Stumbling suburban

[bob g]

When my sub is cold [first thing in morning]it surges and miss's until it reaches full operating temp and it does it until the gauge hits the exact normal operating temp. I have replaced cold advance sensor twice [just in case 1st one was bad] but it did not change,also checked lift pump as per DP instructions and changed filter. Also, I think this may be unrelated but when sub is at op temp and I decelerate slightly, like trying to maintain speed going down a slight grade, it has what feels like an engine miss.Truck is 97 sub, 4l80e,4;10 gears,Truck has good power and starts good. Thanks Bob

[twaddle]

Are you getting any smoke?
When the truck is sitting at idle does the engine sound rough as though it's missing or is the problem only when driving and the engines under load?

regards

Jim Twaddle
Biggar, Scotland.

[bob g]

Jim: When at idle engine is smooth, no smoke just bucks and surges while accelerating until it reaches op temp. I'm pretty sure cold advance is not working but I cant figure out why. Bob

[moondoggie]

Good Day!

Cold advance, & everything else, is controlled by your PCM. The older 6.2's had a temp. switch in the head that advanced the timing a little when the engine was cold, but that's 1993 & older trucks (before the electronic IP).

I'd verify lift pump operation 1st - EXTREMELY easy to do.

Blessings!

Brian Johnson, #5044

'82 6.2 1500 4X4 1/2T pickup, 4spd man w/ OD, bone stock, 335K+, "In Rust We Trust"
'89 6.2 4X4 1/2T pickup, bone stock, 146K+
'95 6.5TD 2500 4X4 heavy 3/4T pickup, Gear Vendors Aux. OD, 185K +
'95 6.5TD 1500 4X4 3/4T Suburban, Kennedy exhaust, 200K +

[ucdavis]

Bob,
A scanner hooked up for the cold start cycle will show timing advance & basically anything the pcm can read (fuel temp, BARO, boost, etc.). Any good non-affiliated diesel shop has one these days (even dealers got 'em ;)
Barring that you should have the codes read. Code reader that'll do this rig is about $100 and a good investment.
Your symptoms are hard to translate into a part failure; the usual fsd trouble doesn't go away when warmed up, but the good news is most other drivability throws a code so you will likely have something stored especially if its 100% of the time.

[bob g]

ucdavis: I didnt realize a code could be stored without the SES light coming on.I'm in Elk grove where is a good place to get one of those readers. Also I'm not sure what the PCM is. I had the IP & FSD replaced under warranty [thank you DP] about 10,000mi ago Thanks Bob

[patrick m.]

does your truck have EGR?

[bob g]

Patrick
My engine code is L65 I dont think it has Egr. I had it checked for codes today, its not storing any> Thanks Bob

[bob g]

Well I had my truck checked for codes again today, this time by a diesel shop they found 1216 & 1217 stored. Am I looking at a new FSD again after only 10,000mi ?

[cesguz]

Hi Bob G, I own a 2001 Hummer H1, it has 9k miles, a few weeks ago I got bad diesel and it began doing the exactly symptoms that you are describing; I didn