K series running issues / possible misfire?

[Stationary M25 Traveller]

Intermittent air leak ...... split hose on inlet manifold maybe ..... or intermittent earth problem to ECU ?

[revilla]

Throttle butterfly valve sticking in plastic throttle body. The throttle body distorts under the pressure of the air filter retaining jubliee clip and the throttle doesn't quite close. Slacken it off and see if the problem goes away.

 

Terry if that doesn't fix it, you may be best to start a separate thread on this one. I don't think your issue and Pete's have much in common and this thread is getting hard enough to leep track of as it is. You will probably get a lot more response too as I think many people tired of checking this thread a long time ago 😬

[evotell]

Quoting revilla: 

Throttle butterfly valve sticking in plastic throttle body. The throttle body distorts under the pressure of the air filter retaining jubliee clip and the throttle doesn't quite close. Slacken it off and see if the problem goes away.

 

Terry if that doesn't fix it, you may be best to start a separate thread on this one. I don't think your issue and Pete's have much in common and this thread is getting hard enough to leep track of as it is. You will probably get a lot more response too as I think many people tired of checking this thread a long time ago 😬

 

That may cause the idle to be high, but it would cause the engine o rev itself up, nor would it cause the reve counter to not work.

[Smithy77]

Revilla - thanks for all your help and research, I salute you sir! 😶‍🌫️

 

This forum never ceases to amaze me and the spirit and generosity is like no other I've come across

 

So then, all signs are pointing towards ECU. The fact that my bulb lit with engine off, and then stayed on at the same brightness on start up and then warm, I suppose backs up this theory - the ECU simply has no control over it. However, I'm now starting to think that with ECUs we are getting into new territory in terms of cost of repair, and for a relatively minor issue. If all this fault does it cause some minor rough running for a minute or so when cold, is it worth the trouble?

 

However, if it is worth doing, then I'd happily take you up on that kind offer to test my ECU. Once we can pin point the ECU we can discuss ways forward after that.

 

[Token Jock]

Smiffy,

 

It does sound like you have the same problems as I did with the O2 heater circuit simply not working.

 

Rather than getting a new ECU or getting it repairer I went with a remap with Z&F which fixed the issue as well as improving drivability etc.

For me it was money well spent.

 

John

[Smithy77]

Well, I think this thread is long overdue an update and I feel I owe it to those who helped out, as well as those that were/are looking to solve their own similar issues or learn something about the K series. I’ve certainly got to know my seven pretty intimately as a result of this thread! Apologies in advance for the length of post, but A LOT has happened since the last post, and this thread really was just the start of a frustrating first 6 months of Caterham ownership.

Firstly, I’m glad to say that ALL of the problems and issues mentioned in the thread have been 100% solved! For some reason my original posts are not linked to me as a forum member (it is just noted as ‘Anonymous’ ), so I am not able to edit the thread title. If there are any mods reading, could you please edit the title to read something along the lines of “PROBLEMS SOLVED….FINALLY!”

Just to recap, the problems I was having were as follows:

1. Poor running before getting up to decent temp, particularly noticeable at low revs in 1st & 2rd gear. Slow driving even when warm was also very difficult.
2. Misfire/flat spot (mid-range)
3. DTC - P0135 - O2 sensor heater circuit malfunction
4. Poor starting (manual throttle required)

The bulk of this thread mainly focused on me trying a lot of things myself based on the advice received on here. A lot of these things made no difference to the problems but were probably worthwhile doing anyway, and these included: new spark plugs; new (second hand) coils packs & leads; cleaning the IAVC, checking/testing all the various sensors; checked/tested the battery; checked loom & earth connections; used a scanner to read DTC codes and live data; all of which didn’t seem to improve things.

Towards the end of the thread I was actually reporting improvements after have fitting new sensors (which was shortly after trying different coil packs). However, having now reverted back to all my original sensors and sending all of Revilla’s spares back (thanks Andrew!), it is clear that they were not the problem. One thing that I never mentioned in the thread was that when I was fitting the coil packs, one of the bolt threads was striped, and so one of the coils was only held down by one bolt! In hindsight, I actually feel that this had an effect on the running, particularly the misfire/flat spot in the mid range – I guess a vibrating coil pack could cause 2 cylinders to fire incorrectly? I just fitted a slightly longer bolt as an interim fix, and it was later helicoiled by DVA.

From this point on I was receiving advice directly from CharlesElliot and Revilla – both of whom I owe a lot of thanks to – and this thread dried up.

So with the flat spot gone, I then set off to see Charles (and RogerFord popped by too). Charles confirmed that the general running and idle was exactly as he would expect from my spec of engine. He did however admit that it was a bit too difficult to drive at slow speeds still. Whilst poking around the throttle body he spotted that the butterfly was loose, which I was quite embarrassed I didn’t spot myself, but I need to sincerely thank Charles all the same for finding that! He also pointed out that the throttle cable was sticky and advised to change it. After changing it, the throttle was a bit smoother but it was still sticky when initially pressing the pedal – this is what was causing the difficult driving behaviour at slow speeds. I stripped the TB for closer inspection to find a landmark discovery in the context of this thread. The sticky throttle was actually caused by a sticky butterfly!! Remember at the beginning when I found what appeared to be fragments of a washer in the throttle spindle cavity after removing the TPS?? Well it turned out this was actually fragments of the circlip that holds the washers and bearings in place around the spindle. All these little bits were just free to slide up and down the spindle within this cavity, resulting in the butterfly sticking. I sourced a replacement throttle body (thanks Revilla!) and it transformed the slow speed driving - so much easier to apply small amounts of throttle. So a loose butterfly and sticky spindle was the cause of the slow speed driving difficulties.

