13 Guests, 0 Users

Author Topic: 1978 Pinto backfire problem  (Read 14820 times)

0 Members and 1 Guest are viewing this topic.

Offline 71HANTO

  • Pinto Sr. Member
  • ****
  • Posts: 507
  • FeedBack: +108/-0
  • Gender: Male
    • Older site

  • Total Badges: 6
    Badges: (View All)
    Topic Starter Signature Poll Voter Windows User Webmaster Fifth year Anniversary
Re: 1978 Pinto backfire problem
« Reply #30 on: November 14, 2011, 02:51:27 PM »
"The timing belt was replaced at a Ford dealer by the previous owner. I CHECKED carefully both ignition timing AND that the cam belt was properly installed. It is spot-on correct. Timing is precise and correct to spec."
 
I know this may be a LONG SHOT but it sounds like the timing belt may have been installed one tooth off. With the cam slightly off (cam degree), the exhaust valve may stay open too long causing raw fuel to pass through and going boom when it enters the hot exhaust manifold. Just a thought...
 
71HANTO
"Life is a series of close ones...'til the last one"...cfpjr

Offline 74WagonMeadowGreen

  • Pinto Member
  • **
  • Posts: 54
  • FeedBack: +0/-0
  • Gender: Male
  • Another Pinto Driver

  • Total Badges: 3
    Badges: (View All)
    Topic Starter Fifth year Anniversary Poll Voter
Re: 1978 Pinto backfire problem
« Reply #31 on: November 15, 2011, 09:48:05 AM »
I tend to think an exhaust leak or gutted Catalytic converter may be contributing to the problem. I plan to look into it as soon as time permits, thanks!

Offline D.R.Ball

  • Pinto Sr. Member
  • ****
  • Posts: 558
  • FeedBack: +36/-2
  • Gender: Male

  • Total Badges: 5
    Badges: (View All)
    Topic Starter Tenth year Anniversary Poll Voter Windows User Fifth year Anniversary
Re: 1978 Pinto backfire problem
« Reply #32 on: December 02, 2011, 01:13:47 PM »
Have you checked the distributor spark delay valve ? It's a small plastic disc  black and white in color that has a vacuum line going from the carb to the distributor.If it's clogged or not connected in the right direction it could be the problem...It's marked on one side carb and one side dist.

Offline 74WagonMeadowGreen

  • Pinto Member
  • **
  • Posts: 54
  • FeedBack: +0/-0
  • Gender: Male
  • Another Pinto Driver

  • Total Badges: 3
    Badges: (View All)
    Topic Starter Fifth year Anniversary Poll Voter
Re: 1978 Pinto backfire problem
« Reply #33 on: December 02, 2011, 03:38:53 PM »
Have you checked the distributor spark delay valve ? It's a small plastic disc  black and white in color that has a vacuum line going from the carb to the distributor.If it's clogged or not connected in the right direction it could be the problem...It's marked on one side carb and one side dist.
I replaced it, but after getting the car on a lift and doing some tests, a friend and I discovered ., I WAS right, the catalytic convertor was a shell, totally empty, so we installed a new one. 2. The TVS valve, which controls air going from the pump into the exhaust was shot, so a new one is ordered. I am quite certain that will fix the problem.

Offline D.R.Ball

  • Pinto Sr. Member
  • ****
  • Posts: 558
  • FeedBack: +36/-2
  • Gender: Male

  • Total Badges: 5
    Badges: (View All)
    Topic Starter Tenth year Anniversary Poll Voter Windows User Fifth year Anniversary
Re: 1978 Pinto backfire problem
« Reply #34 on: December 03, 2011, 04:15:44 PM »
Keep us posted,it's all ways a good thing to know more about these cars.

Offline ToniJ1960

  • Pinto Sr. Member
  • ****
  • Posts: 544
  • FeedBack: +13/-0
  • Gender: Female
  • Another Pinto Driver

  • Total Badges: 5
    Badges: (View All)
    Tenth year Anniversary Topic Starter Poll Voter Fifth year Anniversary Windows User
Re: 1978 Pinto backfire problem
« Reply #35 on: December 03, 2011, 11:27:06 PM »
 That tvs valve is the one on the air cleaner cover isnt it? I think thats what was bad on mine and they cut a chunk out of the vacuum hose that goes from it to the diverter valve. Its was over 10 years ago, but thats all they did to `fix` it. I dont remember if I had a vacuum leak or what happened but its all been redone since then.

Offline nothingtodo

  • Pinto Member
  • **
  • Posts: 49
  • FeedBack: +0/-0
  • Another Pinto Driver

  • Total Badges: 4
    Badges: (View All)
    Topic Starter Poll Voter Fifth year Anniversary Windows User
Re: 1978 Pinto backfire problem
« Reply #36 on: December 04, 2011, 01:18:15 PM »
if it  backfires on decel, check the vacuum line going to the air pump dump valve.

