RPM Instability

[poropode]

Some days ago I discovered with pleasure that the best forum for Peugeot 406 is located in UK. My car, an old 406 Break 16 valves (Id : e2*93/81*0026*02VF38ELFYE80248216), equipped with a petrol engine LFY (I suppose named also XUTJP4/L3), has a problem difficult to solve, and so I ask your help, if possible. I am Italian, sorry for my bad English.
About 2 years ago, I noted occasionally some rpm drops in condition of stand by, in lowest gear conditions (900 rpm), some times followed by engine dead. Also some times an instability occurred in the form of a very slow variation of rpm in lowest gear conditions, from 800 to 1800 rpm, and vice versa. Then the engine returns to 900 rpm by itself. This particular behaviour occurred initially always far from machine-shops.
The local Peugeot assistance centre suggested me to make a complete check-up, with all provided settings and regulations: I did this, I paid, but after some time the problem came out again, exactly as before. It was not possible to demonstrate it, for the previous reason.
I tried to solve the problem with other good shop foremen: all they said to have worked around the butterfly valve that regulates the air flow to the cylinders, actioned by an electric engine; particularly they polished something in the electric engine zone, around a potentiometer that detects the valve position. In a third phase they said to have changed some sensors (temperature, phase, …), but the only result was that NOW the problem has become stable, and this is not what I hoped. A good shop foreman, far from my city, suggested me to change all the butterfly-body (in Italian: corpo farfallato), but the price for a new one is very high. I think to have already spent too much money for not solving works. Perhaps it is better to change the car.

[mjb]

Hi poropode. Our first Italian member I believe - welcome!

It is a little difficult to understand your English so I'll try to translate for people

406oc.co.uk rocks. Got a 1.8 16v XU7JP4. Bad at English, but willing to try (mjb: a lot more than can be said for some on here...)

Intermittent hunting idle (does 'lowest gear' mean 'idle' in this context'?) and occasional stalling which never showed itself when taken anywhere near a garage.

The local dealer said a service would fix it (mjb: yeah right. nice to see they're ripoff merchants in other parts of the world too!)

Other garages have said it's the idle control valve/solenoid or the throttle pot. One garage cleaning something has caused something to be stable and whatever the remaining problem is, a garage has suggested replacing the whole throttle body

The unstable idle can likely be fixed by cleaning or replacing the idle control valve / solenoid, but it sounds like that may have already been done and worked?

You say the problem has become stable. Do you mean that the problem that remains is that it sometimes stalls ("engine dead")? If so I suggest changing the throttle position sensor if it idles well now. I'm sure others on here can explain things better than me as I don't know much about this engine

[steve_earwig]

Hi Poropode, it looks like you have learned there is no phrase book for cars! I am English but I live in Croatia and I have this problem as well. When I try to say which piece of the car I refer to, many times I have to describe it as you have done, it is annoying but it usually works. It would help if I spoke German!

As mjb, I have no experience with this engine but I think the problem is probably electronic, so there is no reason to change the throttle body. It seems to be the throttle position sensor ("potentiometer that detects the valve position") or the idle bypass valve ("butterfly valve that regulates the air flow to the cylinders, actioned by an electric engine"). I am curious as, when they did work before the problem did not happen for a while, so I think maybe there is a problem with the wires for these parts.

Do not go back to Peugeot, they like to guess but they do not care as you will pay. Go to a Bosch service agent!

(Paging Doctor James!)

[Welly]

This problem sounds a bit like James's "FAQ starting and running problems" doesn't it?

viewtopic.php?f=1&t=3489

Welcome poropode

[jameslxdt]

yup sounds like a knackerd stepper motor, click on the link in my sig or wellys link (both the same)

[poropode]

This forum is very collaborative and quick: the received answers have been useful, in particular the topic “FAQ - 406 D8 petrol (Excl. V6) running and starting problem” with very good photos and explanations: I don’t know if it will be sufficient to solve my problems, this morning surely to stress my not-Peugeot mechanic (thanks to Welton and jameslxdt). If not, I will follow the Steve’s advice (Do not go back to Peugeot,…go to a Bosch service agent!): OK Steve, it seems a splendid idea !!

Thanks to mib for help in translating my “Italo-English” into “English for people”: going through Questions and Answers I have understood that when engine’s rpm are at minimum level, with gear in neutral, this rpm condition is called “idle”, instead of “lowest gear”,or in my case “high idle”, isn’t it ?
Q.: “The unstable idle can likely be fixed by cleaning or replacing the idle control valve / solenoid, but it sounds like that may have already been done and worked?”
A.: surely cleaning process performed many times, no replacement of parts till now, except some sensors, for what I know.

Q.: “You say the problem has become stable. Do you mean that the problem that remains is that it sometimes stalls ("engine dead")?
A.: In a first phase, after the cleaning process of the electric engine / potentiometer zone, it seemed that problem was solved, but after 500-800 Km the problem came out again, in a sporadic – randomic form. In a second phase, starting from January 2008, I tried again to solve the problem, but the problem after new mechanic’s works, came out in systematic form: so my mechanic could see and touch directly the problem, that was always the same: high and oscillating idle, with rpm instabilities and rpm sudden drops that frequently cause “engine dead”, or “stalls” as mib says (the engine stops to work, it switches off abruptly).

