I have a 1998 Chevy K2500 Suburban 454 (7.4L) with 108000 miles. I have
been working on (what I believe to be ) some ignition issues. Originally it
would cut out briefly when going up a hill under 30 mph -- more pronounced
when towing. No SES and no codes.
I decided to replace the spark plugs and wires (with AC 41-933 plugs) and a
set of Belden wires from NAPA. Before changing the plugs and wires, I
connected my scan tool (OBDII from carcode.com) to capture some data. I
noticed misfires mostly on cyl 7 and occassionally cyl 4 & 6. But what
really caught my attention was the Camshaft Retard (CMPR) which varies
between 4094.14 and 4095 degrees. I looked over the timing adjustment
procedure in my factory service manual -- but I doubt it would correct that
big of an offset.
After changing the plugs and wires - it doesn't cut out like it did but the
CMPR data is still the same. Misfires are now primarily on cyl 7. Again,
no check engine light or codes. Other symtoms include a slightly rough
idle, lack of power (more noticeable when towing), and knocking.
I am trying to decide if the Camshaft Position Sensor is bad or if the scan
tool is giving me bad data. All of the other data values from the scan tool
appear to be within range.
If the CMPR data is correct - wouldn't it be running a lot worse than it is
? Anyone see a similar situation where the CMPR was this large ?
My next step would be to replace the Camshaft Position Sensor - but I wanted
to get some other thoughts on this first.