mystery mid rpm misfire

rustyrangie said:

Cheers for that Kev worried about afm setting now

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Well don't worry too much. Lambda overrides the afm CO setting but factory setting for car with cats is 1.8v

rustyrangie said:

the lambdas did test ok during the ecu tests but they look original so could be buggered?

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If they tested O.K. wouldn't have thought there is a problem.

rustyrangie said:

I'll try an rtv the trumpets back in, one of ems well loose tho, in fact it's started wearing it's own groove into the plenium top
You're spot on with trumpet lengths, i;ve done a lot of dyno work with bikes and it can really make a good engine sing if you get em right and even 10mm can make a big difference. not sure how finnicky the v8 is though.

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As far as I kow, you can get a 3.9 up to about 280BHP - see the likes of TVR and I think Ginetta, trumpet lengths were shorter than standard Rangie and there were ECU modifications by way of re-mapping the fueling. The power and torque curves were shifted up the rev range a bit but then again, in those light sports cars they didn't have to move 2 tonne of metal with the areodynamics of an oil tanker!!

rustyrangie said:

cool, let me know how you get on with the caps. I wouldn't worry about your miss noise, unless it bothers you, you'll probably end up with more nightmares getting the fannymoulds off and back on! besides most modern motors inject air into the exhaust nowadays to help reduce emissions so it'll probably help with them too, unitl it starts blowing properly

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Well she got me to Kent and back today via benenden Hospital, ran well all the way but she did get a bit ****ed off about3/4 of the way through the dayafter idleing in D up hill in traffic for 20 mins and got a little lumpy in idle but it passed , its like they have there own personality lol.:doh:

will have a feck with caps on sat just on the off chance but it sounded much better after that run today so maybe the new one just needed bedding in a bit with its fancy rotor arm!

fett said:

Well she got me to Kent and back today via benenden Hospital, ran well all the way but she did get a bit ****ed off about3/4 of the way through the dayafter idleing in D up hill in traffic for 20 mins and got a little lumpy in idle but it passed , its like they have there own personality lol.:doh:

will have a feck with caps on sat just on the off chance but it sounded much better after that run today so maybe the new one just needed bedding in a bit with its fancy rotor arm!

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They got personality allright, a bloody grumpy one
I haven't been able to put much time into it, pleniums back on but i need to source some new hoses for vac and coolant as they're a bit buggered.
Cheers for the info on afm setting kev
I'm a bit worried i've fecked the idle up now as i've altered the throttle disc setting, if it's closed up more won't it struggle to idle?

argghhhh dont talk to me about feckin up the idle lol :doh:

rustyrangie said:

I'm a bit worried i've fecked the idle up now as i've altered the throttle disc setting, if it's closed up more won't it struggle to idle?

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When you get your hoses sorted and put the plenum back together you need to make sure there are no air leaks at all, anywhere in the inlet system. Make sure you use enough (but not too much!) Blue Hylomar or similar gasket goo. Re-connect everything and spark it up.

Once you've had it strted, get it warm then switch off and check/set your base idle. Once you've done that, reconnect the stepper motor and the idle should be spot on. It should also be smooth with crisp throttle response.

still waiting for the new hoses to arrive, so in the mean time i decided to go over everything again with the multi meter...
looks like the ig amp is pooped, Getting battery voltage across +bat - coil with ignition off. not sure what it would cause problem wise, guessing bad running, poor starting and rich looking plugs??

the battery + ignition switched-check ignition switch.
The system works by:-
Ignition feed on and amp allowing earth to feed coil-as pick up senses rotor the amp turns off coil and creates a spark.

There is a remote kit for amp and I would recommend thermal computer paste as heat causes issues

Was too cold to fiddle with the caps today, and now its running ok I dont want to break it either!

I have wondered about the amp on mine but it tested ok now I am using the other dizzy, although I have to say all this ****ing about with lucas ****e has made want to bin the lot and fit an all new mallory set up!

Shame about the cost!

another favourite of the lucas Distributor-pressed steel advance weight system partially seizes.

fanatic said:

the battery + ignition switched-check ignition switch.
The system works by:-
Ignition feed on and amp allowing earth to feed coil-as pick up senses rotor the amp turns off coil and creates a spark.

