Misfire

[Supafly]

Been busy with the building work at the house and other peoples cars
Yesterday I went through and checked the sensor readings (resistance/continuity) at the ecu for the tps and cts. Both fine.

I haven't been able to get it to an analyser. Plus it runs so badly that I don't even want to attempt to drive it for more than a mile.

I've completely run out of ideas now. I'm going to go out and put a fuel pressure gauge on it to see what the fuel pressure is and I'll pull the injector rail off again and crank it to see how the injector spray looks and if they stay sealed under pressure.

Also thinking of re-checking the valve adjustment... does anyone remember which pins to short on the diagnostic port to turn the starter?

car's driving me

[Supafly]

Ok, I really didn't even want to touch it so instead of doing more tests I took it to the lpg place and asked them to have a look at it on their analyser.

The results at idle are: -

On petrol

CO % vol 0.14
CO2 % vol 8.93
HC ppm vol 1949
O2 % vol 8.27
lambda 1.447 ( I think its lambda - funny symbol like an upside down y)

On LPG

CO % vol 3.51
CO2 % vol 8.06
HC ppm vol 3025
O2 % vol 4.96
lambda 1.002

Hope this helps.

[Supafly]

bump bump....

any ideas at all anyone??
I've been stood outside looking at it for ages but my mind is now blank....

[Supafly]

Since last time I've finally managed to get enough enthusiasm to go and check some more things...

Fuel pressure is at 3bar with relay bypassed and engine off.

I managed to rig up the injectors and crank the engine with everything else disconnected to see the spray of the injectors. It wasn't so much of a spray more like a squirt one main fairly powerful jet of petrol apart from no.6 which hed a kind of two seperate jet spray pattern.

None of them leaked while under pressure.

Plus they all fired together. Is this right?

It also has an "aeb timing relay registrable" wired into the injector wiring. I'm assuming this is to cut the injectors when its on lpg but it has what looks like an adjustable screw (resistor pot?) underneath. I havent touched this but could this cause it to misfire? or alter the ignition timing?

Any more ideas???

Pretty please with suger and several pints on top???

[Supafly]

just to let everyone know that it is now sorted and hopefully this might help someone in the future.

First of all I would like to thank everyone for their help, especially Brian (fountain of knowledge!!).

after all the checks and parts changed it turns out my problem was...

SPARK PLUGS!!

These were fairly new (less than a month old) ngk's and as such I never suspected them. As I had eliminated everything else I checked the original spec and found that the car came with bosch plugs to start with... So after fitting a new set of bosch plugs all misfiring disappeared!

Had the co checked and adjusted, had the lpg set and adjusted and now I'm a very happy e30 owner once again. Idling better than ever, running better than ever. So all the other things I checked/fixed should keep me going for a while

[old_skool]

Magnificent!

[Brianmoooore]

Congratulations on sorting it! Now you can get back to cheap LPG motoring.
I feel this must be a particular duff plug problem though, rather than the wrong plugs (assuming you have the correct NGK equivalents), as the common wisdom is that NGKs are slightly superior to Bosch plugs.
All goes to prove what I've posted many times before - the chief suspect when searching for any fault, is the last thing you replaced!

[Supafly]

Thanks guys, I'm just glad its running nicely again. In fact I'm actually very happy, its running that good!

As for the plugs its very strange they're NGK ZGR5A's and the misfire had just steadily got worse and worse. First it was a very slight miss here and there then over the course of about a month it slowly got worse, to the point when it started missing on idle and then constantly.

Wish I'd seen your "chief suspect" postings earlier Brian, acted on it and just thrown in a set of plugs as a precautionary measure... oh well we live and learn.

Now I'm very familiar with the workings of my car and also know that I've sorted a tiny air leak on the inlet side and that (fingers crossed) there's nothing more to worry about

Now I can get back to the car that regularly gives me headaches, but it's to be expected from this one... Lancia time again

Thanks again for all your help Brian, it really was invaluable in helping me sort this problem out, and I'm sure it will help others in the future too.

[Rizla_kid]

I feel the pain when it was running bad.

I had this same problem, misfired on idle and always religously misfired around 3000rpm, it went in the shop, they made it better, tappets were out. ive changed the coil, the cps, the tps, cleaned and checked icv and afm, famous blue thermostat, leads, rotor arm and dizzy, plugs.

Even had a diagnostic and nothing coming up, also when I changed all these things, the problem dissapeared for about 20 miles, but I can feel it coming back again. misfire. hmmm any ideas what could be causing this, its intermittent now but occasionally happens and I want it gone.

Im thinking its the injectors, everything else has been checked.....
could they cause intermittent misfires ? Like a judder on the motorway every now and then?

Its getting beyond me.

Headscratch this one:-
Foot to the floor and this problem is never around......its driving normally it doesn't like......

[Supafly]

Sorry for the late reply, I only saw this post after checking it to link to another thread!

Have you had it on a gas analyser (mot stations are usually helpful) and had the co checked at idle?
can't remember exactly what it should be but I think its around 0.8... you'll need to check to make sure.

After I got mine sorted it didn't like cruising on part throttle (full throttle was fine), after the co was checked and adjusted it's been fine. I don't know why this is because the general opinion seems to be that this shouldn't affect running off idle, but with my lancia I also had a similar problem which was sorted by having the correct setting at idle.

Hope this helps. I'll keep an eye on this thread and see if I can help some more...

If you do get it sorted please post up the solution, it may help someone else in the future.