P38 engine hunting at motorway speed

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
K

KeithMiller

New Member
Posts
8
Location
Hazlemere
Hi All,

2000x 4.6 petrol V8 is giving me grief. Around town she seems to be running fine but at higher speeds (50 - 70 mph) the engine is 'hunting' - occasional stutter, never failing though. Can usually accelerate through it but problem returns when cruising.

Local garage (LR specialist) are usually excellent however can't find anything wrong - no fault codes coming up. Said they have reset the ECU - car seemed OK for a few days now happening again.

Has just been serviced & reset again, problem now seems to be coming back. Car had a new air mass meter & fuel pump (with filter) last year but problem is more recent.

Part of the exhaust is rattling & may have a hole - could this be the problem (lack of back pressure?).

Going crazy, next option is to put it into the official dealer but i'll have to sell my first -born to afford that.

Any suggestions much appreciated.

Keith.
 
Are you using 97 octane petrol or 95? I know there'll be many who shout this down, but the 4.6 performs a great deal better on the highest octane fuel - I have had many years of seamless engine performance from my 4.6 V8 and some of this I believe is down to spending the extra on the highest octane fuel and NOT LPG converting it!! Also of course comprehensive servicing etc.

On a few rare occasions when I had to use 95 in the old girl, she had occasional stutters and unexplained hics in the engine revs and performance which vanished when I reverted to the higher octane fuel again. 138 000 miles and still excellent engine performance at present.
 
Tend to use the cheaper stuff to be honest & never really had any problems in the past. It is worth a shot though, I will wait until it gets near empty (doesn't usually take long :)) & then try some higher octane.

Thanks for the tip.

Regards,

K.
 
Dont go near that main dealer. They do not know anymore about your Range Rover than any other garage. Have you checked the O2 sensors ?
 
Haven't looked at O2 sensors yet. Would they not throw up a fault code or cause emissions to increase? (recently passed MOT with no problems shown).

Had it in Sport mode today & it seemed better - will have a proper look at the weekend.

Thanks,

K.
 
Get it on Testbook and look at live data - Airflow first,should be 22-25Kg/hr at idle,90-100 at 3000rpm.Any lower than this and the fuel trims wont cope with the readings.Ignore the Oxy sensors,both fault codes and live data until the airflow readings are correct.Where did the airflow meter come from ?
 
Airflow meter was supplied new by the garage - I trust them to fit decent parts. They are a good outfit, just seem a bit stumped by this issue.
 
Unless you can confirm that they fitted a genuine Bosch or LR part you are wasting your time,NONE of the aftermarket units work properly - your garage may be good,but unaware of this problem.
 
Sealed up the exhaust leaks at the weekend and filled up with Shell V Power - seems much better now - as smooth as a V8 should be!

Thanks for all the comments/suggestions.

K.
 
You must log in or register to reply here.

Similar threads

M
Sporadic lack of power at very low speed
Replies
6
Views
558
Meerkat1234
M
MrGorsky
P38A Occasional "Engine Disabled Press Remote" message on dash.
Replies
19
Views
1K
Datatek
Datatek
Lej
Fast idle speed (tick-over) + other queries!
Replies
3
Views
375
lynall
L
M
Troubleshooting help: Rattling noise right front
Replies
12
Views
1K
Freddie17
Freddie17
tarphenry
p38 diesel
Replies
15
Views
1K
tarphenry
tarphenry
Back
Top