There is a remote kit for amp and I would recommend thermal computer paste as heat causes issues

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Fanatic, forgive me for being thick but i'm not sure i understand? do you mean the ignition switch may be sending a feed to the amp/coil when it should be off? and is a remote amp a better idea than the oe one on side of dizzy?

rustyrangie said:

Fanatic, forgive me for being thick but i'm not sure i understand? do you mean the ignition switch may be sending a feed to the amp/coil when it should be off? and is a remote amp a better idea than the oe one on side of dizzy?

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Yes the battery + to coil should be off when the key is not in the ignition. (I'm guessing yours is carbs and not efi)
possibly
1) faulty ign switch/relay
2) It's been connected to permanent live
3) you may have a ballasted system-what this means is the ignition side feeds through a resistor as the coil will be less than 12v, when the starter is used there is a feed from starter motor that briefly bypasses the resistor for better spark.(there will be a second small wire to starter solenoid normally) and the wire is on the wrong tag on starter solenoid.

With the remote amp-pays your money and takes your chance, if you could pick one cheap second hand may be worth doing, I personally use the heat conductive paste.

You might be interested to know that a misfire at about 2800rpm on some hot wire systems is caused by the ecu apparently. I can't remember the website I saw that but apparently there is a fix for it but the point is that if the ignition system and all the other parts of the injection system are working properly then you should try a substitute ecu.

Thanks fellas, looks like i'm gonna have to keep fiddling for a while yet then

right so this weeks shopping list- ignition switch + relay, ignition amp, coil, oh and an ecu

ok, now i'm confused.. had another look at the coil etc, + pole has a white/black wire from ig amp and another wire which i assume is the rpm pick up?
-pole has a white wire which goes to earth, via a bit of sleeving (resistor?)which joins it with another white wire and a yellow wire which goes to a suppressor fixed under one of the coil mounting bolts.

Surely as the neg pole is connected to earth it's going to give me battery voltage across neg pole and bat + with ignition off?
Also checked the 2 wires in the ig amp plug with it disconnected, both dead with ignition off, both live with ignition on
i had assumed the 2 wires would be in and out of the amplifier so how come they're both live
HELP, i hate electrics

I haven't got a rev counter, but what happens if you neg - disconnect the suppressor and have only wire to amplifier
(bearing in mind it's radio interference suppression, but points systems they cause all kinds of weird running)
Then on the Ignition side+just the ignition feed and amp feed? Does it run, has the missfire gone? need a wiring diagram for it as mines no good as lpg system the wires in sheathing and chopped round. So I don't know what your extra wires are

thanks for the reply fanatic. got haynes and rave but can't find a good diagram for the coil wiring i've never touched the coil wiring in the 2 years i've had the car but i'm wondering if the wires to + and - one the coil are back to front and whether it will make a difference?
It's a late 3.9 with hotwire & electronic ignition.
positive pole on coil has a white/black wire from ignition amp lead, a brown wire that goes into lpg loom and a white wire which i think is the oe rev counter feed
neg pole has a white wire which goes to earth and connects to the other wire from the ignition amp lead, yellow wire to suppressor

what's confusing me is the ignition amp test between battery+ and coil neg, it says in the book it should only be live with ignition on but if the neg pole is permanately earthed surely it's right to have battery voltage between neg and battery+?
I can't spin the motor up yet coz all the vac pipes are fecked and waiting for newuns.

Feel free to come and check mine as a reference

fett said:

Feel free to come and check mine as a reference

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Don't spose you can go get cold and take a piccy of the coil wiring

what's confusing me is the ignition amp test between battery+ and coil neg, it says in the book it should only be live with ignition on but if the neg pole is permanately earthed surely it's right to have battery voltage between neg and battery+?
I can't spin the motor up yet coz all the vac pipes are fecked and waiting for newuns.[/quote]

Pm me a number I'll call you

http://www.landyzone.co.uk/lz/f42/3-9-non-starter-88066.html has all you need and link in the thread to range rovers.net remote amp

rustyrangie said:

Don't spose you can go get cold and take a piccy of the coil wiring

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PM me your email address and I will see what I can do matey