Phaeton :: Surging When Accelerate With Moderate Gas
Nov 13, 2015
I have a 2004 v8 Phaeton and on my drive today I noticed that when I accelerate with moderate (or above) gas the car starts to surge, rev-ing up and down. If I accelerate slowly (Driving Ms. Daisy slowly) the car is fine. When I'm idle (at a stop light) the car is fine, no sputtering or any other strangeness but as soon as I try to accelerate past a small amount the car starts to surge again. Made through a 3 hour trip and the MIL light came on. The car has about 198K kilometers on it but has been very rock solid, this kind of just started happening.
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Yesterday I filled my V10 with diesel and as soon as I started the engine to leave the petrol station the car seemed to shudder.
I joined the traffic and passed it off intially as poor road surface. But as I joined a queue to enter the motorway I realised it was the engine!
It was sort of surging, or perhaps it's better explained by saying it was dropping, shuddering down from say 800 RPM to around 400 then picking back up again. I revved it to 1000 RPM and it seemed fine, but if I let it drop to idle is carried on leaping and jerking for about another 3 or 4 minutes.
I then entered the motorway and it responded fine and the problem has not come back so far.
What could it be? Missing on one cylinder? Is this going to be problem? Hope not
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Currently on a 1 week mini break, and the P has decided to play up. I have had 6 months of worry free driving before this new issue. I have posted before that the 6 speed in my P has never been the best behaved in auto, a bit slippy and jerky, at times, but also perfect shifts 60+% of the time, but I know others share this issue so not unusual - its usually ok when manually going through the gears.
Upto 110k miles now and on this journey had been about 10miles in on the motorway so fully warmed up. Had cruise on doing about 70 mph. Bascially started being very erratic and surging then dropping quite uncomfortably.
I knocked cruise off and observed that under full acceleration no issue. Under no acceleration (foot off gas) no issue. Only when keeping up with traffic, so partial gas, did the issue occur. I waiting for the next exit and pulled off, and it initially carried on even at low speeds around 30mph, then went away. Parked up. Started it up about 2 hours later fearing the worse, but had no issue since. Kicking myself as I have the laptop but forgot the VAGcom lead.
Rang my VW specialist and he said as there were no MIL lights, the only way to know whats going on is to scan the car, and if it does it again get it recovered, which will mean the end of my break. I will scan the car as soon as I get back, but concerned I could do more damage.
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The primary electric fuel pump in the fuel tank of my 2004 W12 failed last month, shortly after I had set out on a cross-Canada trip from Vancouver Island to Toronto. The whole process of diagnosing and identifying the cause of the problem, mitigating it so that I could continue the trip, and finally replacing the fuel pump was kind of complex, so, here's the write-up.
The problem presented itself as a surging of the engine - a momentary loss of power - at normal highway operating speeds. The onset was progressive, but it didn't take very long - only about 60 miles of driving - from the first little cough of the engine until total failure of the pump. The first indication was failure of the car to maintain speed (while on cruise control) when climbing hills. That progressed to failure to maintain speed on flat surfaces, and finally led to the car coasting to a stop, engine stalled, at the side of the road.
I soon learned that if I floored the accelerator pedal and held it against the floor, the car would cough and burp for a few seconds, then take off like a rocket. So, for the next 40 miles, I coaxed the car into the next city by flooring it, accelerating to about 80 MPH, then coasting until the speed dropped to 20 MPH, and flooring it once again and accelerating to 80 MPH. Fortunately, I was on a remote road with few other cars, and no police.
I checked the fuses for the two fuel pumps - fuses 34 and 35 in panel C (above the left battery), and they were both OK.
The next day, I visited a VW dealer in the Canadian Rocky Mountains, and together with the parts manager and one of the technicians, we looked at the Self-Study Guides (SSGs) for the Phaeton, and looked at wiring diagrams. Eventually, we came to a tentative conclusion that the primary electric fuel pump in the fuel tank had failed. The SSGs stated that the primary electric fuel pump (the pump on the right side of the car) operates all the time, and the secondary electric fuel pump (the pump on the left side of the car) only operates during starting and during 'periods of high demand'. That made sense to us - the car started fine, and worked OK when the accelerator pedal was held to the floor (high demand). It just didn't work worth a darn at any other time... the engine would stall, or, the car would not accelerate at all.
