3.5 hotwire runs like crap

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3

3.5disco

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175
Just can't get it run right (took to specialist which only achieved a bill- need to sort now myself or break the darn thing)- dying at idle when warm is back & now have a slight/partial miss from one of the cyls which makes it run a bit rough

Have changed stepper, tps, leads/cap/rotor arm (all lucas). Took off all vacuum pipes, cleaned & re-fitted with new clips etc.

Any ideas what now? injectors, duff ECU?

cheers
 
I have got the same problem on my 3.9 efi #7 was missing but when I took the plug out and held it on metal it was sparking??? I am really confused. Got told it was the ign timing but not sure how to change this or how to set it up?
 
3.5disco said:
Just can't get it run right (took to specialist which only achieved a bill- need to sort now myself or break the darn thing)- dying at idle when warm is back & now have a slight/partial miss from one of the cyls which makes it run a bit rough

Have changed stepper, tps, leads/cap/rotor arm (all lucas). Took off all vacuum pipes, cleaned & re-fitted with new clips etc.

Any ideas what now? injectors, duff ECU?

cheers
Click to expand...

Air leak?
Possibly your ECU, test by substitution
Clean you plenum, check and set the throttle disc and set base idle (if you can get it to run).
Check MAF.
Check ignition timing.
Check temperature thermistor (coolant sensor).
 
sible88 said:
I have got the same problem on my 3.9 efi #7 was missing but when I took the plug out and held it on metal it was sparking??? I am really confused. Got told it was the ign timing but not sure how to change this or how to set it up?
Click to expand...

Timing would be unlikely to cause a miss on 1 cylinder. Check condition and routing of HT leads, make sure the leads are correctly placed and clipped.

To check timing you'll need a strobe light. You could do a rough static check but dynamic timing with warm engine at idle with vac advance disconnected and hose plugged is best.
 
Cheers

Think its holding idle enough not to cut out after adjusting throttle connection screw. Engine completely dies when the maf wire is take off- should it do that?

cheers again
 
3.5disco said:
Engine completely dies when the maf wire is take off- should it do that?

cheers again
Click to expand...

Does the EFI warning light come on when you disconnect MAF? It should.

If you leave MAF disconnected can you start the engine and will it rev O.K.? What should happen is the efi warning light will be on but it should run but it will be VERY rich.

If the EFI warning light doesn't come on with the MAF plug removed then you probably have a sick ECU.
 
Mine runs without the MAF the same as connected so it must be running rich? Will the ign timing sort this out? It only revs to 2000 thin starts to back fire and will die then rev again but really sick?
 
sible88 said:
Mine runs without the MAF the same as connected so it must be running rich? Will the ign timing sort this out? It only revs to 2000 thin starts to back fire and will die then rev again but really sick?
Click to expand...

Have you checked the fuel and coolant thermistors as I suggested in your other thread?

You'll know if it is running rich, you'll be able to smell it. Also take the plugs out and look at them - how black and sooty are they? If it can't rev past 2000 RPM then you need to check your dizzy is actually working properly; have you checked the mechanical advance is working? Have you put a strobe on it and determined if it is advanced to the correct setting or is the timing retarded? If you can't get it to time up properly you might have a stretched timing chain.
 
sorry to hijack slightly, but i'd like a bit of help off kev, and it might help with the OPs topic too.

my 3.5 basically runs ok, but it does seem quite rich. always have quite black plugs.

i have tried to run it with the maf disconnected before i think, but cannot remember what differemce it made.

also, the maf light has never been seen constantly on. it sometimes very quickly illuminates for like 1/4 second when you turn the ignition on.

i had a problem a while back (cant remember what it was!) but i found a website which helped me go through every sensor on the 14CUX system and test the whole lot with the multimeter, and verything seemed ok actually. the car has always been the same for me, and so rich it stinks the workshop out and makes your eyes water after about 10 minutes running. i always thought this was normal for non cat, but maybe not???

as for OP, if the car is backfiring and popping, it is probably injecting, so it could either be spark or IGN timing that are causing the problem.

any help appreciated :)
 
my efi light briefly flashes 1/4 second when turning igntion on when starting, has for months.

My plugs are clean for a v8, especailly with all the short trips I do and she seems to running good for an old motor, I did wonder about the light- is it normal?
 
