my 98 f150 will start but won't idle, it just dies. I can keep it running by feathering the gas pedal. What is wrong with it?

Asked by Dec 31, 2016 at 04:02 PM about the 1998 Ford F-150 STD 4WD SB

Question type: Maintenance & Repair

I can start it up but it won't stay running without feathering the gas pedal.

3 Answers

17,745

Mine did this too. I cleaned the mass air flow sensor, the throttle body and IAC but still did it just as bad. I feared the speed sensor in the transmission next but before doing it I decided to check the spark plugs & wires with a multimeter and found arching had been going on with them and had burned a plug up. I replaced them all because I had arc damage to wires and two other plugs had readings that were near the end of their life span (also there is a tester you can use to test them). It had the standard wire set when I bought it so its a good idea to go ahead and buy the premium set and a tube of dielectric/bulb grease and put it on all wire boots both ends and make sure the coil pack has not gotten moisture around boot fitting or has any cracks to case. Also check the for vacuum leaks, under toward front and back under side passenger side of intake has small 90 degree vacuum hose fittings that go out fast if they are the older style stock fittings, the dealerships parts departments now have the improved versions, I had to replace them twice on my 98 f150 and now that I have the better ones I have not had those problems since.

17,745

If you do decide to clean those parts listed above use only (I like crc) mass air flow sensor cleaner on it and throttle body cleaner on that and the IAC and go ahead pull the PCV valve and clean it too (throttle body cleaner). And you can use the dielectric grease on all electrical connections just use contact cleaner (again I like CRC brand) before applying grease to clean them first (spray out the connectors and put the grease in and plug back up, while I was doing my plugs I did this to all electrical connections I could find while I had it there. By they way My throttle body & IAC worked o.k. but did benefit from the cleaning and gets better gas mileage now.

17,745

If it ends up being the speed sensor it is in the trans and can be replaced by removing the pan. My next thing to check was the safety neutral switch. The trans can be check by a shop that has the trans code reader computer which is not the standard code readers from auto parts stores. I would follow the steps above before the trans sensors which can cause the same systems you have and there is like five other sensors in there and they may never go out but could save some hassle later to just go ahead and replace them all while the pan is off along with filter and fluid too.

Your Answer

F-150

Looking for a Used F-150 in your area?

CarGurus has 9,150 nationwide F-150 listings starting at $922.

Postal Code:

Ford F-150 Experts

  • #1
    OJ
    Reputation
    8,750
  • #2
    dandyoun
    Reputation
    4,480
  • #3
    tennisshoes
    Reputation
    3,010
View All

Related Models For Sale

Used Chevrolet Silverado 1500
158 Great Deals out of 10,639 listings starting at $100
Used GMC Sierra 1500
226 Great Deals out of 10,358 listings starting at $2,995
Used Dodge Ram 1500
59 Great Deals out of 532 listings starting at $2,995
Used Ford F-250 Super Duty
19 Great Deals out of 784 listings starting at $4,994
Used Toyota Tacoma
27 Great Deals out of 801 listings starting at $5,995
Used Ford F-250
5 listings
Used Ford Mustang
7 Great Deals out of 1,191 listings starting at $3,350
Used Ford Explorer
43 Great Deals out of 1,384 listings starting at $3,900
Used Chevrolet Tahoe
7 Great Deals out of 633 listings starting at $6,871
Used Ford F-350 Super Duty
24 Great Deals out of 1,101 listings starting at $8,000

Used Cars For Sale

2018 Ford F-150 For Sale
194 listings starting at $37,433
2017 Ford F-150 For Sale
13 Great Deals out of 5,064 listings starting at $27,096
2016 Ford F-150 For Sale
61 Great Deals out of 778 listings starting at $19,995
2015 Ford F-150 For Sale
75 Great Deals out of 660 listings starting at $23,930
2014 Ford F-150 For Sale
92 Great Deals out of 530 listings starting at $11,995

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.