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Discussion Starter #1
2009 enclave 131k.

About 10 days ago wife reported rough idle at start up and some occasions it would stall. Scanned obd and got po300, po301, po303, po305 as pending codes three days ago. no CELS. Rough idle only during engine warm up cycle. She would turn on engine when cold and would run rough. she'd shut down, restart and it would run fine. no issues once idle 600-700 after that. drives car 40 min to work and back.

Would not duplicate once engine warmed. Ambient temps here 75-90f. Seems if we restart if the engine is somewhat warm (within 5hrs), it would skip warm up cycle and go straight to normal idle and no issues noticed. -- I think is the key point to solving the problem....

Searched the lambda forums and found several possibilities: 1) reflash pcm for upgraded cat warming cycle, 2) possible ignition wire connector pin issue that causes either cyl 135 or 246 to stumble. 3) stretched timing chain excessive on one of the cams, in my case 135.

After reading rbarrios post on engine warm up cycle I started engine the next morning cold in my garage at 75f w hood up and let it run full warming cycle. high idled 1300-1400, then came down to low idle within 30s. after doing this the engine light finally came on. Now hard codes for 300, 301, 303, 305. no other codes than the random abs sensor we've ha pad for a while. When I did this and had my head over the engine, a medium loud rattle was coming from the engine for about 10 seconds. This sound took about five seconds after engine turn on to start. rattled for 10 sec, then went away. This is new just started over week end. I turned on engine Sunday am to try and pinpoint noise. listened passenger side by timing chains very closely. sounded like it was coming from back of engine by firewall. that's the side of engine cyl 135 are on

I was thinking after reading rbarrios post to get the pcm reflashed for upgraded startup program. now w the noise I'm wondering if it's the chain slapping against plastic. The rattle could sound like that. RAttle lasts only short time (10s) during startup when engine pours more fuel to warm faster and heat up the cats. Possibly stretched chain on cam for cyl 135??

Again, engine goes to normal idle in less than thirty seconds. I give it gas in neutral to see if it's an rpm that triggers the rattle but nothing. runs fine.

Replaced plugs w Gm replacements properly gapped at about 110k. coils replaced when they failed one at a time between 45-75k. no stumbling while driving so I'm sure it's not the coils, and not all three at once. did oiled changes 1k ago and cleaned air intake reservoir. did pvc hole conversion last yr so little oil in reservoir. cleaned map and throttle body a year ago but will reclean and inspect here shortly.

my plan to reclean maf and throttle body. look up GM Shop procedure on ignition wire connector and check connection to cycle 135, then go to dealer to reflash pcm. I think it might have been done, but past service records don't show it, thought I'd call dealer we've had it to and see if it's embedded in their records.

after this I'm thinking stretched timing chain or plugged cat??

This issue wasn't a slow daily getting worse thing. seemed to just happen 10 days ago. my wife may have masked cels and rattle at start up by shutting down engine and restarting.

again, runs normal after 30 second startup up on cold engine. restarts normal on a warm engine with in five hours of last use.

any suggestions?
 

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Discussion Starter #2
Called dealer ship we go to for service. They reflashed ecm August 2012 for recall 10287c to modify timing to extend life of timing chain.

He said a new flash release on may 10, 2017 upgrade per doc 4630888 or a Gm code 16na383 was to be performed after top engine cleaning to remove carbon. flash reduced fuel making system leaner to reduce carbon. Also to aid in random cold start misfires not related to a component failure. I Seached web and these numbers did not come up. cost to reflash $129. cost for upper engine/induction clean w fuel tank treatment and oil change w flash was $400.

Found rbarrios post on ignition coil connector. the x3 connector is located under the fuse box of the engine bay. need to lift the boys to remove and inspect for fretting. I'd think if this were the problem, the cylinders would always misfire??
 

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ever had a carbon cleaning?

I think it was around 128,00 or so- my 2010 started showing a little stumble on cold morning drives.
I tried the CRC intake valve cleaner for DI engines. the stumble has been greatly reduced.

Next oil change I may repeat the treatment.


I also did the treatment on our 2013 Equinox w/3.6
on this one-- engine did stumble and want to die and did flash the CEL when I was doing the treatment.
Upon restart.... 1 hr later--- it smoked nicely.
I then changed oil and cleaned MAF and TB. (I found 3 pending codes for random misfires, and barometric pressure etc. (the MAF)).
I left them.
After a couple of drives- codes are gone.


