Thread: starts fine on gas BUT when warms up wont run well

Originally Posted by nat p

ok next problem,
I think its a tune but when its cold on gas it runs fine (at a higher RPM) but when warms up, stalls and carrys on a bit.

IS there a method to tuning gas systems (without a sniffer)?

Its a empco system on a 3.5 RRC 1986


Any ideas.

Cheers NAT

Empco???

If it's Impco model 200 the idle mixture screw hangs out of the mixer body and you screw out for lean, in for rich. Count the turns etc and see which way you get a better idle.

BTW following your other posts if you are suffering from Impco disease no amount of cam/extractor/engine changing will make it go faster. Ditch the Impco junk and get a better gas system.

Haha the good old Empco system That sounds like exactly what used to happen with my 3.9V8 on LPG. It would start fine and while it was cold would idle really nicely but as soon as it got to temperature it started carrying on and even backfired a bit. Turned out a set of new Bosh leads and plugs (the best ones for use with LPG as recommended from forum users here) fixed it right up, also set the plug gaps as recommended from here too. That and I adjusted the timing so that top dead centre was where it should be to benefit LPG (from memory 10 degrees before top dead centre). Also ran it on nothing but the best premium unleaded fuels when running on petrol and it didn't ping or anything. After changing all those things myself and then paying someone to give it a proper gas tune I didn't have any problems again. Pretty sure I had an Impco system too.

It's all about the spark with gas!