Here are two illustrations taken from the SSGs that describe how the fuel delivery system works. The first image is taken from the 'Phaeton Overview' SSG, which applies to all vehicles. The second image is taken from the W12 engine SSG. I kind of suspect that all the Phaetons operate in the same way, regardless of engine, because the fuel tank in all the Phaetons has the same shape - two lower lobes, which means two pumps are required.
Descriptions from the SSGs
I think that there may be an error in the description above. My experience suggests that the right hand pump (identified as G6, above) is the primary pump, and the left hand pump (identified as G23) is the one that switches on during starting and periods of high demand. Note also how the identification of G6 and G23 in the illustration above is reversed from what is shown in the illustration below. I believe that the text and illustration below is correct, and the text and illustration above is incorrect.
The 'effects of failure' in the description above would, I believe, make sense if it was the left-hand pump that failed. In my case, the right hand pump failed, and the effects of failure that I experienced were as I set them out in the beginning paragraphs of this post - quite different from the 'effects of failure' of the left hand pump that are described in the SSG above.
After coming to the tentative diagnosis that the primary electric fuel pump (the right hand pump) had failed, we checked the parts stock status in North America. There was one pump in stock, but it was in the United States, and being that it was a Thursday, the pump could not be delivered before the following Tuesday. I didn't want to spend that much time waiting for it, so, we started thinking about other possible solutions.
If we could somehow get the secondary electric fuel pump - the pump on the left side of the car that only operated during starting and heavy demand - to operate, that just might put me back on the road again. So, I removed the plastic cover from the small relay that operates the secondary pump, and wrapped a rubber band around the relay, thus keeping the relay in the closed position. A short test drive proved that this solution worked just fine, the car once again operated normally. The only "problem" was that the last 25% of the fuel in the tank would be unusable, because that fuel would be left behind in the right-hand lobe of the tank - the lobe with the defective primary fuel pump.
Electric Fuel Pump Relays
Here is an illustration from the Phaeton wiring diagrams identifying the various relays above the left battery.
Here you can see the two relays for the electric fuel pumps. They are identical part numbers.
Here you can see the relay for the secondary electric fuel pump, with a rubber band wrapped around it to keep it continually closed.
Aside from the loss of use of the last 25% of the fuel in the fuel tank, the car worked just fine with the secondary electric fuel pump running all the time. There were no problems noted even under heavy acceleration. It was, however, necessary to physically remove the rubber-banded relay from its position in the relay panel whenever the car was shut down for more than half a hour. The power to this relay comes from Terminal 30 (battery direct) - it is not switched on and off with the ignition as Terminal 15 power is. This meant that if the rubber-banded relay was left in position overnight, the left hand battery would totally discharge, because the fuel pump would operate continuously all night. I discovered this the morning after the first night...
So, for the next 8 days, I drove across Canada, removing the relay each night and replacing it each morning. I didn't bother to remove it when I stopped for meals or fuel. The rest of the 3,000 mile trip was uneventful - except once, when I let the fuel tank run down a bit too close to the 1/4 full mark, and the car began surging again because the left hand lobe of the fuel tank (with the functional secondary pump) had emptied out. That was a close call, but I managed to get to a gas station and refuel.
After arriving in Toronto, I called the parts staff at my home VW dealer and ordered a new primary electric fuel pump. I discovered that the left and right hand pumps are slightly different (the various hoses coming out of the pumps are different), and I also discovered that a pump costs about $400. The parts staff suggested I order two seals (one for each side of the tank), because I would have to remove both the right and left fuel tank covers to change the right pump. The seals were not expensive.
Here are two pictures that illustrate where the pumps sit in each lobe of the fuel tank. Note the fuel filler port on the left side of the pictures (as we know, it is on the right side of the car) for orientation.
Phaeton Fuel Tank, showing pumps
Fuel Pump Access Panels
Below is a picture that shows where the access panels to the two fuel pumps are. It's easy to get to these access panels, just remove the carpeted panel from the floor of the trunk.