The Traverse never stumbled, flashed CEL, or smoked.

Can is only $12 I think.
 

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I was thinking that was a snake oil gimmick by the dealer. I've certainly read several posts on the topic. I posted pix of my intake valves back in January on ur post when the car had 117k. They looked similar to ur pix at the time. Though it was ok. Didn't look like flakes were going to break loose. So if you cleaned yours, due to cold start stumble recently, then ill do mine.

I cleaned the maf and tb at 117k. Drilled out the hole on the pvc at that time as well. Will redo maf,tb, check air filter and use the crc for top end cleaning. Head to dealer for a reflash on the ecm software

I've not seen anyone post wire brush cleaning of the intakes w the upper manifold off for our di engines. Any thoughts?
 

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I figured that for $10 for the bottle--- Id try it (did the mail in rebate on the CRC bottle-- actually submitted online and got my check).

Not hard to do. need someone to hold RPMs at or close to 2000.


I think someone mentioned chipping away at the carbon with manifold off.
But I would think that could cause large chunks to fall into piston?????

but like I said--- at the price of the bottle--- Ill try it several times.

Your issue may be sticky valves (due to carbon) causing the misfires.



2011 Cadillac CTS | CTS VIN D Service Manual | Document ID: 2863222
#PIP5029: Engine Misfires Due To Major Carbon Deposits On The Intake And/Or Exhaust Valves - (May 29, 2012)
Subject: Engine Misfires Due To Major Carbon Deposits On The Intake And/Or Exhaust Valves

Models: 2008 - 2012 Cadillac CTS, STS
2008 - 2010 Chevrolet Cobalt SS, HHR SS
2007 - 2010 Pontiac Solstice GXP
2007 - 2010 Saturn Sky Redline
2009 - 2012 Buick Enclave
2009 - 2012 Buick Lacrosse
2009 - 2012 Chevrolet Traverse
2009 - 2012 GMC Acadia
2009 Saturn Outlook
2010 - 2012 Cadillac SRX
2010 - 2012 Chevrolet Camaro, Equinox
2010 - 2012 GMC Terrain
With any of the Following Direct Injected Gasoline Engines:
2.0 (RPO LNF)
2.4L (RPO LAF, LEA, or LUK)
2.8L (RPO LAU)
3.0L (RPO LF1)
3.6L (RPO LFX or LLT)

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:

Some customers may complain of a MIL and engine misfire. In some cases, the misfire may be more apparent on a cold start, may count on a single cylinder or several cylinders, and may or may not be felt by the driver. Upon inspection, the technician will find one or more misfire codes (DTC P0300-P0306) stored in the ECM and SI diagnosis may or may not isolate the cause of the misfire depending on whether the intake/exhaust valves are sticking at the time of the diagnosis.

This may be the result of major carbon build up on the intake and/or exhaust valves as shown below so the misfires should not have appeared until the engine has accumulated around 5,000 miles or more.

Recommendation/Instructions:

If this concern is encountered, perform SI diagnosis. If SI diagnosis isolates a valve sealing concern and/or eliminates everything else external to the engine, decarbon the engine with Upper Engine and Fuel Injector Cleaner by following the guidelines below:

Important Extreme care must be taken not to hydrolock the engine when inducing the cleaner, especially if it is induced without Kent Moore Tool # J-35800-A. If too much cleaner is induced at too low of a RPM, or if you force the engine to stall by inducing too much cleaner at once, the engine may hydrolock and bend a connecting rod(s).
1. In a well-ventilated area with the engine at operating temperature, slowly/carefully induce a bottle of GM Upper Engine and Fuel Injection Cleaner into the engine with RPM off of idle enough to prevent it from stalling (typically around 2,000 RPM or so). Depending on the engine configuration, induce the cleaner through the throttle body or an engine vacuum hose/pipe. For best results, it is suggested to induce the cleaner with Kent Moore Tool # J-35800-A (shown below).
2. Turn the engine off after inducing the cleaner and allow the cleaner to soak with the engine off for 2.5 to 3 hours (Do not let cleaner soak for more than 3 hours as remaining deposits may start to harden back up again).
3. Add a bottle of GM Fuel System Treatment Plus to the fuel tank and fill the vehicle with one of the Top Tier gasolines listed at http://www.toptiergas.com and/or in the latest version of 04-06-04-047 (USA) or 05-06-04-022 (Canada). See Bulletin 05-00-89-078 for more details on GM Fuel System Treatment Plus.
4. Test drive the vehicle extensively to circulate the GM Fuel System Treatment Plus, which will help to eliminate/reduce any remaining intake valve deposits.
5. Re-evaluate the concern to determine if it is repaired or improved at all. If the concern is improved but not repaired, it may be necessary to perform the above decarboning process a 2nd time.



