Bad head gasket?

[Lins Bravada]

Hello everyone,

I am new to this site. New to forums, actually.
I just got a 2002 Bravada. Drove it from Virginia to Illinois over the weekend, On Tuesday the engine developed a problem. I will list the vehicle info and symptoms. I appreciate any help in diagnosing the problem.

- Car has 164,000 miles on it.
- Check engine light came on. Sometimes will flash for a couple minutes at a time.
- Engine lost power, ran and idled rough, but still drives.
- Took it to Autozone for code diagnostics, it showed the following codes:
- P0171
- P0300
- P0340

- The engine makes a sound under load similar to air escaping. Kind of like an exhaust leak.
- I changed the plugs, fuel filter and cleaned the throttle body. Same problem, though it seems to run slightly stronger.
- Cylinder 3 had oil on the threaded part of plug.
- Cylinder 4 had oil residue in the plug well. I expect I need to change the valve cover gasket but don't see that this is the problem.
- When the Check Engine Light is on, the cruise control doesn't work.
- Oil, dipstick and cap show no evidence of coolant.

Research I've done tells me this could be:

- Bad head gasket
- Cam position sensor
- Bad rings
- Bad coils (would that make the engine sound I'm hearing?)
- ?????

Thanks for any thoughts.

 

[IllogicTC]

The cap check for engine coolant isn't the best method on this platform. It's common for naturally-occurring moisture in the engine to end up collecting there. It's better to actually do an oil change and check for the excess contamination.

P0340 Cam Sensor Missing will disable cruise control for sure. The other ones might, also, but 340 is 100% confirmed to do this.
P0300 Random Misfire. This may be related to its attempts to "limp" without a cam sensor, or more likely it's due to your P0171 Fuel System Lean.

I'm feeling you may have unmetered air entering the system which is causing your P0171, which could also lead to a P0300. The cam sensor may be its own issue. It's common for the intake manifold bolts to loosen from spec over time and allow unmetered air in. It may also provide an air-movement sound of some sort, as there is air slipping past the loosened gasket.

I don't see anything pointing to a head gasket here, I'd suspect your air intake system first (which is going to cost $2000 less than a head gasket to fix!!!!). The intake manifold bolts should be at 12 lb-ft (144 lb-in), this is where you should start. Use a torque wrench, DO NOT go by "good-n-tight" for this check.

 

[gmcman]

Welcome to the nation!

For starters an maintenance history would be good. Codes show MAF, Cam sensor, and random misfire.

Does this vehicle have a dirty air filter or possibly a K&N? I would

First:

Clean the MAF with a MAF cleaner ONLY.

Sounds like a coil or coil could be going bad, could be worn plugs, they may be original.

Second:

Regardless of history, I would change the plugs with AC 41-103 only, use only these plugs. They come pre-gapped but double check the gap, don't try to re-gap them.

After this, pull the cam sensor pigtail and clean the contacts. see if code goes away. Honestly at this mileage the CPAS which is located on the pass side just behind the power steering pump could be either dirty or faulty. Pull that connector and if there's oil on the connector replace the CPAS.

- - - Updated - - -

Illogic I think we were typing at the same time.

Another edit is I see you changed the plugs, sorry. The valve cover has gaskets around the spark plug wells and they sometimes leak. Use some electronics cleaner and clean the coil spring that touches the spark plug. I use dielectric grease to both seal the boot and prevent moisture misfires.

 

[IllogicTC]

2002 wouldn't have a MAF. That's '06+ after they did the engine update.

 

[gmcman]

Check to see if this cap is missing and if so see if it's pulling vacuum. On SWB (5-seat) models it's unused.

 

[gmcman]

2002 wouldn't have a MAF. That's '06+ after they did the engine update.

Thanks....I just replied to Trailblazer13's thread and had 2008 on the brain.

 

[Lins Bravada]

It is missing. Is it just a cap to plug the port?

Check to see if this cap is missing and if so see if it's pulling vacuum. On SWB (5-seat) models it's unused.

 

[Texan]

It is missing. Is it just a cap to plug the port?

I just looked at my 2003 SWB LT and it has a rubber cover. Hope this helps.
Does not sound like a head gasket to me.

 

[Lins Bravada]

I checked the CPAS connection. The CPAS rotates in its mount, should it do that?

Welcome to the nation!

For starters an maintenance history would be good. Codes show MAF, Cam sensor, and random misfire.

Does this vehicle have a dirty air filter or possibly a K&N? I would

First:

Clean the MAF with a MAF cleaner ONLY.

Sounds like a coil or coil could be going bad, could be worn plugs, they may be original.

Second:

Regardless of history, I would change the plugs with AC 41-103 only, use only these plugs. They come pre-gapped but double check the gap, don't try to re-gap them.

After this, pull the cam sensor pigtail and clean the contacts. see if code goes away. Honestly at this mileage the CPAS which is located on the pass side just behind the power steering pump could be either dirty or faulty. Pull that connector and if there's oil on the connector replace the CPAS.

- - - Updated - - -

Illogic I think we were typing at the same time.

Another edit is I see you changed the plugs, sorry. The valve cover has gaskets around the spark plug wells and they sometimes leak. Use some electronics cleaner and clean the coil spring that touches the spark plug. I use dielectric grease to both seal the boot and prevent moisture misfires.

 

[Texan]

I checked the CPAS connection. The CPAS rotates in its mount, should it do that?

I think you may have found part of your problem. I do not think it should rotate. Check the threads on CPAS.

 

[IllogicTC]

I think you may have found part of your problem. I do not think it should rotate. Check the threads on CPAS.

That is indeed a problem, could be the cause of P0014. I don't believe a 0340 should come from this part.

There is two halves to the assembly, which are pressed together. The pressing appears to fail and allow the half on the exterior of the engine turn independently of the half held in by the bracket.

 

[Texan]

Here is a link that will help.

http://gmtnation.com/f93/how-clean-...osition-actuator-solenoid-picture-heavy-2263/


Look at #21 & #22

 

[Texan]

Here is a link that will help.

http://gmtnation.com/f93/how-clean-...osition-actuator-solenoid-picture-heavy-2263/


Look at #21 & #22

You need to read this carefully all the way through. There may be some confusion as to what is required.
If you have questions, just ask.

 

[gmcman]

I'm not a fan of throwing money blindly at a possible problem but knowing the history of these motors, at your mileage I would install a new GM CPAS and be done with it. Not saying Texan is incorrect with his post, just these CPAS' have a history and I would change it if that were my vehicle even if it wasn't rotating....since I would know the history of it at that point.

Then if that port is pulling vacuum, (test with finger) then it needs to be plugged, would cause a myriad of issues.

 

[Jake Blazer]

Mine is Rotating and I have replaced everything else, including engine,How much are one of these doomahickeys

 

[The_Roadie]

Good question for your parts store, although we recommend only AC Delco as a vendor for these items. For a general overview of prices, you can see many alternatives on rockauto.com, or Amazon. I'm thinking $50-60. At a dealer $120.