I bought a 2008 Envoy Denali, with a 5.3. From auction. (1st mistake).

After some investigation, it doesn't have the original 5.3. I know this because it had a dipstick in the block, instead of in the envoy pan. I know nothing about the donor engine, and cannot access the build codes on the back of the engine due to space constraints in the envoy engine bay.

After fixing that profound issue, of a huge oil leak, it has a Camshaft correlation code.

Tech 2 shows CKP functions fine, scope shows the same. CMP however is taking erratic events, and rpm jumps all over the place. Scope for CMP looks good though.

Pulled timing cover, confirmed in time, replaced all sensors 2x, replaced ECM, wires ring good, no shorts, no grounds, trouble still present.

Hard starts/backfires on first start attempt, 2nd attempt engine starts but performs sluggish. This is due to the 180 degree swap the ECM does every other cycle when the CMP is unable to be confirmed.

Now starts the fun. The CMP is/was contacting the cam gear. Physically. Added washer to space it out for testing, still no help.

Senior tech at GM was sourced, and he followed all steps I have, literally, and confirmed everything is in order. Sensors, wiring, ecm, etc.

Tech @ GM started looking and discovered that the part numbers between a envoy 5.3 and truck 5.3 do not match as far as timing cover, and timing set. Sensors are the same.

Before I tear this timing set off and replace it, does anyone believe there is a difference in the cam gear for the envoy 5.3 and a truck 5.3? It leads me to believe maybe the envoy timing cover is compressed, and the gear may be thinner or something similar, leading to the fact that the envoy timing cover is allowing the CMP to strike the reluctors on the cam gear. ​​​​​I am assuming the donor engine came from a truck, and the envoy pan and cover were sourced from the original engine.

Any, and I mean any help, would be appreciated.

Signed,

3 payments in, and still haven't drove it.

 

there are 4 different types of cam sprockets available on LS motors.

if it has a 58x crank reluctor, it should have the matching timing gear.

http://i2.photobucket.com/albums/y20...mSprockets.jpg

 

the only other thing i can think of (and don't know too much about, honestly) is if the truck originally had a 5.3 with VVT and had a cam phaser. from what i just looked up, i don't think it did, but don't quote me on that one.

 

Agreed. Google has sent me to that page about 100 times now, researching this issue. I have confirmed that my gear is "A".

My question I guess is, is there any possible way, seeing as how GM lists 2 different part numbers for the same year, same VIN, 5.3, in a truck, and in the envoy, that there might be slight differences?

I know I have a E68 ECM, and the trucks use a E37, but I can't figure out why the sensor is contacting the cam gear.

Once again, leads me to believe I have a truck motor, with an envoy timing cover, and that's where my problem may be??????? The physical spacing of the sensor is different or the size of the gear, or both may be different for the Envoy VS. Truck..?

 

Your engine should be the one classified LH6.
Do you know if in fact that is what is in your Envoy?
Does it have VVT? (you never said...) The LH6 does not have it. You would have seen it when the timing cover was off. I doubt the VVT timing gear would fit inside a normal timing cover. BUT if it does, that would explain the sensor hitting the gear.

 

There are only 4 timing covers. One for Gen III with no cam sensor and three for Gen IV with sensor. One is for the LS4 front wheel drive and the other is the normal none-VVT. Last, is the VVT front cover.

http://cliff.hostkansas.com/pffimage...g_cover_04.jpg

Sounds like the cam is messed up or there was no cam retaining plate installed. Either way I'd think you would have destroyed lifters by now.

 

that would suck if the cam was walking. but, i am sure he would see some evidence of that with the timing cover off...

 

Didn't think of it before, but not cam plate would mean no oil pressure so that isn't missing. Could still be a cam movement issue, but probably won't know until the cover is off and maybe some measuring is done.

 

Hate to say it, but a full frontal teardown might be necessary.....

 

Is your crank sensor gray, and can you pull it and verify that you do have a 58X reluctor?

 

I tried to run a black sensor on a 58X once with a Holley HP and it didn't work. I wonder if the stock computer which can't even change from 24 to 58 would be able to do it. My guess was the sensor wasn't compatible with the reluctor.

 

Does it still have the VVT cover with a normal cam and sproket in it? I seen this a few weeks ago, cam sensor does not work well .500" away from the gear lol.

 

yep, good call.

 

Gonna stick my neck out and say try a case relearn.

If it's the original ECM and a different engine, this would need to be done.

However, this does not explain an erratic CMP signal.

Checking the harness wiring and try to backprobe the CMP with a multimeter to see if it is getting a continuous source of voltage, the ground is ok, and check the signal it produces.

 

But... you did say you checked the CMP on a scope and it was fine... and you checked the wiring. So CMP signal good, and it's getting to the ECM if the wiring is good. ECM just isn't interpreting the data correctly.

Yeah, try the case relearn. See what happens.