[Busas]

Well , everything was going just great until last Thursday.

I was running down the Highway and i had to kick-down to do an overtake. The car started to misfire , and was losing power.
At idle Speed everything looks ok , once i touch the accel it starts like it is making Popcorns....

It doesn t makes any smoke , no pressure what so ever.

I am waiting for that the mecanic can look at it , and he says it look's like something electric and not mecanic.

Does anyone had a problem like this one ???
I really don t want to believe it is valve spring or something like that.

Any help where to look is welcome .

 

[ju1cy1]

Could be possible ignition coil pack...Had same issue a few years back...Just replaced with new pack and problem went away...A PITA to get to, so if that is the issue, change plugs and wires too, as upper intake mainfold needs to come off...Rave Cd has step by step, just takes some time, but can be done without dealership intervention...

 

[Busas]

Let's see if it is only that . Maybe i'm lucky .

It is making a weird noise , it seems something loose inside of the engine :think: .
If it has a broken valve would do some smoke wouldn't it ??

I have to get something to measure the compression of each cilinder :?

 

[Ferdinand]

I have the same problems!!!!!! (153.000 km) sudden misfiring and powerloss at a constant speed....


let's hassle with this problem together!

 

[996TURBO]

Guys,

Does it rev well on neutral?

 

[Busas]

No , just at Idle speed it is "normal".
If i just touch the accell it starts to pop :x .

 

[996TURBO]

No , just at Idle speed it is "normal".
If i just touch the accell it starts to pop :x .

Ok because mines runs out of steam only when hitting RPM while running but not on neutral. If i run it gradually, it can run but it's not perfect.
Thanksfully, i can run it perfectly on LPG.
I believe i do have something wrong with my injectors or something with fuel setup

 

[Busas]

Mine dos exactly the same thing if it is working on LPG and on Petrol.

Tomorrow let's see if i can measure compression.

 

[Ferdinand]

No problems with rewing it in neutral - except for the loud banging noise from time to time....

 

[hildstrom]

Check your spark plugs and wires, especially if you are already checking your compression. I had rough running under load and only intermittent rough running at idle. Eventually I got a misfire engine code. The wire boot at the spark plug of the offending cylinder was cracked and brittle. The electrical connection to the plug was badly corroded. New plugs and wires fixed it right up.

I am not sure how much revving the engine in neutral will tell you. The throttle position, manifold pressure, and fuel injected will be completely different for a given RPM with little to no load on the engine. It is easier to for a spark to jump a gap under lower air pressure with less fuel under no load. Weak spark or low fuel pressure from various problems could cause the same symptoms: idles fine, but misfires under load.

Others have suggested that a faulty or failing MAF sensor can cause rough running like this. I cleaned mine with CRC no-residue electrical contact cleaner before doing the plugs and wires. I also tried a heavy dose of fuel injector cleaner in the gas tank prior to doing plugs and wires.

"loud banging" does not sound good. Could it be pinging from low quality fuel or pre-ignition from dirty combustion chambers?

 

[szo]

I spit the air intake pipe on my Discovery once.
It was an easy fix but took hours on the side of the road to find. It first went off cruising on the highway and the bang shook the car!!!

 

[AMcK]

Ok because mines runs out of steam only when hitting RPM while running but not on neutral. If i run it gradually, it can run but it's not perfect.
Thanksfully, i can run it perfectly on LPG.
I believe i do have something wrong with my injectors or something with fuel setup

Is it single point or sequential lpg?
If it is single and runs well on lpg, but not petrol it could be MAF as in single point the data from the MAF is not used. If it doesn't use O2 feedback, again this could mean O2 sensors not working well. Also your adaptive values could have been knocked out by the lpg either by the emulation used in single point or if sequential - not calibrated well.

 

[Ferdinand]

Plugs er maybe 25.000 km old - Platinum type Champion - Wires/ leads are brand new Magnecor 8mm... I've also cleaned the throtlle body and IAC with special air intake cleaner (foam type from a spray can - Belladd) Idle has become much more even since then - and occasional start with high revs (2500) but not like it used to behave....

The loud rocker sound at startup is gone... ish.... a few days ago it was there again for a few seconds.....

But if I pull the throtlle cable really fast and hard, there is a loud BANG sound from the engine/gearbox?! like you hit the engine with a hammer.?!

 

[996TURBO]

Ok because mines runs out of steam only when hitting RPM while running but not on neutral. If i run it gradually, it can run but it's not perfect.
Thanksfully, i can run it perfectly on LPG.
I believe i do have something wrong with my injectors or something with fuel setup

Is it single point or sequential lpg?
If it is single and runs well on lpg, but not petrol it could be MAF as in single point the data from the MAF is not used. If it doesn't use O2 feedback, again this could mean O2 sensors not working well. Also your adaptive values could have been knocked out by the lpg either by the emulation used in single point or if sequential - not calibrated well.

