Gas-milage issue: Crank shaft sensor on 1996 P38?

I need help on how to replace or clean crankshaft sensor on a P38 from 1996. Anyone?

Weak power and gas milage going through the roof. Idles terrible, not like a V8. Pulling a trailer (less than one ton) on the freeway at around 100km/h burns around 30l on 100km. That translates to less than 9mpg.

I read out the computer, no error messages. I have new spark plugs and cables and air filter. Head gaskets new. Compression on all cylinders ok. It was loosing oil through gasket like crazy, so my last resort is a dirty or broken crankshaft sensor (cheap) or the air flow meter (too expensive for just a guess).

I'm running out of ideas. Sensor next. Anyone knows how to locate/pictures/guidelines?

Thanks!

Don't know the V8, but usually if a crank sensor is duff the engine will not run.

dirkster said:

or the air flow meter (too expensive for just a guess).

I'm running out of ideas. Sensor next. Anyone knows how to locate/pictures/guidelines?

Thanks!

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Dont guess then ! get some readings from the MAF and compare them with a known good one. Use a simple mulimeter to see what the O2 sensors are doing. A tin of carb cleaner will check for leaks on the inlet side. There is a whole raft of tests you can do before spending any money on her. Work systemacticly and start with the basics.

Its not unknown for the reluctor ring that the crank sensor reads to get damaged giving random readings, but the sensor itself will either work fine or not at all.

rewmer said:

A tin of carb cleaner will check for leaks on the inlet side. There is a whole raft of tests you can do before spending any money on her. .

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Hey, thank you bunches for super-fast reply! Really appreciated! Any insight on the "whole raft of tests" besides spraying a whole can of flammables around the intake (sounds fun, though).

Sparks first. Check for arcing on the leads and coils. A good poke around in the black of night will soon show any problems there.

Carb cleaner - done. or if you fancy, a plumbers smoke pellet in the intake. Find an old metal tin to put it in first, they get very hot and will melt plastic. You will have to bung the inlet aswell. again best done in a darkened garage or similar and use a torch to detect any whisps.

o2 sensors. attach some extensions to the signal leads and run them up into the car and attach multimeter. You can then watch what they are doing.(Thanks Eight for this tip) They should switch lean to rich about every second on idle when warmed up, going rich on heavy accelation and lean on the overrun. I believe your Titania sensors should read .5v for lean and upto 5v rich.

MAF - you will need some kind of OBD reader for this - get some live data for the MAF at various speeds with all loads off - air con etc. and compare to this......
Idle 680rpm - 22Kg
1200rpm - 32.5Kg
2000rpm - 55Kg
3000rpm - 92Kg
These figures are from a later Thor engine so only use as a guide but you should be in the ball park. If you get widly different readings, investigate further.

That should keep you going for a while...... good luck and report back.

Air flow meter expensive?! Was just about to post myself but as i was looking around for one of these - if the same as MAF - then they were £39 new on good old ebay..

NO NO NO. No eBay Mafs. Genuine only or your wasting your money. Slip your local garage £10 to get some readings from yours.

Thanks Rewmer for your hints and MAF data!!! Helps a lot!