99 k3500 454 stumbles at idle and taking off from stops

[2boys1truck]

I had a previous post talking about my truck going though distributors caps to recap that I had the same issue twice loss of power and missing. First time truck started shaking and loss power and eventually no start it was pretty clear that it was missing very bad so I did plugs, wires, and distributor. truck seemed to run better than ever. A few months go by same issue I replaced the cap and rotor this time not the dizzy as I put in one of the after market aluminum ones this fix the problem. so now another 6 months goes by and truck. I was on a 3 hour drive didn't notice anything at highway speeds but when I got off and came to a stop I noticed it was idling weird and was stumbling/ sluggish from a stop. Drives fine while costing or on and off the gas at cruising or highway speed. Off the line It shakes and has hesitation. I just assumed it was the same issue so I put a vented dizzy cap on suggested to me on my last post. This time it did not fix my problem so I'm dealing with a new issue. The truck didn't though any codes initially but after a longer test drive it gave me p0102 and p0122. so MAF and TPS it was shifting very weird on the test drive it had never done this before and I know my tranny is in good shape. I assuming maybe just coincidence but I put a new TPS on now truck shifts as it should. Still dealing with very choppy idle especially in gear and hesitation on acceleration from a stop

I've tried unplugging my front o2 and test driving no change
cleaned MAF and looked at live date with scan tool and the grams per sec seemed normal around 7 to 8 at idle and went up with throttle
rpms are from 530 to 600 in gear and 6 to 7 in park
also the stumble seems to get worse as the truck warms up
I find it odd that the TPS went out my first test drive after doing the cap and rotor but maybe just chance. The truck has not stalled or died on me but seems like it wants to at stops.
when I unplugged the 02 to test I only unplugged the front one above cat do I need to do both?
if my MAF looks good on live data can I rule that out and what else could that code be?
Any help is greatly appreciated I don't know to to check next!

 

[weaponoffreedom]

I have a similar issue. I think it is the transmission, or perhaps more specifically, the Torque convertor. The "hesistation" goes away in neutral?

 

[454cid]

Can you look at live data for the TPS, preferably as a graph? My Volvo 850 had a bad TPS and I found it with live date. It also made the transmission shift weirdly. What was happening is that the TPS was shorting to power. It was received as a valid signal, so the transmission was downshifting as if I had just gone WOT when I had in fact not changed throttle position at all. The short would make and break contact so the transmission would downshift and upshift very quickly randomly. A new TPS fixed it.

You've already got a TPS code, so exploring that more fully is where I'd go from here. A quick Google says that code is a "low output", so it might be a short to ground. Could be internal (sensor) or external (wiring). Since you were in that general area, it's reasonable to suspect the wiring a little more than the sensor, in my mind. Maybe unplug and check pins for corrosion? I don't recall if the sensor is completly sealed or not, but you could remove it, and try spraying it off/out with contact cleaner, as well.....may as well do that to the connector.

 

[inconceivablemotors]

I had a previous post talking about my truck going though distributors caps to recap that I had the same issue twice loss of power and missing. First time truck started shaking and loss power and eventually no start it was pretty clear that it was missing very bad so I did plugs, wires, and distributor. truck seemed to run better than ever. A few months go by same issue I replaced the cap and rotor this time not the dizzy as I put in one of the after market aluminum ones this fix the problem. so now another 6 months goes by and truck. I was on a 3 hour drive didn't notice anything at highway speeds but when I got off and came to a stop I noticed it was idling weird and was stumbling/ sluggish from a stop. Drives fine while costing or on and off the gas at cruising or highway speed. Off the line It shakes and has hesitation. I just assumed it was the same issue so I put a vented dizzy cap on suggested to me on my last post. This time it did not fix my problem so I'm dealing with a new issue. The truck didn't though any codes initially but after a longer test drive it gave me p0102 and p0122. so MAF and TPS it was shifting very weird on the test drive it had never done this before and I know my tranny is in good shape. I assuming maybe just coincidence but I put a new TPS on now truck shifts as it should. Still dealing with very choppy idle especially in gear and hesitation on acceleration from a stop

I've tried unplugging my front o2 and test driving no change
cleaned MAF and looked at live date with scan tool and the grams per sec seemed normal around 7 to 8 at idle and went up with throttle
rpms are from 530 to 600 in gear and 6 to 7 in park
also the stumble seems to get worse as the truck warms up
I find it odd that the TPS went out my first test drive after doing the cap and rotor but maybe just chance. The truck has not stalled or died on me but seems like it wants to at stops.
when I unplugged the 02 to test I only unplugged the front one above cat do I need to do both?
if my MAF looks good on live data can I rule that out and what else could that code be?
Any help is greatly appreciated I don't know to to check next!

Curious if you ever found the reason for the stumble off idle?
Im fighting the same issue. Live data all looks good, timing is correct, did a smoke test no vacuum leaks. So far I have replaced:
-Intake gaskets
-Fuel injectors and regulator
-Fuel pump
-Distributor, wires and plugs
-Idle control valve - It seemed lazy
-Timing chain and sprockets
-Crankshaft sensor
-O2 Sensors

And so far have not been able to resolve this..... Any inside greatly appreciated.

 

[fancyTBI]

Curious if you ever found the reason for the stumble off idle?
Im fighting the same issue. Live data all looks good, timing is correct, did a smoke test no vacuum leaks. So far I have replaced:
-Intake gaskets
-Fuel injectors and regulator
-Fuel pump
-Distributor, wires and plugs
-Idle control valve - It seemed lazy
-Timing chain and sprockets
-Crankshaft sensor
-O2 Sensors

And so far have not been able to resolve this..... Any inside greatly appreciated.

OP hasn’t been here since September of ‘23. Unlikely to get a response but never know. You might have more luck starting your own thread.