1997 Disco V8 Major Misfire Problems

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W

Wookie

Active Member
Posts
128
Location
Ammanford, S Wales
Hi Guys,
As it says I have big problems, from cold it turns over for a bit before firing up, when it does it's ok for maybe 10 secs.
Then it starts to misfire very very bad, clouds of smoke and really stinks of fuel.
Can't even reverse out of the drive before it stalls.

Fires up again but misfiring, if you floor it picks up fine, but if you try to maintain say 30mph revs are all over the place and you can feel the juddering.

So far I have cleaned up the stepper motor, replaced plugs, leads, rotor arm and dizzy cap.
From what I can see from searches the coil tests ok on the LT side, 1.2-1.3 ohms, but I don't know on the HT side tests 7k ohms. One post I read somewhere said 3-4k ohms.
There isn't an ignition module on the dizzy like my classic so it's either internal or hidden somewhere I haven't found.

The stepper motor and tps are from what I can see the same parts so I'm going to make up new gaskets, and try swapping parts from my classic.
Also downloaded Roverguage and bought the cable so in theory I can see most of the readings, but it runs so rough at the moment I have no chance of checking the timing etc. Readings are pointless at the moment I think.

Apart from swapping out the common parts I can identify, could someone suggest a logical way to approach this problem please. The coil is cheap so will order one if it is suspect.

Thanks in advance guys for any help.

Andy
 
Amp will be near coil if not piggy backed. Can't say that's causing your problems though. What colour is the smoke? You haven't poured some 2 stroke in have you?
 
I'll have another look for the amp in the morning, thanks.
Smoke is blue I think. Definitely no 2 stroke.
Only thing fuel wise was to add STP Ultra to 60l of petrol, when the problems started as MOT was due.
Drove like crap to the garage, but when I restarted it to show the problem it was fine. Same for the MOT.
No smoke or anything. Next day......... and it's been the same since.
 
Had another go today, found the amp which has 3 wires so just need to find out how to test.
Double checked that the leads were in order.
Cleared fault codes anyway, none were showing.
Ran really rough from cold, but got better as it warmed up just not right though.
From cold the MAF reading was around 30%, dropped to 3% once warm.
Engine temp rose gradually to 75C.
Fuel temp rose gradually to 27C.
TPS was high when cold and all over the place, but did drop once warm to around 6%
RPM once warm was around 680 - 750, but as you increase revs to say 1000rpm you can really feel the vibration.
Lambda trim was much more variable on the odd cylinders, hoping this doesn't mean a head gasket failure.
 
Check all the pipes connected to the plenum and inlet manifold, sounds to me like one may of split or even come off from your first statement.
It's a v 8 so can be difficult to tell if you are loosing one cylinder, if it's not offer air you could be loosing a whole bank
 
Wookie said:
Hi Guys,
As it says I have big problems, from cold it turns over for a bit before firing up, when it does it's ok for maybe 10 secs.
Then it starts to misfire very very bad, clouds of smoke and really stinks of fuel.
Can't even reverse out of the drive before it stalls.

Fires up again but misfiring, if you floor it picks up fine, but if you try to maintain say 30mph revs are all over the place and you can feel the juddering.

So far I have cleaned up the stepper motor, replaced plugs, leads, rotor arm and dizzy cap.
From what I can see from searches the coil tests ok on the LT side, 1.2-1.3 ohms, but I don't know on the HT side tests 7k ohms. One post I read somewhere said 3-4k ohms.
There isn't an ignition module on the dizzy like my classic so it's either internal or hidden somewhere I haven't found.

The stepper motor and tps are from what I can see the same parts so I'm going to make up new gaskets, and try swapping parts from my classic.
Also downloaded Roverguage and bought the cable so in theory I can see most of the readings, but it runs so rough at the moment I have no chance of checking the timing etc. Readings are pointless at the moment I think.

Apart from swapping out the common parts I can identify, could someone suggest a logical way to approach this problem please. The coil is cheap so will order one if it is suspect.

Thanks in advance guys for any help.

Andy
Click to expand...
Maybe you could check out the fuel pump relay with a multimeter, sounds daft but you never know
 
Willing to investigate anything and rule it out.
Engine temp took ages to get to 75C, thermostat should open at 88C so think it's stuck wide open.
Over the weekend going to unbolt the amp & coil now I know where it is, clean up the earths, test the amp 3-5k ohms I think, and re-bond with high temp cement if it seems ok if not replace.
If no result then I've ordered a new thermostat, so will drain and re-fill the system with new coolant and 2 bottles of steel seal.
After that not a clue.
 
Logically, Pete's post is a worthwhile check as is fuel pressure test. If the smoke is blue it is burning oil and if it's not gone in the fuel tank by mistake, it is most likely head gasket failure (and steel seal won't cure it). no cream cheese under oil filler cap or oil in the coolant?
 
No mate nothing as of a few days ago, I'll check again tomorrow, but the filler cap is hissing a bit after it's been run for a while.
There wasn't any smoke today but it still ran rough, frustrating.
If the leak is on the oil side then I have some work to do, and being off the road not easy getting heads skimmed etc.
Gonna put the steel seal in if the checks are ok, nothing to lose and after adding it to Rover when the rad blew as a precaution, it starts first turn of the key.
If it's oil then.....................
 
Like Pete said, don't be putting sealer in your coolant.

Have you done a compression test (dry and wet). Mine was running like a bag of spanners recently, turned out to be head gaskets and an inlet air leak so as it seems you've checked most of the ignition and EFI bits you need to consider basic mechanical issues.
 
Hi Guys,
Thanks for all your advice.
Spent 1/2 a day yesterday getting access to the ignition module, rusty bolts etc.
Cleaned up the earth connections and renewed the cement on the module.
Cement was still soft so I don't think it's been overheating, on my Classic it was very dry when it failed.
Nothing in the Rave manual etc I could find about testing the module, but the outer pins to the centre gave around 12k ohms.
Checked the oil and water for the usual signs and they were fine, so started it up and it ran lumpy when cold but didn't stall.
New thermostat and compression tester arrived today, but that raises a couple of questions.
What is the best anti-freeze to use for an old V8, and how do I stop the ecu injecting fuel while I check compressions.
Is it as simple as pulling the fuel pump relay, or will it cause problems, never tested a fuel injected engine.
I'm not expecting brilliant readings after 158k but if they are even ish then hopefully ok.
Also got a couple of cans of carb cleaner to check for air leaks when the engine is warm.
Can't afford a huge bill so might have to use the steel seal but only as a last resort.
 
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