Here's a close-up of the right side (primary) electric fuel pump access panel.
The instructions (from the VW Repair Manual, or the ELSA / ErWin system) for replacing the fuel pump are quite well written. The repair manual suggests that the fuel tank be drained before replacing a pump. I didn't want to drain the tank, so, I ran the fuel level down as low as I dared (remembering that 1/4 full is effectively 'empty' with a failed primary pump). That proved to be adequate.
There are a heck of a lot of steps involved in disconnecting all the hoses and loosening the various components before the pump can be removed. I strongly suggest that anyone attempting this task have a printed set of instructions before starting disassembly.
The fuel pump has quite a few hoses and connections on it, but fortunately, each connector is unique in design, thus it is not possible to hook things up the wrong way when installing the new pump. It is possible to 'lose' a hose inside the tank... for this reason, I attached a small piece of string to each hose I disconnected from the pump.
The process goes more or less like this:
1) Remove the two 404 relays, to ensure no power is sent to either fuel pump.
2) Lift the rubber cover, and remove the electrical connections from both pumps (left and right).
3) Using a special tool, lift up the three fasteners that hold the cap over top of the access panel (these are NOT threaded fasteners!)
Here is a side view of the three fasteners that hold the plastic cap in place - they are friction fit, not threaded.
4) Now you have a clear view of the access panel. It will probably be dusty and rusty, and should be vacuumed clean before proceeding, to prevent crap from falling into the fuel tank when the cap is removed. The rust is due to condensation forming on the cold metal part whenever the car is filled with cold fuel from an underground storage tank.
5) A special VW tool is used to remove the locking ring from the access panel.
6) After removing the locking ring, I buffed it up with a wire brush to remove surface corrosion.
7) The plastic access cap can now be lifted. There are two electrical connectors on each fuel pump, but three possible fittings on the plastic cap. Fortunately, the three fittings are keyed differently.
8) This is what you see inside the tank after removing the plastic cap.
9) After following all the detailed instructions for disconnecting and stowing hoses, disconnecting the fuel measurement probe from the pump housing, etc., it is possible to lift the pump out. It will be full of fuel.
10) The old and new pumps, side by side. I was very surprised at the amount of crap that was trapped in the filter screen at the bottom of the pump. The car only has 60,000 miles on it, and I have always used premium fuel in it.
11) I was also a bit surprised at the discolouration of the pump components. Below you can see the old and new pumps side by side.
12) It is necessary to get access to the opposite side (in this case, the left side) fuel pump, because hoses from each pump travel horizontally across the tank and connect to the other pump.
13) Here you can see a new hose from the right side pump connecting into a T fitting above the left side pump. It is easy to thread this hose across the top of the inside of the tank.
14) As mentioned earlier, there are three possible fittings on the base of each plastic cap, but only two connectors within the fuel tank. Everything is keyed, thus improper assembly is not possible.
Once the new pump has been installed, the hoses connected, and the fuel measuring probe reset into the side of the new pump, re-assembly of everything is quite straightforward. I replaced the rubber ring around the access panel opening on each side of the tank, and I also buffed up the locking rings using a wire brush (to remove corrosion) on each side.
It was not a pleasant job - your hands get covered in fuel, and there are some hazards associated with working on an open fuel tank with vapour escaping, but it is not a particularly difficult job. It is time-consuming, though.
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Just reporting following problem that seems to affect most VW TDI engines with DPF - I have just experienced it on my Phaeton - basically as you accelerate you get the engine fault - workshop warning with a flashing coil (glow plug heater lamp) - this is accompanied with reduced performance (no Turbo) in a protect mode, stopping and restarting the engine clears this temporarily. the MIL eventually stays on (performance unaffected until next time the dreaded engine fault appears) - It's a bit scary and if you go to the dealership, they will try to convince you that you need a new sensor and DPF and estimate a cost of 1.5k plus)
I can recommend RD garage services in Shepperton (Richard is an ex VW Phaeton and Touareg Specialist) Richard changed the sensor and performed a forced regen cleared all of the fault codes (the gearbox had even gone into a performance limiting mode due to the faulty exist pressure sensor). All is now well car back to pulling like a train and back to mid 40's mpg on a run.
