AuroraGirl
Full Access Member
- Joined
- Sep 8, 2019
- Posts
- 9,693
- Reaction score
- 6,869
- Location
- Northern Wisconsin
- First Name
- Taylor
- Truck Year
- 1978, 1980
- Truck Model
- K10, K25
- Engine Size
- 400(?), 350
@WFO ALDL diagnostics has a special place in terms of... interfacing problems. unless you have a tech 1 or one of these 50+ dollar systems(for antiquated data reading and code reading), you are in no mans land. At least starting in 1991 my tech 2 can be used in place of a tech 1. my car was a 1990.
OP, does your truck have a speed-density MAF or is it wire? or does TBI not use MAF? A CTS being wrong usually means some rich mixtures, esp before the era of 2 oxygen sensors. if 1990 small blocks had egr, and AIR, i could see maybe egr leaning your intake so it enrichens the mixture itself, causing a high idle?
BARO and MAP are to consider too, Incorrect TPS, etc. My car is OBD 2 and its still able to fool itself as long as incrrect sensors dont have improper settings for too long, and it can even check against itself with other sensors. obd1 isnt gonna be doing that, so if you have 3000ft elevation, 14.2 psi barometric, 13g/s air intake, and 12psi intake vacuum, O2 sensor read normal mv, CTS said -25 degrees F, 3% throttle your engine probably wouldnt be able to tell why it wasnt running right, or stalled.
On v6, a camshaft position sensor that isnt working will lead to incorrect ignition every 9 rounds of firing. not sure if v8 needs it since distributor is there still.
On that subject, do you know service history? People who shouldnt touch engines like to rig **** and touch **** they shouldnt all the time. like the idle stop screw which should not be touched under normal operations or the distributor timing and can screw things up. hell, EGR present or blocked off properly?
OP, does your truck have a speed-density MAF or is it wire? or does TBI not use MAF? A CTS being wrong usually means some rich mixtures, esp before the era of 2 oxygen sensors. if 1990 small blocks had egr, and AIR, i could see maybe egr leaning your intake so it enrichens the mixture itself, causing a high idle?
BARO and MAP are to consider too, Incorrect TPS, etc. My car is OBD 2 and its still able to fool itself as long as incrrect sensors dont have improper settings for too long, and it can even check against itself with other sensors. obd1 isnt gonna be doing that, so if you have 3000ft elevation, 14.2 psi barometric, 13g/s air intake, and 12psi intake vacuum, O2 sensor read normal mv, CTS said -25 degrees F, 3% throttle your engine probably wouldnt be able to tell why it wasnt running right, or stalled.
On v6, a camshaft position sensor that isnt working will lead to incorrect ignition every 9 rounds of firing. not sure if v8 needs it since distributor is there still.
On that subject, do you know service history? People who shouldnt touch engines like to rig **** and touch **** they shouldnt all the time. like the idle stop screw which should not be touched under normal operations or the distributor timing and can screw things up. hell, EGR present or blocked off properly?
