NC 2.0l sport intermittent power loss

Technical Area Engine, Transmission, Exhaust etc
2

I have an issue with my NC1 2.0litre sport which started as an occasional drop in power but is now becoming more regular. It manifests mostly when trying to maintain a steady speed with the revs between 2 and 3000, so awkwardly between 60 and 70 on the motorway. It is a short drop in power that then recovers but will occur again in a few minutes. Car starts and idles fine hot or cold, accelerates fine and pulls well through all gears and right up to the red line without any hesitation or power loss but after a few miles the issue appears and is only while trying to maintain a steady speed. I am not getting any warning lights illuminating and no codes registering on the ODB2, fuel consumption is OK and I always run it on high octane fuel and engine temperature is good and constant. 

Initial thoughts were fuel or ignition but I’ve changed spark plugs and coil packs, no better, fuel filter and pump in the tank and again no change. I’ve also had to do a couple of longish journeys of late (2-300miles) and the problem is not constant, it will run some of the time perfectly then go through phases of the power drop being there then clear again for 50 miles or so before returning.

Any one had similar issues and what was the diagnosis?

My thoughts are either O2 sensor, ERG valve or cat issues but unsure how to diagnose and I would expect any issues with these to throw a code, which it is not, so is it something else?

Any help appreciated.

3

I don’t know the answer but when you say drop in power, is this a hiccup or a total loss of power, ie the car slowing down.

Without any eml it’s diffuclt to say for sure where the fault could be, but i’d start with whatever is the cheapest and easiest to change.

The weather has been kind to us of late, so I guess it’s safe to rule out the scuttle leak.

 

Maybe Crank Position Sensor

 

4

Its more of a hiccup or hesitation rather than total loss. It is always when on steady power and it feels like a very short drop in power, maybe for a second or two then recovers to normal. When it happens and I accelerate it picks up immediately, same if I back off and then accelerate again. This is the annoying bit as its only when your trying to sit at a steady speed that it does it and especially when the revs are below 3,000rmp. I cleaned and visually checked the CPS but haven’t replaced it so might try that. I really thought it would be fuel pump or filter related but having changed both (with improvements felt in general performance) it hasn’t cured the problem.
Thanks for the response.

5

I occasionally get a case where the engine drops power and enters LIMP MODE. With the engine warning light on.The colprit is the throttle sensor which is connected to the top of the accelerator peddle. The remidiy is to remove the cluster connection clean up and refit. 

That doesn’t sound like your problem though, maybe it’s just the LSD activating,  which is more noticeable at constant speeds.

 

 

 

6

Sparks. Do you mean LSD or the Traction Control? 

Bodgit & Hope. Have you tried turning the traction control off to see if it makes any difference? If I remember correctly it is the “DSC” switch.

7

Thanks but definitely not the traction control. I usually switch it off (fully) anyway but have tried it and I get the problem with it on or off. Ordered a new CPS so will swap that out. Read about crank sensors today and it could be it but then again I thought that about plugs, coil packs, fuel filter and pump when I read about them! Trial and error seems to be the way forward.

8

Plugs, coil packs, fuel filter and pump problems tend to show up more when the engine is under load i.e drowning the spark or fuel starvation when asking for more fuel when  accelerating.

 

9

My ‘best guess’ would be a poor/ loose connection?

the reason I say this is I had a motorbike that did something similar and it turned out to be a loose connector plug That vibrates at a certain engine speed (resonance) and for a split second the ECU lost the signal…

over & under that resonance/ engine speed all was well…??

10

I’ve had possibly the same symptoms before, it turned out to be a failing wheel speed sensor for the DSC. In the end it put in a fault code for it. Is it a really light hesitation? Like you’ve lifted the throttle ever so slightly?

I put it down to the DSC “detecting” some wheel slip due to the faulty sensor and closing the throttle slightly to reduce engine torque and stop the “detected” slip.

Even though the DSC off light is on, I don’t think that the system is completely dormant.

11

Hi I was referring to the ‘limited slip diff’ it kicks in sometimes whilst going up hill.

Agree that the coil pack ,plugs and filter would exibit a fault under load.

 

12

 

 

Thanks. That’s really interesting and hadn’t thought of. Your description is bang on its like you lift of a little but haven’t then comes back and could be a symptom of the DSC kicking in slightly. I assume the wheel speed sensor you refer to is the ABS wheel sensor too, if so, then the fronts are very new but the rears (it would be these for the DSC reading wheel spin) are old and been through a bit with rebuilds so maybe suspect. Codes a plenty when the fonts went however, so the no code bit is still a bit baffling unless its to come but I’ve experienced the issue for over 1000 miles now.

I’ve ordered a CPS today so will swap that and see what happens.