REVS HANGING

[Guy Lowe]

No better way to describe it really, so heres the problem:

 

ZETEC 2.0L, Fitted Jenvey 45 throttle bodies + OMEX 600 ECU about a month ago, 500 miles no problem. Going up to Stoneleigh this morning I noticed that the revs where not decreasing as I lifted off for soft up gear changes (felt like a sticking throttle). Okay on harsh acceleration, just happened when we were cruising through some of the villages.

Thought it was a sticking throttle and would sort it out at home later.

Went home via motorway, one hour at 4000 rpm came off at the junction and the revs staid at 4000 for about 15 seconds after I lifted off and dipped the clutch!.

From then on every time I accelerated and changed up a gear the revs did not decrease for about 15/20 seconds each time.

Got home checked throttle cable and return all okay. Checked for any air leaks on inlet manifold, all okay. Re loaded original OMEX MAP to ECU (don’t know why as this has always worked faultlessly out of the box) . Checked TPS min and max settings all the same and okay. Checked balance between TB’s okay, checked butterfly’s closing okay, yep. Checked all individual balance screws were done up tight.

Went out for test drive, all okay but as it warmed up the problem re occurred on the soft up shifing now the engine was hot, if I gave it some stick the problem went away, it’s as if its over fuelling. Any ideas?

 

The Map is a standard OMEX one that is tried and tested and used by many

 

 

Guy

Now with MORE bhp HERE

[Stationary M25 Traveller]

Is it mechanical - try oiling the bush at the top of the throttle pedal. If you disconnect the throttle cable, does the TB butterfly return to the closed position after you open it and let go ? Is the throttle cable kinked when the bonnet is fitted ?

 

 

[Guy Lowe]

Edited to say read SM25T response correctly before replying 😳

Thats what I thought, everything would point to it being mechanical, but with the pedal box cover off and me depressing the throttle peddle the TB butterfly's return to the closed position immediately without any hesitation after I open it and let go, and the problem gets worsre as the engine gets hotter.

 

The cable goes down under the TB's and then up so does not come into contact with or near the bonnet.

 

Guy

Now with MORE bhp HERE

 

Edited by - Guy Lowe on 3 May 2009 23:17:49

[Normans_Ghost]

Guy, whip the TB's off and meke sure the butterflys are not loose. Don't want one coming off and dropping into the head.

 

^{Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here}

You and your seven toThe French Blatting Company Limited

[Guy Lowe]

Will do Norman

The more I think about this the more I am convinced it is mechanical, for it to rev like this air must be getting in somewhere.

I have checked for any leaks engine side of the butterflies and there are non, so the air must be getting in normally. My conclusion being that the problem only occurs when the under bonnet temperature is high (1 hour @ 4000rpm on the Motorway or poodling through quaint Warwickshire villages @ 20mph). By the time I stopped last night, took the bonnet and peddle box off, had a beer, the temperature will have reduced and the throttle action returned to normal.

Well that's my theory but I am still open any other ideas via TWOBC.

So this morning I am going the process of elimination route and will fit a temporary second throttle return spring to see if that cures it.

 

 

Guy

Now with MORE bhp HERE

[Stationary M25 Traveller]

How about pedal box cover off, cable disconnected, warm the throttle pedal pivot with a hot air gun (carefully !), then see if it sticks when warm ?

 

 

[Guy Lowe]

How about pedal box cover off, cable disconnected, warm the throttle pedal pivot with a hot air gun (carefully !), then see if it sticks when warm ?

Interesting approach and it would certainly identify the problem if that it what is causing it, I am off for a coffee and to ponder on the safety implications of this action 😬

Thanks

 

Guy

Now with MORE bhp HERE

[Stationary M25 Traveller]

Hot air gun, (or even the wife's hair dryer) not a gas blowlamp !!!!!!!

 

 

 

Edited by - Stationary M25 Traveller on 4 May 2009 09:35:51

[I.Mupferit]

Put a new cable on ya tightfisted git!

 

Brent

(aka Arfur Nayo)

 

Lotus Elise Probably the best hair dryer in the world! 😬

[Guy Lowe]

Brent

 

I have fitted a new throttle cable

I have fitted a new throttle linkage

I have fitted new throttle return springs

I have fitted new throttle bodies

 

All at great expense, and I can still afford a decent hair cut 😬

Guy

Now with MORE bhp HERE

 

Edited by - Guy Lowe on 4 May 2009 12:10:43

[philwaters]

Guy, I seem to remember having something similar in the dark recesses of my memory. I'm sure it was at the pedal - I think the inner bush had been turning (should be stationary). I fitted some extra packing washers to ensure the pedal was clear.

