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has any body out there in Crocland got a spare working MAF sensor for a 987.1 that they want to part with please. my ongoing woes of random misfires when not fully warmed up and having to drive for 5 miles or so into each journey before it will run on all 6 at low revs, might just be caused by a naff MAF.  cost me a fortune so far replacing all 4 Variocam solenoids, new plugs and coils, new AOS, engine flush, new oil and filter and replacement pre cat lambda sensors. engine starts perfectly every time, no smoke, purrs on six for a minute then drops onto 4, rev it up to over 2k, back on 6. if i let the revs drop whilst driving to below 1500 rpm, back to 4 cyls and sometimes stays on 4 regardless, wont tick over and sounds like a high mileage Beetle. switch it off then restart it, straight back in all 6 again, very baffling and getting really pi**ed off. other forums have indicated that a dirty or dead MAF sensor might cause similar issues. So if any body has a spare one for sale, please give me first option on it. cheers all. Steve

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Wow thats a lot you've spent, you might want to get a 2nd opinion on whats wrong.

 

Does it show any fault codes when the misfire happens?

 

I think I'd be getting a cylinder compression test done and boroscope as it sounds like there maybe some damage in there.

 

 

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10 hours ago, Bushman said:

has any body out there in Crocland got a spare working MAF sensor for a 987.1 that they want to part with please. my ongoing woes of random misfires when not fully warmed up and having to drive for 5 miles or so into each journey before it will run on all 6 at low revs, might just be caused by a naff MAF.  cost me a fortune so far replacing all 4 Variocam solenoids, new plugs and coils, new AOS, engine flush, new oil and filter and replacement pre cat lambda sensors. engine starts perfectly every time, no smoke, purrs on six for a minute then drops onto 4, rev it up to over 2k, back on 6. if i let the revs drop whilst driving to below 1500 rpm, back to 4 cyls and sometimes stays on 4 regardless, wont tick over and sounds like a high mileage Beetle. switch it off then restart it, straight back in all 6 again, very baffling and getting really pi**ed off. other forums have indicated that a dirty or dead MAF sensor might cause similar issues. So if any body has a spare one for sale, please give me first option on it. cheers all. Steve

 

I don't have a spare MAF (or even a non-spare for that matter) but will spread the word for you sir.  

 

Silly question, but have you tried cleaning the MAF?  

 

A diagnostic should show a faulty MAF I would have thought...but not always.   

 

 

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The easiest way to diagnose the MAF is to unplug it and see if the car runs better (it'll go to a sort of default mode). If there is no change then it probably isn't the problem. That said, I agree with GlosRich. Now maybe the time for a second opinion as simply throwing more parts at it, may not fix the underlying cause

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Diagnostics.....dont waste your money without getting the fault codes checked.

 

iCarsoft is only £99

 

http://www.diagnostic-world.com/pages/iCarsoft_POR_V1_0_Porsche_Multi_System_Diagnostic_Reset_Tool_Engine_ABS_Airbags_Oil_Reset__189010-z=605301&p=131248.cfm

 

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Posted (edited)

You can check the MAF readings on the free version of the Torque app. I can't remember what the reading should be for the different engines (maybe something like 14m/s at idle) but it'll be kind of obvious if it isn't working (zero reading or wrong m/s readings). Torque will also tell you the codes 

Edited by Lennym1984
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thanks all, its defo not mechanical as a mechanical issue of any description would not instantly go away be switching off and re-starting the engine. when running on all 6, it purrs all the way past 7000 rpm, pulls strongly , no smoke, normal temps. OBD states random misfires, mainly on 1 and 3. on my Dash Command ( similar to Torque) app via a bluetooth OBD reader, realtime monitoring shows timing floating all over the place at low revs. 

Olive, thats an incredibly kind offer, both for first refusal on your spare one and offering to allow me to swap MAFs, much respect.

Glosrich, its been on 3 diagnostic machines with Porsche software ( not Porsche specialists though), all came back inconclusive but all indicating that the Variocam solenoids were suspect. we thought it was bank 2 variable valve lift solenoid first so swapped it over with bank 1 and the random misfires moves from 4 and 6 to 1 and 3. thought we had nailed it then so changed both solenoids but it only ran properly for an hr or so, an indy then told us that they never just change the lift solenoids on their own but always changed the variable timing solenoids as well. so we did. I found quite a lot of oil in the intake by the throttle body so changed the AOS. all good stuff but hasnt fixed it. tomorrow is a day off so I will collect MAF readings and strip and clean it before I commit to a replacement.

all great responses though guys, cheers for that

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Obviously be careful cleaning it... You don't want to touch the wire at all. Electrical contract cleaner works well. 

 

If the MAF readings look fine, then that probably isn't the cause

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stripped and cleaned the MAF, tried the trick of running the engine with it unplugged but it ran worse. got good readings from live OBD on the MAF gauge varying from 1.2 to 14+. so it not the MAF. Back to the drawing board then!!

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I wonder if it’s an air leak somewhere, worth checking around the plenum and I take etc.  Have you got some carb cleaner or something you can use to spray around the areas and see if it affects the idle? 

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Thought number 2:

 

Maybe an ECU reset/adaption initiation would be a good idea if you haven’t already tried it.  Worth trying anything that doesn’t cost money! 
 

1. Switch ignition on for 1 minute without starting the engine up.  Don’t touch throttle of anything in this procedure 

2. switch of ignition and leave for at least 10 seconds 

 

 

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I had a rough idling / engine dieing problem, was a sod to diagnose, and like you thought the MAF may be the issue, but it turned out to be the fuel pump. New pump installed and all sorted. 

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reassembled all joints from airbox onwards to plenums with good old Vaseline to eliminate air leaks, no difference. Tonite I thought I world change the primary Lambda sensors as faulty ones are known to throw flashing CELs. Two sweaty hrs later, they aint coming out. in fact, they would be less corroded if I had removed them from the Mary Rose.. the whole exhaust from the headers back to where it joins my home made stainless tailpipe looks pretty corroded. 4 hard years of 365 driving and exposure to winter salt hasnt helped. Think I will have to bite the bullet and splash out on Stainless headers and actually get round to building the 3inch stainless system that I started 2  years ago. Not sure it will help with the misfire issues but looks like it needs doing anyway.

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