[acdavis02]

Hello everyone,

I have a 2010 GMC Acadia with about 225K miles on it, and it all at once started having these issues. Scanned for codes, had mis on every cylinder, timing too far advance bank 1, EVAP (Thats a known issue with wiring on tank), and Bank 1 catalyst efficiency low. Started by thinking the cam adjusters and sensors were bad and replace them, but that didn't seem to fix the issues. To my knowledge the timing codes didn't come back, however the misses were still there and it still doesn't run right. The car will not rev above 2K RPM, it stumbles really bad and almost stalls, I did some live data checking on the car and noticed it is at 40-43 PSI on the low pressure fuel at idle and doesn't go above this once running, from my research that seems low and could be causing the issues. The high side is fine, so I am curious if there isn't enough fuel volume with this low low side. I checked on a 2015 Chevy Traverse with a 3.6L and the low side seemed to stay at around 59-60 PSI consistently. Any thoughts? Thanks!

 

[acdavis02]

Hello everyone,

I have a 2010 GMC Acadia with about 225K miles on it, and it all at once started having these issues. Scanned for codes, had mis on every cylinder, timing too far advance bank 1, EVAP (Thats a known issue with wiring on tank), and Bank 1 catalyst efficiency low. Started by thinking the cam adjusters and sensors were bad and replace them, but that didn't seem to fix the issues. To my knowledge the timing codes didn't come back, however the misses were still there and it still doesn't run right. The car will not rev above 2K RPM, it stumbles really bad and almost stalls, I did some live data checking on the car and noticed it is at 40-43 PSI on the low pressure fuel at idle and doesn't go above this once running, from my research that seems low and could be causing the issues. The high side is fine, so I am curious if there isn't enough fuel volume with this low low side. I checked on a 2015 Chevy Traverse with a 3.6L and the low side seemed to stay at around 59-60 PSI consistently. Any thoughts? Thanks!

UPDATE:

I have cleared codes and drove again. Once again, no power, and cant rev above 2K rpm when cold or first start. After driving a little while I cant rev above 1200-1300 rpm, it idles at around 400-500 rpm, and I got the codes: P050A (Cold Start Idle Control System Performance), P0300 (Random misfires), P0301 (Cyl1), and P0305 (Cyl5). Not sure if I start with diagnosing misfires or diagnosing Cold Start Idle Control. Also when I start the car it takes a while for the brake booster to kick in and brakes are hard for the first 30-60 seconds of engine running. Did some more research on fuel values, and everything seems to be with in spec, however still lower then other car at idle, but still in spec. Thinking I will check plugs, and maybe swap coils to see in misfire moves.

 

[speleos]

UPDATE:

... Also when I start the car it takes a while for the brake booster to kick in and brakes are hard for the first 30-60 seconds of engine running. ...

There may be a defective vacuum pump, or a vacuum leak somewhere. That could be a root cause of the condition. Also, the throttle body may be dirty, or defective.

 

[acdavis02]

There may be a defective vacuum pump, or a vacuum leak somewhere. That could be a root cause of the condition. Also, the throttle body may be dirty, or defective.

That's starting to make a lot more sense now that I read what I typed. The plugs and coils were replaced in the last 1-2 years with OEM, so I'm doubting its that. I disconnected the brake booster from the vacuum T where the manifold and pump attach, and hooked my gauge up to that and I got 11 mercury inches or a touch over 28 mercury cm. I can't for the life of me find what these values are supposed be online or in a manual. Do you by any chance know this? Should I try plugging it directly into the manifold and disconnecting the power to the vacuum pump and get a value from that? TIA

 

[speleos]

That vacuum reading seems a bit low. According to information I've read on the 'net, almost all vacuum brake boosters require a vacuum of 16-18 in hg to operate efficiently. I can't find any spec sheet for the vacuum pump itself, however the pump should be able to supply sufficient vacuum when none is available from the engine. Test the pump and look for any cracked hoses and fittings.

