seatkid Posted September 4, 2005 Report Posted September 4, 2005 GSMGUY, before you change the TMAP sensor, try this, the pipe that goes to the Boost Control Solenoid that vents to atmosphere (via a mini air filter) - remove it and try without, why? I rememeber reading somewhere that if this gets blocked or restricted when the ECU tries to reduce boost, it can't because the vacuum doesnt reduce fast enough. Hence an overpressure fault... Good luck! D.McB Its very rare to get a faulty Turbo , sometimes the wastegate/vane actuator sticks but by no means a common fault. Give the above a try. Quote
GSMGuy Posted September 4, 2005 Report Posted September 4, 2005 DMcB, it isn't the boost pressure control valve.. Nor the MAF, and by the sound of it not the accelerator pedal either.. I am thinking more and more that it's the T-MAP sensor, Seatkid, what do you reckon if I join together the VAC and OUT lines of the boost pressure control valve??? Thereby removing it's influence on the vacuum?? I think my turbo is fine as it boosts ok, just something somewhere is calling a halt to the process, and (apparently) opening the boost control valve... Another idea I have is wiring a 12v led to the connector on the boost control valve (correct polarity of course) and then seeing if it is energised or de-energised at the point of the problem happening - may give a bit more in the way of tracking it down.. I really do think T-MAP at the mo though... Will give tour other suggestion a go too...Does anyone know if the boost control valve operates on a variable voltagepulses or is just on/off? Mike Quote
seatkid Posted September 4, 2005 Report Posted September 4, 2005 It's controlled by pulses varying the opening.(PWM I think) what do you reckon if I join together the VAC and OUT lines of the boost pressure control valve??? Thereby removing it's influence on the vacuum?? I think you might very well blow the turbo as it will overblow uncontrollably.:) Just try it with the ATM pipe disconnected....trust me..... I think the scenario is, as you accelerate, the ECU calls for boost pressure (TMAP reports too little) and it opens the Boost Control Solenoid and vacuum is directed to the turbo vane actuator. As boost reaches correct value (from TMAP) the ECU backs off the Boost Control Solenoid and Vacuum should be released to Atmosphere, backing off the actuator and reducing the boost - all in closed loop. BUT if the ATM side pipework is constricted (mini air filter dirty or pipe collapses internally) then the vacuum is released too slowly and the turbo has by this time overshot its target pressure. So closed loop control is lost and a fault is flagged. (TMAP - positive deviation) I remember reading somewhere in the dark distant past that this is a common problem and dealers solution is just remove the pipe to fix it! Quote
GSMGuy Posted September 4, 2005 Report Posted September 4, 2005 Right - after a good knuckle scraping, in the rain and the dark... Torch in hand... Just pulled off the pipe and went for a spin... Did about 6 miles on normal roads, giving it some clog once warmed up - seemed as good as it was before the fault.... Got to the motorway and hoofed it up the slip road .... Still going well... Got to about 95'ish (haven't been able to do that for a while) and .... Yep, loss of boost... Killed the ign at the roundabout, and all back again, gave it some on the way back, but no loss of boost, mind you only got upto about 60, although it would redline in 3rd, and hit 4k in 4th easily when held in Tip mode.. So... Much better, but still not 100%.. Anyone else care to give it a go and comment? Mike Quote
Guest vr6galaxy Posted September 4, 2005 Report Posted September 4, 2005 You have a chip! any chance its gone U/S and is causeing problems? how easy to remove it? if its a two minute job try it and see? Quote
GSMGuy Posted September 4, 2005 Report Posted September 4, 2005 Defo not the chip - has been off and on about 6 times in the past few months - ie each time it's been to a garaga... Still get same problem, but takes longer to get there!! Mike Quote
seatkid Posted September 4, 2005 Report Posted September 4, 2005 Maybe you need to reset the ECU, disconnect the battery, get it to recalibrate everything. Examine the ATM pipe, if its gone soft (from engine heat etc) then likely a lot more have as well. Quote
GSMGuy Posted September 4, 2005 Report Posted September 4, 2005 Hmm.. Will reset the ECU tomorrow and clear the faults.. VAG-COM to the rescue lol.... Will try it out later on, but it will be 10pm before I am home tomorrow... Mike Quote
Guest D.McB Posted September 5, 2005 Report Posted September 5, 2005 GSMGUY; will try T MAP sensor but where is it located? is it the sensor on the top of the inlet manifold, although I thought that was the EGR?I have spoken to another ex seat mechanic who reckons most likely carboned up vanes and waste gate actuator in turbo which can be cleaned out? what do you think? Quote