My mechanic is now working on my 406 from Monday: he will release me the car to-morrow morning and I will trip for a 1000 Km voyage starting from to morrow night… I will see very soon the work’s results, and you after some days. Bye.

[Welly]

Well good luck my friend and have a happy voyage

[teamster1975]

Yes good luck poropode and welcome!

[poropode]

I did the 1000 Km voyage and I found again the same problem, perhaps with lesser occurrencies. The mechanic made the usual cleaning, but leaving disconnected the pipe (hose?) that brings the oil vapours to throttle, just to understand if dirty oil vapours could be the cause of malfunctions. Furthermore he changed the Lambda probe, because computer measurements of exhausted gases gave indications to do it. When the problem came out during the voyage, I tried to perform the suggested procedure to reset the stepper motor (FAQ - 406 D8 petrol (Excl. V6) running and starting problem by Jameslxdt): "now once all is together, get in the car and turn the ignition on for 30 seconds, then switch it off for another 30 seconds, repeat this 3 times, on the 4th time you turn the ignition on DONT touch the throttle, start the car and alow it to idle for another 30 seconds, now go for a drive for about 20 minutes and all should be well!". I made the assumption that the cleaning process would be till valid, and that the stepper motor, or the electronics that drives it, "could" lose some steps, giving a bad idle regulation. Surely it seemed to me to obtain some good results, but the randomic nature of this problem, leaved me many doubts. Also some doubts inside the procedure: during the first 3 times "turn the ignition on for 30 seconds": it means with engine running (idle) or simply switching on the main key-switch with engine blocked ? My mechanic says "simply switching on the key-switch with engine blocked". Is it true ? In any case I have performed both the procedures (many times), but the results leaved me the doubts above, because the malfunctions appear again, before or after. During my voyage inside mountains I noted that the malfunctions appear some times changing altitude, going for example from 1250 to 2300 meters of altitude: the mechanic said that another possibility could be a failed absolute pressure sensor, that also is involved in petrol / air regulation. If so, returning to 1250 m the malfunction would have to disappear, but this is not always true. All what happens seems to be casual, at least in big part.
Another chance could be to obtain a "pope" blessing for my 406, taking the opportunity that Mr. Joseph RATZINGER comes to Genoa, my city, on 17 of May, but this could take away the pleasure of doing a very important discovery. What you say ?

[steve_earwig]

Hello again, sorry you're still having problems.

Did your mechanic follow all the proceedures for your engine type in the "FAQ - 406 D8 petrol (Excl. V6) running and starting problem"?

Yes, when James says "turn the ignition on" he means turn the key to the second position so you see all the warning lights but not far enough to rotate the engine.

I am not sure what else could be wrong with your engine, it could be the absolute pressure sensor but I worry myself that you will change your complete engine one part at a time and still not find the problem. I think that James is your best hope because he knows these engines well. Maybe he would like to go to Italy for his vacation!

I am not sure if this will help you but I occupied myself for a year looking for a similar problem on an old Passat, engine speed random and sometimes death. I cleaned everything, tried a new computer, took apart all the wires, nothing. I was confused because there were TWO faults - two relays controlling different parts of the engine were malfunctioning! Sometimes one, sometimes the other and sometimes both.

I believe a blessing from Papa Benedetto can do no harm

[carpcatcher]

Hi Poropode and all helpers here. I have exactly the same problem on 1996 406 2.0 glx. Have changed the stepper motor and done the 3/4 ignition reset after disconnecting the wire connector block for 30 minutes. Initially cures for 200 - 300 miles and then problem reappears, normally stalling when waiting in traffic by a pub garden full of vocal locals !! Cannot offer any further advice, even though brother works for Pug dealer. Will watch with interest. Good luck

[poropode]

Hello all !
Till to 15 days ago, I acknowledged in the new "icona" of Steve Earwig my personal feeling for my 406.
But things change, sometimes: pushed by my insistence, the mechanic changed the stepper motor, and after a "manual" reset/calibration procedure (he was not totally clear on it), it seems the problem was solved.
He said me that the standard aligning procedure for stepper motor didn't work properly, for some problem in the car electronics: he doubts that the problem could come out again, in the future, and in this case it will be necessary to do the manual reset/calibration procedure again.
He says that normally, on a periodic base, the car electronics performs an automatic reset/calibration of stepper motor: so, probably it will fail.
He showed me the faulty stepper motor and how the rotation axis was very hard to rotate, while the new one could rotate very easily: so there were mechanical problems (ball bearings ?) inside stepper motor, without any doubts.
Now I made only 2-300 Km and the previous instability has been totally removed. Surely, in my opinion, the problem was inside the stepper motor.
Thanks to all people that very nicely helped me, particularly to Jameslxdt, that in only one line "sentence" really caught the problem solution "yup sounds like a knackerd stepper motor, click on the link in my sig or wellys link (both the same)".
Thanks also to Carpcatcher, even if what he says frightens me !!!! (Unluckily I couldn't obtain a "pope" blessing...)

[puggy]

Glad to hear you got it fixed poropode hope you have many trouble
free miles in it

[Welly]

Another happy customer