Caterham juddering like crazy!!!

[Rhys Mann]

Hi

 

My Caterham has just started juddering like crazy!  It started at low speed when the car gets to temperature but now it's constant at all speeds! I have linked a video below, any ideas before I take her to the garage?

https://vimeo.com/manage/videos/870058335

 Thanks

[Jonathan Kay]

What engine?

Any recent work on it? Has the engine been drowned?

...

Does it only happen with the engine running?

Does it happen at rest?

Does declutching have any effect?

Jonathan

[Rhys Mann]

Sigma 1.6

No recent work and not drowned

Only happens when running and up to temp

Had to ride the clutch to get her home today

 Thanks Jonathan

[Rhys Mann]

The issue started with the revs between 2500 and 3000 RPM and once the engine was hot. Power was being lost and coming back in and being lost in a cycle. The only way to drive the vehicle without juddering was the dip the clutch when the power was lost then dip it again and again as the power came in and out. Towards the end of the journey  power was lost even at a higher rev range juddering in all gears. It became worse.

[colindavies56]

Check your tps is still tightly mounted. 

[Jonathan Kay]

Thanks

With the car stationary and the engine hot how is the engine running? Is the power coming and going in the same way?

Jonathan

[Luegonigel]

I had a similar thing when the lead on the starter motor which also goes to the alternator came loose progressively. The car eventually stopped when the nut fell off the end of the bolt. I managed to drive it far enough to get it safely off the road fortunately. I'd also check the earths by the battery i.e. remove and clean. Mine is a 2009 1.6 Sigma too.

[Luegonigel]

I had a similar thing when the lead on the starter motor which also goes to the alternator came loose progressively. The car eventually stopped when the nut fell off the end of the bolt. I managed to drive it far enough to get it safely off the road fortunately. I'd also check the earths by the battery i.e. remove and clean. Mine is a 2009 1.6 Sigma too.

[Rhys Mann]

No it running ok at idle when hot, thanks

[Rhys Mann]

Thanks will try all the above, just spoken to Callum at Turn 7 who's advised me to change over the Lambda sensor so have got this off the car and waiting a replacement, will let you know how i get it resolved and thanks for the replies 

[moorsd123]

I'd check the TPS sensor (and wiring) or the Lamba sensor first?

I had similar symptoms on my R400D, which turned out to be TPS.

[Luegonigel]

sorry I should have added that unless I drove over 3,000 revs when the lambda sensor on mine went, it also kangarooed like crazy. Made keeping to 30mph through town "interesting".

[Luegonigel]

sorry I should have added that unless I drove over 3,000 revs when the lambda sensor on mine went, it also kangarooed like crazy. Made keeping to 30mph through town "interesting".

[Luegonigel]

sorry I should have added that unless I drove over 3,000 revs when the lambda sensor on mine went, it also kangarooed like crazy. Made keeping to 30mph through town "interesting".

[John Vine]

The cut in power could be due to a failed lambda sensor causing over-fuelling, which in turn could foul the plugs.  Did you find that you could rev the engine with the clutch dipped?

Or it could be an intermittent earth at the ECU or engine/chassis.

From your vid, the tacho keeps working, so a problem with the 12v supply seems less likely.

TPS wiring problems tend to be more common on Duratecs.

Do you have access to Easimap and the MBE comms cable?

JV

[Rhys Mann]

Will try the Lambda sensor first, failing that move onto the TPS, thanks for the advice

[Rhys Mann]

I don't have access these Jonathan, and yes I could rev the engine with the clutch dipped, Ive ordered the Lambda sensor to see if that solves it, here's a photo of the one that came out for reference

[Skipper555]

If the lambda sensor has failed, then they can start to swing readings around quite quickly as they bounce between very rich and very lean. Generally they fail by cracking the ceramic inside. From what you've said this could well be the fault. Will be interesting to see how it fairs with a new one. Fingers crossed that's it.

[John Vine]

#17: Being able to rev the engine would fit with your symptoms, as the ECU would then be dropping into open loop and ignoring the lambda input.

How many miles on the car (sensor)?

JV

[aerobod - near CYYC]

Normally with a failing Lambda narrow band sensor, just disconnecting the sensor 4-pin connector should force the ECU into open loop mode and ignore any sensor input. If the engine runs more consistently (although perhaps a bit richer ar leaner than when in closed loop mode), that is an indication the sensor is faulty.

[Rhys Mann]

Hi Jonathan, the car has 14.5k on the clock, thanks

[SM25T]

Second the suggestion to unplug the connector to the lambda sensor. Mine started running really rough. Unplugged sensor, returned to normal. Found number etched on sensor and sourced on line.

[Jonathan Kay]

"Being able to rev the engine would fit with your symptoms, as the ECU would then be dropping into open loop and ignoring the lambda input."

While it's fresh in everyone's mind... from the engine's point of view what are the differences between being revved while stationary and being revved while the car is moving and being revved while powering the car?

Thanks

Jonathan

[John Vine]

#23  Interesting question, Jonathan.  Here's how I understand things:

At initial start, the ECU is in open loop and ignores the lambda sensor signal.   It enters closed loop when the start-up timer expires (typically 60 secs) and the coolant reaches around 60C (although CC lowered this to nearer 40C for some later models).  It drops into open loop whenever revs exceed a certain threshold (around 3K, I believe), or under wider throttle openings.

On that basis, revving while stationary will trigger open-loop mode over, say, 3K rpm.  Revving while moving (having dipped the clutch) will be the same.  Revving while powering the car will trigger open loop whenever the throttle opening (that is, engine load) or revs exceed set values.

Perhaps the experts would put me straight if I've got that wrong?   

JV

[aerobod - near CYYC]

Overall a pretty accurate assessment, John. Typically the rev limit will be a bit higher (just over 50% of max revs, so 4000 to 5000RPM range), throttle site around 8.0 (from range of 0.0 to 15.0) and usually a couple of extra criteria such as throttle is stable (i.e. TPS voltage is not changing more than say about 1V per second) and fuel trim is not out of a given range (typically +/- 25% of fuel map value).

Blipping the throttle while stationary and the engine is over the threshold temperature may still exit closed loop mode due to throttle stability, even if throttle site and revs are kept within the limit. There is also another effect when the throttle is released and revs are above a cut off value of about 2500 to 3000RPM when fuel at throttle sites below 1.0 is cut to zero, hence also exiting closed loop until revs have dropped below the fuel cut rev setting. 

If all the limit conditions are correct, Lambda control is flagged as "Conditions OK" and closed loop mode is entered.