what can i do to fix these problems, starting up,popping or backfire and making it move or roll in drive

Asked by Jul 02, 2014 at 02:31 AM about the 1991 Ford F-250 2 Dr XLT Lariat Extended Cab LB

Question type: Maintenance & Repair

spraying quick start in it to start , high rpms ,popping or backfiring when accelerate , putting it in drive it will roll slowly ,slowly, in 1 it will move like in drive. all other gears work fine. also fuel pump keeps running will not turn off when starting up.          THANK  YOU.

4 Answers

95

It may seem silly but check your air in take if if is electric control remove the connector run car if this works you will need a new air control unit

23,005

What engine is in your truck? Sounds like a bad vacuum leak but your description of your concern isn't very clear. Won't start? Starts but won't run? Runs poorly? Fuel pump runs when? Sorry but your description is difficult to follow.

5,955

So it is running rich. I'm not sure I follow the "roll slowly, slowly" part unless the rich fuel ratio is bogging the engine? But the high rpm would kind of negate the bog. It is kind of unclear but I'm going to guess something measuring air flow is enriching the A/F ratio and I don't know what sensors are inline from your filter to throttle body. So it could be MAF / VAF / a fuel switch sticking. Another guess would be an open injector? or your idle air control valve (or comparable sensor) is sticking open (high rpm). I could honestly be wrong as well, and there are plenty of scenarios to make issues with EFI sadly. @Barry, do you mean a throttle position sensor?

5,955

any updates to this?

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