Erratic lurching/knocking while in traffic

[barbs706]

Hi Guys.

I'm having a bit of an issue with my Mondeo MK4.5 Econetic 1.6TDCI

The car has a terrible knock noise when there is a change of power while crawling in traffic in 1st gear. For example, if I let off the throttle around 10mph I get a harsh clunk and it feels as though I have applied the brakes. The same happens when slightly accelerating (apart from the braking sensation). I get the clunk and a sudden sharp accelerating feel. (it feels like someone has bumped into the back of the car)

It makes driving in slow traffic very difficult to control and I can’t imagine it looks to clever from the outside; lurching forward and backwards all the time!

I find myself trying to compensate for the lurching my constantly feathering the clutch to absorb it all.

Does anyone have any ideas what this could be? The car has covered 102,000 miles. I did think it could be the engine mounts, but the engine doesn't budge if I try and shake it about by hand.

Thanks in advance!

[mrnobody]

Had the same problem with 2.0 idci in traffic it was the egr sticking open,Just cleaned it out or you could fit a blank plate.

http://www.ebay.co.uk/itm/FORD-FIESTA-FUSION-FOCUS-FIESTA-B-C-MAX-EGR-VALVE-BLANKING-PLATE-1-5MM-STEEL-NZ-/172131321876?hash=item2813d38814:g:uXcAAOSwu1VW5AQx

[Tdci-Peter]

On 13/07/2016 at 11:12 AM, barbs706 said:

if I let off the throttle around 10mph I get a harsh clunk and it feels as though I have applied the brakes.

Sounds too severe to be engine mounts.

The older 1.6TDCI engine has a complex EGR system, with an EGR valve (that allows exhaust gas into the inlet manifild), a throttle valve (part closes the main air intake to increase EGR), and an intercooler by-pass valve. I assume this newer version is similar.

It could be EGR sticking or jumping open, or the throttle valve.

On these engines, simply blanking the EGR may not be possible, it may make the warning lamp come on, and cause other problems, like power loss as the throttle valve still operates. But it could be blanked for diagnostic purposes, to see if the fault goes / changes.

I presume no warning lights are on?

Even if not, a diagnostic scanner would be a good idea, there may be DTCs (error codes) present even if the light is not on. Occasional minor errors are stored but do not set the MIL. (warning light).

For diagnostics, you have some options:

1) Go to a garage for a diagnostic readout. Free if they know you and are generous(?), up to £100 otherwise.

2) Find a mate with a scanner: Cost you a pint or equivalent maybe!

3) Get a generic OBD2 scanner. From about £10.00. I got a U480 off eBay, worked fine. Very easy to use, self contained, but limited capabilities.

4) Get a powerful Ford specific system. Cost £15.00 for the interface. Needs a computer of some sort. (COM port, USB, bluetooth or WiFi interfaces available). Not as simple as the self contained OBD2 scanner.

You will find a lot about ELM327 & Forscan on this site, which together provide a very comprehensive diagnosis & maintenance tool. Post here if you want more info.

Note: Simply reading the codes can do no harm, and does not change anything. Just do not reset the codes (and you would have to ask the scanner to do this) if you are going to take the car to a garage.

James (jeebowhite) has done a nice guide: http://www.fordownersclub.com/forums/applications/core/interface/file/attachment.php?id=21196

For an ELM327 adapter, see
http://www.spanglefish.com/TunnelratElectronics/index.asp?pageid=516992

you will also need a program called Forscan, its free and you can get it from

http://forscan.org/download.html