-95 DI hesitates at low revs and idle.

[1784]

About halfway in to Sundays offroad trip, the Disco started to hesitate and "misfire", mainly at lower revs and idle. It was hard to negotiate some passages since power was very fluctuating.
It is a -95 3.9 with auto.
On the highway home it was hesitating while pulling off from standstill but then clears and drives OK until lock-up comes in, then it jumps and jerks a lot, much better if moved into "3"
It sound like it's not just one or two cylinders cutting out but rather the whole engine. It starts just fine but at idle you can hear puffing and coughing in the exhaust.
It got new wires, rotor, cap and plugs about 6 months ago and it has been running fine since that until yesterday.

I'm I wrong in thing ignition is prime suspect and coil could be a first candidate?

Thanks,
Thomas

Ps. Sorry for the poor English

 

[MonLand]

At night, try to see if you see any spark anywhere on the engine bay.
Check to see how to test the cap / rotor (same thing, look for a spark).
Last would be the coil.
I was told (but did not experience) that some wires / rotor arm / distributor cap will not last more than 6 months.

 

[1784]

Hi,

Yes did the night test this evening, no arcing or spark sound as far as I can see. (I did see arcing before changing wires so I know what to look for).

Thanks!
Thomas

 

[MonLand]

Hi,

Yes did the night test this evening, no arcing or spark sound as far as I can see. (I did see arcing before changing wires so I know what to look for).

Thanks!
Thomas

Did you do the distributor cap check and distributor arm arc check?
How strong/what color is the spark at the plug(s)?

 

[1784]

Well, now it doesn't start, just fires some but not enough to run on it's own. Strong smell of gas when trying to start. Plugs are wet.
Changed the cap and and arm to used but OK Lucas ones, no change.
Changed coil to new Lucas, no change.

Spark looks quite small and blue.
Measured resistance of inductive sensor in distr. to 3.3kohms.

Ignition module? Can it be tested?

Help...

 

[singingcamel]

If your high and low tension leads are in the right order i would suspect it is your amp module. check for good snappy spark from your coil and then pull a plug and ground it. weak spark at the plug may indicate a bad module.

 

[DanDan]

Did the problem get solved? I have the same symptons on a 95 D1.

It had veen running fine but of late developed a slight hesitation at idle-and sometimes at high speed so had the neborhood mechanic install new wires, rotor and cap. Started fine and drove the 1 mile home OK but this morning, starts hard and very difficult to accelerate. Nearly dies going from ~1000 rpm to 2500 rpm, then seems to get beter.
Took it back to the mechanic who cleaned the air flow mass meter, with no effect.
No idiot lights illuminated and no codes showing on the box. The mechanic doesn't have any way to read to sensor outputs on anything older than 96 so can't do a thorough check.

Ideas???

thanks,
DanDan

 

[1784]

No, no resolution yet. It's raining and being very cold and dark here now, so I'll try measuring volts according to RAVE and checking sparks tomorrow.

 

[1784]

Hi,

Better weather conditions today so went out to try a bit.
1. Fuel pressure is 36-38 PSI after priming (pump sounds normal building pressure when ignition is switched on)
2. Spark on a plug when connected to HT lead from coil does not look convincing, one or two OK sparks, then just some small arcs jumping all around the plug.
3. Ran tests according to RAVE but could not find any deviations on voltages

I'm thinking on ordering a ign module now, but how about that distr. pick-up, could that be a suspect as well even though resistance checks out according to book?

About singingcamels tip, do you really get a good spark from coil lead if ign. module is broken?

Thanks!

 

[Chris-St Louis]

1) whose spark plugs are you using?
2) Wht was the ambiant temperture when it woudlnt start?

 

[1784]

1. Champion RN11YC
2. We are having around 35-40 F at the moment.

Forgot to mention I also switched ign leads today to an old but OK set but no improvement.

Ordered a ign module just now, will get it tomorrow, let's see if it helps, for around $100 it's worth a try. Somehow we have ended up trusting an old Disco as 2nd car to get child to daycare etc, so if it's not running again soon, I will have to get another car or tow it to some garage.
Seems like fuel is not the issue, but I guess there could be a number of issues in the ign system?

