Boost issue

OK. When driving my car (01 tdi golf) When I get to 3100 rpms there seems to be a boost "lag". This is most noticeable in 3rd gear. Now I was "educated" that Lag is not the term used, but it seems to be the best I've found to describe what happens. Boost is great until then when, it seems to stop or fall off or "lag" behind the pace the turbo was on. RPMs still increase, but at a much slower rate. This doesn't seem to happen when the temp is cooler. I'm not a mechanic by any means nor do I try to be. just looking for some help here. The reason i'm trying to get this figured out is an 03 tdi golf was in the shop I use and blew up. Their turbo wasn't boosting at all. They tried replacing it and that didn't work. At some point the car was running and suddenly Rev'd up. They turned the car off but it continued to run and slowly rev down then seized. The issue I'm having has been described as some what the same as what this other car was doing before the turbo quit completely. Now I've decided to start w/ the Boost sensor before the MAF sensor. Since I saw some rust forming on the housing next to a screw, and its cheaper. Any other sugestions?

Thanks, Zach

Zacho said:

OK. When driving my car (01 tdi golf) When I get to 3100 rpms there seems to be a boost "lag". This is most noticeable in 3rd gear.
....
Now I've decided to start w/ the Boost sensor before the MAF sensor. Since I saw some rust forming on the housing next to a screw, and its cheaper. Any other sugestions?

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Sounds like MAF to me - generally a flaky MAF is likely to cause this type of thing. MAP sensors generally don't cause this type of problem, and if they do, you generally get a MIL.

Zacho said:

The reason i'm trying to get this figured out is an 03 tdi golf was in the shop I use and blew up. Their turbo wasn't boosting at all. They tried replacing it and that didn't work. At some point the car was running and suddenly Rev'd up. They turned the car off but it continued to run and slowly rev down then seized. The issue I'm having has been described as some what the same as what this other car was doing before the turbo quit completely.

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That sounds like a runaway engine. I'm afraid I'd leave that shop.

It sounds like the turbo they put on allowed the oil to flow through the intake so it was running on it's own oil. Not a good thing.

Thats what my mechanic thought when he got the car. It was originally at the dealer. He figured that we may as well start fixing everything now. Boost sensor then MAF maybe even drain the intercooler to make sure there was no oil in it or intake. Sound like a good Idea?

Sounds like turbo has over heated and damaged it self. My suggestion would be to un hook your vacumme resivore hose and drive your car around hte block with that off. after words replace that line to the resivoire. work the the anti shutter vavle. because that sounds a little sticky and (check your lines for leaks too) see where you stand.

Like I said in your other thread, my car did this right before the fuel filter plugged up.

Good luck finding the gremlins.

Is your mechanic the one that "helped" the other car you were mentioning? If so, get the car away from him. If not, why start replacing stuff that is very unlikely to be a problem? MAP sensor?

If the filter hasn't been changed in a while, replace it. It could cause the low power issue, and if it's due anyway, it's not wasted money.

A MAP sensor would throw a code. If there is no code, it is wasted money (or a boat payment).

After the fuel filter, if there is still low power, have a MAF run done to see if that is likely the problem. If your mechanic doesn't have the tools to diagnose the problem, it is your money that will go towards his eduction.

MAPs are generally reliable. The only issue is when oil builds up in them and scews the readings.

Dimitri16V said:

MAPs are generally reliable. The only issue is when oil builds up in them and scews the readings.

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In which case you should get a boost deviation code, right?

My mechanic was the guy that ended up w/ the mess. The fuel filter has been changed. The MAF will be done soon. The last Mess didn't throw ANY codes. The MAF was shot as well as the MAP and the Turbo wasn't even boosting. The dealership told the people to buy a new turbo and call it good. My mechanic insisted something was wrong and started investigating the issue when it Blew. He's a Very good mechanic just got a crap deal on that one. He drove my car and thats why we're starting the gremlin hunt. I just thought it'd be a good Idea to check w/ you guys as well

1) any codes?

zacho - a mechanic can be very good but no know anything about a TDI. The prior engine went into runaway mode - which generally happens through a bad turbo seal.

You can test the MAF and MAP with the proper diagnostic equipment. If your mechanic doesn't have a computer with proper programming on it, he's making wild guesses with your money.

Good luck with this. I'd take it to someone with TDI experience myself. But it is your car.

Thanks for all the advice guys. We went through the car yesterday. Replaced the MAP ( it had some oil build up) cleaned the MAF and re-did the Strut Bearings and Mounts. Car has no more issues w/ boost as of right now.

My PD would give an "implausible co-rellation " error during start up. Cycle ignition , everything would be normal. Then the error became permanent . MAP would show around 1700 mBar instead of 1 Bar with engine off. cleaned it and all is OK BUt that's a sign it's time to clean the IC.