P38A Misfires and Diagnostics?
- Thread starter kooky_guy
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kooky_guy
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I did do some myself on an old Rover P6 many years ago but certainly don't have the time to do them myself now. I'd be more than happy to pay £500, but not £1500. Where's your indie...?
The thing is that I really don't believe that this is the cause of the misfire. I'm not really sure that I believe the head gasket is leaking either.
I guess I'm just going to have to pay them off and get it back and literally start the whole diagnostic process again.
My indie is in Sheffield so a long way from Berkshire but this seems to be the going rate for most indies (factoring in both head skims - £80 ish) & another £80 for head bolts & gaskets, £170 day labour is reasonable. If it's blowing between cylinders you will get a really bad mis-fire. My HG's have generally gone the same way. Usually between the middle 2 cylinders so never lost water from a failure. First you will notice is a mis-fire / lumpy running slowing to a stop until eventually it mis-fires constantly.
Compression check is the way.
Compression check is the way.
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If you can get the car back, there's several of us with Nanocom diagnostics nearby. I'm in Slough, but often pop over to Camberley cos my brother lives there. Sandhurst is an easy detour for me.
Back in 2010, a local bloke had a Jaguar XK8 with poor performance. Local garage told him he needed a whole new engine. Another told him HG failure.
I got it and diagnosed a bad O2 sensor, that helped a bit, but there was more. Turned out the temp sensor was bad, it was actually leaking coolant through the plastic bits. I also found the fuel pressure lacking. The in tank pump was original, so I took it out (mare of a job) and found the wiring which started white, was burned about six inches from the pump. Clearly, the pump was drawing too much current so new one fitted.
The car went from running poorly and intermittent worse running to a belter of a car with instant throttle response and far better fuel economy.
So, in summation, fuel pump, O2 sensor & temp sensor.
Any poor running can be traced to faulty components. If intermittent, it needs a live data diagnostic...... All they need to do is compare standard parameters with whats showing on the readout.
I got it and diagnosed a bad O2 sensor, that helped a bit, but there was more. Turned out the temp sensor was bad, it was actually leaking coolant through the plastic bits. I also found the fuel pressure lacking. The in tank pump was original, so I took it out (mare of a job) and found the wiring which started white, was burned about six inches from the pump. Clearly, the pump was drawing too much current so new one fitted.
The car went from running poorly and intermittent worse running to a belter of a car with instant throttle response and far better fuel economy.
So, in summation, fuel pump, O2 sensor & temp sensor.
Any poor running can be traced to faulty components. If intermittent, it needs a live data diagnostic...... All they need to do is compare standard parameters with whats showing on the readout.
kooky_guy
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Got the Rangey back on Saturday. That was a mission.
We were in a rush as had a family do we had to be at by 12.
Almost at the garage and hit a massive stationary traffic queue to some event that clearly wasn’t being well managed in the pouring rain.
After about 30 mins, we managed to get past it and got to the garage to find a fire engine blocking the entrance, jet washing their gutters…
Had another argument with them about how disappointed I was that they were stiffing me for so much without having actually fixed anything, eventually gave up, paid up and drove off.
First off, found they had run it dry so had to stop and put some petrol in it.
Got to a petrol station. Filler flap wouldn’t open. Apparently there is no emergency release either. Grr!
Had to sit in the massive traffic jam again to get back to the garage. Got there eventually where they managed to rig up a manual override for the solenoid on the flap and got back to the petrol station.
Drove most of the way home without any problems, which was nice (and rather suprising), but just as I got to the large busy roundabout near the house, I noticed the temperature gauge was jammed on the top stop and the red light was on. Oops.
Had to stop and open the bonnet to find steam and coolant blasting out of the expansion tank. Had to wait for it to cool down a bit before I could put all of my spare water into it (about 7 litres!).
Restarted it to notice that the lpg system was running – I had previously disabled it because of the problem with the diaphragm in the vapourizer, but I’m guessing the garage must have reconnected it. Thanks guys.
I suspect it had been running all the way home which was why the car ran so well, with the slight downside that it blew all the coolant out because the diaphragm in the heat exchanger is knackered.
