C70: ETS light come on.

[toctictim]

Hello,

I am looking to others members for their ideas and advice on which way to head with the problem I have with my car! Sorry for it being a bit long winded but I have tried to give as much info as possible.

I have a 2001 C70 t5 conv. auto which I have owned for 2 years.

I consider myself a competent mechanic even though I have not worked in the trade for 25 years. As a diesel fitter my electrical knowledge is not perhaps as good as it should be, and I'm a little out of touch with some of the systems on more modern cars.

For 18 months the car ran fine.

6 months ago I fitted a replacement Mass air flow meter, as the car was choking when I tried to accelerate or go over 70mph on the motorway. This was relatively easy to identify as I just unplugged the electrical plug to the unit and the engine revved freely. Once the new unit was fitted the problem disappeared.

However, 2 weeks ago, the engine started to idle irratically. The engine revs go up to 1500rpm and then drop down to near stalling and then back up. When I put it in drive the revs level out a bit, but the engine nearly stalls at junctions and then I get an increase in revs, which in an auto is not good.

At the time I was not aware of the fault with the ETS system on volvo's, so my intial thoughts were that the mass air flow meter was faulty again. I unplugged the unit as I did before and the revs levelled out but this time the ETS light came on on the dash. I assumed this was because the flow meter was unplugged. The car however ran much better. I am still running the car with the flow meter disconnected.

When talking to a fellow Volvo owner he told me that the ETS light was more likely to be on because of a fault with the throttle control unit attached to the inlet manifold. This was my first knowledge of any problems associated with the unit and he suggested there may be a carbon build up around the butterfly valve in the unit and some times de-carbonising the unit will cure the problem. I did this the next day. There was a fair bit of build up which was cleaned and polished.

As things stand at the moment the mass air flow meter is disconnected (unplugged) and the car drives and idles fine except if I blip the throttle to move off and then have to stop, (traffic jams), then the car revs drop and then rise up to 1500rpm, but only once then level out quickly. If I try to reconnect the flow meter the idle is very rough and the engine is constantly searching for the idle revs. The ETS light does not go out. As such I leave it disconnected.

Also, now my cooling fan comes on for 5 minutes every time I switch the engine off, even if it was only running for a few seconds and no where near operating temperature!

Can someone suggest where I go from here? Do I replace the throttle control on the manifold to extinguish the ETS light or is there something more sinister going on. Will the ETS light come on because of the mass air flow meter being disconnected?

Any suggestions would be appreciated.

Many thanks,

Tim

[mikealder]

Tim, start by getting the fault codes read on the vehicle, I have a code reader and ain't too far from you if you want to try it, from the fault codes you can then have a better idea of whats wrong.

Cooling fan running on, does your temp gauge get to the three o'clock position as normal or is it sitting low? (Thermostat jammed open is a possible)

ETS and rough idle is probably the ETM pots worn out but fault codes will confirm this.

PM me if you want to meet up to try the fault code reader on your vehicle - Mike

[deathrider311271]

hi

i had exactly the same problem a few weeks ago, changed ETM and was still rough running, changed Air Flow Meter reset ecu all sorted

cheers

simon

[silestanix]

Mine had the same faults mate; including the ETS light coming on whilst putting on some power with my MAF being faulty.

I bought a replacement MAF (Mass Air Flow) unit, still no luck...BUT I then bought a BOSCH MAF Sensor; I disconnected the battery whilst replacing the Aftermarket MAF sensor with the BOSCH one. I then reconnected the battery (disconnecing the negative terminal for 30 seconds erases error codes).

I've driven the car near enough 1k miles now at many speeds etc, and no problems to report.