6. To complete the repairs, advise the customer to only use one of the Top Tier Gasolines listed at http://www.toptiergas.com and/or in the latest version of 04-06-04-047 (USA) or 05-06-04-022 (Canada) to minimize future deposits. It can also be recommended to add a bottle of GM Fuel System Treatment Plus at every oil change as mentioned in the latest version of 04-06-04-051.
Kent Moore Tool # J-35800-A
Upper Engine and Fuel Injector Cleaner
 
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Discussion Starter #6
Rbarrios, we all here appreciate what u do for us! As soon as I run through this, I'll report findings.
 

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OK. Removed upper intake manifold and swapped coils 135 w 246.

removed valve cover for the left bank, cyl 135. inspected underside of cover thinking the rattle was something hitting the cover. all looked good. I did not rotate engine but the chain looked good and tight. cam area was had a golden hue wo sludge build up. underside of cover had Carson residue.

touched the valve stem of cylinder 3 and I think there's definitely enough carbon on the backside of the valves that require a good scrubbing. left as is

put back together and drove ten min to test my reassembly. cold engine, during high idle it was rough. and the rattling noise was present beginning about five seconds after cold start. noise lasted ten seconds.

sprayed crc upper engine cleaner. while waiting the hour per the can. I removed the tb and cleaned both sides. sprayed maf.

drove about 60 miles bc I cleared the engine codes. rough start due to cleaner but no codes after the 60 miles.

let the car side 5 hrs. obd read coolant temp at 99f. cold started it. ran to engine bay and five seconds after start up the rattling begaan. I felt the upper manifold close to the timing belt during the rattle phase. felt like it was coming around timing chain to cyl 1 area. rattle went away 10 sec later I shut down the engine before the idle dropped below 1000 rpm.

I was at the engine so didn't notice misfire. Paying attention to the rattle. looked for codes and no pending neither hard codes.

since engine is relatively cold, going to keep cold starting using stethoscope to see if I can pinpoint before I drive it down the street and have to wait the five hours to cool.

Possible the upper engine cleaner could have stopped misfire. just haven't driven enough yet to know yet.


any idea on rattle? when I put my ear to the top of the manifold, the rattle is loud enough to bother my ear. you can hear it from the passenger area through the firewall and cabin sound deadener
 

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RAn several more cold starts over night. ran engine only 30 seconds and used box fan to cool engine after each cycle. Could do one every hour or so.

I've isolated the rattling the best I could to the two cam gears one the left bank, closest to firewall by cyl 1. I have the plastic motor cover off of course. Could feel rattle w hand on valve cover just above timing gears. used stethoscope to confirm. hard to get in there rest of valve cover has sound deadener on it. I don't think it's an actual valve. Noise is too Loud over gears.


found several YouTube vids under "Acadia engine rattle at start up" led me to some enclave and traverse vids. Sounds exactly like my issue. Some describe noise as sewing machine. More of a think, not a tick. Only at cold start. Only lasted a few seconds. They posted replacement of cam actuator components to fix problem. Not clear if it's sensor, solenoid or the actual actuator inside the timing gear. One vid showed engine w chains off. Guy wiggled each cam gear. One gear would freely rotate 25-50 degrees wo the cam moving. I'm thinking that's what I might have

There's 8 plus inputs that make the cam actuate differently. Thinking cold start up just condition just makes it do this.

Have not had codes for cam or crankshaft related items yet. Rattle just began few days ago.

I know something is wrong. I feel I should drive it around town some more to see if it will throw a code. Anyone have experience here that I might damage my engine doing this?

Will move this portion of the thread to a new post under rattle or something.

