Hello All,
I'm looking for some troubleshooting pointers on this issue where my idle will stumble/drop when the radiator fan kicks on. After a moment the idle will return to normal. Then once the fan turns off the idle will jump a bit and then return to normal. Sometimes (but not very often) the engine seems like it will stall when the fan comes on.
I think this has been going on since I bought the car 6 years ago, but it has been getting markedly worse in the last year.
We're dealing with a 1999 Mustang GT.
Here are 2 videos showing the event. In the first one (which also shows running voltage at the battery) try to ignore the lifter noise and concentrate on the deeper exhaust note. That is where the idle drop is most noticeable.
I look forward to any help you guys can offer.
I'm looking for some troubleshooting pointers on this issue where my idle will stumble/drop when the radiator fan kicks on. After a moment the idle will return to normal. Then once the fan turns off the idle will jump a bit and then return to normal. Sometimes (but not very often) the engine seems like it will stall when the fan comes on.
I think this has been going on since I bought the car 6 years ago, but it has been getting markedly worse in the last year.
We're dealing with a 1999 Mustang GT.
- 177k miles
- Runs well (except for this issue and A/C needing attention).
- Alternator replaced at 148k miles 4½ years ago due to constant charge light.
- Replaced with a 110A from O'Reilly Auto Parts.
- Charging system and battery tested ok at Interstate battery.
- No codes.
- Radiator fan is original (as far as I know).
- Stock pulleys. Good tensioner and belt.
- Electrical mods:
- Sequential rear turn signals.
- Modest LED strip lighting in trunk.
- Modest LED strip lighting in all foot wells.
- Fog light mod to have lights on without parking/headlights.
Here are 2 videos showing the event. In the first one (which also shows running voltage at the battery) try to ignore the lifter noise and concentrate on the deeper exhaust note. That is where the idle drop is most noticeable.
Radiator fan kicks-on (and engine bogs down) at 0:02.
Then fan shuts off at 0:29.
idle stumble with radiator fan tach
You may need to turn-up your volume to hear when the engine bogs down, which happens at 0:05.
Fan shuts off at 0:31.
Then fan shuts off at 0:29.
idle stumble with radiator fan tach
You may need to turn-up your volume to hear when the engine bogs down, which happens at 0:05.
Fan shuts off at 0:31.
I look forward to any help you guys can offer.