General New throttle body caused a new problem...

[stevendrums24]

Hi guys,


My van is a 2007 2.3 120 Ducato with 205,000 miles on the clock.
She used to run as sweet as a nut.

Last week I got the dreaded power dropping out whilst cruising down the motorway. Engine management light came on and sure enough it was the classic P0638 Throttle Actuator Control Range/Performance.

Purchased a new throttle body along with the new wiring harness and successfully fitted it.

Sure enough it fixed the error code.

However, it now idles in a very strange way in that it sounds like the engine is being starved of air then all of a sudden it gets the air back again.

I removed the intake pipe from the throttle body and sure enough the butterfly valve is closing then opening then closing then opening etc.

But sometimes it doesn't do it say after it's warmed it. Come back and start her up 10 mins later and it's back to doing this strange idle.

I've tried to figure out what it is but I'm at my wits end, plus I don't have the time at the moment to spend a good day or so looking at all the various bits.

So I figured I would ask here and see if anyone could point me in the right direction.

I've attached a few screenshots of various sensors so you can see what's going on.

I do have a YouTube video but I seems I don't have the privileges to post the link....

Any help or guidance would be greatly appreciated.




Cheers


Steve

 

[corcai]

Egr stuck open?

 

[stevendrums24]

I should have mentioned that the EGR valve is successfully blanked and has been for the past 60,000 miles.



Cheers


Steve

 

[RS3100]

Something I saved relating to P0638 from a knowledgeable guy on another forum:

"The first thing to bear in mind is that if the EGR is blanked off, neither
the throttle body or solenoid can do their job properly. Get the EGR
removed and cleaned if necessary and it should be fine. Problems with
these engines are almost never the EGR valve. The other two
components will be working very hard to balance the inlet manifold
pressure with one arm tied behind their backs. It won't end well.

In addition, after fitting a new solenoid or throttle body it is advisable
to run a procedure using a diagnostic device 'Re-learn self-learned functions' so that new items can be recognised and adjustments that have been made automatically will be reset.

You must also check the pipes to and from the solenoid to make sure
that there are no splits in them and that they are not blocked.

If after all this there is still a problem; you may have a wiring issue.
These can normally be found in the loom that supplies the injectors etc
or in a blue connector underneath the fuse box. There are other possible
locations for the fault but these are the most common."

 

[stevendrums24]

Re: New throttle body caused rough idle

Hi guys, quick update on this.

I never actually sorted this issue. It would sort of come and go but I managed to live with it for a bit.
I've now decided to fix it as it''s only going to cause another issue down the line.


I've hooked it up to MultiECUScan and carried out a few tests

Attached are the screenshots and XML files from ECU Scan.


I've carried out a leak test by hooking up a smoke machine to the air inlet and seeing if I can see any leaks. Everything looks fine.
I'm not exactly sure how to carry out a vacuum test.


If you have a look at the graph, for some reason on tickover the ECU is trying to open the EGR which seems really strange.


Has any of you guys seen this before?





Cheers


Steve

 

[Radialhead]

Hi Steve, did you ever solve this? I've got the same issues with a 2009 3.0. Water killed the original throttle body, then the new one started giving the P0638 error after a few hundred miles. It's been intermittent but now seems permanent.

 

[tidewatcher]

Have exactly the same problem after fitting the Piersburg replacement throttle body. Engine starts well and idles smoothly then after a couple of minutes it starts hunting the the butterfly is partially closing then opening. Stuck EGR? Did you get to the bottom of the problem?

 

[tidewatcher]

Same problem on 2009 2.3. Tickover smooth on start up then hunts. Butterfly open then closes to two thirds closed then opens in time with the hunting. Piersburgh throttle body fitted with the wiring link. Anyone found out the cause and remedy yet?

 

[tidewatcher]

now getting confused. When the surging tick over happens the butterfly in the throttle body goes from fully open to three quarters closed in time with the hunting occurs. Where does the signal come from? If I close the small breather at the bottom of the electro pneumatic valve just under the scuttle with my finger the tick over stabilises. So is that valve telling the egr valve to open and close? If so is it also telling the throttle body butterfly to fluctuate.

I have now changed the throttle body, the electro pneumatic valve, the maf sensor. I have run the engine at over three thousand revs for twenty miles with dpf cleaner and top grade diesel.

I still have the tick over problem and if you very slowly open the throttle then it becomes a heavier misfire until about 1500 revs. Really hitting a bit of a wall, anyone had this and/ cured this problem?

 

[Anthony489]

Hi tidewatcher. I can only give some general pointers. At idle, the air (oxygen component) needed to burn the fuel is a very small proportion of the air consumption when driving normally, so unless the throttle body closes almost completely the idle speed should be OK. A petrol engine at idle has the throttle disc barely cracked open, yet enough air still flows. The throttle body is controlled directly by the ECU.

EGR is only supposed to happen when cruising, and not under idle or full power conditions. If EGR happens at idle, the oxygen content of the recycled gas is tiny so I guess this won't help with combustion. The solenoid valve is electrically controlled by the ECU to send a variable vacuum to the EGR valve - I'm pretty sure that more vacuum acts to open the valve so it's fail safe in that no vacuum means no EGR. If you block the atmospheric port of the solenoid valve I would imagine this would increase vacuum on the EGR valve and open it up, so that's all rather odd.

The ECU does have a sensor for inlet manifold pressure (combined with one for inlet air temperature) and it may well use this as part of its EGR strategy to control inlet manifold pressure by activating the throttle body. It might be worth checking that a feasible signal is coming from this sensor.