Rudolf

Member
Evening Guys
Do we have any ignition – injection specialists available? I’m running a 2000 P38B 4.6 on LPG @94k miles. Been running fine but noted some time ago that it seemed a little short on power. This has got worse over a period of weeks and began to definitely hold back at around 2500rpm under load and seemed a little worse on gas. Since the plugs and air filter were due for a change I did just that. The recent cold snap saw thing deteriorate, from cold start up (on petrol) is fine however it won’t respond to throttle and so you can barely pull away, more throttle just leads to backfiring. Give it just a little while to warm up and thing get much better although slow to accelerate. Once switched to gas its much better still and, with a little coaching, can be driven but 2500 RPM seems to be a blocking point, out of gear it will rev higher. On the motorway 50MPH in top gear is OKish but it is most reluctant to go any faster, switch to petrol and now things are much worse, holding back misfiring etc.
Had the codes read on a generic ‘Smartbox’ code reader with 11 codes coming up. Lambda bank 2, multiple misfires, misfire Cyl 8, misfire cyl 4, misfire low fuel, emission relevant misfire cly 8, emission relevant misfire cly 4, Plausibility check throttle angle(probable because driving requires a lot of throttle for not too many revs) and two unspecified codes 62,65,4,18 & 62,65,4,01.

Since then I’ve fitted new coil packs and plug leads (which on inspection were in a bad way) but no different. Now it starts no problem, I let it warm up and swt to gas and its drivable but way down on power with a ceiling of about 2500 RPM complete with misfiring and holding back. On petrol it’s much worse and will barely do 25MPH.
I've checked all the obvious connectors and wires, all see ok. I've even cleaned the crank position sensor.

Provided I leave it with him all day my kindly local dealer will read the code with his testbook for only £99, which is a bugger because then I can’t get to work to earn the £99 needed for his half hours work!

Thoughts Gentlemen please
 
Whats the condition of the Oil and/or coolant..??

Possible Head Gasket problem!

Also, start engine and disconnect the MAF, running should be noticeably worse...if there is no change, suspect MAF
 
OIl good, cooland good, compressions all equal. Old plug all even biscuit brown colours when removed. I like the idea on the MAF though,
Thanks
 
Ok, so just for all those poor souls searching the forum for answer I can confirm the MAF sensor fixed the problem. Having taken the advise offered I ran the car with the MAF disconnected and guess what, it made no difference. I then removed and cleaned the MAF with Meths and this made a vast improvement, but it wasn’t perfect. What the hell we’re on the right track so I removed it again and gave it a more aggressive cleaning with brake cleaner, this made it much worse! Having ordered a new MAF and with nothing to lose I cleaned it again with Meths and once again it was almost fixed. Subsequently the new sensor has returned all to normal. Interestingly the gear change timing and quality seems to have improved also, I hadn’t noticed a deterioration but perhaps the fault has been coming on slowly for some time.

During my internet searches I also discovered some good info on the MAF sensor, see links below

Hope that helps People


http://www.bosch.com.au/content/language1/downloads/sensors_airmass.pdf

http://rbaa.bosch.com/boaasocs/?template=page_product.vm&ccat_id=72&prod_id=338&lang=en
 
So here's a thing. I've been having some problems with the EAS (see separate topic) and ran a diagnostic check just in case there were any fault codes stored. Of course there weren't any for the EAS but the was one for the MAF, low out put. So I checked the electrics and sure enough everything ok but for a MAF output, which was stuck at 0.2Volts. since the MAF I fitted above is now out of warranty that meant another new one. That fitted and all back to normal but..... I couldn't tell there was a problem driving the car! May be with hindsight a little down on power but otherwise ok. So why when the first one failed did it cause so much disruption to the running and this time next to none?
 
So here's a thing. I've been having some problems with the EAS (see separate topic) and ran a diagnostic check just in case there were any fault codes stored. Of course there weren't any for the EAS but the was one for the MAF, low out put. So I checked the electrics and sure enough everything ok but for a MAF output, which was stuck at 0.2Volts. since the MAF I fitted above is now out of warranty that meant another new one. That fitted and all back to normal but..... I couldn't tell there was a problem driving the car! May be with hindsight a little down on power but otherwise ok. So why when the first one failed did it cause so much disruption to the running and this time next to none?
Depends on the failure mode.
 
Just out of interest did you buy a genuine MAF? I've never actually had a MAF problem on any of the cars I have owned but have experienced them first hand on other peoples cars. the first on a 320d that I was fixing with a master tech (start of apprenticeship trial at a BMW main dealer, those two weeks taught me a startling amount!) and also on E39 M5's and 300ZX Z32's as well as another friends P38 4.6. We found that the genuine MAF from my P38 made his run like new (much like mine does!) He bought a "New" item from motorfactors against my advise and it was worse than with the broken genuine item. He ended up going for a used genuine known good example from emmots for cost but even that was 100x better than the new non genuine part. I experienced the same on the 300zx's and M5's. Most items you can get away with but MAFS seem to have to be genuine regardless of the car!
 
Hi guys I've noticed recently in threads p38a and p38b being referred is the a 1995-1999 and the b 2000-2002?
If not what does it mean?
 
Nice idea though. Distinguishes when Thor came in and 4W ETC etc.
 
Nice idea though. Distinguishes when Thor came in and 4W ETC etc.

So on the diesel you could have P38A up to 1997. P38B 1998 to 1999. And P38C 1999 to 2000 then P38D 2001 to 2002. Makes a lot of sense that does. NOT. Or you could call them all P38A and base the changes on chassis number. Which seems to work reasonably well. :D:D
 
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So on the diesel you could have P38A up to 1997. P38B 1998 to 1999. And P38C 1999 to 2000 then P38D 2001 to 2002. Makes a lot of sense that does. NOT. Or you could call them all P38A and base the changes on chassis number. Which seems to work reasonably well. :D:D




quite sure mine's an F :D
 

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