Diagnosis Please :)

[kate205gti 4]

can anyone suggest or rule out what might be causing the following please?

 

mi16 on tbs with emerald management:

 

car "hiccups" from hot or cold since rebuilt engine went in

 

feels exactly like it does when you run out of petrol - no misfire no popping or banging or flames, just losing power randomly then coming back on again, no change in any of the dials (apart from speed dropping if it has a long hiccup) or lights coming on

 

my theory therefore is that its being starved of fuel, so wuld this be likely to be:

 

fuel pump? (althou it starts ok on the key every time)

 

fuel pressure regulator?

 

sticking injector? (although last time i had that is misfire and shot flames!!)

 

random bit of crud in a pipe? (is it worth putting redex in?)

 

any thoughts or advice appreciated! thankyou

[Alastairh 47]

Quick and easy suggestion to try out.

 

Gear box earth.

 

Had similar things with my 106, and remember dino having the same issue in his 205 last year.

 

possibility.

 

Alastair

[Anthony 1,000]

James has got another TPS to try hasn't he, as it looked somewhat suspicious from the datalog?

 

Very much doubt it's anything trapped in the fuel pipe nor a FPR fault, and an injector issue seems unlikely as well. Symptoms don't sound right for a fuel pump problem, but could at a stretch be a failing fuel pump relay intermittently cutting power to the pump.

 

The fault sounds electrical to me anyhow. Firstly I'd let James swap that TPS over to rule that out if it's suspicious anyway, and go from there if it doesn't fix it.

 

Oh, and didn't the fault first occur after a trackday and was fine up until that point?

[kate205gti 4]

if it was electical surely there would be unburnt fuel and cause popping and banging though?

 

my basic understanding of tps after doing a search..

 

The TPS on the 8v & 16v is just a simple open & closed switch(closed at idle & WOT, open between the two), it doesn't have any reading underpart throttle.

 

is that it affects idle as well as driveability, he idles dead on 1k on the flick of a key from cold or hot, and is definately hiccuping on part-throttle (but hasnt hiccupped at WOT so far - although not saying he wont)

 

where is the fuel pump relay please? and alastair can u remember the full symptoms of gearbox earth? (did battery light come on on dash?) ive checked and cleaned it before though and its all bare metal contact

Edited April 16, 2006 by kate205gti

[Anthony 1,000]

my basic understanding of tps after doing a search..

is that it affects idle as well as driveability, he idles dead on 1k on the flick of a key from cold or hot, and is definately hiccuping on part-throttle (but hasnt hiccupped at WOT so far - although not saying he wont)

That's for a standard 8v/Mi16 TPS, which is indeed a glorified idle / WOT switch.

 

The TPS on your car however is progressive, so it tells the ECU exactly how far open the throttle is and this is the ECU's sole measurement for engine load. The further open the throttle, the more voltage the ECU sees from the TPS. As such, if that sensor fails or theres a bad connection, the ECU no longer knows what's happening and would (I assume) just cut the injectors.

 

where is the fuel pump relay please?

On your car I wouldn't like to say as it's all been rewired - I suspect it's in that bundle of wiring under the dash near the Emerald ECU, but I'd need to see the car to be sure.

[Super Josh 4]

my basic understanding of tps after doing a search..

is that it affects idle as well as driveability, he idles dead on 1k on the flick of a key from cold or hot, and is definately hiccuping on part-throttle (but hasnt hiccupped at WOT so far - although not saying he wont)

 

It is true that the TPS ( Throttle Position Switch ) on the standard 8 and 16V is just a switch to indicate either idle or WOT. But on an installation like yours, with a 3rd party management, the TPS is a Throttle Position Sensor and is a potentiometer( like the volume control on a radio ) and is used the indicate the angle of the butterflies in your throttle bodies. This indicates the engine 'Load' to the ECU, so if the track inside the TPS is worn( in a similar manner to the carbon track in the AFM wearing out ) then it could behave fine at idle, but misbehave at different throttle angles.

 

 

Josh

 

EDIT

Looks like Anthony beat me to it

Edited April 16, 2006 by Super Josh

[kate205gti 4]

have swapped the tps and reset the throttle pot and has cured the hiccups i think..

 

but now wont rev above 3.5k!!

