Enuff

Enuff

Well-Known Member
Hi all,
1998 p38 4.0 170k. Idles in park and neutral at either 1000, 1700 and occasionally 2800rpm,
Idles in gear at 900rpm.

At 1700rpm throttle shows at 12% open. If i switch off and on then idles fine 700rpm for 30 seconds before climbing back to 1700rpm.
Idles at all ranges smooth as silk on petrol and LPG.

Last month I repaired 02 sensor that had a melted cable, loose exhaust manifold bolts and a disconnected engine temp switch (near starter motor)
I had to borrow diagnostics kit to reset adaptive stft and ltft and still have idle problem.
I suspect ecu or becm, all plugs and connectors are clean...has anyone had or heard of these symptoms or suggest summat to try.

There are no fault codes displayed but she is running rich and costing me a fortune in both petrol and LPG.

Many thanks.
 
Enuff said:
Hi all,
1998 p38 4.0 170k. Idles in park and neutral at either 1000, 1700 and occasionally 2800rpm,
Idles in gear at 900rpm.

At 1700rpm throttle shows at 12% open. If i switch off and on then idles fine 700rpm for 30 seconds before climbing back to 1700rpm.
Idles at all ranges smooth as silk on petrol and LPG.

Last month I repaired 02 sensor that had a melted cable, loose exhaust manifold bolts and a disconnected engine temp switch (near starter motor)
I had to borrow diagnostics kit to reset adaptive stft and ltft and still have idle problem.
I suspect ecu or becm, all plugs and connectors are clean...has anyone had or heard of these symptoms or suggest summat to try.

There are no fault codes displayed but she is running rich and costing me a fortune in both petrol and LPG.

Many thanks.
Click to expand...
Sounds like the engine temperature sensor is faulty causing it to run on cold settings.
 
Enuff said:
disconnected engine temp switch (near starter motor)
Click to expand...

I didn't think there was a temperature sensor next to the starter motor? There's the coolant temperature sensor in front of the plenum, the intake air temperature sensor in the air box and the fuel temperature sensor on the fuel rail.

Only thing I can think of down by the starter motor would be the knock sensor, or the crankshaft position sensor but since it runs it more than likely won't be that.
 
jacckk said:
I didn't think there was a temperature sensor next to the starter motor? There's the coolant temperature sensor in front of the plenum, the intake air temperature sensor in the air box and the fuel temperature sensor on the fuel rail.

Only thing I can think of down by the starter motor would be the knock sensor, or the crankshaft position sensor but since it runs it more than likely won't be that.
Click to expand...

Correct no temp sensor near starter. Only CPS sensor.
 
There are 2 knock sensors ,one on each bank ,just by the starter,crank sensor Is on other side of engine facing towards the gearbox.sounds like it could be an air leak,which will be showing lambdas its running lean which in turn will richen the mixture up to compensate,
 
Now its stopped raining for 10 minutes I will double check for air leaks around the knock sensors..

The sensor between the starter and the exhaust looks fine and secure, with my sausage fingers I can't actually reach it but it didn't move when I prodded it with a screwdriver. :D

I don't really want to drop the starter motor just to check a sensor is secure but I would like to shake the very small hand of the person that thought of that...
 
You won't have an air leak around knock sensors ,it will be on the intake side of engine after the maf sensor,could b inlet manifold gasket,to check for a leak I would use spray can of brake cleaner and spray around suspect areas while the engine is running,if the revs rise while you are doing this without touching throttle ,you've found the leak.however this can be very dangerous,do this at your own risk,be very wary of where you spray it,like over red hot exhaust manifolds etc ,could burst into flames,I accept no responsibility for any damage that may happen whilst you do this,so be warned use common sense.
 
dove said:
You won't have an air leak around knock sensors ,it will be on the intake side of engine after the maf sensor,could b inlet manifold gasket,to check for a leak I would use spray can of brake cleaner and spray around suspect areas while the engine is running,if the revs rise while you are doing this without touching throttle ,you've found the leak.however this can be very dangerous,do this at your own risk,be very wary of where you spray it,like over red hot exhaust manifolds etc ,could burst into flames,I accept no responsibility for any damage that may happen whilst you do this,so be warned use common sense.
Click to expand...

Or you could spray something a little less explosive than brake cleaner! WD40 perhaps? Which will still cause an idle change but without the potential flash bang!
 
