[carswaps]

I have a 94 5.7 SBC running both petrol and LPG.
She Starts fine and idles well on petrol and also idles fine when warm on lpg.
Normal driving around town is no problem including hills etc (both on petrol and lpg)
Anyway we set of for the bank holiday weekend camping and the car ran fine with only a very occasional backfire through the TB on long hilly stretches.
This cleared and was fine again on the flat or downhill.
However when we set off back again it behaved itself for 3/4 of the journey (100 miles or so) then started to backfire loads.
It makes no difference if you switch it back over to petrol it still does it , we were coming back up windy hill on the M62 when it started and I wasn't sure it was going to get over the top at one point as we were losing power and speed very quickly.
Once over the top it sorted itself out and got us home (5 miles)
Started it again this morning and its started on the button and driven to work (3 miles) no problems.
Where do I start to look guys? :tup:



The air filter pan top doesn't fit very well but I wouldn't have thought that would have made much difference?

 

[docjohn]

Spitting or coughing back through the intake is usually due to the mixture going lean, unless there's crossfiring on the HT leads under load. Are you on a dissy with carb and vaporiser or injection?

 

[carswaps]

Sorry docjohn its actually injection with a throttle body my mistake :wanker:
I have also updated the 1st thread details.
It does have a Dizzy.

 

[docjohn]

After you've eliminated all the usual suspects, it does sound ominously like throttle icing or what used to be called carb icing. Cool and very damp weather with small throttle opening on cruise are classic conditions for it. In some ways it's surprising as there should be plenty of heat around there. Anyway, worth a thought once you've eliminated stray sparks, dirty fuel, low fuel pressure, lean calibration and whatever other forum members suggest.

Just one other thing, and it's an expensive way of solving a one off problem, but I've found that having wide band lambda sensors in both manifolds has been invaluable in diagnosing problems with a Holley.

Good luck

John

 

[beach57]

Sticking dizzy ,air leak maybe.

 

[kapri]

Run a compression check first then you know you are mechanically sound and at the same time reading the plugs as to whether one ( or more) plug is letting go.