Which to Fix First...?

Freddy G.

Original poster
Member
Dec 4, 2011
55
So I staled again. I Cleaned my Throttle Body when I got home that day. I know I need to Clean or Install a New Camshaft Position Actuator Solenoiod. I read up on the staling problem some more and found it could be my Oil Pressure Switch, so I bought a New Switch(haven't installed it yet). And for like maybe 5 months now my Oil Pressure Guage has been broke. I am also aware it may be the Stepper Motor. Which do I fix first?
 

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The_Roadie

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Nov 19, 2011
9,957
Portland, OR
Stalling can be CAUSED by a sticky throttle body or a malfunctioning CPAS. Wherever you read about the oil pressure switch as a CAUSE was wrong. Hope it wasn't here. After the engine stalls, the oil pressure goes to zero and that illuminates a warning light or reports the problem in the DIC, but that's an EFFECT of the stall, not the cause. You may or may not need a new switch, but you could find out in a few seconds by connecting a scan tool that can look at what the PCM thinks is the oil pressure.

The gauge is a bad stepper motor, but that's not worth fixing before the other stuff because it's also just a display, and a dumb one at that, and can't be the root cause of anything.
 

Voymom

Member
Feb 3, 2012
2,523
I would clean the CPAS first, it's extremely easy, and I have an article on how to do it. It literally takes all of 10 minutes to get it out, however long to clean the CPAS and 10 min to put it back in. Very simple.
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
Thank You. I will clean that today. On my way home from work, I pass right by Autozone, I will have them Scan to see what my Oil Pressure is, and if all is fine I should return the Switch and get my money back. Correct?
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
the roadie said:
Stalling can be CAUSED by a sticky throttle body or a malfunctioning CPAS. Wherever you read about the oil pressure switch as a CAUSE was wrong. Hope it wasn't here. After the engine stalls, the oil pressure goes to zero and that illuminates a warning light or reports the problem in the DIC, but that's an EFFECT of the stall, not the cause. You may or may not need a new switch, but you could find out in a few seconds by connecting a scan tool that can look at what the PCM thinks is the oil pressure.

The gauge is a bad stepper motor, but that's not worth fixing before the other stuff because it's also just a display, and a dumb one at that, and can't be the root cause of anything.

Nope, It wasn't here Roadie. I found it on Google.
 

Voymom

Member
Feb 3, 2012
2,523
Freddy G. said:
Thank You. I will clean that today. On my way home from work, I pass right by Autozone, I will have them Scan to see what my Oil Pressure is, and if all is fine I should return the Switch and get my money back. Correct?

Returning the oil pressure switch is up to you, changing it would be a personal opinion I believe. The oil pressure gauge is not a correct reading if I remember correctly, however personally I would have to fix it if it were my truck lol You can try the switch, if it turns out to be the stepper motor you can always return the switch and get a refund.

I know cleaning the CPAS won't help your sticky oil pressure gauge, but it helps if your truck is putting out a p1345 and or a p0014 code. I cleaned my CPAS and my SES light went off without needing to be reset and my truck no longer had the p1345 and p0014 codes.
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
and just to clarify: If a Stepper Motor Breaks, it could go all the way to zero or go all the way to the right? It is always all the way to the right even when the vehicle is off.
 

Voymom

Member
Feb 3, 2012
2,523
Freddy G. said:
and just to clarify: If a Stepper Motor Breaks, it could go all the way to zero or go all the way to the right? It is always all the way to the right even when the vehicle is off.

If I'm right a broken stepper motor will cause the needle to get stuck in one position or act crazy. Don't hold me to that info though lol I have never dealt with a bad stepper motor before. My info is coming from simply reading other posts on here. Hopefully someone will correct me if im wrong. But I would guess it's the stepper motor by the fact that it is not returning to "0" when the truck is turned off.
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
Voymom said:
If I'm right a broken stepper motor will cause the needle to get stuck in one position or act crazy. Don't hold me to that info though lol I have never dealt with a bad stepper motor before. My info is coming from simply reading other posts on here. Hopefully someone will correct me if im wrong. But I would guess it's the stepper motor by the fact that it is not returning to "0" when the truck is turned off.