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I have a question, regarding the 5.0 v10. When i accelerate from stop, it has a delay, and a slow start, something like it would start in 2nd gear, but it doesn't (it's in 1st). Is the torque somehow limited whet accelerating from a complete stop? Because while driving, the acceleration is instant, and drives normally.
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While using moderate braking just enough that only the electric motors are retarding the car if I hit a decent bump, say a pothole, I momentarily lose the brakes. We're talking a fraction of a second, but it is still noticeable.
My initial thought is that it's programmed into the car to save the drivetrain from a shock load when the tire regains proper traction, or possibly there's a concern about the tire skidding. Either way, it's a bit of a strange sensation to me and I'm wondering if it's normal.
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Was back east this past weekend seeing some family. Went out with a friend of mine, who has lent me his 2011 DSG GTI APR Stage 1(car currently has 24k miles) many times in the past and it has always performed flawlessly.
We were out the other night and the car hesitated under moderate acceleration between 3500-4500rpm in second and third gears. It almost felt as though it was bucking a little, really odd. The hesitation comes in threes or fours, then moves on in the revs.
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I've a little over 60k on my '12 Golf TDI and I think it's time to replace the brake rotors and pads (a lot of vibration and pulsing under moderate to heavy braking). I'm looking to replace front and rear rotors at the same time, but have a question about the rear rotor size:
Websites like Tirerack & Partsgeek give several options for the rear rotors - 256mm, 260mm and 272mm.
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Both my wife and I noticed that whenever we brake moderately to hard, we can hear water sloshing around. The sound is coming from the driver side underneath, like maybe from the gas tank? Is this normal? We just purchased this car last month (2007 LS 460L) and love it! This is our third LS (Ls 400, 430 and now 460). What's going on?
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My windstar has for a while been making moderate/slight jerks when stopping. It tends to happen typically just before coming to a complete stop, although sometimes it happens during low-speed turns when coasting (also sometimes have the issue where it shifts downshifts harshly after a "sweeping turn," as mentioned in one of the windstar TSBs). The RPMS don't appear to visibly drop when it occurs (although the tach in the 'stars seems a little slow sometimes). The only trouble code present is P0133 for the Bank 1 downstream O2 sensor slow response.
Also, it tends to worsen when the car is warm. The jerking is less severe when the engine is cool, and tends to worsen after the car warms up. Also it sometimes almost feels like the jerk occurs in two stages. I do not believe it is the TCC solenoid failing to disengage, due to the fact that it even happens if I get up to 15mph for a hundred feet, and then stop.
Probably unrelated, but the car also tends to run rough for 10-15 seconds after starting the first time if left sitting for a few days.
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I have started to hear a slight (but getting louder) squeal from my brakes when I am braking from moderate speeds (20 mph and under). I know that the car had new stock brakes put on it less than a year ago. What I should do about it?
Stock 1.8T 5spd 2001 discs all around.
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2011 SF. 52000kms.
A little while ago I noticed a brief vibration (felt through floor and steering) with normal acceleration from stand still... I attrributed this to the cold weather and perhaps oil thickening, as the problem went away after the car was warmed up. Since then I have noticed that it's continually happening on a regular basis, but only for a short period.. I was still thinking that it was the cold, but that wasn't the case because I left the car idle at start up for 20 minutes until well warm.
Now.. If I slowly accelerate (not putting much load on the car) there is no vibration at all. When the car reaches a certain speed, the vibration goes away. There is also no vibration after about 15 minutes of driving.
I had a neighbor test it with me to confirm and he felt it, and initially thought differential oil, but then suggested myriad other things from the CV boot to bearings to etc etc.
I need to take it to the dealership so they can experience the vibration but would certainly need to leave it there over night so they can check it out when "cold".
