stalling, low oil pressure...pulling my hair out.

Voymom

Original poster
Member
Feb 3, 2012
2,523
So I went to go pick the kids up from the bus stop as it was raining. I backed out of the driveway like I normally do, and as soon as I hit the break and put the truck into drive...the DIC said low oil pressure and the truck died. Mat came out and we started it back up, and it started perfectly fine, and as soon as I touched the gas pedal....boom stalled again.

I have an issue with the RPM's dropping when I lightly press on the gas pedal..it drops to the point of an almost stall, the RPM's drop from about 600 to 200-300. I have had this issue for a while now and could never diagnose the problem. I kind of just learned to deal with it because it has only ever stalled once in the last 8 months. But having it stall out twice back to back in the same day is a concern to me. No codes, no nothing. Oil pressure is fine. Besides the dying fan clutch and a few bad end links the truck is mechanically sound.

I did notice on my OLM that the oil is reading 88% when we have just recently(a month ago) changed the oil, seems like the oil is getting dirty a lot faster, and due to the weather it's my time to stop driving like a bat out of hell, so I have actually been taking it pretty easy on the truck lately. I used Mobile 1 full syn.

I'm at a loss and I appreciate all the help, opinions and advice I can get.

Would an injector cleaner be a good place to start? If so....please let me know what would be the best one to use, don't care about cost at this point, just want my truck better.

http://www.youtube.com/watch?v=FIibJnOAPzE&feature=youtu.be
 

MAY03LT

Member
Nov 18, 2011
3,425
Delmarva
Voymom said:
No codes, no nothing.

Was that verified with a code reader/scan tool? There is one code that comes to mind that can cause intermittent stalling and can set in the pcm memory but won't turn on the CEL until it fails X amount of times in X amount of drive cycles.

Voymom said:
Would an injector cleaner be a good place to start?

IMO, nosolutely.:no:
 

Voymom

Original poster
Member
Feb 3, 2012
2,523
MAY03LT said:
Was that verified with a code reader/scan tool? There is one code that comes to mind that can cause intermittent stalling and can set in the pcm memory but won't turn on the CEL until it fails X amount of times in X amount of drive cycles.



IMO, nosolutely.:no:

May- Yes that was with a scan tool. I don't have one on hand but whenever there is an issue I can get the codes ran free at the O Reilly's. There was nothing stored and nothing immediate, clean as a whistle.
 

Voymom

Original poster
Member
Feb 3, 2012
2,523
What about the IAC valve being bad??? I know it is located in the throttle body, and with the low, slightly rough idle, and the stalling issues....I would think that this could be possible. But if this were the case wouldn't the truck throw a code?
 

RayVoy

Member
Nov 20, 2011
939
Tami, the oil pressure switches fail on the I6 engine. Mine failed ('05 Envoy), and a number of others have had the same problem.

The switch is mounted just above the filter.
 

Voymom

Original poster
Member
Feb 3, 2012
2,523
RayVoy said:
Tami, the oil pressure switches fail on the I6 engine. Mine failed ('05 Envoy), and a number of others have had the same problem.

The switch is mounted just above the filter.

Would that cause the other symptoms as well? I found that the Envoy does not have an IAC (Idle Air control) valve....so that can't be right. I was thinking about the throttle body sensor but apparently I don't have one of those either?? My other guess would be the fuel pressure sensor? I did have the fuel level sensor take a shit on me, and isn't the fuel pressure sensor and the fuel level sensor the same thing?

I don't have any other oil lights or oil issues except when it stalls out completely. How much was it for you to fix? I would hate to throw $80.00 here and $90 here for it to not be the issue.

The stealership cannot diagnose it because they can't replicate it, when I told them up front that in order for it to happen they need to keep the damn thing over night and do a cold start. I know it will be hard to diagnose because there are no codes. But something has to give.

I wanted to mention that I ONLY got the low oil pressure light on the DIC once and only when it stalled. If that makes a difference at all.
 

RayVoy

Member
Nov 20, 2011
939
Mine didn't die, the 2nd time, as fast as yours, it would restart and run fine for maybe 30 mins, then be fine for the next time I would use the truck. but, over the couple of days before I fixed it, it may have died 10 times.

The dealer had one in stock, told me they keep a couple because they fail so often, only a few $, I don't remember, but I'll guess at $25 (I get a discount if the right parts guy is there).

Easy to change, one hour tops.
 

Voymom

Original poster
Member
Feb 3, 2012
2,523
RayVoy said:
Mine didn't die, the 2nd time, as fast as yours, it would restart and run fine for maybe 30 mins, then be fine for the next time I would use the truck. but, over the couple of days before I fixed it, it may have died 10 times.

The dealer had one in stock, told me they keep a couple because they fail so often, only a few $, I don't remember, but I'll guess at $25 (I get a discount if the right parts guy is there).

