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Has anyone had a Vitesse MAF go bad?

Old 02-03-2018, 10:32 AM
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MM951
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Default Has anyone had a Vitesse MAF go bad?

Hey all,

I haven't posted here in a while as I've been distracted with my Cayenne Turbo and the 951 has had Toyota like reliability for probably almost 10 years now, thanks to Lindsey Racings replacement harnesses, the (late) Ice Shark ground cable kit, replacing every piece of rubber in the engine bay, and most importantly, my Vitesse MAF which has been absolutely fantastic for nearly 100k miles and almost 10 years. That said, I'm having some strange issues recently and I'm zeroing in on the MAF. Has anyone had to replace theirs? Obviously these do go bad in many cars, but I've never heard of anyone needing to change one of these out and was wondering if anyone had any diagnostic info or experience to share.

My issues are a very lean idle, popping through the intake, no power and hesitation, with a surge of power above 4K. Sounds like a post MAF intake leak I know. but...it's not. Obviously I haven't driven any more since these issues cropped up. Strangely, it came after changing the air filter after the car sat for about 2 months during a suspension rebuild. Like I said earlier, there were zero running issues for years before hand and nothing has changed or been messed with in the engine. As part of the parts grenade I am planning on throwing at it, I did replace the used pump I put in back in 2006 with a new bosch unit, so we can rule that out..

Mike
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Old 02-03-2018, 12:11 PM
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100K miles in 10 years, good for you for using and enjoying your car.

The symptoms you describe could be caused by various things some of which:

- TPS: bad or improperly adjusted (run a check)
- MAF: bad, dirty element or bad wiring. Start by cleaning the MAF, by using a MAF cleaner spray (if new filter has excessive oil, it'll contaminate the MAF).
Next check the MAF signal at idle, it should be around 0.5-0.6V. Check the signal at the MAF connector then at DME #7. If idle is not steady, then it'll be hard to check. If you have a piggyback look at the MAF value as well.
- Fuel pressure or faulty injector...
- O2 sensor - take it out of the loop.
​​​​​​....

If you have the Motronic Monitor, it makes most of the above tests a simple and quick task.

Any component can go bad including the MAF. However in the 17-18 years in business, I have seen less than a handful of damaged MAF due to physical damage (wrecks), water getting on the electronics (engine wash) or a short in the wiring.
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Old 02-03-2018, 12:51 PM
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What is the brand and the number of your new air filter ?

I had a similar issue after the install of a new dry injen filter (the design of the neck connected to the MAF has changed) and had to play slightly with the PB to get the perfect values back.

My conclusion is that the MAF is very sensitive to the orientation and the fitment of the cone filter
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Old 02-03-2018, 08:30 PM
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Originally Posted by marcoturbo View Post
What is the brand and the number of your new air filter ?

I had a similar issue after the install of a new dry injen filter (the design of the neck connected to the MAF has changed) and had to play slightly with the PB to get the perfect values back.

My conclusion is that the MAF is very sensitive to the orientation and the fitment of the cone filter
That's curious -- I've clocked my MAF every which way, and have run 4 or 5 different K&N cone filters over the years (trying make it bigger, cooler, newer, etc.) and have never noticed a difference really. My MAF has maybe 70k miles I'd estimate and never a single issue. I did try cleaning it a while back with MAF cleaner when I was having a stumble but, as usual, it turned out to be weak ignition.

Re the OP's car -- I'd go over everything you touched when it sat two months for work. When a car doesn't run well immediately after doing work, there's a good chance something didn't go back together right. Switched oil breather and ISV hoses? Backwards maf? Damaged the MAF while off the car? Water in gas while sitting? Vacuum leaks you're sure aren't there... Electrical connectors are tight?

Since it is idling poorly, you should be able to confirm the MAF voltage at pin 7 of the DME with relative ease. If it's around .6vdc at idle +/- .1 (slightly higher on 3L) , and goes up when you rev it, then your issue is probably not the MAF. I'd also want to disconnect the O2 sensor plug to see if it may be bad and forcing the car lean. Beyond that, it will take good old diagnosing -- fuel pressure, temp sensor, ignition, TPS, air leaks -- could be just about anything...
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Old 02-09-2018, 07:35 PM
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In my experience changing many, many MAFs in my life for both drivability issues or the getting cars through emissions, I notice the opposite of what you are experiencing with a bad MAF. However, as John said, clean your MAF if you installed a new oily filter.

When a car ( 80% of the cars I work on are Mercedes ) comes into my shop with a check engine light for a fuel trim issue, I immediately know the MAF is bad if the idle value is RICH and part load value is LEAN. Other than that, a shorted MAF will keep a car from starting or the car will start and run fine, but WOT there is flat spot in terms of power.

Also, the air intake temp sensor is very important as well. Make sure it reads properly.
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Old 02-09-2018, 10:39 PM
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Originally Posted by MM951 View Post
Hey all,

I haven't posted here in a while as I've been distracted with my Cayenne Turbo and the 951 has had Toyota like reliability for probably almost 10 years now, thanks to Lindsey Racings replacement harnesses, the (late) Ice Shark ground cable kit, replacing every piece of rubber in the engine bay, and most importantly, my Vitesse MAF which has been absolutely fantastic for nearly 100k miles and almost 10 years. That said, I'm having some strange issues recently and I'm zeroing in on the MAF. Has anyone had to replace theirs? Obviously these do go bad in many cars, but I've never heard of anyone needing to change one of these out and was wondering if anyone had any diagnostic info or experience to share.

