Philwalfc Posted June 18, 2007 Report Posted June 18, 2007 Hi Guys,I got My new Maf last weekend. Just followed the instructions from this great forum, and fitted in 10 minutes. It really is great to have some acceleration again.Now, I have another small problem. When I drive along I have noticed a dead spot that wasn't there before. Has anyone else had this problem after changing a maf. Cheers. Quote
mumof4 Posted June 18, 2007 Report Posted June 18, 2007 when abouts is this dead spot..revs?speed? Quote
Philwalfc Posted June 18, 2007 Author Report Posted June 18, 2007 I will have to have a good look tomorrow and give the proper details. I have noticed it when I pull away mainly on low revs. If I floor it acceleration is excellent. Quote
seatkid Posted June 18, 2007 Report Posted June 18, 2007 Disconnect the battery (check the radio code first) for 5 minutes and reconnect thereby reset all stored MAF data. After reconnecting, the ECU will retrain in the first few miles of operation. Quote
mumof4 Posted June 19, 2007 Report Posted June 19, 2007 Do'h forgot the battery bit........turbo does take a short while to kick in anyway, around 2k revs. Quote
tim-spam Posted June 19, 2007 Report Posted June 19, 2007 (edited) Is this more of a pause or slight stumble at around 2000rpm in first or second gears? If it is, it will almost certainly be caused by the boost control system. The sequence of events is as follows:1) The turbo boost kicks in at around 1300rpm (cutting in at such a low engine speed is one of the advantages of a variable geometry turbocharger)2) As you accelerate, the boost increases until the point at which the boost control should start to back off - this is done by reducing the vacuum to the VNT mechansim on the turbo.3) Because there is a tendency for the VNT to stick slightly, it does not quite keep pace with the demand to reduce boost - this causes the ECU to reduce the vacuum to the VNT more until the point at which the VNT backs off. When this happens, it backs off quickly and a little more than it should. This is what causes the pause or stumble.4) Once the ECU senses that the boost is somewhat less than called for, it then increases the vacuum to the VNT until the boost is correct and normal acceleration resumes. All of this takes place very quickly, and, unless the VNT sticks to the point of causing a trip into limp mode due to excessive boost pressure, there is nothing to worry about. In the higher gears, the engine speed accelerates more slowly and the requested and actual boost pressures remain more closely matched. Hope this helps. Edited June 19, 2007 by tim-spam Quote
mumof4 Posted June 19, 2007 Report Posted June 19, 2007 Thanks tim-spam...its what i meant to say but im cr@p at explaining things :lol: Quote
Dave-G Posted June 19, 2007 Report Posted June 19, 2007 Thanks tim-spam...its what i meant to say but im cr@p at explaining things :lol:Â Â That sounds like such a fib Maz ^_^ Quote
mumof4 Posted June 19, 2007 Report Posted June 19, 2007 Moi????Noooooo..... :lol: ..I know how the turbo works,,but i never can explain everything properly..i mean..i know the turbo works from the exhaust thingies...and i still have all the work i did on the course i completed...but what i want to say, and how i end up saying it are two completely diff things when it comes to technical things.LOL..so i keep it simple. Quote
Philwalfc Posted June 19, 2007 Author Report Posted June 19, 2007 Just got back in. Thanks for all the replies. It stutters at between 1500 and 2500 revs in first and second gear. Thanks Seatkid, I will dis-connect battery like you suggested and see if this sorts it out. I'll let you know if this sorts the problem out. If that fails, thanks for the explanation Tim-spam. Quote
corskey Posted June 19, 2007 Report Posted June 19, 2007 Hi all, sounds a little like my problem (2001 TDI, 115): 1. I replaced the MAF about 6 months ago, performance was better, but I don't think that the MAF was totally knackered.2. Occassionally, especially when under load, eg accelerating up a hill I loose my pulling power and get quite excited when I reach 30.3. I can cure the problem by switching the ignition off and on again, though I don't like doing this uphill. the battery has been dis-connected so I think that the memory has been reset. ???????????????????????????????? any ideas ???????????????????????????????? Corskey Quote
Philwalfc Posted June 20, 2007 Author Report Posted June 20, 2007 My engine is a 1.9 tdi 110 bhp Quote
tim-spam Posted June 20, 2007 Report Posted June 20, 2007 any ideasDefinitely a sticking VNT causing a positive deviation of the boost pressure and the ECU to trip into limp mode. This can be reset by keying off and on again. If you do a search, you will find plenty of information on how to diagnose and fix. By the way, the dealers usually replace the turbo at some considerable expense. Quote
Philwalfc Posted June 22, 2007 Author Report Posted June 22, 2007 Cheers Tim spam, Having read a few posts about the Vnt sticking, it looks quite ba major stripping job. Do you think it is do-able by a Diy-er. Do you think it could be the coolant temp sensor as suggested in a few posts that is causing the stuttering. I'm just looking for easier solutions first. Quote
Ivor_E_Tower Posted June 22, 2007 Report Posted June 22, 2007 Hi all, sounds a little like my problem (snip)I loose my pulling power and get quite excited when I reach 30. I've reached 40 (and 45) and I can tell you that I have still to get truly excited ^_^ Quote
mumof4 Posted June 22, 2007 Report Posted June 22, 2007 Hi all, sounds a little like my problem (snip)I loose my pulling power and get quite excited when I reach 30. I've reached 40 (and 45) and I can tell you that I have still to get truly excited ^_^  Oh my lord.....you lads are sooooo smutty at the moment!! :( Quote
seatkid Posted June 23, 2007 Report Posted June 23, 2007 I notice Philwalfc got his MAF off "Fleabay". I'm inclined to think he got sold a recon/cleaned up/counterfeit/wrong model one. Hence the flat spot. I'm sure others here have had the same problem Quote
mumof4 Posted June 23, 2007 Report Posted June 23, 2007 i disagree SK..i bought mine off Ebay and i never had any probs with it.Mine was a brand new bosch one and the correct part. Quote
seatkid Posted June 23, 2007 Report Posted June 23, 2007 One good trader does not make them all good. Quote
mumof4 Posted June 23, 2007 Report Posted June 23, 2007 Very true...i totally agree there..and as ive always said..research before you buy so that you know what it is that you are paying for. Quote
Philwalfc Posted June 25, 2007 Author Report Posted June 25, 2007 Are you suggesting there are dodgy dealers on fleabay Seatkid. Surely not. :16: :D . Seriously though, you could well be right. It had got the same part number on it. and definiately !! looked !! brand new. Tim-spam gave a good explanation as to what might be the cause, but it sounds like a major job. Bit apprehensive stripping the turbo. A couple of questions, wouldn't the flat spot of been noticable before I changed the Maf if the VNT was sticking, also would connecting to vag- com, pick up a faulty Maf. Thanks. Quote
mumof4 Posted June 25, 2007 Report Posted June 25, 2007 if da maf was nadded then u wouldna notice ane flar spot....as the car wood b flat as a fart! Quote
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