Strange Intermittent Judder/Loss Of Power, Now Cutting Out!

[silencer51]

I noticed this in the last couple of months.

While driving around, out of the blue, the car feels like its momentarily losing power causing a very small but noticeable 'judder', like when you press and release the gas pedal repeatedly in a low gear. This happens for 1-2 seconds.

This has happened 3 times so far that I can remember. It has happened in 3rd and 5th gear if I remember correctly.

There are no fault codes stored in the ECU.

A few weeks before I first noticed that I had cleaned the throttle body (I do so every 3-4 months) and disconnected the battery.

Also I have recently had the TDC sensor replaced. The dephaser system works fine.

Could something else be knackered? Any ideas?

[fitshase]

Could be a blocked filter. I had the same symptoms on my old car and it turned out to be a clogged air filter.

[silencer51]

Almost everything in the engine compartment is new, oil, air filter, sparks, etc.

I'm really at a loss here... Usually I can locate the cause of a problem with my car easily but this time I'm stumped...

[markren2004]

sounds like a temporary mis-fire is happening, is there any oil showing on the bottom on any of your spark plugs ? if so it's a cam cover gasket thats failed.

other possibility is a failing coil, loose or bad spark plug, or a bad electrical contract between coil wiring , a coil & spark plug.
just check everything in that area is well fitted and connected up correctly.

if all that is ok, then next step would be to check the fuel pressure ?

[silencer51]

I'm thinking there's a sensor problem somewhere. Today the car took it to 'the next level'.

Specifically, I was waiting at a red light and the engine rpm started dropping and then it died. I pressed Start and it came back to life instantly. A few minutes later, again at a light, it died without warning.

Also around 3000 rpm there was a noticeable 'cutoff' or surge in power that shook the entire car.

If I hadn't replaced the TDC sensor only a few months ago I would be almost 100% certain that would be it (the symptoms match). However, the car starts fine every time, so its not that...

I'm thinking perhaps the camshaft sensor.

I'm afraid my amateurish OBD scanner cannot detect the errors regarding the VVT system...

[silencer51]

Could someone who's had a problem with the camshaft position sensor in their car report exactly the symptoms they encountered?

[silencer51]

I tried a new camshaft position sensor as well as a new TDC sensor + wiring. No difference, the car still occasionally cuts out while waiting at a traffic light.

I have a spare MAP sensor I got from a mechanic friend which I'll try tommorow... Although I doubt that could be it... Any suggestions?

[AlexB]

You asked about the camshaft sensor. This is what I understood from my recent reading.

It belongs to the dephaser feedback control loop. If something in this loop is playing up then occasionally you will get stalling at idle due to abnormal cam advance and/or sometimes you may lose performance at high revs due to cam retarding. Fuel consumption, as I understand, should go up significantly. Is it your experience?

One can break this control loop for the purpose of testing by disconnecting the dephaser solenoid. Then performance in high revs will be lost and the warning message will appear on the computer.

[AlexB]

Another thought. Use your OBD reader to check the temperature readings. You may actually try driving with the laptop connected. If the temperature sensor is glitching, then it affects pretty much everything. The mixture becomes rich, ignition retarded, dephaser locked in the retarded state, etc.

[Masta_Inc]

Mine was doing the same before I got the Cam sensor replaced, random cutting out etc. Your symptoms sound exactly like that

It's now doing it again although slightly more aggressively/frequently and it's a suspected TDC/MAP sensor.