Anyway, drove the rest of the way home on petrol and it wasn’t quite as happy, but it got me there.
Interestingly, I suspect that this has proved conclusively that it can’t possibly be the head gasket causing the misfire so I’m back to square one again now. It runs fine on lpg (other than the vapourizer issue) and randomly suffers from periods of heavy misfire when running on petrol.
Think I’m going to drop the fuel tank and replace the pump.
Before I do that though, has anyone come across a Bluetooth pressure gauge that I could plug onto the fuel rail to monitor the fuel pressure? It would be nice to be able to confirm that this is the actual problem. I assume this sort of data isn't logged anywhere in the ecu?
We were in a rush as had a family do we had to be at by 12.
Almost at the garage and hit a massive stationary traffic queue to some event that clearly wasn’t being well managed in the pouring rain.
After about 30 mins, we managed to get past it and got to the garage to find a fire engine blocking the entrance, jet washing their gutters…
Had another argument with them about how disappointed I was that they were stiffing me for so much without having actually fixed anything, eventually gave up, paid up and drove off.
First off, found they had run it dry so had to stop and put some petrol in it.
Got to a petrol station. Filler flap wouldn’t open. Apparently there is no emergency release either. Grr!
Had to sit in the massive traffic jam again to get back to the garage. Got there eventually where they managed to rig up a manual override for the solenoid on the flap and got back to the petrol station.
Drove most of the way home without any problems, which was nice (and rather suprising), but just as I got to the large busy roundabout near the house, I noticed the temperature gauge was jammed on the top stop and the red light was on. Oops.
Had to stop and open the bonnet to find steam and coolant blasting out of the expansion tank. Had to wait for it to cool down a bit before I could put all of my spare water into it (about 7 litres!).
Restarted it to notice that the lpg system was running – I had previously disabled it because of the problem with the diaphragm in the vapourizer, but I’m guessing the garage must have reconnected it. Thanks guys.
I suspect it had been running all the way home which was why the car ran so well, with the slight downside that it blew all the coolant out because the diaphragm in the heat exchanger is knackered.
Anyway, drove the rest of the way home on petrol and it wasn’t quite as happy, but it got me there.
Interestingly, I suspect that this has proved conclusively that it can’t possibly be the head gasket causing the misfire so I’m back to square one again now. It runs fine on lpg (other than the vapourizer issue) and randomly suffers from periods of heavy misfire when running on petrol.
Think I’m going to drop the fuel tank and replace the pump.
Before I do that though, has anyone come across a Bluetooth pressure gauge that I could plug onto the fuel rail to monitor the fuel pressure? It would be nice to be able to confirm that this is the actual problem. I assume this sort of data isn't logged anywhere in the ecu?
eightinavee
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What you need to do is watch the oxygen sensors as live data,along with the airflow reading. Those fuel pumps are very reliable, if the oxy sensors can switch down rich to 0v, then there is sufficient fuel pressure.
kooky_guy
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Thanks for that but I don't have any means of doing that.
It's very borderline whether this goes on the bay now, so I'm not going to be able to justify spending much more on it.
I'm sure that it's a petrol supply problem but I don't know how to confirm it. I expected the garage to have at least investigated this, given the 9 months they had it, but they apparently knew best.
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A cheap ELM327 OBD2 dongle and the free EasyOBDII software will read the 02 data required......the dongle can be had for around a tenner.....
kooky_guy
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I didn't realize they worked on the P38. I have a cheap one that I bought for my BMW - I might try that when I get a mo. Not that I know what I'm looking at really, but I'll have a play.
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Definitely try the cheap OBD2 dongle, but you might need to check the diagnostic connect pins for corrosion if it won't connect.
As I said earlier in this thread, I could do Nanocom check for you at some point, but away on holidays this week until 14th Oct.
Pete
As I said earlier in this thread, I could do Nanocom check for you at some point, but away on holidays this week until 14th Oct.
Pete
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I would bite his hand off for a trace and maybe reset trims.
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Petrol P38's will talk to a cheap OBDII scanner...and give basic engine parameters...
