Misfire on V8 Gems with lpg

Over the past week my 96 RR has been dripping a small amount of water from the near side of the rad. nothing major and only needed a small top up now and again. Yesterday the engine developed a heavy misfire (similar to an HT lead or two being removed) and I could hear popping through the exhaust, i suspect this being unburnt fuel. Going up hill she struggles to go over 2000 rpm and feels like she is towing a huge weight.

This morning I checked the coolant, no loss, the heater worked really well yesterday with no loss of heat ( as happened on the old engine when the heads and eventually the cylinder block cracked) there is no yellowing of the oil (a small amount in the cap the other day has gone but none on the dipstick at all). I checked the HT leads and one on the near side bank was a little loose so pushed it back on.

Took it for a short run a mile or so and while there was a slight misfire and judder it didnt seem as bad as last night.
On my return checked the top hose which i could squeeze and wasn't at hard like when the heads went last time. Cant smell Hydro carbons in the water like previously

Would it suggest a service is due as I had the engine replaced in April and havent done a service on it yet and have no idea what state the plugs are in.
Ideas please :doh:

Could be a faulty coil pack....

Also check the MAF aswell as this will give rough running symptoms and loss of power too....

also what are peoples opinions on Irontite and Holts wonderweld for head gasket leaks. I used irontite before on the old engine and it held the block for about 5000 miles through that very cold winter last year. I need to keep her going a few more days til i break for Xmas.

MAF? Mass airflow meter. can that be cleaned to see if it is the culprit or is it replacement only?

I could be wrong, but a test to check the MAF would be to start the car and get it to idle...then disconnect the MAF, if the engine starts to run rougher...the MAF is fine....

If it stays the same roughness..the MAF *could* be at fault....

Someone more knowledgable than I could possible give a better MAF test....

Does it only do it on lpg?

change the plug's anyway if a sevice is due . lead's may also be an idea .

newt888 said:

Does it only do it on lpg?

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Not sure, will check over the coming days and get back to you. As I recall though it was from start up as well as on gas.

Check timing? If loosing coolant hold hand at exhaust and check for moisture on hand. My RRC 92 had a buggered inlet manifold gasket, would not start when cold due to taking in air/coolant from it. Changed gasket and she stared 1st time. Dont use any fancy plugs, i spent a small fortune on fancy four point spark plugs but RRC 's dont like em, get the recommended BPR6ES (Check these are right as im doing this from memory) . Get some Magnecor 8mms too. If you are feeling flush get a dual timing power amp and time it for petrol and gas (they use different timing). Errr what else? if doing manifold gasket might as well do head gaskets too. Not much more work. I did all this having v limited knowledge of mechanics and as long as you take piccys and label everything its pretty easy. Let us know if you get it sorted. Prob something really simple (timing?)

Stu.

Thank you for the comments so far. The misfire is there on petrol and LPG and at tick over she seems ok but once you rev it or pull off she struggles under load.
I am going to start with the plugs, give her a service, then new leads if that doesnt cure it. Then change the coil pack. My next question is is the coil pack easy to reach and change? I have a moderate mechanical ability.

Oh and the coolant leak is down to it dripping from a drain plug on the bottom near side of the radiator.

sfaulkner said:

Thank you for the comments so far. The misfire is there on petrol and LPG and at tick over she seems ok but once you rev it or pull off she struggles under load.
I am going to start with the plugs, give her a service, then new leads if that doesnt cure it. Then change the coil pack. My next question is is the coil pack easy to reach and change? I have a moderate mechanical ability.

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The coil pack on the Gems is a doddle to swap out. If you are going to start changing parts start at the plugs and work back from there.

Its best not to drive the car until the misfire is cured.the misfire will play havoc with the fuel trims,narrowing the injector pulse width down so much it will run lean on all the remaining cylinders that can fire properly - making a bad situation worse.
NGK BPR6ES plugs are all you need and genuine LR leads,ideally it should have an adaptive reset once the miss is cured,otherwise it could take 2-300 miles to get its long term trims right.

The good news is that new plugs and a decent set of leads has cured the misfire. Thanks for all your ideas and input guys.