting but during the propane test it never does even though the STFT seems to max out at 32.

Propane Test

Propane and Vacuum Leak Test

Gary

Nice ScanShare links. I see what you mean... Not sure? The 'FUEL TRIM LEARN' PID is enabled in both cases. :huh:

I'm speculating that it's a programmed behavior, as they may not want the PCM to adapt too quickly to a false rich condition. Then you end up with stalling, poor acceleration, high cylinder temps, ect. I wonder what would have happened if you'd have kept the propane on it longer? :huh:

Tyler wrote: Nice ScanShare links. I see what you mean... Not sure? The 'FUEL TRIM LEARN' PID is enabled in both cases. :huh:

I'm speculating that it's a programmed behavior, as they may not want the PCM to adapt too quickly to a false rich condition. Then you end up with stalling, poor acceleration, high cylinder temps, ect. I wonder what would have happened if you'd have kept the propane on it longer? :huh:

Thanks, the credit goes to you though for letting me know about the scan share site.

I left the propane on long enough that the tips (I used both torches that I have) frosted up and the bottle pressure started dropping, you can kinda see the STFT start to rise slowly so I shut them off. I will try again and time how long that takes and also see how quickly the LTFT takes to react to the vacuum leak. Those tests that I show here were actually the third and fourth tests so the bottles had lots of time to get cold.

I want to get an extension hose that I saw in a video that will allow me to keep the bottle upright and see if that that helps keep the frosting issue down, it seemed like it was restricting the flow but I am not sure, it may have all been the chilling of the bottle. The hose will also let me partially submerge the bottle in warm water, which is a trick I use extensively for recharging air conditioners.

Gary