What's causing my 351 Modified to start backfiring...?

Asked by Bob_351m Jun 24, 2015 at 09:34 AM about the 1979 Ford F-150

Question type: Maintenance & Repair

Recently, my '79 F-150 has begun to backfire and it's getting worse.  It had been running rough so I replaced the plugs, wires, cap and button(?)...  But now, the backfiring...! I know I have the wires in the right order as I replaced them one by one...  Could it be vacuum, timing or other (electrical)...?

5 Answers

Bob_351m answered 8 years ago

Obviously I'm not a seasoned mechanic - but I am mechanically inclined... Is that under the dist. cap also...?

Mark helpful
73,370

OJ answered 8 years ago

Is it backfiring through the intake manifold or an afterfire through the exhaust. Since you replaced plugs and wires and distributor parts are you sure you replaced them correctly to the proper cylinder? Is there a chance you moved the distributor slightly, could affect the timing. Hopefully you do not have a bent valve.

Mark helpful

Your Answer:

Related Questions

  • What's causing my 351 Modified to start backfiring...? 5 Answers

    Recently, my '79 F-150 has begun to backfire and it's getting worse. It had been running rough so I replaced the plugs, wires, cap and button(?)... But now, the backfiring...! I know I have the wire...

    1979 Ford F-150

    -

    Maintenance & Repair

  • How to time my 351 modified 6 Answers

    1993 Ford F-150

    -

    Maintenance & Repair

  • My 79 f150 started backfiring & now wont start 6 Answers

    I was driving My 79 F150 351M, down the freeway it was running good, had to stop quickly due to traffic, so I down shifted and braked, the truck started running sluggish and backfiring when I tried to...

    Ford F-150

    -

    Maintenance & Repair

  • What's causing my truck to run low voltage? 5 Answers

    Truck had a short with old alternator. 9v while running. Turn on lights or wipers drops below 8 and gauges quit working. Installed new bat and alt. Starts with 12v. Runs with 10v.

    1994 Ford F-150 XL LB

    -

    Maintenance & Repair

  • What's my gear ratio 1ftpx14v98fa82647 1 Answer

    Need to know my gear ratio

    2008 Ford F-150 60th Anniversary SuperCab 4WD

    -

    Maintenance & Repair

F-150

Looking for a Used F-150 in your area?

CarGurus has 13,473 nationwide F-150 listings starting at $3,888.

Postal Code:

Shortcuts

Search Ford F-150 Questions

CarGurus Experts

  • #1
    OJ
    Reputation
    41,870
  • #2
    Gene Arnett
    Reputation
    15,990
  • #3
    Rowefast
    Reputation
    15,490
View All

Find great deals from top-rated dealers

Search

Related Models For Sale

Used Ford F-250
6 listings
Used Ford Mustang
35 Great Deals out of 1,596 listings starting at $7,999

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. Content will be removed if CarGurus becomes aware that it violates our policies.