Rough acceleration from idle

**StuRR80** · 13th September 2012, 02:22 PM

On fast acceleration from idle, in my 3.5 carb Rangie, it coughs and splutters and feels as though it's going to stall (which is no fun when pulling out from an intersection) and then gets up to speed slowly. It's been a slow development since it was tuned last (approx 5000kms ago). I've resized the plug spacing, etc. previously and had new diaphragms put in with the last tune. Does it sound like flooding? Can you flood on LPG?!! Or maybe it just needs a new tune up?

I've noticed I do need a new distributor cap as one of the ports looks a little corroded which I've tried to clean up as best I can but is still not as good as the other ports. I also need a new vacuum advance according to the last mechanic. So since I need these new bits, should I fork out for a new distributor too? It's running a Crane XR700 ignition module - not sure what distributor it is though. Perhaps there's something better nowadays to cope with LPG?

Thanks in advance
Stu

**StuRR80** · 16th September 2012, 08:47 AM

Anyone have an idea on what might be causing this or elimination steps? Please.........

**460cixy** · 16th September 2012, 08:55 AM

I would check the diaframs and damper oil first for sure mine used to **** out a lot .

**bee utey** · 16th September 2012, 04:23 PM

You can be running too rich or too lean on gas, both will reduce power. What brand of LPG converter is fitted? There are adjustments on all gas systems. Mark them with a marker pen, change some settings and note any changes in performance. You can always go back if you know where you started from.

Crane XR700 units were good when new, what coil are you using? A better coil may improve your spark.

What plug gap and idle timing are you running? Gap should not exceed 0.028"/0.7mm with a stock coil.

What leads are you running? Some leads, e.g. Top Gun, are less good than some others, eg Bosch. This kind of running used to drive me mad before I threw out the Top Gun leads I had, and the problem was more prevalent when the engine was hot.

The best upgrade for a points dissy is a Disco 1 electronic dissy running a Bosch 024 ignition amp and high energy coil. Either that or a Scorcher brand electronic dissy, much the same thing functionally.

**UncleHo** · 24th September 2012, 09:37 PM

That sounds very like a dead Vacc advance,if it will pick up OK if you accelorate slowly it would indicate a vacc advance problem, if so get onto Mike Bushnell for an exchange unit, (www.advancediaphragmoptions.com) at Caboolture in Qld and he will send you one,we just had one fitted to the daughter's Disco 1,which is dual fuel, it now goes like it should and does not hesitate.

cheers

**StuRR80** · 3rd October 2012, 05:48 PM

Sorry for the delay in replying. I don't get on the computer as often as I used to, at the moment.

Some answerrs as below.

Thanks

Stuart

Originally Posted by bee utey

You can be running too rich or too lean on gas, both will reduce power. What brand of LPG converter is fitted? "Reg by OMV" is the only thing I can see on it. Not sure whether that refers just to the regulator or the whoile thing though....?
There are adjustments on all gas systems. Mark them with a marker pen, change some settings and note any changes in performance. You can always go back if you know where you started from.

Crane XR700 units were good when new, what coil are you using? A better coil may improve your spark. It's a Bosch GT40-R

What plug gap and idle timing are you running? Gap should not exceed 0.028"/0.7mm with a stock coil. The gap had been set to 0.7mm as you've advised in a previous post.

What leads are you running? Some leads, e.g. Top Gun, are less good than some others, eg Bosch. This kind of running used to drive me mad before I threw out the Top Gun leads I had, and the problem was more prevalent when the engine was hot. Bosch Leads

The best upgrade for a points dissy is a Disco 1 electronic dissy running a Bosch 024 ignition amp and high energy coil. Either that or a Scorcher brand electronic dissy, much the same thing functionally.

**bee utey** · 3rd October 2012, 06:12 PM

The converter is an "OMVL" and the idle adjustments are two brass screws sticking out the side. One has a 10mm hex and controls the sensitivity, i.e. the rate if increase of gas from idle upwards, and the other (8mm hex) controls the fixed gas flow at cranking and idle.

Try adjusting the 8mm hex adjuster in a bit say 1/2 turn, then adjust the 10mm adjuster out until you achieve a smooth idle nd transition to fast idle.

The other adjustment is a screw in the main gas hose to the carbies, try opening or closing 1/4 of a turn at a time, rev the engine by hand to see if it gets better or worse. You may have too little or too much gas, either will feel much the same.

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