 

it just flat spots and makes pllllhhh noises (like when ur pretending to be horse ) and got no power

 

its worse when its warmed up but still does it a bit from cold, idles still perfect

 

is that likely to be tps still or something else please?

[mfield 20]

Did you make sure that it was giving the correct voltage when at WOT ?

[kate205gti 4]

wots dat?

[mfield 20]

wots dat?

 

dunno

 

on my old setup i had to have something like 0.75v on idle and 3.5v at least when the throttle was fully open.

[kate205gti 4]

i'll plug in the laptop and see wot i can find cheers mark

[James_R 3]

dunno

 

on my old setup i had to have something like 0.75v on idle and 3.5v at least when the throttle was fully open.

 

Think that's the MBE set up that's like that.

 

 

Think going for a spin see what data you get on the logger will point you in the next direction of things to look at is a good plan though.

[Anthony 1,000]

Does it stick at 3500rpm regardless of throttle position or what gear you're in? Up until 3500rpm, does the engine still pull strongly and feel OK, or is it running like a sack of spanners?

 

I can't see how the TPS would stop the car revving past a given point, as logically atleast it should fail depending on throttle position (as that's what it's measuring), not revs. Might be worth swapping the old one back on and seeing if that affects anything if that's all that's been changed between when the car revved fine and now that it doesn't.

 

Otherwise, crank sensor maybe? Normally I'd suggest the ignition amp, but from memory I don't think your car has one.

 

As James says, seeing what the log shows around 3500rpm should give you a clue as to where the problem is.

[kate205gti 4]

its down on power and running unhappy throughout the rev range, and worse when it warms up

 

it just hits a huuuge flat spot about 3.5k regardless of gear and makes the horse noise

 

i cant swap the old one back on as its dissintegrated lol, will buy a new one in the week and see if that improves things

 

no banging/flames/pops - which is what has happened the last two times my crank sensor has failed and idles fine still

 

i have no ignition amp

[Anthony 1,000]

Hmmm. If it's running like a sack of spanners throughout the (limited) rev range then it might be the TPS then - does it appear to function OK as far as Emerald is concerned (ie it's reading a low value with the throttle closed and then smoothly increases to a large value as you open the throttle further) when you've got the laptop connected?

 

If that's all that's changed between it working fine for the most part then certainly that's where I'd start in diagnosing the problem. The only reference that the ECU has for load (and hence fuelling) is that TPS sensor, so if it's not working or not calibrated properly then you'll have horrendous running problems.

[TT205 42]

Before you try anything else, maybe try reversing the wiring to the throttle pot as if it is the wrong way round it will run, but it won't rev - this happened to both me and Pugtorque

[kate205gti 4]

a new tps hasnt solved the problems

 

it seems to hit a wall about 3.5k, you can force it and after a flat spot will go a bit higher but spluttering and popping and not happy

 

ive reset the throttle pot ok and the data logger shows a nice happy line for this

 

it idles perfectly and very well mannered under 3k and the exhaust fumes look normal

 

no banging or flames, just a "phutphutphut" noise and a wall when it hits 3.5k

 

it was revving higher fine before the tps was relaced but the old tps was definately knacked and causing random "hiccups" as the power lead was v corroded

 

the injectors dont appear to be sticking and *my theory* (which could be wrong) is that the injectors are asking for more fuel but just not getting any over 3.5k

 

the rev limit is set at softcut 7600 and hard cut 7750

 

the throttle pot idle control is set to come in under throttle pot number 33 and engine speed below 1250 (tp set 27 - 680)

 

the cut off fuel on overrun is not ticked

 

theres no lambda sensor

 

how do i test the bar on the fpr please?? ive got one of these

 

but where do i stick it :D

Edited April 21, 2006 by kate205gti

[kate205gti 4]

update - its not the Fuel Pressure as that sits quite happily at 4bar throughout the rev range

[mfield 20]

id now check your cam timing

[kate205gti 4]

just taken it for a blat with the laptop plugged in on the original map and it will rev up to 7k nicely if u boot it however it doesnt like driving at a constant speed/revs now

 

looking at the data log the inj PW line (injectors i presume) is very squiggly at constant 3k or 4k but ok on hard acceleration

 

how do i check cam timing please?