After wheeling hard last weekend, my truck started acting funny. No check engine light came on but when I checked for codes, 12 and 14 appeared. I cleared them but have not been able to reproduce them even after driving several places which makes me think that they may have been stored for some time.



Truck: 1994 Pickup 4wd, 22-RE manual.


Symptoms:
-Fuel pump whines when I have the ignition keyed hot without the truck on. I can’t tell if it is still on when the truck is on but I assume it is. I can hear the injectors clicking normally when the truck is running.
-Idles like crud: It will stay on when cold but dies at idle when warmed up. It puffs smoke when quickly revved above idle. It also has a lot less power. It drives fine above 2000rpm but dies at stoplights.
-I can smell gas in the exhaust.


What I have done so far:
-Changed plugs and wires: I destroyed a wire when checking spark so I thought I would replace them anyway. No change in symptoms, but I didn’t expect one.
-Investigated the 12 and 14 codes: I checked the resistance of the distributor pickup and main coil. Both were within FSM specs. I don’t know if I should just replace the pickup since I know it could cause the idle issues if it is bad but what about the fuel pump sound?
-I thoroughly checked the undercarriage to see if I damaged wires while wheeling but found nothing.
-I checked the vacuum lines in the engine compartment and all are intact.
-I plan to replace the fuel filter this afternoon.

This is my daily driver. I really don’t want to take it to a mechanic both out of pride and lack of money. I assume this has something to do with my wheeling trip last week since it happened immediately afterwards. I did bang up the left side pretty good but kept it water/mud free.
I really appreciate any input or insight into this issue. Where should I go from here?
Rob

 

Check the Air Flow Meter and the wiring harness

 

Punchy,

You were right!

I finally gave up and took it to a mechanic friend of mine. It turned out to be the Mass Airflow Sensor. The spring had broken and it was stuck open. It makes sense since it was sending a message to the fuel pump to increase flow explaining the whining and the smell of gas. I also got the truck body damage appraised for my own curiosity; $2800.



Good diagnostic skills!

Thanks again.

Rob