It is single point LPG with O2 feedback.
I'll testbook it this week end to know. Last time i did, there wasn't any code and i resetted adaptive values with no gain on fuel.
I already cleaned the MAF (OEM). Will try a crappy chinese one that i have in stock to see.

 

[Busas]

Well , after lot's of ideas , the error in the computer was telling us that was the MAF sensor , but it seems it is not.

It seems it is the crankshaft sensor ....

I am waiting for it , and then i will post some more feedback.

 

[Busas]

Done , the crankshaft sensor was bend over...
One of the screws of the tork converter has loosen it self and hit the sensor.
Everything is working fine now.

.

Just waiting for a new sensor to everything be excelent.

It could be alot worse....

 

[p38a4.6]

Continuing this thread; similar problem different P38:

Bad misfire on my '99 4.6 Bosch after complete top end rebuild (valve job, milled head, head gaskets, timing chain and sprockets etc...). Did all work myself and feared I made some boneheaded mistake. Which turned out to be the case.

In the unlikely chance someone else has such a misfire problem here are my symptoms and solution:

1) Checked all obvious stuff; spark wires tight etc. (Installed new plugs and wires during rebuild.)

2) Connected OBD code reader, showed following faults:

P0300 Random/multiple cylinder excess emissions detected Excess emissions detected on more than one cylinder
P0301 Cylinder 1 misfire detected Injector 1 excess emissions/catalyst damaging level of misfire
P0304 Cylinder 4 misfire detected Injector 4 excess emissions/catalyst damaging level of misfire
P0306 Cylinder 6 misfire detected Injector 6 excess emissions/catalyst damaging level of misfire
P0307 Cylinder 7 misfire detected Injector 7 excess emissions/catalyst damaging level of misfire
P1319 Misfire detected with low fuel level
(This last was no doubt due to initial start up with dry fuel line. In fact this fault was not present on next check.)

3) Cylinders 1,4,6,7? Seems weird I thought: 2 on each bank. Being a novice P38 _non-mechanic_ (and used to early Pleistocene mechanical distributor-with-rotor and single coil ignition) did not realize each side of coil packs ran 2 cylinders on each bank. Duhhh....

4) Was afraid I had mis-connected HT leads to coil packs. Found a diagram of proper ignition wire order on coil packs (see below).



Left pack fires 1,4,6,7 (my misfires) and right fires 2,3,5,8. Or looking at the packs as one unit, top row L to R: 1-6-5-8. Bottom row L to R: 7-4-3-2. Pain to get back to the coil but followed each lead; all tight and correctly in place.

5) Problem solved: found coil multiplug on left side off; probably bumped it loose when trying to bolt on the bracket that holds wiring harness to left rear head. Or just missed connecting it; nothing back there is easily visible. Reconnected and engine runs like new, no fault codes. More power, smooth as silk at 155k miles.

Amazing how much difference a fresh top end -- and correct ignition -- makes.

late 1999 P38a 4.6 Bosch North American Spec
previous Rovers: Series IIa 88 and 109, non-USA spec Defender 130
daily driver: 2008 Ural Gear-Up 750

 

[peby14]

Mine had the same problem, I had to overtake someone and did a kick down, once it passed 4,000rpm it started shuttering and the service engine light blinked for a few seconds and blinked again. I pulled over and shut the car off and back on and drove back home. I cleared the fault once i was home but every few seconds the car suddenly bumps. I got a 'rebuilt" valve 1,500miles ago and by rebuilt i mean a used one my mechanic probably pulled of an old p38 in cylinder 6. So I'm thinking its something to do with that. I just got it back form a new mechanic and got new o2 sensors and a new purge valve. Any thoughts? Not a real mechanic but I try my best.

 

[RagnaRn]

I have the same problem.
Engine from RPI with about 40000 km on it.
Bougt the car with error on oxygen sensor and it bogging on about 4000 rpm
Belived that O2 sensor was causing this.
New sensors in place, magnacore wires and new plugs and still bogging

This weekend it misfired on cold engine and worked ok when getting warm

I have not reset the errorcode on the O2 sensor, could this cause problem?

 

[RagnaRn]

A update

Did a adaptive value reset and O2 error code cleared out.
A bit better on misfiring ,but not all good.

O2 error code appears on cold enginge, but can be erased on warm engine without getting back.

have been driving som miles after reset and its almout back to the old status with misfire / bogging.

It boggs around 3000 rpm and seems like misfiring with trottle applied.

Have read around and found many possible causes, cats, engine ECU heat sensor, fuelpump, MAF +++

Its the same on gas and LPG

Can a worn battery cause this, it starts ok, but i had gearbox fault last week