245 hemi problems

HI

gee the old girl is testing me,

my DODGE 300 has the Hemi 245 dual fuel. with the 4 speed,
the old girl has been runing like a gem,

now the old girl is ideling rough and wont idle on petrol!! and has a rough run as it builds in the revs but once she revs over about 1500 rpm, it all seems good untill you come to a stop or slow down and go to take of again, the rough runing returns and it has no pulling power.
I have changed the plugs and a couple of the leads and moved the timing a little to c if this help but it doesnt seem to help.

does any one have any ideas for me to try?
(no vacum leaks I can find)

thanks
ed

maybe no vacuum leaks ..but most likely dried up carby components (gaskets etc) from lack of lubrication and the dryness of the lpg

Ed,check coil or Ballast resistor,lead from coil to dissy,run a hot wire from battery to positive side of coil and go for a drive ,if that improves it then the coil is the problem,if it still plays up get a new ballast resistor Hemi performance is a good place for these items also Billy who owns Hemi is a wizz when it comes to all things mopar

Ed,
Take the guess work out of the diagnosing, a vac gauge at least to check the mechanicals. Does it have 20in of vac at idle, if not, a mechanical issue is present. The best tool of all to diagnose beyond all reasonable doubt, a good quality exhaust gas analyser, works on all engines, regardless of size or what fuel, the old saying, what goes in, must come out, & that is where you will find what is going on. If the fuel delivery is correct at a Lambda of 1:00, anything to do with getting the fuel into the engine must be correct. A good quality gas bench will be able to then display the combustion efficiency & the wasted fuel fuel due to incomplete burn if it exists, eg, if it idles at a Lambda of 1:00, wasted Hc should be less than 250ppm. Incomplete burn will be caused by ignition or mechanical issues,& with the process of elimination, a vac gauge will guide you to a mechanical condition. Without a means of basic testing, start throwing parts at, you will eventually find the problem. Gas analysis---$40.00, Parts????
You decide,
Gilly

thanks guys for the help,

after thinking about my current problems with the old girl I took some advice and done a pressure test on all cylinders and to my surprise this was the result

cylinder 1,2,5 and 6 were all with equal psi with a 1 or 2 pound difference


cylinder 3 and 4 were 0 psi,

so with i removed the head and,
( you guessed it as you read this you are saying to your self? )
"BLOWN Head Gasket" between cylinder 3 and 4, and yes it was.

now to order the parts and put the old girl back to being used as a daily driver.


thanks
ed