Huge Backfire now won't run right.....

CMac89

Registered User
Well I was going around on a joy ride and when I let off of the gas after a test run it backfired through the intake. As a result of this it blew off some vacuum lines, an intercooler tube blew loose, and bent the flap of the throttle body forward. Since it did that to the throttle body the motor would shoot to 5K whenever I started it so I changed it out to the stock one. Made it better, but still hangs at about 4K after I start it.

Searched for more, but haven't found anything.

Ideas?
 
iac bad? egr blown?backfires are not common sounds like major vac leak ,
you said ic tube blew off???? wow is ic unit cracked am i reading this wrong?
 
I removed all EGR. The IAC has been bad for a while, but it still ran decently. Wouldn't rev itself past 2K and would idle fine half of the time. I have a custom FMIC setup so i can see how it blew loose.

What surprised me is that the flap on the throttle body got bent all the way forward at the top.

I think there is a vacuum leak somewhere because a few vacuum hoses blew off. The boost gauge, one on the vacuum diaphragm behind the inlet plenum, and two on the inlet plenum.
 
Wow!

You think you have a stuck valve or something? What did you ever do about the vlave train?

Didn't you find out that you were running a bad installed height for your springs or something some time back?

Wow....
 
I'll have to do a compression test to see if the valves are okay which i'm sure they are.

The only problem I had with the valvetrain was getting all of the valves to come out right so I had to use different shims in other valves, but it worked out okay.
 
problems

back firing on these s/c cars is not good. would have to agree with the other guys about the valve train. mine back fired and broke one of my rocker arm bolts at the shoulder of the bolt. ran really bad, might just want to pull the valve covers just to be safe.
 
I found something I couldn't see last night. This vacuum diaphragm blew apart that connects to the bottom of the main vacuum bridge behind the inlet plenum.

Hopefully this is something I can just get from Advanced Auto.
 

Attachments

  • HPIM0504.JPG
    HPIM0504.JPG
    138.3 KB · Views: 98
I forgot about the throttle body pictures too.
 

Attachments

  • HPIM0506.JPG
    HPIM0506.JPG
    156.6 KB · Views: 64
  • HPIM0508.JPG
    HPIM0508.JPG
    85.9 KB · Views: 60
  • HPIM0509.JPG
    HPIM0509.JPG
    181.1 KB · Views: 74
  • HPIM0510.JPG
    HPIM0510.JPG
    82.2 KB · Views: 91
I have one of those vac diaphrams that looks a lot like that. I got mine from a crown vic when I did my brake conversion. Im sure lots of Fords from the 90's have that piece under the hood somewhere. :)
 
back fire

no wonder you had a back fire, mod to much without tunning, can destroy a blown engine( turboed or supercharged ) fix it and get it tuned before somthing worse happens. next time might not be so lucky.
 
Sounds like you had some puddling of fuel and it exploded. Check eveything including your IC, and all pipes and intakes for cracks.
 
I have a computer chip, the car just isn't tuned yet.

My old belt was slipping and I could only get 8psi max and then I changed the belt out and got 15psi. It was okay at 8psi, but then at 15psi it seemed like the water temperature was getting higher than normal.

I'm sure it was pre-ignition since the intercooler pipes are all black on the inside now.
 
wow, just wow. Be glad our cars are so old that they arent part of the plastics age. Plently of strong metal under our hoods.
 
scbird1 said:
Sounds like you had some puddling of fuel and it exploded. Check eveything including your IC, and all pipes and intakes for cracks.

Heads too.....:eek:
That's the first time I've ever seen a bent throttle valve like that!
Hope it comes together for you
 
Casey,

I thought the couple of nitrous backfires I had were bad, but they didn't cause nearly as much damage. I think it hung a valve open or jumped time.

I would be pulling the rocker covers and looking very closely at the geometry of all the rockers, springs and pushrods.

David
 
As scbird1 said, wouldn't a backfire like that require some puddeled fuel somewhere? I just can't imagine the fuel charge for a single cylinder being big enough to cause that kind of damage. Especially since he said it happened on decel when the injector duty cycles should be quite low.

That resembles what I've seen on blown drag cars where they inject fuel before the blower to keep it cool. Then when a valve hangs... :) Bent blower rotors, destroyed intakes, lots of shattered steel. Heck they even run weakened areas (burst panels) on the intakes designed to relieve the pressure when a backfire happens.
 
Back
Top