I have twice checked for air intake leaks and around the top of the engine..hoses connectors etc... No change with copius amounts of carb cleaner.
I think an open loop due to a failed sensor is more likely as the idle is sweet and rises steadily as high as 2800rpm and sits there, steady.
Its also steady at 1100 or 1800rpms.
Occasionally starting it when warm she idles at 750 for about 20seconds then climbs very steadily to either 1100 1800rpms, and sits there burning to much fuel, it stinks, I'm actually glad the neighbors don't smoke....
It does this on either petroleum or LPG so I'm thinking as LPG runs piggyback to petrol ecu it points again to a sensor... There are no fault codes showing but summat is very wrong as my wallet is empty
:confused::confused::confused:
 
What you need is to get the live data readings when engine is running,post up the results and can compare with someone else's readings,throttle position sensor voltage,idle control valve,lambda readings etc
 
Enuff said:
I have twice checked for air intake leaks and around the top of the engine..hoses connectors etc... No change with copius amounts of carb cleaner.
I think an open loop due to a failed sensor is more likely as the idle is sweet and rises steadily as high as 2800rpm and sits there, steady.
Its also steady at 1100 or 1800rpms.
Occasionally starting it when warm she idles at 750 for about 20seconds then climbs very steadily to either 1100 1800rpms, and sits there burning to much fuel, it stinks, I'm actually glad the neighbors don't smoke....
It does this on either petroleum or LPG so I'm thinking as LPG runs piggyback to petrol ecu it points again to a sensor... There are no fault codes showing but summat is very wrong as my wallet is empty
:confused::confused::confused:
Click to expand...

Air leak somewhere. Excess fuel can't make revs rise excess air will. Maybe you have more than one problem.
 
Thanks, you were correct, The sensor just above the starter motor is a knock sensor, this is what had a disconnected multi plug. Now fixed.

My local Indy wanted to charge 2 hours labour for resetting adaptive values... FFS..:mad: don't mind paying, as i know the kit is expensive but for less than 5 mins.

Would like to get live engine running data to post here as I will fix this problem eventually.

Can anyone recommend someone who can plug in, reset adaptive values and let me write down the live running data figures in the Bristol / Bath area. Again, don't mind paying.
 
At that rate....2 visits to the dealer would pay for your own Nanocom....
 
Enuff said:
Thanks, you were correct, The sensor just above the starter motor is a knock sensor, this is what had a disconnected multi plug. Now fixed.

My local Indy wanted to charge 2 hours labour for resetting adaptive values... FFS..:mad: don't mind paying, as i know the kit is expensive but for less than 5 mins.

Would like to get live engine running data to post here as I will fix this problem eventually.

Can anyone recommend someone who can plug in, reset adaptive values and let me write down the live running data figures in the Bristol / Bath area. Again, don't mind paying.
Click to expand...
If you can wait till Monday afternoon I'll have a look at it for you.
 
Many thanks for the offer eightinavee.... Monday is fine..

Will keep you all updated, have a good weekend.:clap2:
 
Went to see eightinavee last night.... Never known a night like it..rain, wind and proper flooding everywhere, my now vandalised TomTom took me and my very bored son 15 miles out the way and after several phone calls to get directions there was a large fallen tree totally blocking the long muddy single track lane we were in.
Sod it, I thought and phone eightinavee to admit defeat..
As I was on my phone, a muddy guy with a chainsaw approached my window and cheerfully said 'I think your calling me'. I wasn't going to argue as the movies 'Texas chainsaw massacre' and 'cabin in the woods' flashed though my mind.
Within 20 minutes Jon the tree surgeon and p38 guru had made light work of the rather large tree and had started on my badly running v8 lump.
What a top guy, I got a lesson in common p38 faults, what the diagnostic figures mean, what a duff right bank oxygen sensor does and doesn't do and had the adaptive values reset.
I was sent on my way with a couple of things to do and a nice normal idle on my motor......for a very fair price.
I can recommend his services as he knows his beans, just make sure you have a working satnav and a chainsaw should you visit. Many thanks Jon.
 
Glad your idle is OK again,I didn't do a full adaptive reset,should have explained better... One of the nice things about Testbook is that it will let you reset the stored closed throttle voltage on its own,leaving all the other adaptive values alone.Now the actual voltage is the same as the stored value with the throttle closed,the ecu will control the IACV properly.
I didn't want to do a full adaptive reset for two reasons,firstly because only one oxy sensor is active and the maf reading is slightly down.Secondly,your LPG system to me is an unknown,and without being able to see it running properly in a closed loop state,I could have made matters worse doing a full reset.If that s/h sensor I gave you works and you get it running better there is a better chance of seeing if the trimming of the LPG system is close to how it runs on petrol.
Having your own diagnostic tool would be a great help to you,esp as you run LPG,others on here know a lot more about the Nanocom and Hawkeye systems - my knowledge of them is very limited.
Good luck !
 
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