Technical Management light on code P0638 2009 2.3

[tidewatcher]

Management light came on after a very minor misfire that lasted seconds. Got the code read and it is the butterfly regulator, it only happpened after rain and when going over a bumpy part of the road. I fiddled about to see if anything was loose and sprayed with WD40 then started the engine few times. Next morning the light was out for a good few miles, stopped and went for a walk. When I restarted the light was on again but the motor running fine.

So in the camper van in France at the moment, tempted to drive it until either it remains the same and the engine runs fine or it gets worse and there is a definite fault to fix.

Having a bit of a dither as to how serious the problem may develop or just carry on with care. Is this a common problem?

Any experience in this problem would be appreciated.

Thanks.

 

[Anthony489]

Hi tidewatcher

As you have found, the P0638 code relates to a problem with the Throttle Body (TB) which is part of the EGR system. As far as I know, the performance of the butterfly flap in this device is not monitored directly by the ECU, but is instead implied from measurements of other sensors.

I'd suggest you undo its electrical connector and clean both halves with switch cleaner (Not ordinary WD40 unless its an emergency, then clean off afterwards). Then plug and unplug a few times. If you want to go further, remove the large air hose (one big jubilee clip) and check that the butterfly flap is not siezed closed - it should be movable with finger pressure against its spring. One proviso to this, if the TB has been replaced with a newer servomotor type there is no spring action. Oily carbon on the flap is normal. Most of the original Wahler brand TBs will have failed and been replaced by now, as they were not well sealed against moisture.

As long as the TB isn't seized closed or nearly closed you should be able to drive around without problems until you can get a permanent fix.

 

[tidewatcher]

Hi tidewatcher

As you have found, the P0638 code relates to a problem with the Throttle Body (TB) which is part of the EGR system. As far as I know, the performance of the butterfly flap in this device is not monitored directly by the ECU, but is instead implied from measurements of other sensors.

I'd suggest you undo its electrical connector and clean both halves with switch cleaner (Not ordinary WD40 unless its an emergency, then clean off afterwards). Then plug and unplug a few times. If you want to go further, remove the large air hose (one big jubilee clip) and check that the butterfly flap is not siezed closed - it should be movable with finger pressure against its spring. One proviso to this, if the TB has been replaced with a newer servomotor type there is no spring action. Oily carbon on the flap is normal. Most of the original Wahler brand TBs will have failed and been replaced by now, as they were not well sealed against moisture.

As long as the TB isn't seized closed or nearly closed you should be able to drive around without problems until you can get a permanent fix.

Many thanks for your time and knowledge. I will start with the connector and if no change try the butterfly freedom. The light did go out after a few restarts but came back on shortly afterwards after a wet and bumpy drive. At least now I have something firm to work on much appreciated.

 

[tidewatcher]

Did some wire wiggling then a good dose of WD40 around the area and light didn’t come on this morning. First start of engine after turning off with light on. Didn’t do the five or so restarts. I think it’s little electronic brain is messing with me.

 

[tidewatcher]

OK so got home although some misfiring persisted. I have removed the throttle body and the butterfly is free and springs back easily. There does not appear to be any water ingress in the actuator area. So how do I test the actuator? Also there is a serious amount of soot deposits in the throttle body and inlet manifold. I have tried to show this in the photo. Am I looking at the right area? Checked error code again when I got home after it was cleared and it was still P0638.

 

[jackwhoo]

Is your engine like that?

 

[tidewatcher]

Is your engine like that?

 

[tidewatcher]

Yes she starts normally with no noticeable tick over fluctuations. Seems to drive ok and then a sudden serious hesitation or two and the light comes on. You can then feel an unevenness. At a constant throttle position. Would like to test the actuator but feel that a replacement is the only fix. Still concerned about the soot build up which seems far too excessive.

 

[jackwhoo]

Soot build up is inevitable as it is diesel exhaust gas being ingested by engine.

 

[jackwhoo]

I have seen far far worse soot build up

 

[tidewatcher]

I have seen far far worse soot build up

Thanks for that. Back to the actuator or connectors then.

 

[tidewatcher]

Replaced throttle body with the Piedmont one as in the video using the extra converter cable. All back together but on start up the tickover is lumpy, hunting a little. Took her for a drive and very hesitant then a backfire which blew the intake pipe off the TB as the clip was not up to the job. Refitted the pipe with jubilee clips and ran the engine, againhunting on tickover but revved freely and then would tick over clean until revved again. Couldn’t re road test as out of time. So has some of the soot etc been disturbed and got to the dpf valve? When you put your hand on the electro pneumatic solenoid you can feel it clicking in and out, is this normal? Bit miffed to be honest but onwards and upwards…..