ORRRRRRRRR...I have AWESOME Oil Pressure :thumbsup:
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
Finally cleaned my CPAS. When I pulled the Plug off the CPAS I was surprised to see it dripping oil. I looked in the plug and it had a small bit of oil in the plug. The CPAS didn't seem all that dirty and the screens were all in place and looked to be in good shape. I removed the Rubber O-Ring and Spraed both the plug and CPAS out with Throttle Body Cleaner and let them dry.

I am not staling anymore when the Ac is on, but the rough idle is still there!
 

gmcman

Member
Dec 12, 2011
4,656
Freddy G. said:
Finally cleaned my CPAS. When I pulled the Plug off the CPAS I was surprised to see it dripping oil. I looked in the plug and it had a small bit of oil in the plug.

I'm fairly sure you should replace the CPAS. Mine was saturated with oil also and my GM buddy told me they will continue to leak at that point.


Doesn't these engines either not start or shut down at the sign of very low oil pressure? I know some GM engines wouldn't fire until there was oil pressure at the switch.
 

Voymom

Member
Feb 3, 2012
2,523
I had a small bit of oil in my CPAS as well. I cleaned it up and the codes are completely fine. I had the rough idle until I did the engine flush and filled it with mobile 1 full synthetic, now he purr's like a kitten. Although cleaning my CPAS could have helped the harsh idle too??

I know what worked in my scenario but it sounds like something else may be going on with your truck. How are your spark plugs? T-stat? What oil are you running? Have you put any oil additives in the engine? Have you put any fuel additives in? Are you getting any codes? Is the harsh idle in park or when in drive, with or without the 4wd on?

There could be so many other issues going on, a bit more info on what your experiencing might help as well. Any history of major mechanical work or recently replaced any parts?
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
Plugs have not been changed yet. As far as Oil goes, I bought Pennzoil High Milage( I am at 96,000). Never use any additives. Should I be using a different Oil? Synthetic?
 

gmcman

Member
Dec 12, 2011
4,656
Freddy G. said:
Plugs have not been changed yet. ( I am at 96,000).

So those are the original platinum plugs? I would swap them for some fresh iridiums for sure.
 

Mikie

Member
Dec 5, 2011
15
Dumb question, but did you disconnect the battery during all of this work? If not I would do so for 20 minutes. If you did, you may not have run it enough for the PCM to relearn.
 

Voymom

Member
Feb 3, 2012
2,523
I agree with doing the spark plugs, disconnect the battery if you haven't and as far as oil goes I like mobile 1 full synthetic although it's not mandatory to use for your vehicle to run, it's just not as dirty I guess you can say from your regular oil. I heard pennzoil isn't the greatest oil for either dino oil or full synthetic.

I did a good engine flush on my truck when I changed it's oil and cleaned the CPAS too. Rough idle can be from a lot of different things, but start with the cheapest route first, you may still need to change the CPAS but I would try doing the sparkies and if your not biased to it using full synthetic with a good oil filter(I use K&N).

Also if your truck ran with a spoiled t-stat for any length of time you could have a clogged cat, you can get that tested for around $30(here anyways) with a back pressure test I do believe it's called.
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
Mikie said:
Dumb question, but did you disconnect the battery during all of this work? If not I would do so for 20 minutes. If you did, you may not have run it enough for the PCM to relearn.

Yes. I disconnected the Battery. I am not sure how long it was Disconnected But I am guessing for an easy 20 minutes.
 

RayVoy

Member
Nov 20, 2011
939
20 mins is lots.

Just a few comments on the past posts without attaching them to this posts.

Oil pressure and OP switch.
Having great oil pressure is not a symptom of a faulty switch, a bad switch (or an open wire at the switch) will read zero, but the engine is still providing proper pressure.
I had a bad switch on my '05 Envoy, the pressure reading would drop off to zero and, the PCM thinking the real pressure had dropped to zero would turn the truck off; but, only after the truck was stopped and the pedal was at idle (I assume to ensure you were not in the fast lane of the freeway).
It is an easy change.

Stepper motors may fall off to zero and stay there; but usually, as Voymom said, they find a new zero and bounce around from it.

