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Discussion Starter #1 (Edited)
V6 Lag II hesitation

Took the car into a independant diagnostics center, to try and rectify this long term hesitation problem, got fed up with keep taking it to the local Renault dealer for them to tell me we can't find anything wrong, no fault code's etc.

Anyway picked it up on friday, they told me the car was fixed,they had removed the throttle body and stripped it compleatly cleaned all the internal electical circuitry, it did seem to drive slightly better at first, seems to have cured an initial flat spot, but after trying it over the weekend the hesitation is still there.

Regarding the hesitation running of the car at light throttle I had just backed the car into the garage i sat there with the car ticking over just fine at about 650 rpm (which renault say's is about right for the V6, i thought it was a bit low) and slowly increased the revs at about 1100 to 1500 the revs seem to drop off i cant keep it steady the revs fluctuate
and the running is lumpy once past the 1800 mark its fine again, it does this if the car is hot or cold, worse when cold, when driving the car on light throttle the car is holding back hesitating feels like you are on an uneven road surface and its in this rev range that it does this (1100 to 1800).
I have found that disconnecting the air temp sensor cures the hesitation, but that brings on another prob, the engine starts to knock.
Renault have told me this is a normal charictoristic of the car it is trying to shut fuel off as you are on light or no throttle :confused: the diagnostic center are telling me much the same, the chap at the diagnostic place said, when you sit in the car with it in neutral and rev it between 1100 and 1800 the ecu is sensing this is not normal and trying to shut the fuel off as there is no load no forward motion, as for disconnecting the air temp sensor you are just fooling the ecu into thinking the outside air is a lot colder than it is and richens the fuel air mixture, the knocking is happening because its altering the ignition timing, he told me they have many modern cars in with simular probs , BMW Vauxhall etc, remapping the ecu can cure it.
This place is a superchip place but no prog exists for the Lag II V6.

I can't belive a modern engine should act this way and I think it is a fault,
I have asked Vass who drive's a V6 lag II who told me his car drive's fine and the rev's don't fluctuate when trying to hold them between 1100 and 1800.
So if anyone can shed some light on what the prob may be, or if other V6 owners could let me know how their cars are
that would give me some ammo for the diagnostic center & Renault
Thanks
Polecat
 

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I think I read about a similar thing on an Avantime forum - I shall look it up for you.

Is it obvious when you gradually build up the revs (whilst in neutral) from 1 - 2k? I'll try on mine on my way home.

Hugh
 

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Discussion Starter #5
Thanks for the reply Hugh
Yes it is very obvious, trying to hold the rev's anywhere between 1 and 2k (while in neutral) the engine rev's start to surge/hunt and the engine become's lumpy like a missfire, the rev's drop about a 150 to 200 and back up again, the lumpyness and surging seem worse about 1200 to 1400, past 2k and it seems ok.
Ive noticed from cold when traveling about 30mph and you lift off the gas sometimes the revs will drop right down to 650 the bounce back up again a few times like a flipper on a pinball machine, I'm not quite sure but I think it may be a normal operation of the gearbox for it to go into freewheel mode when you lift off the gas (hot or cold), but the revs should'nt bounce like this.

Work done by Renault main dealer
Replaced all six coils
Reprogrammed fuel injection computer
Reprogrammed gearbox computer
Replaced piston seal in gearbox

I have replaced all six sparkplugs
Added a double dose of injector cleaner
Cleaned throttle body choke plate

Diagnostic center has
checked for vacuum leaks, they said they spray some sort of flammable gas/mist around all the seals and gaskets and when this gets sucked in the engine revs increase, but all was ok.
Removed throttle body cleaned electrical connections and internals of throttle body motor
Checked throttle pedal potentiometer.
They seemed to think cleaning the throttle body connections did the trick, but they were wrong:( .

I have been thinking about the ecu, the coils going could have spiked it and the car had to be jumped started a few times after the battery started to fail.
 

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I had a play tronight - difficult to say as I wasn't sure the exact way to make it happen. Further to your post #i have a much better idea.

I would also point out that the rev counter is a digital bar - 1 blob per 250rpm so I need to do it more by ear if you get my drift! Shall report back!

Hugh
 

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will have a look at mine also. i`m not happy with mine at time when i start the car up hot or cold it sound lumpy as if one of the cylinders in tapping but as soon as i tap the gas it goes away not to be heard again. it is also at time poor when i put my foot down at mid range the car seems to stop your body moves forward and then it kicks in , i have had it checked and it is saying no fault codes now or in the history..but the knocking on start up wides me up..its as if it too low revs for all the cylinders to function untill the gas is pressed. but will check the idle out tomo and report back/
 

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I had a play last night - there wasn't too much fluctuation on the revs. There were more when cold as you'd expect.
 

