Misfire - Please Help

[Adam Evans]

My car has had a misfire since I bought it and I have not been able to plug into it with any machine at all and it is too new for a flash test

Anyway we LPG converted it as we can switch from cylinder to cylinder to try and narrow it down but that didnt't seem to help

I would like to know what resistances the coils should be when cold and warm

Its is a 1998 plate VVTI with pencil coils on there

Any help would be great as this will certainly narrow down my fault

Thanks in advance

[John N]

Try measuring the resistance of all the coils, and see if one or two of them are much higher or lower than the rest. It worked for me to identify the faulty HT suppressors on an old Merc.

John N

[ManicMark]

Hi does it have a misfire at all revs or does it just hunt slightly at tickover.

[Adam Evans]

Just under a load as you put your clog down on the straight.

It's simple really just don't drive it like a bat out of hell and it will be fine

Bearing in mind I still did that cup of water test on the engine when it had a misfire, shows how balanced they really are.

I will take all 8 coils off tomorrow and compare impedance, just thought someone here may have had the same problem before and might have known

I will post up the most common impedance for reference tomorrow.

[Adam Evans]

If I can't figure it out I will just buy 8 new coils for it !!!

[John N]

Before you spend a lot of money on coils, start with the cheaper things.

Unless you have personnaly changed the spark plugs start with them, don't believe any service history. For what it costs change all 8 plugs and use the Denso iridium ones from you local Lexus spares department.

Is it misfiring on both LPG and Petrol under the same conditions? If it is, you are right to look at the ignition system, but if it only does it on one fuel check that system.

Best of luck.

John N

[Adam Evans]

Does it on both fuels so its definately ignition

I changed the plugs with NGKs when I got it and it still did it.

I will dig a bit deeper soon