tim-spam Posted September 5, 2005 Report Posted September 5, 2005 Although a bit out of sequence on this thread, an update on the general hesitation and flat spot problems between 2000 and 3000 rpm on my 115 TDI. I checked all vacuum hoses and all was OK, checked the turbo boost pressure with a manometer, and that seemed OK. As I said before, so long as the accelerator pedal was moving, there was reasonable acceleration.Anyway, the new MAF arrived from GSF on Saturday and this has fixed all of the problems - goes better than ever now.It appears that the later engines rely much more on the MAF for the fuel mapping than earler ones. Some people have reported that disconnecting their faulty MAF on earler engines improved performance, confirming the diagnosis of MAF problems. Disconnecting mine resulted in performance so feeble that for it to be any worse with the MAF reconnected, it would have required a yellow flashing light to be road legal. In other words, just because the performance may be worse with the MAF disconnected does not rule out the MAF as the cause of poor performance.I'm also hoping that the fuel economy will return to 40+ MPG - over the last couple of months it has steadily dropped from around 41 MPG to 36 MPG (pretty much in line with the drop in performance). Quote
Guest edthedead Posted September 5, 2005 Report Posted September 5, 2005 Ed, was the boost pressure sensor (T-MAP) in the manifold pipe near the battery changed, or the boost pressure control valve/solenoid (behind the engive on the bulkhead) I am pretty certain that the former is causing my problems too... How much did you pay (if that's what you changed) Mike I think it was the boost presure control valve thingy... the garage i used charged about Quote
dave_m Posted September 5, 2005 Report Posted September 5, 2005 Hurrah, I have found what is causing the intermittent loss of boost on my galaxy. See photo's to make sense of my descriptions.... I followed the several vacuum pipes that are connected to various control aspects of the Turbo and one in particular goes into a Plastic Black ball shape on the front of the engine and is connected to this via what looked like a rubber bung.This is the Vacuum Reservoir according to my TIS disk. I think this pipe may head for the boost control Solenoid but i'm not 100% Upon further inspection this was found to be a very loose fit and seemed to be a funny shape like it had split/separated from the bottom of the hole it was connected into. In fact it could even be that the connection on this vacuum reservoir is broken and the rubber bung is someones attempted bodge at a repair as it does just look like a bigger bit of hose around the smaller piece. I tried driving the car with this completely disconnected and had no turbo boost at all so i tried putting a bit of insulation tape round the rubber plug to seal it in the hole with a much tighter airtight seal. Took it for a test drive and it had loads of power like it used to been about 60 miles and car is fine whereas before it use to be ignition on and off every few minutes to clear the problem. it may not be the same problem on all of your cars but certainly worth checking as Ford did not find it on my car, I may try and get back my money from them for the failed diagnostics as i feel they should have checked for and spotted a vacuum leak before they changed the solenoid/maf etc. See these photo's for a clearer picture of what was wrong. and thanks to everyone on here who has offered help and advice to me on this <_< <_< <_< http://www.icstele.com/galaxy/DSCF0387.JPGhttp://www.icstele.com/galaxy/DSCF0390.JPGhttp://www.icstele.com/galaxy/DSCF0391.JPGhttp://www.icstele.com/galaxy/DSCF0393.JPGhttp://www.icstele.com/galaxy/DSCF0394.JPG Quote
GSMGuy Posted September 5, 2005 Report Posted September 5, 2005 Well I always wondered what that black thing was... Looks like I'll be finishing work early tomorrow to investigate... Will ley ya all know, and cheers for the info!!Mike Quote
howardjprice Posted September 10, 2005 Report Posted September 10, 2005 I have a manual '99 TDi 110 that has a 3rd/4th/5th gear flat spot starting at 2750-3000 rpm (revs through it in 1st and 2nd but VERY noticeable in 3rd, particualrly when going up hill). Up to this rev range everything is normal. Been living with this for ~2 years after drawing a blank when it was checked out by a so-called diesel specialist who fitted a new MAF (to no effect). Ford garage put it on WDS (whatever that is) yesterday and found no faults (and made no charge - but I am a regular customer). Reading the posts sounds like the TMAP is probably favourite but would that not show on the diagnostics? Fuel economy is better than ever and I get no visible particulates when accelerating as hard as it will go. This makes me think it is under-fuelling because the turbo pressure is not being measured correctly. Any views? Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.