Easy to change, one hour tops.

Well at that rate I can start there then. But if it doesn't fix the issue, I am finding Iowa's biggest cliff, getting a few gallons of gasoline and lighting this bitch on fire :biggrin:

But on a serious note, thank you! It's better than what the dealership told me to do, and a million times cheaper lol

I'm still open to other idea's and option too, so feel free to keep chiming in. At this rate I'm willing to try just about anything.
 

RayVoy

Member
Nov 20, 2011
939
On these trucks, the I6 oil pressure switch is like the ignition switch, not a case of "if it fails", reality is, "when it fails".

Good news is, both are cheap.
 

Voymom

Original poster
Member
Feb 3, 2012
2,523
RayVoy said:
On these trucks, the I6 oil pressure switch is like the ignition switch, not a case of "if it fails", reality is, "when it fails".

Good news is, both are cheap.

Well if all goes well I will be replacing the oil pressure switch on Monday....I just hope the truck makes it up north for the wedding this weekend lol
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
In general, if the switch is OK, then the low oil pressure is a RESULT of the low idle and stall-out. Not a CAUSE.

Dirty throttle bodies and crappy CPAS solenoids are the typical causes of low/erratic idle. I think you have cleaned the throttle body recently, and I don't know the state of your CPAS.
 

McGMT

Member
Jun 17, 2012
621
the roadie said:
In general, if the switch is OK, then the low oil pressure is a RESULT of the low idle and stall-out. Not a CAUSE.

Dirty throttle bodies and crappy CPAS solenoids are the typical causes of low/erratic idle. I think you have cleaned the throttle body recently, and I don't know the state of your CPAS.

ahhhh she had that CPAS problem not long ago from an additive, maybe it IS on its' way out.... Here comes the big brain... :wink:
 

Voymom

Original poster
Member
Feb 3, 2012
2,523
Yes..I did indeed have the cpas issue a while back, thanks to Mat and his engine restore lol. I did an oil flush and cleaned the cpas as it did throw a code back then, but after cleaning it the code was gone and I thought nothing of it. Do I just change the solenoid part that I cleaned, or is it a bit more difficult than just swapping it out?

Also would a faulty cpas cause a restriction in fuel/air mixture? Or I guess in other words, when they do fail what is it that causes the disruption?

My Throttle body is clean as a whistle!! I just checked it a month ago when I changed the oil.
 

Voymom

Original poster
Member
Feb 3, 2012
2,523
So, I talked to Mat and after careful consideration we have decided to just go ahead and get a new CPAS since we have had issues with it in the past, it just makes sense. If that does not clear up the issue we will try the CPS...does the cam position sensor need a relearn? I know the CPAS does not, but wasn't sure about the CPS.

If neither of those clear up the issue, I am going with plan B...Gas, cliff, match :biggrin:

As always, thank you everyone who has helped me with this very frustrating issue. :thumbsup:
 

C-ya

Member
Aug 24, 2012
1,098
Voymom said:
isn't the fuel pressure sensor and the fuel level sensor the same thing?

The fuel pressure sensor would most likely be in the fuel rail, in the engine bay. (I have not looked in the manual, just theorizing based on experience.) The fuel level sensor is in the tank - this is what provides the input for the fuel gauge.
 

Voymom

Original poster
Member
Feb 3, 2012
2,523
the roadie said:
Camshaft PS does not need a relearn. Only the Crankshaft position sensor, and that's at the back of the engine near the flywheel.
Thank you Roadie!!! I don't think I need to worry about the Crankshaft Position sensor, or at least right now I don't.....hopefully.

Edited- Hey Roadie do you have any references to where I can do some reading on the CPAS? I'd like to know how it works, and aside from filtering the oil...what else it does for our trucks. I tried google, but I get 50 answers to one question and I don't know which one is the correct answer.

C-ya said:
The fuel pressure sensor would most likely be in the fuel rail, in the engine bay. (I have not looked in the manual, just theorizing based on experience.) The fuel level sensor is in the tank - this is what provides the input for the fuel gauge.

Thank you C-ya for letting me know the difference. I got really confused talking to the parts guys :redface:
 

jimmyjam

Member
Nov 18, 2011
1,634
the roadie said:
Camshaft PS does not need a relearn. Only the Crankshaft position sensor, and that's at the back of the engine near the flywheel.
or in the unlikely event you have an auto trans, by the flexplate :tongue:
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Voymom said:
Edited- Hey Roadie do you have any references to where I can do some reading on the CPAS? I'd like to know how it works, and aside from filtering the oil...what else it does for our trucks.
Google for VVT (Variable Valve Timing).

Deep reading: AutoZine Technical School

Our system:

www.roadie.org/vvt.pdf
 

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