At this point, running when cold was still a little rough and DTC P0135 was still present. The fault code we attributed to a lambda heater circuit malfunction, perhaps the reason for the cold rough running. With the help and dedication of Revilla over email, we carried out various electrical tests and came to the conclusion that there was a fault in the ECU circuitry relating to the lambda heater circuit.

Next up was a trip to DVA to have the cams timed with verniers, telling myself that this might smooth out the rough running, but in reality this was more of an excuse for an upgrade I think. Dave also port matched my inlet ports to the VVC manifold. This work alone gave a noticeable kick of extra torque in the low & mid-range, whilst allowing the engine to pull harder for longer. I asked him to time the cams at the more aggressive end of the timing range, and as a result, the idle was actually considerably more lumpy than before – I kind of liked it actually haha!

I think it was less then two weeks later I took a visit to Z&F. He had to apply a fairly bespoke map (rather then his ‘off the shelf’ Supersport map) due to the aggressive tune of the cams. He raised the idle speed to 1150rpm, which smoothed out the idle somewhat, set the limiter at 7200rpm and also added the nice overrun burble :-) He also put the mapping onto a new ECU, and when we next plugged in a scanner, the P0135 was gone – so Revilla correctly diagnosed the ECU at fault here. After this work, and combined with the DVA work and sorting out the throttle body, it was like driving a different car. Smoother, more tractable, much more grunt and pin sharp throttle response. Compared to how the car was when I bought it, the performance increase I would say felt the same as when you go from driving with a passenger to driving solo, at least – it was that stark an improvement! When I took a trip to see Revilla we went for a little blat, and with him in his SV 1.6 VVC with Z&F remap I was able to keep him more than honest in a straight line, which I guess is a good yard stick to compare against when you factor in the extra weight of the SV.

So after all that, all that remained was the starting issue. Mark at Z&F pointed out that the ECU was momentarily dropping out and re-setting when you turned the key. This threw out the settings of the IACV stepper motor and, as a result, you hade to take over the ‘idle control’ manually until the ECU re-set. It was suggested that I just live with it and get used to applying throttle to start, as all other aspects of running were now perfect. However, I’m a perfectionist and so is someone else I know…..Step in Revilla (again!) and what pursued was an arduous few months (I lost track how long) and two trips to Loughborough of electrical testing, diagnosing and tinkering. We knew that something somewhere was creating unusual amounts of resistance, drawing too much current for the ECU to sustain its function. We found resistance across the FIA switch, so I replaced with new. We also found even more resistance through the engine wiring loom – at first we tried bypassing the feed to the starter, but with no improvement - so like a K series/Caterham warrior that he is, Revilla set about building me a brand new engine loom…. from scratch!! (I struggle to express how grateful I am to this man). However, although we eradicated some unwanted resistance, it didn’t make a blind bit of difference to the starting issue! I think two hearts sank that day when we fitted the new loom. 

All that was left in the equation was the starter motor. It was fitted with an ‘upgrade’ Brise starter – a common replacement for the Magneton among those running a K-series. Revilla lent me his spare Magneton to take home with me to try, and low and behold with a Magneton fitted, I had consistence and reliably perfect starting every time – HALLELUJAH!!!

EDIT: Just to add Re. the starter... obviously Revilla wanted his spare Magneton back so I was looking at the prospect of footing the bill for a new starter (c.£175). I called Tim at Brise and explained the situation. He was extremely helpful and, as it wasn't the first instance he had heard of this particular problem, he agree to do a straight swap with my 2 year old Brise for a brand new Magneton starter.... free of charge! So big thanks to Tim too.

In conclusion, the poor running issues were probably caused from a combination of a few things – loose coil pack; dodgy throttle body; cam timing; ECU lambda heater fault. The starting issue was primarily caused by an incompatible Brise starter, which wasn’t helped by an old & tired FIA switch and engine loom.

Can we put this to bed now please?!?! I’d just like to end by saying one last big thanks to all those who contributed, particularly Charles who potentially saved me an engine re-build, and also Revilla who has given a tremendous amount of his time, dedication and expertise to help. 

[revilla]

Hehe glad it's all sorted. It's been a challenge but, as you know, I've enjoyed it!

For completeness it might be worth linking to this thread where tracked down the precise nature of the problems caused by the Brise starter with some comparative oscilloscope traces.

By the way you've got mine down as a 1.6 VVC, it's a 1.8, however as you were kind enough to mention the extra weight of the SV and not mention the extra weight of the driver (who clearly requires an SV after going for a blat in yours with my backside hovering above the seat and my head sticking out of the top like I was in a Noddy car) I'll let you off

All's well that ends well ... let's get blatting!

[Smithy77]

Andrew, I had thought about that thread but I knew you'd be along to do the honours 

[CharlesElliott]

Great to hear about the follow up and resolution, and glad to have helped along the way.

[Smithy77]

Charles, more than worthy of a mention - would dred to think of the outcome had one of those butterfly screws let go at full chat.

P.S. Love you avitar pic by the way! I thought Caterham recing was supposed to be gentlemanly and respectful, but it looks like you got into a bit of a tangle there....

[martyn]

Great thread!  Just read it from start to finish.  Well done to all those who gave up their time to help.

Is particularly interesting and useful for me because I'm currently trying to diagnose a misfire myself.

[Smithy77]

Martyn, I'm glad my misfortunes are helping others! The thread actually got up to 7 or 8 pages IIRC, but we are only left with the 1st and last 2 pages, I'm guessing as a result from the switch over to the new forum. Probably for the best TBH as it was mostly just me flapping like a true noob...

[Nick Chan]

What a read!  i've just spent an hour and a half going through all 14 pages and there are definite similarities to how my supersport car now starts and drives.  i'm off to check some of the points covered

Nick