Tempritscher
Newbie
Hi,
I am Markus from Northrhine-Westphalia, Germany.
Here in the "old world", trucks are not common like in North America,
so there are no GM garages here and no experts for these type of cars :-(.
I've got a friend who drives a '88 GMC Sierra, but he has not a vortec engine with
CSFI, like i had. So he doesn't really know how to help me, since I replaced some parts
at my truck, including to convert from the CSFI to the MPFI...
Engine coolant temperature, intake temperature, mass air flow and manifold absolute pressure
seem to be okay for me (using torque app for android for checking OBDII).
I have a 1998 Chevy Tahoe 5.7 Vortec, 4 speed auto
Here is the story:
A few weeks ago, maybe four or five, my engine began to run poorer, starting with sometimes bad idle at the traffic lights.
One time I stopped at a gas station, I touched a spark plug wire and got an electric shock,
so the first things I replaced were the spark plug wires, the distributor cap and the distributor finger, but no improvement.
Engine still ran creeping poorer than a month ago.
Next I replaced the MAP-Sensor, the new one works great I can see via Torque app for android.
But still no improvement.
Anytime the MIL started to flash and i got misfire in the exhaust and in the intake manifold.
By googling, I found out that many guys have converted from the CSFI I had to MPFI
because the CSFI is deemed to be unreliable.
So I orderer the MPFI from rockauto, and a week later it was here in Germany.
When unmounting the upper intake manifold, saw much carbon debris in the front,
where the nozzles for the cylinders 1, 3 and 2, 4 are positioned, backside with
5, 7 and espacially 6, 8 were only little debris.
After cleaning and installing of the MPFI, still no improvement.
Still flashing MIL, backfire in the exhaust.
The worst engine run with backfires is under load an lower rpm,
higher rpm and less load is better.
So after the MPFI conversion with the still existing problem,
I changed all eight spark plugs (old from AC Delco, new from NGK),
but still now improvement in engine run, and still backfires
Please give my an idea how to search further...
I am Markus from Northrhine-Westphalia, Germany.
Here in the "old world", trucks are not common like in North America,
so there are no GM garages here and no experts for these type of cars :-(.
I've got a friend who drives a '88 GMC Sierra, but he has not a vortec engine with
CSFI, like i had. So he doesn't really know how to help me, since I replaced some parts
at my truck, including to convert from the CSFI to the MPFI...
Engine coolant temperature, intake temperature, mass air flow and manifold absolute pressure
seem to be okay for me (using torque app for android for checking OBDII).
I have a 1998 Chevy Tahoe 5.7 Vortec, 4 speed auto
Here is the story:
A few weeks ago, maybe four or five, my engine began to run poorer, starting with sometimes bad idle at the traffic lights.
One time I stopped at a gas station, I touched a spark plug wire and got an electric shock,
so the first things I replaced were the spark plug wires, the distributor cap and the distributor finger, but no improvement.
Engine still ran creeping poorer than a month ago.
Next I replaced the MAP-Sensor, the new one works great I can see via Torque app for android.
But still no improvement.
Anytime the MIL started to flash and i got misfire in the exhaust and in the intake manifold.
By googling, I found out that many guys have converted from the CSFI I had to MPFI
because the CSFI is deemed to be unreliable.
So I orderer the MPFI from rockauto, and a week later it was here in Germany.
When unmounting the upper intake manifold, saw much carbon debris in the front,
where the nozzles for the cylinders 1, 3 and 2, 4 are positioned, backside with
5, 7 and espacially 6, 8 were only little debris.
After cleaning and installing of the MPFI, still no improvement.
Still flashing MIL, backfire in the exhaust.
The worst engine run with backfires is under load an lower rpm,
higher rpm and less load is better.
So after the MPFI conversion with the still existing problem,
I changed all eight spark plugs (old from AC Delco, new from NGK),
but still now improvement in engine run, and still backfires
Please give my an idea how to search further...
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