The Diesle P38's won't.....
The Diesle P38's won't.....
If it runs fine on LPG and runs rough on petrol, it's clearly an issue with the oxygen sensors.
LPG runs "clean" so when the sensors sniff they find a weak output so they up the fuel mix and as it gets richer, it upsets the ECU when it returns to petrol it runs like a bag of nails.
First thing to do is get the trims reset then run it on petrol to see if it makes a difference. If not, I would suspect the sensors.
If it has been troublesome for a while, perhaps they were the cause all along. I fitted genuine sensors I bought from a local specialist (Inverness 4x4 Centre, Hamish Grant) I think they were Bosch. Anyway, I went the whole hog with new plugs, new leads and new air filter.
When I first got the car, I was getting 70 miles out of my tiny petrol tank (sore point, removing the two gas tanks underneath and replacing with a proper sized fuel tank). But then I was getting 100 miles, now after running the car in I'm getting 130 miles on the teeny wee tank.
I guess I'm lucky as the car had a new engine 30 odd thousand miles ago so it's going well.
Anyway, what I'm getting at, is start again. Get OE sensors, plugs and leads.
But FIRST have the fuel trims checked, reset and a live data reading to see what the O2 sensors are saying....
LPG runs "clean" so when the sensors sniff they find a weak output so they up the fuel mix and as it gets richer, it upsets the ECU when it returns to petrol it runs like a bag of nails.
First thing to do is get the trims reset then run it on petrol to see if it makes a difference. If not, I would suspect the sensors.
If it has been troublesome for a while, perhaps they were the cause all along. I fitted genuine sensors I bought from a local specialist (Inverness 4x4 Centre, Hamish Grant) I think they were Bosch. Anyway, I went the whole hog with new plugs, new leads and new air filter.
When I first got the car, I was getting 70 miles out of my tiny petrol tank (sore point, removing the two gas tanks underneath and replacing with a proper sized fuel tank). But then I was getting 100 miles, now after running the car in I'm getting 130 miles on the teeny wee tank.
I guess I'm lucky as the car had a new engine 30 odd thousand miles ago so it's going well.
Anyway, what I'm getting at, is start again. Get OE sensors, plugs and leads.
But FIRST have the fuel trims checked, reset and a live data reading to see what the O2 sensors are saying....
kooky_guy
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Interesting comments about the O2 sensors. The cats were replaced with 2nd hand items and new O2 sensors fitted. This is when all of the trouble started. The garage (same one that its just been on an extended holiday to) seemed to have a lot of trouble finding the correct sensors so I guess it is entirely possible that the wrong ones are now fitted. Is there an easy way to check?
Would bad O2 sensors cause intermittent massive misfiring? It literally runs perfectly one minute and the next it's like someone has hit the brakes. Then it's back to perfect running again.
Would bad O2 sensors cause intermittent massive misfiring? It literally runs perfectly one minute and the next it's like someone has hit the brakes. Then it's back to perfect running again.
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How oily or corroded are the various sensor connectors ? O2, Camshaft & Crankshaft sensors are all in places where crap gets into the connections.
kooky_guy
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I imagine the O2 connections ought to be ok, but have no idea about the rest - I've had trouble in the past with oil on a connector to the transmission which caused interesting random behavior. Hmm.
The problems all started on the way home from the same garage 2 years ago after they replaced the cats and the o2 sensors, so they seem a good place to start looking. I hadn't really thought that they could cause these symptoms though, particularly as the garage scoffed at me when I suggested the connection.
I'm getting married in 3 weeks with a honeymoon shortly afterwards so time is going to be short for any actual investigations in the short term - I'm saving up all the suggestions though so keep em coming!
kooky_guy
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Can anyone recommend some software that wil run on an iPad?
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kooky_guy
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I suppose I should have expected that!Candy crush will give you hours of fun.
There seems to be a large number of free ODBII reader apps available - I was just hoping someone might be able to recommend one of them that might help me in this scenario... I need it to work with a Bluetooth code reader.
I'll even pay for one if it's worthwhile!!
