7.4L CMP Retard -16

[Zephian]

Hello,
as the topic says I have a 97 k2500 suburban with the 454 7.4l.
Running great, just smogged it, then BOOM check engine light several hours after smog check.

Looked in the to check engine light with my handy OBDII bluetooth adapter and Torque Pro.
P1345.

I narrowed it down to the cam offset/retard. Had to purchase a different app to monitor these values (Dash Command + advanced GM PIDs)

I was at -16 degrees at +1k RPM. Rough idle, weak start.
Loosened the distributor hold down bolt, turned it counter clockwise as far as I could (Spark plug is against the intake plenum ) and only gained 2 degrees.
I am now at -14.

Is it possible my distributor jumped a tooth? Should I just pull the distributor, advance it one tooth and check again? Or is my distributor shot and needs replacement?

Thanks for any input.

 

[454cid]

That's weird. It shouldn't through a code until it's further out than that, unless the threshold changed over the years. Spec is +/-2, but I've heard the code doesn't get triggered until it's like 20 something out.

I do beleive it's supposed to be checked at a bit higher rpm.... 1100, I think. When I did it, I wedged a small screwdriver in between the throttle cam and stop screw.

 

[Schurkey]

My '97 K2500 7.4L was 29 degrees out when I bought it. Turned the distributor and got it to "1" degree.

First Guess: Your distributor gear is worn-out. Apparently, the distributor gear can wear without tearing up the gear on the cam.

Pull distributor (yeah, it's a pain) and verify. Wouldn't hurt to check for timing chain slop, too.

 

[smokymtn65]

Hello,
as the topic says I have a 97 k2500 suburban with the 454 7.4l.
Running great, just smogged it, then BOOM check engine light several hours after smog check.

Looked in the to check engine light with my handy OBDII bluetooth adapter and Torque Pro.
P1345.

I narrowed it down to the cam offset/retard. Had to purchase a different app to monitor these values (Dash Command + advanced GM PIDs)

I was at -16 degrees at +1k RPM. Rough idle, weak start.
Loosened the distributor hold down bolt, turned it counter clockwise as far as I could (Spark plug is against the intake plenum ) and only gained 2 degrees.
I am now at -14.

Is it possible my distributor jumped a tooth? Should I just pull the distributor, advance it one tooth and check again? Or is my distributor shot and needs replacement?

Thanks for any input.

How many miles on this truck?

 

[Zephian]

How many miles on this truck?

~150k

 

[Zephian]

I purchased a summit distributor...
If I'm going to pull the old one I might as well replace it since I'm sure it's stock. Apparently some aftermarket distributors are not CARB legal. Stupid California. Don't think anyone will notice a distributor though...

 

[yevgenievich]

Also worth verifying the play in the timing chain while working with the distributor. I am going the pathway of distributor first, then timing chain second.

 

[Zephian]

Also worth verifying the play in the timing chain while working with the distributor. I am going the pathway of distributor first, then timing chain second.

What is the best way to test for slack if you don't mind my asking? Not something I've really had to do before. Some instructions state to remove distributor cap, find TDC then turn the motor backwards until the rotor starts to move. Does this motor have accurate enough markings on the (I believe) harmonic balancer, or do I need to measure it another way? What is the acceptable 'slop' allowed?
I am more of a weekend tinkerer than an expert. Luckily my first vehicle was a 99 S10 with the 4.3 so I've been able to relate a lot of the problems I had with that motor to this 454...just on bigger scale.
Thanks!

 

[Zephian]

I forgot to mention I moved the truck across the street yesterday to wash some cars in my driveway (I have too many) and now it won't start.
Click.
Click.
Click.
F**k

Looks like im doing my troubleshooting on the other side of the street. At least I have no neighbors directly in front of me.

 

[yevgenievich]

What is the best way to test for slack if you don't mind my asking? Not something I've really had to do before. Some instructions state to remove distributor cap, find TDC then turn the motor backwards until the rotor starts to move. Does this motor have accurate enough markings on the (I believe) harmonic balancer, or do I need to measure it another way? What is the acceptable 'slop' allowed?
I am more of a weekend tinkerer than an expert. Luckily my first vehicle was a 99 S10 with the 4.3 so I've been able to relate a lot of the problems I had with that motor to this 454...just on bigger scale.
Thanks!

Does not have to have a motor in any specific spot. Just see how many degrees can the motor turn before the rotor starts to turn.