 

Anyway, I also didn't like the TB return spring - wasn't very strong, so I made a bracket (3mm Ali bend through 90°) which is fitted under one of the inlet manifold bolts (i.e. the middle one) and a stronger spring then comes up to the throttle arm of the TB. It snaps shut nicely now.

 

Certainly doesn't sound electrical - it would need a supply of air to maintain 4k rpm, so the throttle must be open.

 

Ooo - just had a thought - what linkage are you running? I remember there was an issue with the top mounted Jenvey throttle linkage - it could get caught on the bonnet louvres.

 

Phil Waters

[philwaters]

Ignore my last bit - just looked at your photo's and you've got a 'pull down' arrangement like me.

 

You've got quite a long bit of free cable showing (with tape around it) here - when the throttle is down does it point upwards? It isn't catching on the underside of the bonnet is it?

 

Phil Waters

[I.Mupferit]

That's probably because you don't have very much hair for them to work with in the first place therefore they would be embarrassed at charging you very much - that's how you can afford it.

 

If you got it, flaunt it!

 

Brent

(aka Arfur Nayo)

 

Lotus Elise Probably the best hair dryer in the world! 😬

[Guy Lowe]

SM25T many thanks, tried you idea with the acetylene torch and it has eliminated the throttle pedal pivot as the cause 😬, the (BRAND NEW) cable is free and slides ok.

 

Went out this morning no problem when cold, as soon as it gets hot the problem is back. Got the bonnet off quick but the throttle returned without any problems.

 

Then I had an idea , test it with the engine running, Hey Presto as soon as I did it with the engine at tick over the linkage took about 3 or 4 seconds close the last 5% or so and without load, revved quite high. Its as if the air flow into the engine is just too much and causing enough resistance to prevent normal operation, but only when hot.

 

To cut a long story (sort of) short, I have fitted an extra return spring and this has solved the problem, so now I have to decide if I pay the horrendous £118 for the puka Jenvey throttle linkage or fabricate my own arrangement.

 

_{(Phil thanks just seen your advice, will give the Jenvey throttle linkage a miss, I don't like the way it sits so high on the top anyway).}

 

Got any springs in your garage Brent?

 

 

Guy

Now with MORE bhp HERE

[philwaters]

Great that you found the problem!

 

For what it is worth, I've been running my own linkage for 4-5yrs with no problems. I used the old weber cable bar (the 'Y' shaped thing) and mounted it on a couple of brackets which fit under the TB's. The outer cable comes up and is retained by this with the inner going up to the TB - where I made a small bracket to hold the cylindrical nipple of a bike brake cable.

 

My TB cable arm looks different to yours though, mine is just a straight bar with a hole at the end and another further down. The 2nd hole is where I've added my extra spring. I can take some close up shots this afternoon if you like and post them on the web...

 

Phil Waters

[I.Mupferit]

Got any springs in your garage Brent?

Yes thanks.

 

 

 

Brent

(aka Arfur Nayo)

 

Lotus Elise Probably the best hair dryer in the world! 😬

[philwaters]

Some pics uploaded to my Picasa web album here

 

Phil Waters

[Guy Lowe]

Phil

I have a similar bracket (I copied yours) HERE and HERE but I changed the cable fitting to the "roll over" quadrant type so I need to have a spring that pulls up and back towards the top of the cam cover, not sure how I am going to do it yet.

Also, I have had a couple of suggestions from non members who have had the same problem, so I want to investigate those, this one in particular as it may well be what I have done:

I am not a club member (own a Westfield in the States) so couldn't respond to your thread. I have had the same problem with my Jenveys and the cure was ridiculously easy. It turns out that there is enough spring in the throttle cable as it makes the 90 deg bend in the linkage that it overcomes the tension from the linkage spring when the throttle is only opened just a bit. Try screwing in the cable sheath to shorten it a small amount. I was reluctant to try this fix myself because a visual inspection made me think there was already too much slack in place, but it worked

Thanks John, I'll let you know how I get on.

 

Guy

Now with MORE bhp HERE