Check Timing?

[RIP]

After owning a GC for 11 years I recently learned apparently you can't check the timing in the conventional way with a timing light, at least on a 3.8ltr. It appears the only way to check it is to pull the chain cover and align the marks. What a PITA to go through just to verify the timing is correct. Please educate me on why this is or better yet tell me I'm wrong and there's a better way.

I was reading through the exhaust overheat thread below and thought - Timing. If there was only a way to check it.

[earlyrizr]

it's done because there is no distributor anymore.like in the old days if it was running rich or lean a few degrees on the dist.. was all that was needed.but now with the advent of all the computer stuff monitoring everything from opening the door to using the lighter to the timing we cant manually adjust anything.remember too that every spark plug is constantly firing on every cycle even when not needed,it's just the injectors now which fire at the right time to cause proper combustion.and with all the sensors being monitored,the computer is the one to adjust it when need be.I dont like it either.pulling the covers will only tell you that the chain is lined up correctly(no jumped tooth etc..)it wont tell you if it actually timed correctly.they..dealer.. tell us that the computer is foolproof,but I've seen some pretty foolish computer actions.hope this helps.

[MT-2500]

Originally Posted by RIP

After owning a GC for 11 years I recently learned apparently you can't check the timing in the conventional way with a timing light, at least on a 3.8ltr. It appears the only way to check it is to pull the chain cover and align the marks. What a PITA to go through just to verify the timing is correct. Please educate me on why this is or better yet tell me I'm wrong and there's a better way.

I was reading through the exhaust overheat thread below and thought - Timing. If there was only a way to check it.

The timing is controled by the pc.
Base timing is set by the crank sensor.
Timing chain has nothing to do with engine timing.
MT

[RIP]

So what it boils down to is it's like the situation 20 years ago when they went to permanently lubed ball joints, tie-rod ends etc and stopped using Zurk fittings to grease the joints, you just had to trust the job was getting done. Guess the powers that be found too many mechanics and DIYers were miss adjusting the timing and screwing up emissions so they took that option away and handed the job over to computer chips. Wander what's next? No drivers? It's on the way!

MT - So if you say the timing chain has nothing to do with timing, does that mean if the chain gets slop in it and skips a tooth or two you'll never know it?

Thanks for taking the time to educate a behind the times DIYer.

[earlyrizr]

QUOTE "MT - So if you say the timing chain has nothing to do with timing, does that mean if the chain gets slop in it and skips a tooth or two you'll never know it?"

you should know it because the valve opening/closing wont be insync with the piston. thats where you can get misfire and possible engine damage.but the computer should pick that up as the crank and cam sensors wont match anymore and should set CEL

[MT-2500]

Originally Posted by RIP

So what it boils down to is it's like the situation 20 years ago when they went to permanently lubed ball joints, tie-rod ends etc and stopped using Zurt fittings to grease the joints, you just had to trust the job was getting done. Guess the powers that be found too many mechanics and DIYers were miss adjusting the timing and screwing up emissions so they took that option away and handed the job over to computer chips. Wander what's next? No drivers? It's on the way!

MT - So if you say the timing chain has nothing to do with timing, does that mean if the chain gets slop in it and skips a tooth or two you'll never know it?

Thanks for taking the time to educate a behind the times DIYer.

The timing chain/gears/or timing belt still has control over the camshaft and valve timing.
If they jump a cog you will lose power and engine vavume.
You will notice a lose of power and if they jump very many notches the engine will quit running.
But the ign will still fire the spark from the tdc of crankshaft sensor .
Most newer computer systems also use a camshaft sensor that checks the camshaft timing.
If the engine camshaft jumps a notch the computer will let you know about it.
MT

[RIP]

OK that makes sense. I appreciate the posts. One more question. So if the timing chain/belt jumps and timing goes out to lunch should I expect to get a fail code for a crank sensor or other sensor failure or is there a code specifically to indicate timing is out of spec that would at least lead you to think there is a timing chain/belt issue. Again, thanks.

[MT-2500]

Originally Posted by RIP

OK that makes sense. I appreciate the posts. One more question. So if the timing chain/belt jumps and timing goes out to lunch should I expect to get a fail code for a crank sensor or other sensor failure or is there a code specifically to indicate timing is out of spec that would at least lead you to think there is a timing chain/belt issue. Again, thanks.

Sometimes but not always or all computer systems.
The newer the more the pcm deepends on camshaft sensor signal.
Older gm used the camshaft sensor to time injector pulse.
They would run without the camshaft signal but not as good.
Real new systems may even shut down if the camshaft signal is not there.
MT

[RIP]

Hey, thanks again MT. I'm sure sooner or later I'll have to deal with a timing issue. My GC has 190K miles on it and runs great. Always has. Odds are sooner is closer to the truth. I'll keep your and earlyrizr's info in mind. Still, it sure would be helpful if when the gurus design these engine elec systems they would include a way to at least check to see where the timing is at. I'm sure even certified mechanics would like the option instead of hooking up a scanner everytime.