chevy venture missing, jumping (long)

[Terry]

I have a 1998 Chevy Venture minivan with 210,000 miles. For the past seven
month, the van has had a miss or stumble that occurs occasionally. It
seems to happen most while traveling on the interstate as I begin to go up
a grade. The miss happens only one time per hill, it is usually very
strong and harsh. I can sometime cause it to miss if I begin to increase
the speed as if I had encountered a hill. The gas mileage has not
decreased, nor has the power of the motor decreased. No smoke at any time
and the van does not burn oil. Other than this single miss every now and
then, the van runs great.

Things I have replaced or checked:

Spark plugs. (AC/Delco plugs)
Plug wires, twice. Last time with Delco wires.
7X crankshaft position sensor.
Fuel filter.
PCV valve.
Checked the fuel pressure, it is in spec and seems to change pressure
properly.
Both oxygen sensors.
Catalytic converter twice, last time with a GM converter.
New battery.
Rebuilt alternator.

No codes are stored, the service engine light does not come on. I have an
interface and can connect the OBD II to my laptop, but this does not show
any problem with the various sensors, and the OBD indicates a "pass" on all
onboard tests.
Any ideas or help is greatly appreciated,
Terry

[Shep]

Look at misfire counts as this happens on a full function scanner, try some
Chevron Techron FI cleaner, look as s/t fuel trims if you can get this to
happen.

Post by Terry
I have a 1998 Chevy Venture minivan with 210,000 miles. For the past seven
month, the van has had a miss or stumble that occurs occasionally. It
seems to happen most while traveling on the interstate as I begin to go up
a grade. The miss happens only one time per hill, it is usually very
strong and harsh. I can sometime cause it to miss if I begin to increase
the speed as if I had encountered a hill. The gas mileage has not
decreased, nor has the power of the motor decreased. No smoke at any time
and the van does not burn oil. Other than this single miss every now and
then, the van runs great.
Spark plugs. (AC/Delco plugs)
Plug wires, twice. Last time with Delco wires.
7X crankshaft position sensor.
Fuel filter.
PCV valve.
Checked the fuel pressure, it is in spec and seems to change pressure
properly.
Both oxygen sensors.
Catalytic converter twice, last time with a GM converter.
New battery.
Rebuilt alternator.
No codes are stored, the service engine light does not come on. I have an
interface and can connect the OBD II to my laptop, but this does not show
any problem with the various sensors, and the OBD indicates a "pass" on all
onboard tests.
Any ideas or help is greatly appreciated,
Terry

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[Terry]

Post by Shep
look as s/t fuel trims if you can get
this to happen.

I watched the fuel system trims and they change as I drive, mostly staying
in the negative, but they do occasionally go to +2.00 or so as I
accelerate. I am not sure what they should be, however.
I will try the Chevron Techron FI cleaner, but I did use some gas drier
last winter, no change.
Thanks, Terry

[Woody]

If you have enhanced option on your OBDII scanner check it for misfire
counts as Shep said. These wont set a code until they reach a threshold but
may give an indication where the problem lies.

Post by Terry

Post by Shep
look as s/t fuel trims if you can get
this to happen.

I watched the fuel system trims and they change as I drive, mostly staying
in the negative, but they do occasionally go to +2.00 or so as I
accelerate. I am not sure what they should be, however.
I will try the Chevron Techron FI cleaner, but I did use some gas drier
last winter, no change.
Thanks, Terry

[Terry]

Post by Woody
If you have enhanced option on your OBDII scanner check it for misfire
counts as Shep said. These wont set a code until they reach a threshold
but may give an indication where the problem lies.

Unfortunately, my scanner seems to not have this option. Thanks for the
reply anyway.
Terry

[Behode ApaleHorse]

If your Chevy Venture is missing, then I would call the athorities and
report it as being stolen asap. The sooner they know the better chances of
getting it back. You say it is also jumping....sounds like a low rider with
the air shocks for jumping, but I don't know why you would invest that type
of setup in a Chevy Venture.

[Rod]

Post by Terry
I have a 1998 Chevy Venture minivan with 210,000 miles. For the past
seven month, the van has had a miss or stumble that occurs
occasionally. It seems to happen most while traveling on the
interstate as I begin to go up a grade. The miss happens only one
time per hill, it is usually very strong and harsh. I can sometime
cause it to miss if I begin to increase the speed as if I had
encountered a hill. The gas mileage has not decreased, nor has the
power of the motor decreased. No smoke at any time and the van does
not burn oil. Other than this single miss every now and then, the
van runs great.
Spark plugs. (AC/Delco plugs)
Plug wires, twice. Last time with Delco wires.
7X crankshaft position sensor.
Fuel filter.
PCV valve.
Checked the fuel pressure, it is in spec and seems to change pressure
properly.
Both oxygen sensors.
Catalytic converter twice, last time with a GM converter.
New battery.
Rebuilt alternator.
No codes are stored, the service engine light does not come on. I
have an interface and can connect the OBD II to my laptop, but this
does not show any problem with the various sensors, and the OBD
indicates a "pass" on all onboard tests.
Any ideas or help is greatly appreciated,
Terry

I had the same problem on my 97 Trans Sport. New plugs took care of it.
Have no idea what's happening with yours, although I am interested in
hearing what others may have to say.

[John Horner]

Post by Terry
I have a 1998 Chevy Venture minivan with 210,000 miles.

Have you had the intake manifold gasket checked? These have a nearly
100% failure rate by your mileage.

John

[Terry]

Post by John Horner
Have you had the intake manifold gasket checked? These have a nearly
100% failure rate by your mileage.
John

Yes, it has been replaced.
Terry

[John]

replying to Terry, John wrote:
I have the exact same problem w my 99 venture. Replaced plugs,wires,computer.
Found loose coil where the bolt had backed out. Replaced the coil and it ran
fine for 1 month then started it again. Any ideas would be appreciated.
John C.

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