misfire on acceleration.

125

Asked by Jun 07, 2013 at 06:07 PM about the 1990 Ford F-150 XLT Lariat 4WD LB

Question type: Maintenance & Repair

i have a 1990 f150 larait 300 6cyl. i recently did a tune up and got cyl 4 and 2 reversed on the cap.. i feel dumb but now it runs alright at idle. took it for a test drive and i made it about a block and it started to misfire badly and stumble. it would accelerate but not at the rate it should. i think i need to adjust timing? also there is an intake gasket leak and a friend told me that the leak may be causing it because there is too much air getting into the cylinders. any possibility that could cause it? i appreicate any help because this is stumping me. the fuel pump is only a couple years old. i just replaced the fuel filter.

3 Answers

78,565

An intake leak will cause all kinds of issues, I would have that fixed before tackling anything else, make sure that the manifold assembly is flat, you might need to have it machined as they do warp. Might check the distributor cap for carbon tracking, it only takes a few arcs across the electrodes to etch a cap.

21,845

While the 300 is a great workhorse - it is prone to warping the exhaust manifold and taking the intake with it. When you do address the concern, don't try to fudge it - you'll only have to do it again. Gaskets help but they aren't the fix. Tennisshoes knows what he's talking about here - vacuum leaks cause all kinds of drivability concerns as well as the carbon tracking issue)

125

thank you for your answers. i did get it fixed, the timing was badly off. runs much better now.

Your Answer

Add photo

Related Questions

  • my F150 ides rough, hesitates on acceleration and shakes at low rpms. Any ideas? 1 answer

    Changed the gas and used fuel injector cleaner.

    2005 Ford F-150

    -

    Maintenance & Repair

  • Truck Hesitates when accelerating 13 answers

    I can be driving down the road and my truck rides fine. I'll be going 30mph and step on the gas and it kinda hesitates, it will rev real quick then actually accelerate. I guess it is thinking about ...

    2006 Ford F-150 FX4 SuperCrew Styleside 4WD

    -

    Maintenance & Repair

  • why bad fuel use and poor acceleration 6 answers

    87 f150.5.0. injected. new pump/filter on frame.bypassed rear tank and switch.new gas regulator.drove 45 miles and it used most of tank.gas gauge bounces but can see it go down.poor acceleration. he...

    1987 Ford F-150 XL Standard Cab SB

    -

    Maintenance & Repair

  • 2010 F150 - clicking when accelerate 2 answers

    Whenever we accelerate, there is a clicking/rattling noise coming from under the passenger seat. It gets loader when we tow our travel trailer. What is it? How expensive to fix?

    2010 Ford F-150 FX4 SuperCrew 4WD

    -

    Maintenance & Repair

  • 2003 Ford Taurus SES Misfire only at idle 1 answer

    I have a 2003 Ford Taurus SES with the 24 Valve engine. It started misfiring about a month ago and the trouble code reads cylinder #3 misfire detected. It only misfires while idling, under accelerat...

    2003 Ford Taurus SES

    -

    Maintenance & Repair

F-150

Looking for a Used F-150 in your area?

CarGurus has 208,122 nationwide F-150 listings starting at $1,273.

ZIP:

Search Ford F-150 Questions

Ford F-150 Experts

#1 OJ
OJ
Reputation 6,300
#2 dandyoun
dandyoun
Reputation 3,980
#3 tennisshoes
tennisshoes
Reputation 2,400
View All

Related Models For Sale

Used GMC Sierra 1500
1,189 Great Deals out of 58,894 listings starting at $2,499
Used Ford F-250
569 listings starting at $1,977
Used Ford Mustang
718 Great Deals out of 39,272 listings starting at $1,995
Used Ford Explorer
1,479 Great Deals out of 74,562 listings starting at $985
Used Ford Ranger
219 Great Deals out of 7,085 listings starting at $1,500

Used Cars For Sale

2017 Ford F-150 For Sale
44,201 listings starting at $17,605
2016 Ford F-150 For Sale
210 Great Deals out of 93,762 listings starting at $17,937
2015 Ford F-150 For Sale
271 Great Deals out of 8,386 listings starting at $18,891
2014 Ford F-150 For Sale
585 Great Deals out of 11,520 listings starting at $9,600
2013 Ford F-150 For Sale
812 Great Deals out of 14,811 listings starting at $7,527