As above, but mine only flashes briefly every so often. I assumed some sort of primitive lamp check, but why only occasionally?! :)

Anyway, when ive got a minute im gonna check see what she does with the MAF unplugged.
 
Mr Noisy said:
also, the maf light has never been seen constantly on. it sometimes very quickly illuminates for like 1/4 second when you turn the ignition on.
Click to expand...

This is NORMAL. You might also find from time to time the engine will start and for no apparent reason the efi warning light will come on. Just switch off, disconnect ecu (it only takes 1 or 2 seconds not 30 min because there is no volatile memory in a 14CUX) reconnect then turn ignition on (do not start), listen for the relays to click check dash to make sure efi light isn't on then fire her up. Should be O.K. But if efi light comes on while running, expect to use a lot of fuel, it will normally switch to limp home which is a very basic fuel map to allow the engine to run but it is VERY rich.

Hope that helps ya.
 
Thanks kev, yep, your knowledge is very helpful! :)

I'm gonna see what happens with the maf unplugged, see if there's any difference.

I do hope mines running ok, cba having to track down what's up this time!! :D
 
Mr Noisy said:
Thanks kev, yep, your knowledge is very helpful! :)

I'm gonna see what happens with the maf unplugged, see if there's any difference.

I do hope mines running ok, cba having to track down what's up this time!! :D
Click to expand...

1: I try - after all the problems I had in the first year with my RRC I know
how frustrating it is trying to get one to work.

2: It will run, best if you use wide open throttle (EVERYWHERE!) expect about 6MPG:eek:

3: If you suspect fuel mixture is out then you can check/test MAF with a multimeter (DO A SEARCH!;)) or you'll find out at MOT time when you fail on emissions. I suppose the other option is to ask anyone with a gas analyser if you can borrow it to set your MAF so your emissions are where they need to be (MOT testing station, plumber, gas man?).

cheers.
 
Thanks again kev!

As a matter of fact, when I motd the car this year in June the gas results were better than they had been for the two years previously.

This was probably due to my intervention and: exhaust refurbishment, no more gasket leaks or rusty holes, ignition system overhaul, engine clean out Inc breathers etc, and a general tune-up.

The stinking exhaust has been the same for years, yet it's never had major trouble at MOT.

Sometimes it is helped through with revs, bit I think this time it made it through by the book.

Anyway yeah I'll test the maf, it's the only sensor I didn't check whilst working my way through the troubleshoot section on britishv8.org

Thanks buddy :)
 
Hi kev I have took the plugs out and they are very sooty and black so like you said it's over fueling? Taking plenum off now but does look very black/ oil? Sorry for all the questions but is it the Allen key on the plenum next to throttle body for air fuel mix? Think my mate undid this when trying to remove the plenum if it is I am going to kill him
 
Yo kev :D

I decided to bring the disco home tonight, she usually lives at work.

Took her out for a little spin before getting home to warm it up nice, and I remarked to myself how nicely she was running tonight, nice power and not too jerky (sometimes there is minor hesitations around 2-3k but not like a misfire, more like fuel mix fluctuatingor ignition timing jumpy) so then when I got home I ticked over for a bit and then unplugged the maf. NEARLY cut out, with the idle control doing a good job of saving the day and stabilising the revs just in time. I sniffed the plume and it did smell very rich, perhaps more so than normal aswell.

Unfortunately there was no warning light on! :( I don't like to thinky error checking is not working...

Anyway, plugged back in and a minor lump and back to normal.

Then held at about 2k and unplugged. Again nearly cut out, and then jumped back up to revs, but with lots of lumps and popping in the exhaust I think. Nice n rich then!

Bit still no light on :(

Plugged back in, gave a few revs to clear out, and shes good as ever again.

Just a shame I can't get the light on.

Anyway, I assume it's working ok, when I'm at the workshop I'll run some tests with the multimeter, but it's nice to know it's doing something!

Cheers! :)
 
sible88 said:
Hi kev I have took the plugs out and they are very sooty and black so like you said it's over fueling? Taking plenum off now but does look very black/ oil? Sorry for all the questions but is it the Allen key on the plenum next to throttle body for air fuel mix? Think my mate undid this when trying to remove the plenum if it is I am going to kill him
Click to expand...

Thats the base idle screw , dont mess with it! I did and a world of hurt ensued :doh:
 
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