Intermittent hesitation when warm. No codes.
 

Hello all.
Car has developed an intermittent fault where there will be a sudden loss of power for a split second that can make joining roundabouts pulling out from junctions a bit hairy when it occurs. If this was a sensor fault, cam, crank, throttle position, etc I would expect it to log a fault code but non logged. Again if it is a fuel pressure fault would this not also log a code ? The engine runs fine at all other times. The fault only seems to occur when engine up to temperature. Any ideas ?

Check for boosts leaks - likely culprit is intake hoses connected to the throttle body.

Puzzler
 

Thanks Yobbo. I have checked all hoses. If this were a petrol engine it is like the ignition has been turned off for a second and back on again. It is a very abrupt loss / return of engine power. I. e. no response at all from accelerator then normal response. What we used to call a " flat spot ". The fuel filter is new and the throttle body clean. The EGR has a blank fitted with a hole in centre. DPF has been replaced.

My car had this exact issue and it turned out to be a failing engine ECU.

While mine is the C30 D3 I believe the V50 ECU is in the same location and suffers the same issue.

Water gets in the housing for the ECU and rots it. Luckily my car was under warranty so Volvo replaced the ECU and modified the housing to stop water collecting in it.

Picture of ECU location on a V50 (same as C30 location) and two screenshots of the diagnostic video Volvo sent me showing the corrosion to my ECU and corrosion from the ECU in the plastic housing... Hope this helps.
http://i32.photobucket.com/albums/d4...psgbzdboz1.jpg
http://i32.photobucket.com/albums/d4...psgqpr6jtf.jpg
http://i32.photobucket.com/albums/d4...psmv03nlkl.jpg

Thank you very much for that info I will check it out. Did yours also occur only when up to temperature ? That is why I suspect an electronic problem. Did yours also have no codes showing ?

In regards to the ECU, what baffles me is that there is an open hole directly above the damned thing which could allow rain water to get in, there are no drain holes beneath either!

Nonetheless I used some gaffer tape to block it off, next time I have the bumper off whenever that may be I might take the ECU off the car, give a dust down and apply some form of light sealant around the crevices on the ECU housing.

Yes mine seemed to only do it once the car was up to temp. It gradually got worse and would on rare occasions do it when the engine was colder too. No fault codes or warning lights on the dash.

By the time the car went in to Volvo the ECU had dried out a bit due to some warmer weather and it hadn't done it for about 4 days.

Best way to access is to remove front wheel and peel the wheel arch liner back

Intermittent Hesitation when COLD....and up to Temperature
 

My 4 Year old V60 D4, <30k miles, has an intermittent fault; it hesitates for 3-4 seconds OCCASIONALLY when responding to the accelerator. This is looking like potential suicide when joining roundabouts or pulling out from a junction; only other driver's reactions have prevented an accident. It was reported at 3 year service and dismissed as "turbo lag". I have been out with a Dealer Technician to try to show the problem, but of course it would not happen. Subsequent complaints resulted in Volvo instructing Dealer to replumb the EGR valve. Not the solution.

The issue arises more frequently when not up to temperature, but ALSO occasionally when temperature reached. It will occur most often when crawling in traffic for several minutes using minimum throttle, say leading to a junction, then when max acceleration required....zilch! The engine maintains tickover speed. Recently in a queue it did not respond at all. After 30 secs switched engine off, then restarted it and it was cleared. After 3-4 mins in same queue, same performance and got going again. Surprisingly problem did NOT occur again for the remaining 50 minute journey! There are no warnings or error codes.

Essentially the Dealer does not want to know. It's out of warranty. Who can I turn to who can diagnose, not just swap parts?