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Discussion Starter #9
will have a look at mine also. i`m not happy with mine at time when i start the car up hot or cold it sound lumpy as if one of the cylinders in tapping but as soon as i tap the gas it goes away not to be heard again. it is also at time poor when i put my foot down at mid range the car seems to stop your body moves forward and then it kicks in , i have had it checked and it is saying no fault codes now or in the history..but the knocking on start up wides me up..its as if it too low revs for all the cylinders to function untill the gas is pressed. but will check the idle out tomo and report back/
Yes the knocking/tapping bugs me, I seem to get it now from cold sometimes but blipping the throttle takes the knocking/tapping off, before I had only noticed it when I had disconnected the air temp sensor and no amount of blipping the throttle would take it off.
 

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Discussion Starter #10 (Edited)
Still trying to rectify this problem, I got the car back about a week ago after the diagnostic center had removed the ECU and sent it for testing the report came back no fault found.

The chap at the diagnostic center said we could replace the MAP sensor as a start, or it may be something we have missed.
I have checked the coolant temp sensor the voltage and the resistance rise and fall ok with the changing temp, the MAP sensor voltage fluctuates when the engine is surging and you can see the throttle plate on the throttle body opening and closing in time with the surging, I have removed the engine rebreather hoses cleaned them and checked for splits etc plus all other hoses connected to the manifold or throttle body, I have checked around the inlet manifold with an unlit propane torch for vac leaks, most of this and more I assume would have been done at the diag center.

A vacuum leak or a faulty MAP is suspected

But my ? is this

If it is a faulty MAP shouldn't the surging stop if i dissconnect the MAP as it has no affect when disconnected
only disconnecting the air temp sensor cures the surging.

If it is a vacuum leak shouldn't the idle speed be higher ?, this is not the case, it is lower if anything it's about 600 to 625 rpm and slightly fluctuating.
 

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Discussion Starter #12
I have recently done an oil & filter change and replaced the front bank spark plugs, no change
I have noticed since the oil change the rattle/knocking comes back quicker, I normaly had to leave the car over night before the rattle would happen, but now its back after the car is left for 3-4 hours, so the new oil is draining out of the dephasers faster me thinks.
I found this on a jaguar forum

97xk8 4 liter - On cold startup, I have a noise at the top front of the engine in each cam. It is a knocking kind of sound. If I rev. the engine to 1,500 rpm, there is a quick grinding kind of noise and then all noises disappear. It is not the secondary tensioners as I have had them replaced.

The dealer advised me that it is in the V V T mechanism and is caused by the oil leaking out of the V V T sealer rings overnight. As soon as the engine is revved to 1,500 rpm's, oil flows back into the mechanism and the sound stops. It does not happen when the engine is warm and is stopped and restarted, only when the engine is cold.

The dealer says that it will cost approx. $800 to install new sealer rings in both sides of the cam.
97xk8 4 liter - On cold startup, I have a noise at the top front of the engine in each cam. It is a knocking kind of sound. If I rev. the engine to 1,500 rpm, there is a quick grinding kind of noise and then all noises disappear. It is not the secondary tensioners as I have had them replaced.

Very similar eh
I think it could be a dephaser prob.
quoting this from dialogys

The camshaft dephasers are located on the inlet camshaft there function is to modify the timing adjustment.
They are controlled (all or nothing by the injection computer via two solenoid valves located on the cylinder head cover.
These allow oil to flow through to control the dephasers
If the coolant temp is above - 40c
If the air temp is above - 30c
After a period of 2 seconds after the engine has started
Engine speed between 1500 & 4500 rpm
If there is no injection fault.

So I am guessing disconnecting the air temp sensor is fooling the ECU into thinking the air temp is below - 30c so the dephaser solenoids do not operate, I have checked with a multimeter and they don't, but with the air temp sensor disconnected the ECU would richen the fuel thinking the air temp is low, but I guess the lambda sensors would cut it back again.
Tried disconnecting both dephaser solenoids but after a few miles of driving it the MIL came on and anounced anti pollution monitor faulty.

Ok so disconnecting the air temp sensor before starting the car from cold the knocking cannot be removed no matter how many times you rev the engine because the dephaser solenoids will not function with the air temp sensor disconnected, reconnect the ATS and blip the throttle and there is a click and the rattle/knocking stops, I guess oil must be filling the vvt mech, but according to dialogys the dephasers should cut in at 1500 and out at 4500, mine cuts in at 1000 which is wrong,(it cuts out ok at 4500) maybe this is screwing the timing up causing the hesitation and lurching at low speed, cant think why its cutting in at 1000 rpm though, its the ecu that controls the vvt via input from map sensor, coolant sensor, speed sensor, oil temp sensor unless I have missed something and a sensor is out of range.

I think I will email Renault again see if I can speak to Renault technical.
I think I have spent far to much time and money on this vehicle and this is my last attempt to get it fixed so if mister Reno cant or wont do it the [email protected]@kin thing is going and I will prob get a Volvo S40 S60 or S80.

Sorry for the long post guy's just thought I would keep you up to date.
 

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A very interesting post Polecat,and one that shows that diagnostics is not as straight foward as plugging in a computer!.

