"Dave Milne" wrotE:

> If you tell us when it happens more precisely, should be able to narrow it
> down for you. (e.g. at idle / when accelerating / when lifting off )

Under heavy acceleration at higher RPMs when the engine is hot. e.g.,
I have been driving on the freeway in hot weather for an hour and pull
off to an exit ramp and sit at a stop light. The light turns green, I
hit the gas hard to get back up to speed quickly, and I let it rev
fairly high in gear before up-shifting (so that I can accelerate more
quickly.) This is typically the point at which I hear a backfire.


> Worst case scenario - backfiring can set fire to your engine bay (blow back
> in the carb), blow your exhaust apart or even crack piston rings. You want
> to fix it.

Ouch, no kidding. If I drive it like granny (no quick
acceleration/high RPMs) I seem to avoid backfiring so I can do that
until I figure out the bigger problem... but that's just not a fun
way to drive. :-)

 

That sounds like an air leak.

You could have a leaky exhaust manifold or a bad EGR valve. My first
bet is the exhaust.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Joshua Nelson wrote:
>
> "Dave Milne" wrotE:
>
> > If you tell us when it happens more precisely, should be able to narrow it
> > down for you. (e.g. at idle / when accelerating / when lifting off )
>
> Under heavy acceleration at higher RPMs when the engine is hot. e.g.,
> I have been driving on the freeway in hot weather for an hour and pull
> off to an exit ramp and sit at a stop light. The light turns green, I
> hit the gas hard to get back up to speed quickly, and I let it rev
> fairly high in gear before up-shifting (so that I can accelerate more
> quickly.) This is typically the point at which I hear a backfire.
>
> > Worst case scenario - backfiring can set fire to your engine bay (blow back
> > in the carb), blow your exhaust apart or even crack piston rings. You want
> > to fix it.
>
> Ouch, no kidding. If I drive it like granny (no quick
> acceleration/high RPMs) I seem to avoid backfiring so I can do that
> until I figure out the bigger problem... but that's just not a fun
> way to drive. :-)

 

That sounds like an air leak.

You could have a leaky exhaust manifold or a bad EGR valve. My first
bet is the exhaust.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Joshua Nelson wrote:
>
> "Dave Milne" wrotE:
>
> > If you tell us when it happens more precisely, should be able to narrow it
> > down for you. (e.g. at idle / when accelerating / when lifting off )
>
> Under heavy acceleration at higher RPMs when the engine is hot. e.g.,
> I have been driving on the freeway in hot weather for an hour and pull
> off to an exit ramp and sit at a stop light. The light turns green, I
> hit the gas hard to get back up to speed quickly, and I let it rev
> fairly high in gear before up-shifting (so that I can accelerate more
> quickly.) This is typically the point at which I hear a backfire.
>
> > Worst case scenario - backfiring can set fire to your engine bay (blow back
> > in the carb), blow your exhaust apart or even crack piston rings. You want
> > to fix it.
>
> Ouch, no kidding. If I drive it like granny (no quick
> acceleration/high RPMs) I seem to avoid backfiring so I can do that
> until I figure out the bigger problem... but that's just not a fun
> way to drive. :-)

 

Could also be running too lean (intake leak or badly set up carb). Exhaust
runs extra hot as a result and any unburned fuel in the exhaust goes bang.
You can see the flames flickering out the back of decelerating touring cars
as a rather extreme example.