Thanks again!

 

[RovinNC]

I had the same problem in my 96 and my Jeep. Had the TPS replaced in both and its gone now.

 

[Chris-St Louis]

1. Champion RN11YC
2. We are having around 35-40 F at the moment.

Forgot to mention I also switched ign leads today to an old but OK set but no improvement.

Ordered a ign module just now, will get it tomorrow, let's see if it helps, for around $100 it's worth a try. Somehow we have ended up trusting an old Disco as 2nd car to get child to daycare etc, so if it's not running again soon, I will have to get another car or tow it to some garage.
Seems like fuel is not the issue, but I guess there could be a number of issues in the ign system?

Thanks again!

Good choice in plugs! Was this the first time its been this cold since you owned it?

 

[Ed Cheung]

From post#5, is it over fueling? MAF or O2 sensor maybe.

 

[1784]

Good choice in plugs! Was this the first time its been this cold since you owned it?

No, I think it has been down to around 5 deg F and it has always started on first turn of key, no issues getting flooded before.

Tried spraying some ether in intake, but no change.

I guess it could be pretty flooded by now, don't now how long wife tried to start it :banghead: before she gave up, but plugs are definitly wet.
But I don't think flooding was original cause, as I mentioned, it was misfiring quite bad when I parked it and usually it starts without hesitation.

 

[Chris-St Louis]

OK.... I woudl check the fuel pressure bleed off.... It should hold pressure for about .5-1 hour... after you turnoff the pump. If it doesnt, I would pull the injecotrs for inspect for leakage.

If the pressure is good, I think you are looking at a spark thing. The coils used to take a poo after the oil would leak out them, they woud get too hot. If you see wetness aroundyoru coil....Its junk.

 

[1784]

From post#5, is it over fueling? MAF or O2 sensor maybe.

Could be....
Had an issue with MAF once before after washing engine to much, then it would rev up and down without control. As I remember it ran OK when I disconnected MAF, I guess I could try that if MAF is sending misinformation?

O2's.. Haven't touched those, could they be tested somehow?

But on the other hand, the misfire didn't sound like overfuelling as long as it ran, it ran quite well but then got into bursts of misfires and then cleared again. No black clouds or strong smell of gas as long as it was running.

Thanks!

 

[ptschram]

Again, in a Rover, oxygen sensors will not cause a no-start condition. If the ECU sees something it doesn't like from the oxygen sensors, it just goes full rich.

I've only seen a few coils go bad. My off-road rig has 224K miles on original ignition amp and coil.

Air gap maybe? Ground? I probably would have thrown a new rotor in before buying an amp, but I also keep a coil around for testing

 

[1784]

OK.... I woudl check the fuel pressure bleed off.... It should hold pressure for about .5-1 hour... after you turnoff the pump. If it doesnt, I would pull the injecotrs for inspect for leakage.

If the pressure is good, I think you are looking at a spark thing. The coils used to take a poo after the oil would leak out them, they woud get too hot. If you see wetness aroundyoru coil....Its junk.

I took the battery out to give it a charge to ensure maximum cranking speed and good spark to clear wet plugs when I try the new ign module tomorrow. If that does not work out, I'll check how the fuel pressure holds over time.

The coil is all new as I think I wrote somewhere further up, but the new coil did not improve things.

Thanks!

 

[MonLand]

Could be....
Had an issue with MAF once before after washing engine to much, then it would rev up and down without control. As I remember it ran OK when I disconnected MAF, I guess I could try that if MAF is sending misinformation?

O2's.. Haven't touched those, could they be tested somehow?

But on the other hand, the misfire didn't sound like overfuelling as long as it ran, it ran quite well but then got into bursts of misfires and then cleared again. No black clouds or strong smell of gas as long as it was running.

Thanks!

Actually, this is a good point: if you unplug the MAF, then the ECU will detect a fault and go in limp mode (i.e. do not read any sensor [O2, MAF, etc]). So, unplug the MAF and you will rule out (or not) a sensor problem.
The TPS can be tested with a simple ohm meter.
Make sure you did not unplug anything when replacing your HT wires/spark plugs/etc.