My issues are a very lean idle, popping through the intake, no power and hesitation, with a surge of power above 4K. Sounds like a post MAF intake leak I know. but...it's not. Obviously I haven't driven any more since these issues cropped up. Strangely, it came after changing the air filter after the car sat for about 2 months during a suspension rebuild. Like I said earlier, there were zero running issues for years before hand and nothing has changed or been messed with in the engine. As part of the parts grenade I am planning on throwing at it, I did replace the used pump I put in back in 2006 with a new bosch unit, so we can rule that out..

Mike
This all sounds like a large vacuum leak. Are you 100% sure everything is tight? Otherwise, are you sure the MAF connector/wiring is OK (maybe something came loose during the air filter replacement)? Check any area that has been apart recently before throwing parts at it.

Same as Lee, I have replaced more MAF sensors than I can count, but on Porsches (mostly 9x6/9x7), and it is exceedingly rare for them to fail in a manner that makes the car barely run (the sensor generally goes out of range, but engine otherwise runs mostly OK). But, the failure mode depends on the type of MAF sensor as I pointed out in the other recent thread about MAF sensors and K&N filters.
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Old 02-15-2018, 05:45 PM
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Thanks all for the responses. So I had some time to dig into it the other day and remembered how much I hate taking the DME/KLR out of their home, not to mention holding the multimeter pins in place on the DME connector while trying to operate the gas pedal. Fun fun! The Motronic Monitor is absolutely my next purchase.


So, MAF voltage at idle is ~0.7 v and goes up with a blip of the throttle.

TPS checks out at the DME connector, KLR, and TPS itself. Idle, WOT, the sweep is smooth and consistent. I still wonder if it has an intermittent fault but unlikely?

ECT also is dead nuts on spec, at the sensor and at the DME.

I did find a mouse chewed on a vac line coming from the the vac canister in the battery tray T's off in the engine bay. The MAF pipe also had a cap on an unused port that after all these years was cracked and getting hard. I replaced those and also reset the idle per Lindsey Racings procedure.

I noticed my running voltage was a bit low, so I removed the hard pipes to access the adjustable voltage regulator I installed long ago and bumped it up to 13.8v, cleaned all the grounds, and put everything back together and went for a drive.

The car runs great, 840 rpm idle with 18-20" of vac, spools quickly etc - but after about 30 minutes I encounter a new problem. The car wont rev above 1800 rpm and has no power, not even enough to move the car. Let it sit for an hour, no change. Let it sit overnight? Car runs great again, for about 30 minutes.... and wont rev above 1800rpm. Like its very softly hitting a rev limiter. Out comes the broomstick and I tab the DME while its doing this and no change. I left the car in the parking lot and fetched my Cayenne. Tonight I will continue my diagnostic...
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Old 02-15-2018, 08:53 PM
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Good job on finding the leaky vacuum hose & cap.
Save yourself lots of time and frustration and get the Monitor.
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Old 02-16-2018, 11:50 PM
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Originally Posted by fast951 View Post
Good job on finding the leaky vacuum hose & cap.
Save yourself lots of time and frustration and get the Monitor.
+1000 -- It's like having 20 multimeters hooked up and logging 24/7....
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Old 02-19-2018, 06:24 PM
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Originally Posted by MM951 View Post
Thanks all for the responses. So I had some time to dig into it the other day and remembered how much I hate taking the DME/KLR out of their home, not to mention holding the multimeter pins in place on the DME connector while trying to operate the gas pedal. Fun fun! The Motronic Monitor is absolutely my next purchase.


So, MAF voltage at idle is ~0.7 v and goes up with a blip of the throttle.

TPS checks out at the DME connector, KLR, and TPS itself. Idle, WOT, the sweep is smooth and consistent. I still wonder if it has an intermittent fault but unlikely?

ECT also is dead nuts on spec, at the sensor and at the DME.

I did find a mouse chewed on a vac line coming from the the vac canister in the battery tray T's off in the engine bay. The MAF pipe also had a cap on an unused port that after all these years was cracked and getting hard. I replaced those and also reset the idle per Lindsey Racings procedure.

I noticed my running voltage was a bit low, so I removed the hard pipes to access the adjustable voltage regulator I installed long ago and bumped it up to 13.8v, cleaned all the grounds, and put everything back together and went for a drive.

The car runs great, 840 rpm idle with 18-20" of vac, spools quickly etc - but after about 30 minutes I encounter a new problem. The car wont rev above 1800 rpm and has no power, not even enough to move the car. Let it sit for an hour, no change. Let it sit overnight? Car runs great again, for about 30 minutes.... and wont rev above 1800rpm. Like its very softly hitting a rev limiter. Out comes the broomstick and I tab the DME while its doing this and no change. I left the car in the parking lot and fetched my Cayenne. Tonight I will continue my diagnostic...
I had that problem once, and it was because my fuel pressure was dropping to 20 psi after 40 minutes. Check your fuel pressure, and leave the gauge on the car as it warms up. If it drops low as the car warms up, check and make sure youre getting good voltage to the pump ( the DME relay powers the pump ) and if everything is kosher, replace the fuel pump.

This issue cost me a headgasket....
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