The rough idle may disappear when the plugs are changed (96,000 is longer than I like to leave them in there), O2 sensors wear out as well, have it (the front one) changed when the plugs are changed. Also, a good time for a new air filter (and if an '02 to '04 truck, a new fuel filter as well).
 
Dec 16, 2011
110
RayVoy said:
20 mins is lots.

Just a few comments on the past posts without attaching them to this posts.

Oil pressure and OP switch.
Having great oil pressure is not a symptom of a faulty switch, a bad switch (or an open wire at the switch) will read zero, but the engine is still providing proper pressure.
I had a bad switch on my '05 Envoy, the pressure reading would drop off to zero and, the PCM thinking the real pressure had dropped to zero would turn the truck off; but, only after the truck was stopped and the pedal was at idle (I assume to ensure you were not in the fast lane of the freeway).
It is an easy change.

Stepper motors may fall off to zero and stay there; but usually, as Voymom said, they find a new zero and bounce around from it.

The rough idle may disappear when the plugs are changed (96,000 is longer than I like to leave them in there), O2 sensors wear out as well, have it (the front one) changed when the plugs are changed. Also, a good time for a new air filter (and if an '02 to '04 truck, a new fuel filter as well).

What's the significance of the MY's? Are there no fuel filters after '04, or is there something wrong with the ones from '02 to '04?
 

Wyle

Member
Dec 4, 2011
200
UMEXT said:
What's the significance of the MY's? Are there no fuel filters after '04, or is there something wrong with the ones from '02 to '04?

'02 to '04 have a classic in-line fuel filter. '05 and up have one inside the fuel tank thats integral with the fuel pump/sender assembly. The in-tank ones are not expected to require replacement. YMMV.
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
I changed the fuel filter about a year or 2 ago. Could my rough idle be from a bad Oxygen Sensor?
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
What I mean on a rough idle is....When I turn on the Ac it feels like a big strain on the Engine. There is like a rough vibration. The biggest affect it has is when I pull up to a stop sign or Traffic Light, I stop and it feels like the idle goes to like 4000rpm and back up, like it's gonna stall. Next is to change my Plugs or should I just try the Oxygen Sensor First?
 

RayVoy

Member
Nov 20, 2011
939
Freddy G. said:
. Next is to change my Plugs or should I just try the Oxygen Sensor First?
You have 96,000 on plugs that are worn out at 100,000.

Change the plugs.

AND, it is my suggestion, that the front o2 sensor should be changed when the plugs are changed.
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
Thank You for all the help. I will be changing my spark plugs on Saturday. I will also look into changing the Oxygen sensor. I know there is a "HOW TO" for the Spark Plugs, What about for the Oxygen Sensor?

Again.. I gotta say Thank You for all the help to everyone. Alittle bit of "TMI" My Father was a Famous Tattoo Artist, Not at all Mechanically inclined, so I never learned anything about Cars. I prefer to do the work myself, If I know what I am doing and How to do it. Thank You.
 

RayVoy

Member
Nov 20, 2011
939
There is a lot of experience here, if you get stuck, just ask.................we can help :biggrin:
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
Installing my spark Plugs tomorrow. I will give an update when I am done. Maybe someone can help me with locating the o2 Sensor so I can change that next.
 

Matt

Member
Dec 2, 2011
4,030
Freddy G. said:
Installing my spark Plugs tomorrow. I will give an update when I am done. Maybe someone can help me with locating the o2 Sensor so I can change that next.

In the manifold for the front sensor. Access through the drivers wheel well. It will be only thing coming out of the manifold with wires attached to it. Just make sure you have run it for a bit to expand the metal and use PB or magic piss to help, just don't burn yourself.
 

Freddy G.

Original poster
Member
Dec 4, 2011
55
Throttle Body Cleaned, CPAS Cleaned, New Spark Plugs Installed and still idleing at 500rpm's. Why?
 

Menthol

Member
Dec 8, 2011
177
Sounds like a typical Throttle body issue??? Which plugs did you use? Only AC Delco or NGK IX Iririum(positive about this one, I'm using them) Did you try to gap them?
 

RayVoy

Member
Nov 20, 2011
939
I wonder if you have a vacuum leak?

Or, maybe a plugged PCV hose (we don't have a PCV value, but there is a hose).
 

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