Offline 74WagonMeadowGreen

  • Pinto Member
  • **
  • Posts: 54
  • FeedBack: +0/-0
  • Gender: Male
  • Another Pinto Driver

  • Total Badges: 3
    Badges: (View All)
    Topic Starter Fifth year Anniversary Poll Voter
Re: 1978 Pinto backfire problem
« Reply #37 on: December 05, 2011, 09:19:31 AM »
As soon as our 18 inches of snow clears, and temps rise above the single digits, I hope to verify the TVS (TVR??) valve, the little circular plastic job located in the air cleaner and connected directly to the air pump, amusingly shoved on several Ford products well into the 1990s, has been the culprit, as I was able to install the new one the night before the latest onslaught of snowstorms, and although covered, my poor car has to sit outside.

Has anybody encountered difficulty removing air from the heater lines when servicing the water pump? The previous owner did a lovely job replacing the water pump, until I drove the car in cold weather and discovered there was no heat!  Does anybody know any easy (outside of "bleeding, hence leaking fluid out to get rid of bubbles) method to remove air in the heater lines?

Happy holidays, and thanks for the input!

RSM

  • Guest
Re: 1978 Pinto backfire problem
« Reply #38 on: December 05, 2011, 05:27:28 PM »
You really shouldn't have to "bleed" the lines going to the heater core. Usually after a few minutes of running the core is full and the air gone.  There might be a possibility of a restriction in the core or in the lines. When the car was running before, did you feel the hoses to see if both were hot or at least one of them?

Offline 74WagonMeadowGreen

  • Pinto Member
  • **
  • Posts: 54
  • FeedBack: +0/-0
  • Gender: Male
  • Another Pinto Driver

  • Total Badges: 3
    Badges: (View All)
    Topic Starter Fifth year Anniversary Poll Voter
Re: 1978 Pinto backfire problem
« Reply #39 on: December 07, 2011, 03:55:34 PM »
I did not, as time was of the essence, I simply planned to get back to it. I will check several things, including hose temp (when warmed up) as well as if the valve is working/conected, etc. Thanks!

Offline 78txpony

  • Pinto Sr. Member
  • ****
  • Posts: 413
  • FeedBack: +3/-0
  • Gender: Male
    • Old Faithful

  • Total Badges: 4
    Badges: (View All)
    Topic Starter Signature Webmaster Fifth year Anniversary
Re: 1978 Pinto backfire problem
« Reply #40 on: December 09, 2011, 10:33:17 PM »
As for your early question on valve guide seals, I have to replace mine every 12-15 years (avg 75k miles) when oil consumption is sky high.  They deteriorate, wear, and no longer seal.  Not sure if it is a design issue or i expect too much from them. 

Did you notice how much total timing advance at idle you had when checking your timing?  Check it with the advance hose hooked up as well as removing it and plugging it. 

I am leaning towards an ignition / cam timing issue here. 
-Rob Young
1978 Pinto Pony sedan (Old Faithful) a.k.a. "the Tramp"
http://www.flickr.com/photos/thelonerider2005/sets
1972 Cutlass Supreme Convertible (442 clone) -"Lady" (My mistress...)
http://www.flickr.com/photos/robsalbum/sets
1986 Cutlass Supreme Coupe - "Pristine"
1997 H-D Sportster

Offline 74WagonMeadowGreen

  • Pinto Member
  • **
  • Posts: 54
  • FeedBack: +0/-0
  • Gender: Male
  • Another Pinto Driver

  • Total Badges: 3
    Badges: (View All)
    Topic Starter Fifth year Anniversary Poll Voter
Re: 1978 Pinto backfire problem
« Reply #41 on: December 12, 2011, 10:03:51 AM »
As of yesterday, the backfire problem is solved... exactly what we discovered... That TVS valve in the air filter housing WAS the cause, and except for needing a choke adjustment the car is running nicely when warmed up. Add to that, the heater bled itself! Once I left the valve open it purged the air block and works nicely. It still tends to stumble a bit when cold, but again, the choke is not in the correct position, so it improves enormously once warmed up. I am confident it should do OK passing emissions at this point, and as soon as both time and weather permit, I will head over to the testing station. Then I can finally get my plates and drive it!!

Thanks everybody for the help.

Offline D.R.Ball

  • Pinto Sr. Member
  • ****
  • Posts: 558
  • FeedBack: +36/-2
  • Gender: Male

  • Total Badges: 5
    Badges: (View All)
    Topic Starter Tenth year Anniversary Poll Voter Windows User Fifth year Anniversary
Re: 1978 Pinto backfire problem
« Reply #42 on: December 27, 2011, 01:21:05 PM »
Out standing, now what is the testing process to find the TVS failure in the first place? Hook it up to a Mitty Vac ?

Offline 74WagonMeadowGreen

  • Pinto Member
  • **
  • Posts: 54
  • FeedBack: +0/-0
  • Gender: Male
  • Another Pinto Driver

  • Total Badges: 3
    Badges: (View All)
    Topic Starter Fifth year Anniversary Poll Voter
Re: 1978 Pinto backfire problem
« Reply #43 on: December 27, 2011, 09:34:24 PM »
Once the valve was removed, it was easy to see if it was jammed open, which it was...no special testing required!