Hey guys, I have a problem that I am hoping someone will be able to help me diagnose. The car in question is a 2010 Mondeo 2.0 TDCI 140. Since I have owned the car it has had a power surge issue, mainly under hard acceleration, but I have experienced hesitations under light load. It can also run a little rough on first start idle, it's not massively rough, but its enough to notice its not as smooth as it should be. Almost like an occasional misfire.

I'm getting around 50mpg mixed usage. I have seen up to 61mpg so I don't think fuel economy is affected. No black smoke out the back, no EML or limp modes. You just accelerate, boost builds, it then disappears for a second, then its back again. It can happen multiple times when accelerating through one gear.

 

Things I have done:

* Changed the intercooler as it was leaking

* Changed the two brown solenoids above the gearbox for the EGR/Turbo

* Used a bottle of wynns turbo cleaner with a tank of diesel

* Cleaned the MAF, MAP, IAT sensors and throttle body

* Forscan shows no codes, I have used it to measure things like EGR position, turbo vane position, throttle position etc and it seems to be normal.

 

I have searched the forum, but there doesn't seem to be a definitive answer as to what the problem may be. Any advice on what to check with forscan would be appreciated.

Split in a rubber boost pipe is most likely on a car that age.

Check for vacuum leaks

2 hours ago, nicam49 said:

Split in a rubber boost pipe is most likely on a car that age.

If I had a boost leak it would happen all the time?

1 hour ago, DaveT70 said:

Check for vacuum leaks

Again, because its an intermittent problem, I don't think its going to be a leak.

The rubber pipes have got a mesh lining that holds any split in the outer rubber together. When the engine is cold, the rubber is cold and stiffer than when it warms up. As the boost kicks in, the pressure in the boost pipes builds up, but the mesh holds the split together, until the boost pressure overcomes the mesh resistance and the split opens up, momentarily reducing boost pressure, 'cos it escapes from the split, which results in what you're experiencing,  some describe it like the engine is missfiring. As the boost is still increasing, it overcomes the pressure loss so you don't feel it again for a while. In my experience, it occurs around 2k rpm.

'cos the mesh lining holds the split together, it can be quite difficult to find the split. Sometimes you'd have to remove pipes and twist and bend 'em to reveal the split.

Sometimes you'll see a smear of oil on the pipe from where it has opened up.