mostly_broncos
Active Member
- Joined
- August 22, 2019
- Messages
- 73
- Reaction score
- 62
- Year, Model & Trim Level
- 78 bronco
4.0 2003 explorer sport trac , tried 3 different known good meters all read 1.3 to 1.5 volts at idle ?
Scanner claims that corresponds to 2.66 lb/m
that voltage is consistent across different sensors that work fine in a 2005 escape.
When its cold it idles for a little while badly then dies with a very rich smell.
Idles much better with the MAF unplugged.
Changed intake port to cylinder head gaskets no help , blocked off PCV hoses to isolate potential vacuum leaks , no help , pulled , EVAP line plugged it no help , pulled brake booster hose and plugged it no help.
Tried every vacuum hose I can find , I don't think its a vacuum leak behind the throttle plate , the MAF sensors all think they are seeing that much airflow but why?
I pulled the PCM harness and have continuity between the C and D also A and F to their respective pins.
Full battery voltage on the hot wire , the ground is fine , the signal return sometimes is a little lower than the other ground say .5 volts not consistently
I checked and cleaned the neg post to radiator support ground , the main cable ground on the starter bolt , the ground near the wiper motor, the ground near the PCM .
This is weird what am I missing? the MAF is legit outputting that high voltage so that appears to rule out the D wire to the PCM .
Does the C wire labeled signal return go elsewhere , other sensors ? Could a short in another sensor feed back to the MAF and change the reading on the C wire and bump up the voltage output on the D wire?
Scanner claims that corresponds to 2.66 lb/m
that voltage is consistent across different sensors that work fine in a 2005 escape.
When its cold it idles for a little while badly then dies with a very rich smell.
Idles much better with the MAF unplugged.
Changed intake port to cylinder head gaskets no help , blocked off PCV hoses to isolate potential vacuum leaks , no help , pulled , EVAP line plugged it no help , pulled brake booster hose and plugged it no help.
Tried every vacuum hose I can find , I don't think its a vacuum leak behind the throttle plate , the MAF sensors all think they are seeing that much airflow but why?
I pulled the PCM harness and have continuity between the C and D also A and F to their respective pins.
Full battery voltage on the hot wire , the ground is fine , the signal return sometimes is a little lower than the other ground say .5 volts not consistently
I checked and cleaned the neg post to radiator support ground , the main cable ground on the starter bolt , the ground near the wiper motor, the ground near the PCM .
This is weird what am I missing? the MAF is legit outputting that high voltage so that appears to rule out the D wire to the PCM .
Does the C wire labeled signal return go elsewhere , other sensors ? Could a short in another sensor feed back to the MAF and change the reading on the C wire and bump up the voltage output on the D wire?