 

[Anthony489]

Hi

The solenoid valve (mounted high up in the centre above the engine) takes vacuum from the vacuum pump/brake servo supply. Inside, a diaphragm moves up and down rapidly, switching the output pipe between full vacuum and no vacuum (via a stub pipe with a foam filter). Depending on what proportion of the time it spends in each position, the average amount of vacuum on the output pipe can be smoothly varied under ECU command from nil through to full. This variable vacuum is then applied to the EGR valve to alter the amount of exhaust gas (5 to 15%) being recirculated to the inlet manifold (via a water jacketed cooler). Placing a hand on the solenoid, you should feel it vibrating at about 140 cycles per second. The control sense is: higher duty cycle = more vacuum = more recirculation, so if the pipe falls off the EGR valve it reverts to closed and no EGR takes place.

The ECU also controls the Throttle Body, and uses it to restrict "fresh" incoming air flow and lower the intake manifold pressure to encourage Exhaust Gas Recirculation to take place. From the Fiat descriptions, control of these two valves by the ECU is an open loop process with values derived from a stored map. The two main inputs to this process are the RPM and the Throttle pedal position, with some refinement from Atmospheric Pressure and Water Temperature.

EGR principally takes place during part load cruising, and it is not invoked during cold running, idle or full power conditions. It reduces combustion temperatures and thereby reduces NOx emissions. There are no other benefits, the engine does not need it to run.

Clearly, if there is a problem with any of the inputs used for EGR calculation by the ECU then it won't work properly. By the same token if there is a problem with either of the two valves it won't work properly. I guess the worst case is the EGR valve stuck partly or fully open, giving EGR when it's not needed.

 

[tidewatcher]

Thanks. I did test the egr valve with a vacuum gauge and blowing down a pipe to see if it opened and closed with or without vacuum which it did. With a finger on the control valve you can feel a slight vibration. So my thoughts are a visual check on the throttle body butterfly moving first the if that ok go for an run and see how she feels. Thanks.

 

[tidewatcher]

Did a visual check on the TB and it is opening and closing when the engine is revved perfectly. Took her for a run and drove really well now though the spritely performance may well because the “touring weight” has been removed. However the tick over is still “hunting” and uneven. If you turn the sound up on the video you can hear it. Will be changing the solenoid valve tomorrow and have also put a good dose of dpf cleaner into the fuel.

 

[tidewatcher]

And so it goes on. Changed the vacuum dpf controller, checked there was vacuum at the inlet pipe. Engine starts and ticks over perfectly for two to three minutes and then begins to hunt. It revs freely if you blip the throttle but if you gradually increase revs it chugs a bit until about 1500 then is clean. Beginning to run out of ideas though as yet have not been able to give the van a good run. Hopefully early next week I can do ten to fifteen miles up the motorway at 2500 to 3000 rpm if that sounds about right. The only thing not changed is the dpf valve but hopefully a good run and the dpf cleaner would help, that is if it IS the dpf valve. Really need to sort this as not confident to go for long trips with the van in its present state. Sorry to keep popping up like this but do appreciate the help.

 

[tidewatcher]

tidewatcher​

May 23, 2023 91 145Funster No96,162MHTimberland Destiny

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Todays update! Wondered if the new throttle body needed pairing with the management system so a googling I did go. As usual you can pick your answer, however there were a number of sensible looking posts which suggested it should be and they gave two ways of achieving it. First was the good old removed the starter battery earth strap for twenty minutes and the other was to turn on the ignition for two minutes but not start the engine a few times. Took the easy option of suggestion number two. Then started the van and maybe a slight improvement on the tickover but headed out and gave the van a fairly heavy pasting but only for about five miles as time was pressing. Some white smoke from the exhaust and the engine did get well up to temperature. The result was an improvement though not yet perfect. Very little sign of lumpy tick over, engine revved freely and pulled cleanly and well. No management light on.
Sooo…..
Hope to give her a good ten mile plus run up the motorway now it seems it will keep going, as I said not perfect but a big improvement which makes me think the fault is (was) ninety per cent EGR and ten percent confusion in the management system.
We will see. Thinking of selling the film rights as I reckon it would make a good mini series on Dave.

 

[tidewatcher]

Another bulletin on the palace gates…. Took her for a twenty mile round trip on the motorway keeping in fourth and fifth at 3000rpm or just above when traffic permitted. Slight change in that when the lumpy tickover starts a quick throttle blip seems to cure it for a while. If the engine is on idle and the lumpy tickover starts if you open the throttle very slowly the lumpiness gets worse until about 1500 rpm then clears. It’s very hard to tell if it is the low revs or the throttle position causing it, I think I favour throttle opening position as you could just feel a unevenness in higher gears and that sort of rev range or a shade higher. Booked for a more sophisticated obd read out on Friday to see what’s there though the management light never came on.

 

[jackwhoo]

Good you are taking it for further diagnosis. Don't rely just on computer diagnosis. Often injectors or other things cause problems without always causing fault codes.

 

[tidewatcher]

Ok so here is the latest. Took the van in to a local repairer used to camper vans. It seems the turbo waste gate is seized partly shut. Consensus is it’s ok to drive in a moderate fashion as essential use needed over Xmas. Booked in for after Xmas…. Any thoughts?