--
Dave Milne, Scotland
'99 TJ 4.0 Sahara

"Mike Romain" <romainm@sympatico.ca> wrote in message
news:3F69E061.6D9C9A09@sympatico.ca...
: That sounds like an air leak.
:
: You could have a leaky exhaust manifold or a bad EGR valve. My first
: bet is the exhaust.
:
: Mike
: 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
: 88 Cherokee 235 BFG AT's
:
: Joshua Nelson wrote:
: >
: > "Dave Milne" wrotE:
: >
: > > If you tell us when it happens more precisely, should be able to
narrow it
: > > down for you. (e.g. at idle / when accelerating / when lifting off )
: >
: > Under heavy acceleration at higher RPMs when the engine is hot. e.g.,
: > I have been driving on the freeway in hot weather for an hour and pull
: > off to an exit ramp and sit at a stop light. The light turns green, I
: > hit the gas hard to get back up to speed quickly, and I let it rev
: > fairly high in gear before up-shifting (so that I can accelerate more
: > quickly.) This is typically the point at which I hear a backfire.
: >
: > > Worst case scenario - backfiring can set fire to your engine bay (blow
back
: > > in the carb), blow your exhaust apart or even crack piston rings. You
want
: > > to fix it.
: >
: > Ouch, no kidding. If I drive it like granny (no quick
: > acceleration/high RPMs) I seem to avoid backfiring so I can do that
: > until I figure out the bigger problem... but that's just not a fun
: > way to drive. :-)

 

Could also be running too lean (intake leak or badly set up carb). Exhaust
runs extra hot as a result and any unburned fuel in the exhaust goes bang.
You can see the flames flickering out the back of decelerating touring cars
as a rather extreme example.

--
Dave Milne, Scotland
'99 TJ 4.0 Sahara

"Mike Romain" <romainm@sympatico.ca> wrote in message
news:3F69E061.6D9C9A09@sympatico.ca...
: That sounds like an air leak.
:
: You could have a leaky exhaust manifold or a bad EGR valve. My first
: bet is the exhaust.
:
: Mike
: 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
: 88 Cherokee 235 BFG AT's
:
: Joshua Nelson wrote:
: >
: > "Dave Milne" wrotE:
: >
: > > If you tell us when it happens more precisely, should be able to
narrow it
: > > down for you. (e.g. at idle / when accelerating / when lifting off )
: >
: > Under heavy acceleration at higher RPMs when the engine is hot. e.g.,
: > I have been driving on the freeway in hot weather for an hour and pull
: > off to an exit ramp and sit at a stop light. The light turns green, I
: > hit the gas hard to get back up to speed quickly, and I let it rev
: > fairly high in gear before up-shifting (so that I can accelerate more
: > quickly.) This is typically the point at which I hear a backfire.
: >
: > > Worst case scenario - backfiring can set fire to your engine bay (blow
back
: > > in the carb), blow your exhaust apart or even crack piston rings. You
want
: > > to fix it.
: >
: > Ouch, no kidding. If I drive it like granny (no quick
: > acceleration/high RPMs) I seem to avoid backfiring so I can do that
: > until I figure out the bigger problem... but that's just not a fun
: > way to drive. :-)

 

Joshua Nelson wrote:

> Cal Wheeler <cal@whee.ler> wrote in message news:<bkb7uo$6o9$2@pita.alt.net>...
>
>>What kind of "sabbatical" do you call that?
>
>
>
> I thought several days off, including a weekend, would be long enough


for people to forget how much of a troll and liar you are?

 

Joshua Nelson wrote:

> Cal Wheeler <cal@whee.ler> wrote in message news:<bkb7uo$6o9$2@pita.alt.net>...
>
>>What kind of "sabbatical" do you call that?
>
>
>
> I thought several days off, including a weekend, would be long enough


for people to forget how much of a troll and liar you are?

 

Thanks Mike & Dave. It's fuel injected so it's probably not a carb
problem. :-) I will see about getting the exhaust looked at.

>
> You could have a leaky exhaust manifold or a bad EGR valve. My first
> bet is the exhaust.
>
> Could also be running too lean (intake leak or badly set up carb). Exhaust
>runs extra hot as a result and any unburned fuel in the exhaust goes
bang.
>You can see the flames flickering out the back of decelerating
touring cars
>as a rather extreme example.

 

Thanks Mike & Dave. It's fuel injected so it's probably not a carb
problem. :-) I will see about getting the exhaust looked at.

>
> You could have a leaky exhaust manifold or a bad EGR valve. My first
> bet is the exhaust.
>
> Could also be running too lean (intake leak or badly set up carb). Exhaust
>runs extra hot as a result and any unburned fuel in the exhaust goes
bang.
>You can see the flames flickering out the back of decelerating
touring cars
>as a rather extreme example.