Was getting rough engine idle last night as well. but no codes on misfire yet

Again, any thoughts if I should stop driving it? My risk, I know
 

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the only thing I can think of-- is an oil passage is partially blocked... enough to cause a bit of 'oil starvation' upon start up and when oil is thicker.
once pressure builds up-- and the oil gets flowing-- it quiets down....
 

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I've been reading up on the 3.6 VVT theory of operation. My only guess at this time is the cam actuation assembly gear and ur thought of oil passage. I think I can get to the cam sensor and solenoid components from the side of the engine, but still no codes to tell me what to do.

100 miles since I cleared codes. Hightailed it to get the emissions passed since my readiness codes were all good.

At the moment I'm letting my wife take the car again and putting my spare car back in storage. Just starting the engine and the instant the rattle begins at cold start, we shut her down then restart five seconds later and it's fine.

This band aide will give me more time to research and more drive time on car to see if this is that transitional period when a sensor is intermittent before it goes bad and throws a light.

I think this is my 12th engine light on this car requiring repair. I'd be broke if I couldn't fix these myself


Is there a viable oil flush method to clear the actuator passageways wo pulling the motor? Unless i get a light, I think I'm looking at pulling the motor.

Going to do one more can of crc, then do the oil change.

Another indicator of a VVT problem is bad gas mileage and dirty oil. Monitoring as well
 

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No new info, just some brain farts from researching....

1)There's a YouTube for a 2015 Acadia cold start up rattle where a guy pulled the motor and had chains off cam gears. one of the gears could be rotated 25-50 degrees w the cam stationary - bad cam actuator assy. The other three cam gears were locked as designed and did not move. I'm thinking pulling the valve covers again and grab the camshaft w a wrench to see if it will move about the cam gear actuator assy. The timing chain will hold gear in place. If cam moves, then the cam lock has failed. I think this is an easy test wo removing the motor. any risks beyond putting cam back into original position and preventing metal shavings from wrench?

2) PIP4948 for Cadillacs 2010-2011 discussed removing cam actuator solenoid and inspect for assembly mis installation causing binding. Maybe sludge will show on end of solenoid to give me a clue of my cam oil ducts??

3) can I inspect, test oil passengers w engine in car and valve covers off?

4) does this engine have an oil check valve? the 04-09 caddy 3.6 apparently has p/n 25014612 "oil bypass valve" it's purpose it to prevent oil from draining upper end of engine for better startup lubrication.

I use 5w30 dinosaur oil and ac pf48 filters. I used full snythetic the last change, but the engine leaked more oil on the garage floor. So I went back to dino 1000 miles ago. I might try synthetic again to since the viscosity is more consistent over temperature. Wonder if that might be a short term bandaid

Thoughts
 

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Since last post, my wife starts engine cold start. maybe 2 in 3 it will made the sewing machine rattle for a few seconds. she shuts it down the instant she hears it, then restarts engine a few seconds later and it's fine. this process is masking the problem I'm sure. no cels. no pending codes n the obdii sys.

not getting better or worse.


my best plan is to pull the firewall side valve cover again and use a wrench to see if I can get cam to move about the gear actuator assy. I'm thinking the rattle noise is the actuator locking pin dragging inside the assy. suppose the cold start condition just puts the parameters in the right sequence for this to happen
 

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Nothing done to car yet. sewing machine rattle getting worse. SHutting down car on start up as soon as rattle begins works to keep engine light off. yesterday we began reving car to 2k rpm at start up instead. no rattle. but engine light came on for misfires p0304 and pending on p0303, 302, 306 . Interesting the misfires mostly followed the coils I swapped.

pulling bank one cover to wiggle cam shafts this weekend. concerned the rattle might be grinding metal off cam actuators and I'm toasting engine.

Gas mileage seems to be okay. Bad mileage indicator of bad cam actuators

More to come
 

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Car at 167K now. Been condemned to garage for past 6 months for other issues. I'm pretty sure this sewing machine rattle at cold start up is indeed cam actuator sprockets. At cold start, as long as we shut down engine as soon as the rattle began, then restart, the rattle wouldn't generally come back. I think its the oil getting to the actuators, or lack of. So doing the engine shut down/restart, kept the misfire engine codes off all this time. We haven't really noticed an MPG reduction as the car is normally driven around town.

Anyway, finally pulling cradle next week. Will post up if chain/actuator replacement solves this.
 
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