Engine hunting for revs

Started last Saturday - when changing gear, it seemed to be hanging on to the revs, or even climbing sometimes.

If I was giving it some real beans, it climbed to around 6k rpm and stayed there.

Blipping the throttle sometimes helped them drop. Typically, it would then sit at around 1200.

Intermittent (obviously…) and not only when hot.

Car is DVA’d with Jenveys, Emerald, etc.

Note to King K - please DON’T take this as another opportunity to do some back-stabbing…

Hi Chris

sounds like it might be the throttle position sensor

I seem to remember this being on of the symptoms, although I may be completely wrong

could it be something as daft as the throttle sticking somewhere? Simon E had a hell of a problem with 2 sets of standard TB’s before it was sorted?

Just a thought???

Dumb comment over there mate, TB’s have nothing to do with anybody other than the owner (basic maintenance)

Both sides of the TB’s (yes, they are paired) are connected by a slotted wheel, to absorb any kind of misalignment: one side has a circle with a slot cut in it and the other another circle with a ridge protruding, same shape as the slot on the other one.

These get dry and need to be lubricated.
I recommend a silicon grease spray, WD40 will evaporate too quick.
Try spraying from the underside towards the min link in the middle, from several angles, plenty of it while somebody presses and releases the throttle pedal(and then clean the excess).

I got a big can of that spray so I’m going to do mine asap

Dobbo, I had similar problems after changing over to the S2 throttle cable, due to misalignment of the bracket at the cable end. Have a look under the dash and make sure that the cable runs nice and straight from the bracket where it leaves the outer part. It may be binding midway along the cable run as others have suggested, but if it’s the bracket end then it’s simple to realign, so that’s an easy win.


-= mike =-

Note to King K - please DON’T take this as another opportunity to do some back-stabbing…

ps don’t do backstabbing, anytime you want to visit here to see cables or failed heads etc , you are welcome as long as you come open minded

I’m as open minded as the next guy / gal, but I NEVER mentioned heads - I have simply have a minor rev problem that I think I’ve solved (as well you already know if you’ve read other posts) with a squirt of Teflon spray.

Thought you didn’t do back-stabbing …


The Jenveys have a very different pairing mechanism which is simpler and easier to adjust.

My money is also on the cable, an engine needs air to run no matter what the ECU is doing. It is possible for the bushes on the TB spindles to tighten and cause the TBs to stick, although I’ve only ever seen it once.


Sorry, didn’t notice he had Jenveys.


Just as an aside Uldis,

Are those two plots genuine curves from your engine or not.

That way we can clarify or amend them accordingly.



I’ve had this problem for quite a while now but only when its hot.

My car was fitted (as a few on you may know ) with a new set of OE throttle bodies, IACV and throttle cable at the factory only a few thousand miles ago and its only happended since then.

Nick Whales very kindly had a look a few week ago and found even though it was racing in between gears I was still only getting 47% at full throttle.

A bracket had broken on the naff throttle pedal mecnahism which they replaced and then set up the cable correctly.

At first it was ok but then the next time I used it on a very hot evening(!) it played up again. Until I gave it a right thrashing and then it seemed to reset iteself and has been running fine since (touch wood)

I guess and hope it was just a combination of the pedal bracket, cable and the throttle position sensor then reseting itself somehow.

Might be worth a look and I hope it might help!

Just as an aside Uldis,

Are those two plots genuine curves from your engine or not.

That way we can clarify or amend them accordingly.


Come on Dave, you could have PM�d me for that question, non relevant to this thread.
We don�t want to make all thread is this forum about my (humble) engine, right?

I find it strange that you ask me if the plots are true, but answering your question yes, they are.
Everything that I�ve posted so far in ANY forum has been sharing my experiences and results for the benefit of others.

BTW, the change in power has all been due to manifold and trumpets/airbox changes. I have left even the cam timing as on the first run at Emerald and never opened the engine. The purpose was to find the best bolt-on power upgrade to any engine.
Once I settle on something (which I assume will be the next airbox) I can start playing with cam timing.

The engine has hard a hard life because most of those 10K miles it�s done has been on the rollers, trackdays or Scottish roads (which if you went with the Scottish_Elises bunch you�d see how hard they are)

Sorry for the hijack guys, back to the original theme.

The reason I ask is that your footnote appears to disparage the plots on dyno-plot and suggests that they might be false. If they are not then it needs to be made clear.

The reason it is mentioned on a thread is because your postings have that permanent footnote and I want any conversation to be entirely transparent and above board.

I am not knocking you or your engine, just seeking clarification, as I have said before it makes creditable power and you are happy with it, that is good enough for me. However, I did not make those uploads to dyno-plot either but I am keen to know if they represent genuine curves or if they are incorrect.I am sure there are other readers of these threads who would also like to know.

Where is the harm in that?


P.S. sorry for the thread hijack Dobbo…

Fair enough.

I have not seen all those plots on Dyno plot so don’t know how they compare.
If you see a discrepancy please let me know, either by PM or post, as that would be foul play on the uploader’s part.

As a note of interest, I started an Excel file long before I knew about Dyno plot, it now has 18 tabs and countless formats that I’m not interested on doing it all again, all for the benefit of somebody else and to finally be criticized for one reason or another.

Besides, Dyno plot gives me the chance to see the true colours of some people.


The two plots are here Click me, they were posted before your latest manifold, I believe they are bonafide.

Just found another one its here together with the 238BHP Caterham with the same spec.


Fair enough.
Besides, Dyno plot gives me the chance to see the true colours of some people.

Sorry uldis the dyno-plot colours are fixed, plot 1 is red, 2 is blue, 3 is orange and the graphs are arranged alpabetically, admittedly the colours are a bit manky.

If you have a colour scheme in mind for the KingK stuff (shades of yellow springs to mind) I am sure that can be accomodated.

At a glance, the red one seems to be with 2bular JV3, long trumpets and the prototype airbox that I was using until last month.

The blue seems to be the run at Dastek with same setup as I had at Emeralds BUT my first experimental long trumpets (which were very crude). At least it showed me the gains due to longer trumpets was not limited to the low and mid range.

No problems there other than the lack of details so people can see the differences.
This is why I keep track of changes in my Excel file and why I have 18 different plots to understand them.

Thanks Uldis, perhaps we can then annotate them so there is no confusion.

First I have to find out who owns them…


What, no apologies for saying categorically that everyone knew the Dastek RR up here reads more?

See, this is the thing that disappoints me about you, you’re so definitive and eager to point fingers when somebody gets it wrong (we all do) but you keep on very quiet when you get something wrong yourself.

For the chart “incompleteness” and spreading the wrong idea look no further than your very own Johnboy above.