98 5.7 k2500 timing

[richardj23]

i have a 1998 k2500 with a 5.7 in it, i just put another 5.7 in it out of a 97. The truck runs amazing at idle but when i put it in gear its fine then when i drive it starts backfiring. I have moved the distributer back and fourth moved teeth back and fourth i just cant figure it out. On top of that it no longer reads on the speedometer aswell as it wont shift out until over 4k rpms. everytime i try to adjust timing i just cant seem to get it below 20 spark adv on my scan tool. Do i keep trying to chase the timing part or what could it be? Also the reason of the engine change was the old engine just ran like crap it was not reliable.

 

[Schurkey]

Turning the distributor DOES NOT change the ignition timing. Ignition timing is NOT ADJUSTABLE on the '96-up Vortec engines.

Turning the distributor does change the "cam offset"; and it screws-up the rotor-tip-to-distributor-contact alignment.

Reclock your distributor using a scan tool to get the cam offset within + or - 2 degrees at 1100 RPM, tighten it down, recheck, and if it's still good, then leave it alone.

Something ELSE is wrong that the speedo doesn't register, and the shifting is screwed-up. My first guess would be a disconnected vehicle speed sensor, damaged VSS harness, or failed VSS sensor/reluctor in the transmission or transfer case. There's other possibilities, but verifying EVERY sensor with the scan tool, especially the VSS would be the first priority.

 

[richardj23]

could it possibly be i jumped timing on the chain to cause backfiring?

 

[Schurkey]

Probably more likely that the spark is jumping to the wrong terminal of the distributor cap because the distributor position is messed-up.

Re-set the cam offset, verify all the sensors when the scan tool is connected, see what happens.

 

[1998_K1500_Sub]

could it possibly be i jumped timing on the chain to cause backfiring?

A timing chain "jump" won't affect the ignition timing, it would affect at least the valve timing and the camshaft position timing, the latter manifests as the "cam offset" value reported by the ECU.

See here:

Having a bad issue with my 5.7 Vortec

I had my motor rebuilt from a very well known engine builder in my area. I got the engine put back in at replaced everything back but with all brand new parts either ac Delco or Dorman parts. My issue I'm having is it runs like crap spitting, sputtering, and backfiring but once circuits close...

www.gmt400.com

NOW, as @Schurkey noted, if the distributor is turned WAY to far one way or the other from ideal (~22deg of cap rotation), the spark can jump from the rotor to the wrong spark tower and thus fire the wrong cylinder and/or fail to fire the desired cylinder.

 

[richardj23]

after still struggling with it i still cant figure it out. I have moved teeth forward and teeth backwards. But like i said the truck runs amazing at idle but when you put it in drive or reverse it backfires. so i dont know how to set the timing if it only runs bad in gear.

 

[1998_K1500_Sub]

after still struggling with it i still cant figure it out. I have moved teeth forward and teeth backwards. But like i said the truck runs amazing at idle but when you put it in drive or reverse it backfires. so i dont know how to set the timing if it only runs bad in gear.

Have you followed the procedure in the FSM on how to install the distributor?

Find it, attached, from the 1998 FSM.

The V8 and V6 instructions are similar. The instructions may appear a bit dizzying but, if you think through them a bit, it's very straightforward. Don't be dissuaded.

 

[99xcss4]

I do not know if this is how the manual says to do but I have done like in this video and no codes after install

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[east302]

so i dont know how to set the timing if it only runs bad in gear.

The computer controls the timing - you aren’t setting it like we used to do with timing lights and marks on the balancer.

You’ll need a scanner to read the CMP Retard (a.k.a. CMP/CKP correlation or offset) as mentioned by others above. The distributor, stabbed properly at #1 TDC compression, is twisted to get to the correct value. It’s not the same as the timing advance number reported by the scanner.