I hope you do get a decent response from Renault as your hard work deserves some recognition.:)
 

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Discussion Starter #14
Well the local Renault dealer have spent hours of diagnostics on it, and three other independant diagnostic centers have tried, all of which don't seem to want to go much further than connecting their OBD equip and doing a few basic checks, then advise me to throw this part and that part at it, not cheap I can tell you :steam:
No codes and they seem to be stumped

So its left down to me and the help I have had from this and one or two other forums to diagnose the prob, plus countless hours trawling the internet, oh and dialogys has been a good help.
I may be still off target here but I can do no more, I have not got the equipment or the knowledge to tackle this any further, most of my tools date back to the seventies :)
 

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top man! love your persistance! your pretty much 100% on all your thinking and logic intresting that you had access to dialogy's and that you understood it! i know lots of Renault tech's that dont! only thing really i'd add is that if you have an issue with oil pressure through the system or wrong grade of oil this will cause the dephaser to opperate incorectly also if the dephaser solonoid valves arent working correctly you will also have the same faults! the v6 engines ran a spacific oil which I thing was a 0w50 fully synthetic oil! also if the front plugs have been replaced and not the rear the lambda sensor and knock sensor will notice a different mixture and ignition burn which will cause the ecu to make adjustments which could weaken the mixture to the rear bank and you may end up with a surging of the engine where it is richening and leaning off! not sure technical will contact you as the only deal with rte's and that's only usualy via email system (cir) which is monitored by the big brother in france! I will look into this futher for you though and see if I can come up with anything else!
 

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Discussion Starter #16 (Edited)
Thanks guy's
The rear back plugs were replaced a few months back while I had the inlet manifold off for the dreaded coil probs, the car had only done 47k but I thought what the heck may aswell replace them while the manifold is off, so the plugs have prob only done 4k, but at 16 squid each, me being a tight git just got three ;) , and just swapped the plugs around at the front,I got the other three from eurocarparts 6 squid each ( same plugs as the one from Renault) so you could say it has six new plugs and coils now.
As for the oil it is 5w40 fully synth, which according to the service book is fine, maybe there is an issue with the oil pressure I will have to check this.

The last diag center said I should replace the coils again :crazy:
I said I can't see that curing it as disconnecting the ATS would not instantly cure a faulty coil.
I had narrowed it down to three poss faults top of the list as it stands is the
VVT mech,
Air induction leak but all tests to find it failed plus emissions are fine, and the idle speed ok at 650 just rising and falling by10-20rpm every now and then,
partly clogged injector or injectors, but the car pulls fine on load, I would have thought if it were an injector prob it would be noticable through the rev range not just between 1000 and 1800 off load.
 

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Discussion Starter #17
Thanks bigshow any help would be appreciated :)

As for the dephaser valves being faulty I removed them some time ago and checked the on a
12 volt supply, as dialogys states these are all or nothing eg fully open or fully closed, and they were operating fine , as I can only hear the rattle on the rear bank I swapped the valves round but it made no differance the rattle still persists on the rear bank.
 

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Discussion Starter #18
Update
Over the past few months after contacting Renault uk, one of their senior chaps has been helping, this is the reply to the email I sent with information & the Renault forum threads
----------------------------------------------------------------------------

Thankyou for your recent email to Mick Moore, Director, Customer Management.

I have discussed your email and forum threads in detail with our technical manager here at Renault UK. I would like to discuss this matter with you in more detail to try and resolve the issue you have highlighted on your Laguna.

Please email me with your phone number and I will contact you direct, alternatively you can call me on 08000 72 33 72.

I look forward to hearing from you so we can discuss diagnosis further.

Kind regards

Peter
Senior Customer Relations Manager
----------------------------------------------------------------------------
In the meantime I had been speaking to the RTE at sunwin & we agreed that the rattle was caused by a defective dephaser pully on the rear bank, but he said if we change it I can't guarantee it will cure your hesitation, so I thought long and hard about it and took the plunge, as it has an after market warranty on it so it shouldn't be too costly.

To do the job the cambelt has to come off so I had this renewed with the kit and aux belt aswell, I would have been a fool not to as I only paid for parts (not dephaser parts) still well over a couple of hundred quid, the whole job was well over a thousand with all labour and dephaser parts paid for by the warranty.

So had the car back nice new cambelt & dephaser with no rattle, but guess what THE [email protected]@KIN LUMPY RUNNING HESITATION IS STILL THERE :steam: :steam: :steam:

Spoke to Renault uk again who spoke to the tech's again, and they have come to the conclusion that the ECU needs replacing so the said they are going to replace this FOC,
But the first independant garage that had it sent the ECU away for testing and came back no faults found, I told Renault uk this, but they said not all faults can be detected with ECU's.
So it going in again on friday (I was 90% sure it was the bloody dephaser :mad: )
Just have to wait and see :(
 

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Discussion Starter #19
Still need help on this one.

Just when I thought I was going to get some help off a Renault tech off this site someone upsets him and he quits the forums :rolleyes:

Are there any RTE's that may be able to help or anyone else that has an idea
PLEASE.
 
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