problems after second original ETM replacement

[micn]

Hello,
I'm trying my luck here – maybe someone has an idea.
Volvo V70 2002, 103 kW (2.4 petrol), 380 000 km.
For the last 3 years the throttle body (Magneti Marelli ETM) was slowly dying – typical symptoms: occasional motor rpm fluctuating regardless of accelerator pedal position, sometimes "stuck" at higher rpm, getting slowly worse.
In august workshop (not official Volvo, but Volvo specialised and trustworthy) confirmed bad ETM → replaced with a new original remanufactured unit (as they said, all "new" original Volvo units are the old ones fitted with new sensors).
At the same time done: new spark plugs, new ignition coils, full check-up (cylinder compression, pcv crankcase ventilation, etc.) – everything mechanically perfect.
Car ran beautifully for about 300 km, then suddenly complete idle collapse: misfiring cylinders / surge, engine choking or revs jumping up and down.
Back to the workshop → everything looked mechanically fine, electronically it again pointed to a faulty throttle body → car sent under warranty to an authorised Volvo dealer. Warranty claim accepted, another new genuine remanufactured ETM fitted.
Car again drove perfectly for about one hour → then the same idle collapse + surge as with the previous “new” ETM, loss of power, I barelly made it back to the workshop (I live 10 minutes away). They disconnected and reconnected the ETM cable - everything works fine again, like nothing happened. They cleared all fault codes and drove the car for some time, but the error did not come up again, so they cant find the problem and think it is not the ETM's fault, told me to drive it and see. I took back the car, drove the car for 2 months. During that time there was occasional (random, roughly like several minutes every 1 or 2 hours of driving) slight but clearly noticeable loss and return of power - several times, as if the accelerator pedal was faulty – otherwise the car ran fine.
After those two months the full idle-collapse episode happened again (engine choking, big loss of power), but the problem fixed itself during the 10-minute drive back to the workshop. In the workshop they checked again, the fault never shows up while the car is with them. They replaced the accelerator pedal to check if that might be the problem.
I have the car back now, drove some 800 km, but the occasional short loss of power continues as described continues (so I guess the accelerator pedal was OK).

Additional info - the car runs on LPG too, but all the symptoms appear on petrol as well, even with the entire LPG system and its ECU completely disconnected. The LPG installation itself works perfectly (for 10 yrs).
Workshop said they have checked the cable connectors to engine and ETM and everything seems fine.
Years before the first ETM change, I had the clutch pedal sensor error, which sometimes brought up the orange warning triangle on the dash board, but as the workshop said - in my car without tempomat it does not have any function, so it was not necessary to replace it. However, I noticed, that after the first ETM change, the warning light never comes up again - the workshop has not tested this yet, as I realized it just today...
Does anyone have any idea what else this could be?
Thanks in advance!

[scot850]

Is the car not throwing any engine codes? Hard to believe you get all these issues without any codes.

The issue may not be ETM, it could be a crank or cam position sensor starting to fail or even (on your car I believe it may have a cvvt solenoid on the exhaust cam only being an 02).

Neil.

[micn]

Yes, the car has been in the shop 3 times and on Vida diagnostic, however I did not ask for the codes before - I expected they will manage to fix it. But now it seems they cant find what causes this problem. I asked them now by email, if they have recorded the codes, will send them if they did...

[jonesg]

the wirig harness is suspect, a volvo tech said they swap it out with the ETM, seems the gold plating on the plug wears of from unplugging and replugging. I believe they snip the old one off and use butt connectors for the new plug.
If you're getting a communication error it wouldn't hurt to do a drag test on the plug.

[micn]

the wirig harness is suspect, a volvo tech said they swap it out with the ETM, seems the gold plating on the plug wears of from unplugging and replugging. I believe they snip the old one off and use butt connectors for the new plug.
If you're getting a communication error it wouldn't hurt to do a drag test on the plug.

Which wiring harness do you mean? The workshop told me, that they have checked the main connector from engine to ECU, asi well as the ETM connector... however it does look like an random electrical error to me, so I would not be surprised, if it was in the cables somewhere, and could have been caused by the change of ETM, as the total idle breakdown did not occur prior to the first ETM change. However I am surprised, that the official dealer has accepted the warranty claim, I would expect that the wiring would be the thing they would test in the first place...

[jonesg]

the plug that connects to the etm,

[darylrobert]

check the wiring, i had a bad connector once,very difficult to solve. Does it fail while going over bumps in the road? check all connections while engine is running.

[dikidera]

Btw, as you know there is dielectric grease, but there is also electrically conductive grease, to improve conductivity. worth a try.

[micn]

Thank you all for suggestions. I keep focused on the ETM connection. Now I tried securing the whole ETM cable to the air hose, so its not so loose below the ETM / infront of the engine - I had some drives 3-4 hrs, none of the problems has reappeared so far yet...
(To answer previous question though, it did not seem to be related to driving over bumps)...
Conductive grease - should I use it to grease the contacts inside the connector?

Also would anyone suggest some type of universal diagnostic, OBD II ? Is it worth trying - buying (I never used one before)? (I guess the original Vida is too expensive and maybe difficult to operate)? Beause the when I had the idle breakdown problem, the repairshop said they just cleared the error codes (they have not sent them to me yet) and that fixed the problem, they were not able to recall it afterwards. I am thinking of getting some diagnostic reader myself, just in case this problem gets me somewhere difficult far from home, so I might be able to fix it just as the shop did at least to get home.

[jonesg]

Thank you all for suggestions. I keep focused on the ETM connection. Now I tried securing the whole ETM cable to the air hose, so its not so loose below the ETM / infront of the engine - I had some drives 3-4 hrs, none of the problems has reappeared so far yet...
(To answer previous question though, it did not seem to be related to driving over bumps)...
Conductive grease - should I use it to grease the contacts inside the connector?

Also would anyone suggest some type of universal diagnostic, OBD II ? Is it worth trying - buying (I never used one before)? (I guess the original Vida is too expensive and maybe difficult to operate)? Beause the when I had the idle breakdown problem, the repairshop said they just cleared the error codes (they have not sent them to me yet) and that fixed the problem, they were not able to recall it afterwards. I am thinking of getting some diagnostic reader myself, just in case this problem gets me somewhere difficult far from home, so I might be able to fix it just as the shop did at least to get home.

If you own a laptop, I believe you can download vida for $5 direct from volvo, then buy a JRL cable from david leach for $120.

or buy a $300 topdon scanner, it does bi-directional control, you could do a sweep ttest of the ETM same as vida. Its better if you own other cars beside volvo.