Problem with dad's truck
06-10-2019, 05:10 PM
#1
Team Owner
Thread Starter
Problem with dad's truck
1995 Z71 350 auto 4WD - High miles (about 285k)
It stumbles and runs rough when cold.
Settles down when warm.
After a fair amount of "at temp" driving, it starts to sputter a bit. If you shut it off and immediately restart it, it smooths out. This is repeatable every time is starts to sputter. Turn it off and restart and it's fine for a bit.
TPS has been replaced
Disty has been replaced
Wires have been replaced
Plugs have been replaced
Two different shops have had it and no one can figure it out. No codes.
It stumbles and runs rough when cold.
Settles down when warm.
After a fair amount of "at temp" driving, it starts to sputter a bit. If you shut it off and immediately restart it, it smooths out. This is repeatable every time is starts to sputter. Turn it off and restart and it's fine for a bit.
TPS has been replaced
Disty has been replaced
Wires have been replaced
Plugs have been replaced
Two different shops have had it and no one can figure it out. No codes.
06-10-2019, 05:33 PM
#2
Team Owner
Fuel pressure checked at cold start and again when up to temp? It's TBI correct? Could be an injector problem....285K miles is a lot. Original O2 sensors as well?
06-10-2019, 05:49 PM
#5
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Member Since: Sep 2005
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St. Jude Donor '11, '17
Problem with Dad's truck is that Dad is too cheap to buy a newer one. Should be some reasonable deals on 2 -4 yo trucks. Stay away from any dealers near Lars, Gixxer, Wezzy, koko, etc.
06-10-2019, 05:50 PM
#6
Team Owner
06-10-2019, 05:55 PM
#10
Team Owner
I'm thinking it's got to be more with the MAF than fuel delivery. IF the filter was clogged, it wouldn't run well period. If it was the pump, it wouldn't run at all the way GM does things.
Sounds like it's not reading the correct air flow at different temps and turning the car on/off to reset everything fixes it temporarily until it sees the same conditions.
Sounds like it's not reading the correct air flow at different temps and turning the car on/off to reset everything fixes it temporarily until it sees the same conditions.
06-10-2019, 05:59 PM
#11
Race Director
Things that come to mind,
O2 sensor acting up , but not enough to trigger a CEL,
Coil - weak, they act up when hot, run rough when cold as the spark is weak,
There are a few other items, but you need to drive with a data logger to see which item is going out of / close to limits..
O2 sensor acting up , but not enough to trigger a CEL,
Coil - weak, they act up when hot, run rough when cold as the spark is weak,
There are a few other items, but you need to drive with a data logger to see which item is going out of / close to limits..
06-10-2019, 06:06 PM
#12
Race Director
Member Since: Apr 2007
Location: long Island NY
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1995 Z71 350 auto 4WD - High miles (about 285k)
It stumbles and runs rough when cold.
Settles down when warm.
After a fair amount of "at temp" driving, it starts to sputter a bit. If you shut it off and immediately restart it, it smooths out. This is repeatable every time is starts to sputter. Turn it off and restart and it's fine for a bit.
TPS has been replaced
Disty has been replaced
Wires have been replaced
Plugs have been replaced
Two different shops have had it and no one can figure it out. No codes.
It stumbles and runs rough when cold.
Settles down when warm.
After a fair amount of "at temp" driving, it starts to sputter a bit. If you shut it off and immediately restart it, it smooths out. This is repeatable every time is starts to sputter. Turn it off and restart and it's fine for a bit.
TPS has been replaced
Disty has been replaced
Wires have been replaced
Plugs have been replaced
Two different shops have had it and no one can figure it out. No codes.
O2 sensors lazy?
06-10-2019, 06:17 PM
#14
Race Director
06-10-2019, 06:35 PM
#18
Team Owner
Thread Starter
Things that come to mind,
O2 sensor acting up , but not enough to trigger a CEL,
Coil - weak, they act up when hot, run rough when cold as the spark is weak,
There are a few other items, but you need to drive with a data logger to see which item is going out of / close to limits..
O2 sensor acting up , but not enough to trigger a CEL,
Coil - weak, they act up when hot, run rough when cold as the spark is weak,
There are a few other items, but you need to drive with a data logger to see which item is going out of / close to limits..
It behaves like a bad vacuum leak when cold...or too rich.
None of that applies to the restart being immediately different.
Also mentioned was MAF, but I'm 99.9% sure it doesn't have one. It's TBI.
06-10-2019, 06:38 PM
#19
Team Owner
Thread Starter
this year and he likes his truck so I want to help keep it running if I can.
06-10-2019, 06:40 PM
#20
Team Owner