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2012 gti, completely stock, 21,000 miles. Perfectly smooth ride right up to 69mph, then mild/moderate vibration in the steering wheel at 70+mph... figured it was an out of balance wheel up front, had the tires rotated, but still vibrates. I suppose ALL the wheels could be out of balance, but seems unlikely?? Will have the balance checked on all wheels...
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I have a 2003 BMW 325xi wagon with mileage of 56k. In warm weather and when the car warms up, on roads with lots of alternating curves, at moderate speeds, on some right turns, the steering will offer a slight resistance and then give. On left turns, there is sometimes a slight loose feeling and a corresponding resistance when I straighten out after the curve. This intermittent problem occurs rarely in a parking lot, as if the workout on a curvy road is necessary to cause the issue. When it occurs in a parking lot, the "give" after the resistance is accompanied by an audible "thump". This noise presumably occurs all the time but is masked by the noises of the car in motion.
The dealer in my home town could not recreate the problem until the visit where I took the mechanic for a ride and the thunk noise happened once. They said the steering U joint was the problem and "Replace steering u joint and filter housing gasket and vanos oil line. Perform power steering flush".
After this work and a trip to the mountains, the problem seemed worse, with the issue spreading to left turns. I complained to my home town dealer, who offered not much more than his sympathies.
I took the car to a dealer near our mountain retreat. He said my home town dealer had not performed the power steering flush and that he recommended doing it, even though he doubted it would fix the problem. He did hear the thunk (he called a pop) when the car was on the rack, and he ruled out every issue but the power steering rack, which he says to replace. What steps can I take to ensure proper diagnosis?
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So, my 2004 with its constant tick is now "Missing", but only under moderate acceleration, between 1k and 2k rpms. i.e., : When in OD and wanting to gain a few MPH, but not drop down a gear. I have noticed it in OD and in 3rd. Feels like the engine stops for a split second, several times.
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I have a 2007 Camry SE V6. Under moderate to hard acceleration, it sounds like a deep throaty sound coming from where the intake/throttle body is located, almost as if I have a SRI, but I do not. I checked for anything loose, hoses, airbox, etc. Then checked the intake resonator below and to the left of the battery, all seemed normal. Everything seems normal! Only happens when I push the accelerator a little more than usual, for example, when I go on the highway.
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My 2010 III, not 3 or Three since it is a 2010, will brake loose the tires when wet with moderate acceleration. If i floor it it will alternate spinning right to left until I back off the throttle. I"m not really complaining since I had an 08 that would not spin a tire and could not be driven in snow. Just wondering if this is normal on a 2010.
I turned right with moderate acceleration on wet pavement today and the tyres broke loose and the car was headed for the curb. Oh the traction control light does come on when this happens but, no brake application or engine speed reduction.
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So I just had the 10k service done on my GTI and after I got it back everything seemed fine. That is, until under moderate acceleration there was a weird buzz or vibration that came on around 2800-3400rpm coming from what I think is the engine bay or near the firewall on the passenger side. I was able to repeat the issue multiple times and it showed up every time. However, with the car at a stop and in neutral and revving it I can't make the problem occur only when under load, in gear, and traveling at speed. If I could describe it, it sounds like a playing card against bicycle spokes (for those of us who did that when we were kids)..
Anyways, I drove it straight back to the dealer and at that point had closed their service shop but they did do the right thing and give me a loaner car until they can look at it on Monday. How the heck could this pop up after a 10k service? What all do they do besides oil change, tire rotation, and fluid inspection?
I did pop the hood and one of the side of the fuel rail sounded louder than the other, I suspected that maybe one injector is starting to go and it seemed like an isolated noise but perhaps its not an injector at all. Nonetheless it seems this is a non-related issue..
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I have an 04 V8 and have consistently noted a valve(?) clatter noise under moderate to hard acceleration. I mentioned it to my VW sales associate and he stated this is typical of this engine and that after warm up it should no longer occur. I hear the clatter at any time, warm or cold.
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I have a 2002 Saturn SL with about 160k miles. She's been a great car but recently she starts to oversteer when making moderate left turns over 35 mph. It always happens when the car's weight shifts to the right side. It is predictable but it still feels unsafe to drive. Unfortunately My mechanic couldn't find anything wrong with it.
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