mystery mid rpm misfire

If your lights is playing up it could well be your alternator on it's way, check what your alternator is putting out, both with all electric load off then again with everything turned on, see previous posts here for what volts you are looking for..

Looks like my timing was a bit out, well quite a bit, i got the strobe out, it was so far out i had to take the dizzy out and take it round a notch on the gears I didn't get to road test it as it was too late but it seems to be idling ok at least.

Are there any test values for the efi sensors anywhere? gonna go though everything just to make sure now

rustyrangie said:

Are there any test values for the efi sensors anywhere? gonna go though everything just to make sure now

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Yes and have fun!

If you've got a Haynes manual/Rave/workshop manual you should be able to find all the necessary information. You should check the following (in no particular order of importance)

Ignition tests - (all of them). careful check on pick up air gap and resistance. Coil resistance, ignition amplifier switching. Ignition timing, condition of all ignition leads, rotor arm, distributor cap and spark plugs.

Check alternator output and battery charge.

Air flow meter - check CO Trim value also check air flow output signal.
Throttle potentiometer - check base setting and scaling.
Coolant thermistor
Fuel thermistor.

Think that should pretty much cover it.

I may have found the prob I haven't finished checking all the ignition bits yet kev, i can't find reference to the ig amp and air flow meter checks in the haynes, is it in there somewhere?

But i did the ecu checks, everything was spot on, both left and right injector resistances were over by about .2 ohm but the fuel temp thermistor is fooked, nothing at all, open circuit, hopefully that's the problem? Thing is i checked around and its eighty fookin quid for a newun

For ignition system checks look in Haynes - Section 13. Look for page 13.46, Electronic ignition - fault finding, diagrams 13.61 and 13.62.

Fuel temp thermistor could well be your gremlin. Where on earth did you get that price from? I'm pretty sure one of them is only a couple of quid.

Air flow meter, you're looking to set it at between 1.0v and 1.5v measured across sensor ground and CO Trim. I set mine to 1.2v -1.25v. Another check is to measure resistance between the outside pins and set to 3000ohms. Theres a few posts in here on this.

Just cos I'm a nice guy here we go one more time!!

For a 3AM hot wire air flow meter as found on my '91 Classic:

The wires going in to the air flow meter are as follows. RED with Black is sensor ground (ECU pin25). BLUE with Green is air flow signal (ECU pin 35). BROWN with Orange is ignition switched live, (ECU pin 2). BLUE with Red is CO Trim (ECU pin 22). If you measure voltage across sensor ground and co trim you're wanting a voltage 1.0v - 1.5v, adjustment is made by turning the screw under the tamper proof plug.

cheers kev i looked up thermistor via part number on the usual websites, lr series, craddocks etc all around £80+vat... i did find one for £56+vat from famous four, still seems bloody expensive for a thermo switch I'll order one and the alternator bits soon as i get paid, think i'l havew a go at fixing the alternator meself
I'll have a good go through the rest on monday and let you know what happens

U r right, they are £80 genuine and I was going to change mine as a matter of course untill I heard that, they are alot more than the coolent one.

If its fooked u gotta change it!

Yeh i'll have to change it, just seems bloody expensive i was half tempted to go round the scrappy with a multi meter the only other thing i was considering, as a tempory bodge like was to disconnect it and run a resistor inline to a mid resistance figure and see if i can get away with it? i'm assuming the ecu is just having a fit as there is no signal

If you can find a normal breakers rangie its all good , but they all seem to be in the hands of specailist breakers. If you want to go down that route Martin toole in Southampton will probably have one.

Good idea, i have used him a few times, nice fella. I haven't been up there for a while but last time i was up me local scrappy they had 2 ranges and a disco 1 v8 I cut the whole boot floor and inner rear wings outa one of em, cost me £20

Bargain!

Just spent bloody hours trawling the net for the thermistor, found a new one for £24 inc vat on a lr parts site but it's supplied by xxitpart, what do you reckon

Try a local motor factor or auto electrician, I'm confident Inter-Mota will do one that won't cost the earth.

I have an inter-mota one for the coolant but my landy specailist said dont fit that, even the britpart one I had in my other hand would be better. now if thats not a bad recommendation I dont know what is lol

Cheers will get to it now that can last more than five in the garage without freezing my jewels off.

two different opinions feck it i'll get a lucas one when i get paid
It managed a days lanin today and ran okay, still missed a bit but not as bad as before. The idle is still playing funny buggers though, fine 99% of the time then just drops out and wont run in gear due to idling really really low and occasionally the idles hunts. I'd guess that's stepper motor?

fett said:

I have an inter-mota one for the coolant but my landy specailist said dont fit that, even the britpart one I had in my other hand would be better. now if thats not a bad recommendation I dont know what is lol

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I have an Inter-Mota ignition amplifier on mine and it is absolutely fine. Can't say I've heard bad reports on Inter-Mota parts - the thing is this, if you can't bring yourself to pay for OEM parts then you've got to be ready to take some grief - you gets what ya pay for (most of the time)

rustyrangie said:

The idle is still playing funny buggers though, fine 99% of the time then just drops out and wont run in gear due to idling really really low and occasionally the idles hunts. I'd guess that's stepper motor?

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Check/clean stepper motor. You might even have a stretched timimg chain that might be causing the ignition timing to wander (happened to me) resulting in funny idling and running symptoms.

I reckon thats what I have got as stuart cant get it running exactly perfect but there is no logical reason for it!

i did clean the stepper motor but gave up checking stuff when i found the thermistor was fecked, i'll get onto it this week

fett said:

I reckon thats what I have got as stuart cant get it running exactly perfect but there is no logical reason for it!

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There is always a logical reason!! You just haven't found it yet.

If you suspect a slack timing chain then you need to investigate. If the ignition timing keeps wandering that's a pretty good sign. The other method I use to check slack in the chain is to use a home made tool that is the bottom end of an old distributor which engages the cam gear and enables me to feel for slack in the chain by gently turning the shaft back and forth - in essence it's like getting hold of the rotor arm and rocking it (but don't do that, you'll break it).