Here’s a video of what is happening now. I’m just touching the accelerator slightly. The car is revving itself then cutting out or carrying on hunting.
2005 TD4 Starts But Won't Rev!
- Thread starter Bont Boy
- Start date
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Here’s a video of what is happening now. I’m just touching the accelerator slightly. The car is revving itself then cutting out or carrying on hunting.
andyfreelandy
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Glad you got it. Keep an open mind though. If fault returns it could still be wiring or connector. Remember that it all started when you changed the starter which is right in that zone!!
comeinhandy
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On my car that wouldn't rev, it was just the position of the crank sensor that was the problem. The o ring wasn’t pushed into the recess so the sensor wasn’t flat against the block, so it couldn’t pick up higher frequency signals.
andyfreelandy
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I beleive mine was the same problem but couldn'tbe arsed to refit old and test it. O ring was trapped and squashed though. If the sensor is not fully home it won't work properly. Looks like we may have another stock fault for revs failing to increase when all else looks o.k. Can B Boy confirm that his suspect sensor was fully seated correctly or not??
I can’t be 100% certain either way sorry. I did fit the first crank sensor in a bit of a rush though so it’s quite possible that it wasn’t fitted correctly.
comeinhandy
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It is a bit of a bug*er to get the o ring in. I had to swap what was in there for a narrower one as no way was it going in. Might stick it on YouTube when I have time.
The car idles perfectly now with the Bosch reconditioned injectors and second hand crank sensor. However, it is misfiring and smoking at about 2,200 rpm. I’m wondering whether the crank position sensor is again faulty or not quite seated correctly. The strange thing is that I had a similar problem before taking this set of injectors out. I replaced them with a second hand set and all was fine until my recent starting problem. They have been professionally rebuilt and tested so should be as new.
Bont Boy.
GrumpyGel
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I think misfire and smoke at about 2K revs on TD4 is very common. There's lots on here about it - not sure there are any fixes, I think a lot of people just live with it.
I haven't read back, do you still have an EGR installed or has it been deleted?
comeinhandy
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I’ve been working through checking everything on my td4, to fix the white smoke at 2000-2500 rpm, that does indeed seem quite common going by reports. (First the video on the crank sensor I got around to, combined with glow plug testing: I found that the crank sensor has to sit with it’s metal body flush against the engine block. If it’s not then the o-ring hasn’t gone in enough.)
I checked and did my best at cleaning the injectors ( ) Not a professional test, more DIY, but they seemed OK. No smoke at idle or at over 3000 rpm. The fuel pressure was ok, so next suspect was the amount of air getting in.
I could actually remove the white smoke by manually activating the turbo control solenoid. Supply 12v to it = no smoke. Leave it connected to ECU = smoke at 2000-2500 rpm in neutral. 12v direct to the solenoid makes the turbo actuator move a bit more and make the turbo vanes a bit more forceful to increase the air pressure, getting more air in.
I have stripped and checked the turbo solenoid and measured the vacuum line at over 30 inHg so I think that is Ok.
I thought maybe the MAP sensor had gone wrong (so the ECU then drives the turbo solenoid incorrectly) but a new one made no difference and measuring it’s output voltage versus manifold pressure showed that it seemed to be giving about the right readings. I also pressure tested the turbo hoses, intercooler and manifold for air leaks, which were ok.
Also tried different MAF sensors, Bosch and Pierburg with synergy2 on various settings, which made no difference.
So the only solution now left is to make an independent turbo boost controller. Which I’ll knock up shortly using an off the shelf comparator board (cheap). If the solenoid is permanently at 12v then the danger is that you could get too much boost and blow the engine, hence the need for a safety cut out circuit. My plan is to turn the solenoid off when the MAP voltage gets over a set limit (so limiting boost pressure) and optionally also turn it off at idle. The rest of the time it will be on max boost with 12v on the solenoid. That will fix the smoke and should also give more power.
As to why it smokes when the ECU controls the turbo the only theory that I am left with is that the engine ports and valves are perhaps gunked up with carbon to a degree (which I know they are a bit, I’ve done all I can cleaning manifold and intercooler) such that the air flow is less than it should be. Forcing more air in by cranking up the turbo maybe compensates for this. The ECU should only inject the right amount of diesel to match the air flow measured by the MAF. Maybe it just doesn’t measure it accurately enough.
guineafowl21
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Just my two pence worth, but Td4 lumpiness and smoke at 2000 rpm is a commonly reported thing on here. But it’s usually mentioned when another problem is being fixed or investigated. Why? Maybe because if your car’s running OK you don’t sit on your driveway revving it in neutral. Maybe all Td4’s do it.
The Td4 ECU takes in all sorts of inputs - clutch, brake, gear, G, engine load... - in working out when to actuate the variable vanes. Perhaps it decides not to actuate them if the car isn’t being driven, leading to a glitch at that engine speed.
@comeinhandy my question is, does your Td4 misbehave at 2000 rpm under load? And is the turbo actuated any sooner?
comeinhandy
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You could be right. It would be interesting to do a survey of ‘good’ td4’s and see if they smoke or not. I’ll report back on mine when I get it MOT’d so I can drive it. It’s a bit of a previously neglected project car so I few more things to fix yet. The turbo is given some activation by the ECU as it’s a lot worse if the solenoid is just disconnected, but giving it more activation cut’s out the smoke. I would like it having no smoke for the MOT now that they are getting stricter. I’m guessing that they weren’t smokey like this when brand new as I’m sure the factory tests would have spotted this. It’s not that satisfactory an end solution having to build your own controller, but I’ve run out of things to check now, apart from taking off the head and cleaning everything. Also I’ve not done a compression test which might be an issue but hard to believe it would cause this.
guineafowl21
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Sounds like the turbo vane solenoid is PWM controlled. Could it be, given the turbo’s position, that the vane actuator mechanism gets a little sticky with age? Or how about the vacuum getting weaker?
Edit: can you scope the solenoid signal?
comeinhandy
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Yep the solenoid is normally PWM from the ECU. The actuator moves all the way in or out when I manually control the voltage to the solenoid, with no sticking of the actuator. The vacuum I tested at over 30inHg vacuum which I think is enough. It is as if the ECU can’t or chooses not to drive the solenoid enough. When I manually drive it more to give a bit more actuator movement the smoke disappears I’ll scope the ECU signal later to see if that reveals anything.
guineafowl21
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So you might need a solenoid bias circuit?
comeinhandy
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I may be able to boost the ECU signal (or maybe remove some wiring resistance) as an alternative. If the solenoid has a constant bias it won’t turn off completely.
EGR has been deleted.