 

[acdavis02]

That vacuum reading seems a bit low. According to information I've read on the 'net, almost all vacuum brake boosters require a vacuum of 16-18 in hg to operate efficiently. I can't find any spec sheet for the vacuum pump itself, however the pump should be able to supply sufficient vacuum when none is available from the engine. Test the pump and look for any cracked hoses and fittings.

That is what I thought, The hoses seem fine, and that test was on both the pump and engine. I'm curious what the PCV pressure is supposed to be. I hooked my gauge to the dipstick hole and got absolutely nothing. Also the engine doesn't run any different with the dipstick pulled out or not, rough idle when warm. Also the car warms up very very fast, faster than normal. Not sure if I may be experiencing a PCV issue here or not. Pulled the manifold and cleaned and replaced gaskets still have my issue, have great compression, new plugs because the old ones were pure black and coated with soot. Also this engine has been known to consume a LOT of oil, 3-5 quarts in-between oil changes. Just recently about a week before these issues started the low oil pressure light came on and it took 2.5 quarts of oil, didn't think it had been that long since I checked.

 

[speleos]

Never heard of such a thing as "PCV pressure." Any reading you'd get at the dipstick would likely be result of blowby from the pistons. Would probably be good to clean the PCV tubes and orifices.

 

[acdavis02]

Never heard of such a thing as "PCV pressure." Any reading you'd get at the dipstick would likely be result of blowby from the pistons. Would probably be good to clean the PCV tubes and orifices.

Yeah that is what I discovered now. I'm used to working on Germain turbocharged engines which the PCV is a mess in themselves. Anyways, at this point I have tried almost everything I can think of with this car. Its got great compression which eliminates head gasket, bent or leaky valves, rings, and timing. Has fuel pressure up front on the shrader valve, has brand new spark plugs and intake gaskets. I'm gonna go check again, but I don't think the engine has thrown any new codes. When the car is in park I'm able to rev it up to 2-3k RPM, but as soon as I put a load on it doesn't want to run or rev up at all. I could potentially get another throttle body from a 2015 traverse that runs fine to eliminate that being bad if you think there could be an issue there.

 

[acdavis02]

Vacuum pump fuse was blown. This shouldn't affect the engine though right? I have completely disconnected the engine vacuum lines from anything and tested it to make sure it was not a leak in the brake booster, and it still had low vacuum. There are check valves to keep the engine and vacuum pump separate.

 

[acdavis02]

Issue solved, and of course the last thing I check. Clogged catalytic converter. Bank 1 CC fell apart and plugged the 3rd converter. I pulled the third converter and knocked it out completely and the car has power I never knew it had now. Gonna get bank 1 and bank 2 converters replaced so they match. Thanks for all the help!

 

[speleos]

Good news!

 

[09AWDAcadia]

Hello everyone,

I have a 2010 GMC Acadia with about 225K miles on it, and it all at once started having these issues. Scanned for codes, had mis on every cylinder, timing too far advance bank 1, EVAP (Thats a known issue with wiring on tank), and Bank 1 catalyst efficiency low. Started by thinking the cam adjusters and sensors were bad and replace them, but that didn't seem to fix the issues. To my knowledge the timing codes didn't come back, however the misses were still there and it still doesn't run right. The car will not rev above 2K RPM, it stumbles really bad and almost stalls, I did some live data checking on the car and noticed it is at 40-43 PSI on the low pressure fuel at idle and doesn't go above this once running, from my research that seems low and could be causing the issues. The high side is fine, so I am curious if there isn't enough fuel volume with this low low side. I checked on a 2015 Chevy Traverse with a 3.6L and the low side seemed to stay at around 59-60 PSI consistently. Any thoughts? Thanks!

I'd check the fuse box under the dash on the passenger side behind the glove box for water damage seems to be a common problem with all the symptoms your describing.