Mass Air Flow Sensor Replacement - 996 TT
#16
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pretty much everyone knows that hot wire mafs fail for two reasons:
contamination.
excessive voltage.
i neglected ( or did i? lol..) to mention also that your symptoms mimic failed plugs, and burnt spark plugs are common and more frequent on a tuned car than on stock. "breaking up" is coils and/or plugs, more often than not.
that said, you could have a failing maf and plugs and if you don't know whats been swapped recently or since you took possession of the car? i'd swap them them ALL, incl a new maf. gl w it!
contamination.
excessive voltage.
i neglected ( or did i? lol..) to mention also that your symptoms mimic failed plugs, and burnt spark plugs are common and more frequent on a tuned car than on stock. "breaking up" is coils and/or plugs, more often than not.
that said, you could have a failing maf and plugs and if you don't know whats been swapped recently or since you took possession of the car? i'd swap them them ALL, incl a new maf. gl w it!
Think he would get misfire codes, not boost issue codes
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The car goes into the shop (not a dealer), but a shop that maintains PCA racing cars, tomorrow. All this will be provided to them. I'll make sure I update this thread! Thanks again everyone.
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For those of you who believed that the problem was not the MAF, you were correct. Took the car into the shop. My car blew off a cold air intake hose on the turbo, and it appears that the only fault code it knew to kick out was for an MAF-related failure, which is logical. Also, the technician cleared the codes, then re-started the car; the codes almost instantly reappeared, leading him to conclude that it wasn't a boost leak, since the turbo hadn't been engaged.
Drove the car home; seems to be running fine. I plan to order an upgrade kit to correct the problem. Seems that it's not unheard of for the clamp in question to let loose, especially under high loads. I also looked into rolling back the software upgrade; my guy recommended against that. I'm sort of relieved at that. While I was on the track, I was watching the revs pretty closely. I know I probably came close to 6K, but I don't think I really over-reved the car. But I will say that I'm much more conscious of that now. Finally, the recommendation was to leave the plugs and coil alone for the meantime. We'll give it all another go at a mid-September event. Thanks for all your comments and recommendations.
Drove the car home; seems to be running fine. I plan to order an upgrade kit to correct the problem. Seems that it's not unheard of for the clamp in question to let loose, especially under high loads. I also looked into rolling back the software upgrade; my guy recommended against that. I'm sort of relieved at that. While I was on the track, I was watching the revs pretty closely. I know I probably came close to 6K, but I don't think I really over-reved the car. But I will say that I'm much more conscious of that now. Finally, the recommendation was to leave the plugs and coil alone for the meantime. We'll give it all another go at a mid-September event. Thanks for all your comments and recommendations.
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Did you snug up the other half dozen or so hose clamps on the turbo system? I just changed the spark plugs on my car and quite a few clamps needed a turn to snug them up ...
On the coils, I waited until I removed my existing coils to inspect them. Every single one of them had micro-cracks, so I replaced them all. The plugs were toast too, 58K on the coils, 26K miles on the plugs. It's a bit of a PITA to change the plugs and coils, but a very good chance it is close to needing them.
On over-rev's, i don't think you have to worry at all about hitting the rev limiter. You can't really over-rev the car by simply accelerating, that's what the rev limiter is for. What you want to avoid is a 'money shift'... Downshifting into the wrong gear and significantly over-reving the engine.
On the coils, I waited until I removed my existing coils to inspect them. Every single one of them had micro-cracks, so I replaced them all. The plugs were toast too, 58K on the coils, 26K miles on the plugs. It's a bit of a PITA to change the plugs and coils, but a very good chance it is close to needing them.
On over-rev's, i don't think you have to worry at all about hitting the rev limiter. You can't really over-rev the car by simply accelerating, that's what the rev limiter is for. What you want to avoid is a 'money shift'... Downshifting into the wrong gear and significantly over-reving the engine.
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Thanks for the suggestion on the clamps. As I said, I'm ordering the upgrade kit for that particular portion of the intake system on the turbo. I'll make sure we snug up the other clamps. If you look at the beginning of the thread, you'll see that the car has only 15,000 miles on it (I bought the car with 12,500 on the odo), but I don't know its history. I do think (99%) the car has been tracked before, so I'll ask again about the plugs and coils. Could very well be a spark plug/coil issue. Last point: Coming into a couple of big turns, where a shift from 5th to 3rd is necessary, I watched the revs pretty closely, and by the time I was finished braking, the downshift to 3rd took the revs up to the 5K range. I didn't notice anything higher, but I think your advice is well taken.
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The factory interval for plugs is 30K, but most tuners seem to recommend changing them as often as 10K or 15K if the car has an aftermarket tune. Not really a track issue to my knowledge.
I saw your mention of an 'upgrade kit', not sure what that is... Aftermarket boost hoses?
Gotcha on 'watching' the tachometer... I assumed you were watching it on acceleration, not on an intentional 5 -> 3 downshift.
I saw your mention of an 'upgrade kit', not sure what that is... Aftermarket boost hoses?
Gotcha on 'watching' the tachometer... I assumed you were watching it on acceleration, not on an intentional 5 -> 3 downshift.