idle and constant speed problem getting worse

[Popeye_6]

Hey all,

My slight splutter at idle is getting worse. was sat in traffic earlier and the idle got very rough, sounded like the car wanted to cut out. quick blip on the throttle sorted it, but it came back a few mins later.

its also doing it more often at constant speed low revs, around 2krpm whether im poodling around town or holding 60mph in high gear.

i replaced the icv today, but it seemed to be a bad part because the idle was all over the place with the new one. i checked for air leaks but there were none, fitted the old one and it went back to how it was before so got to wait til the new one comes in.

ive been reading up and it seems like its either this or the MAP sensor.

is there a reset procedure you have to do when putting a new icv in or should it just be plug in and off you go?

thanks

[Niall]

Because its not just doing it on idle, I would suggest a new map sensor and while your at it, give the icv a bloody good cleaning.

[Popeye_6]

New map sensor, no difference. Do i need to disconnect the battery to reset?

[lewisdmz]

New map sensor, no difference. Do i need to disconnect the battery to reset?

Could be the wiring which connects the MAP to the ECU. Can you check if the plug is getting 5v or whatever it is?

[Popeye_6]

Seems fine according to that

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its now running like crap at idle and though the range at light throttle

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Ive had it hooked up. Lambda reading is all over the place, but coil packs, map icv all seem to be working fine.

[Niall]

Lambda reading will change often. If it sits still, there's something wrong!

Is it a gti? If so I reckon it could be a coil pack. Dont pay no notice of what the obd reading is for the coil packs.

[Popeye_6]

Is there a way to be certain before i go and get one

[Popeye_6]

New coils in, no difference stuck for ideas now. Lambda reading goes between 0 and 700 in a split second like, fast lol.

[Niall]

It shouldn't go to 0. Should go between 0.30 and 0.80 on a 6.
What are you using to read the lambda voltage? If you have a multimeter, tap the lambda black wire and see if your still getting 0v occasionally. If so, you need a new lambda.

[Popeye_6]

oh, this was the reading from diagnostic port. im going back to the place tomorrow, as they were able to supply and fit a bosch lambda for cheaper than i could get one for.

up til now its had:

new plugs
new coils
new MAP sensor
new ICV (genuine)
new lambda (bosch)

on top of that, since i got it not even a month ago, its had a full cambelt kit including the water pump. was doing it before this.

at my wits end with it

[Popeye_6]

so another new lambda went in as a replacement to an apparently duff one...no change.....changed the fuel filter too...still no change. also tried a tps and inlet air temp sensor from another '6 which also made no difference.

comes up with "lambda malfunction 2" when plugged in. the only other thing i can think of that would affect the fueling is the coolant temp sensor, got one coming monday morning.

if that doesnt work, im fresh out of ideas

[Ruan]

Check the electrics going to the Lambda, sounds to me like there's no power to the Lambda....

Should be power to it to heat it when it's cold especially...

[Niall]

Lambda needs 12v to one of the white wires.
Are you resetting the ECU are fitting these parts?

[Popeye_6]

is there a fuse or anything for the lambda heater?

yeah ive been resetting every time ive changed something then hooking it up to a bosch diagnostic. every time it brings up the same fault code. im getting a coolant temp sensor tomorrow morning and il get the multimeter out again.

edit: i got the haynes manual out, i know it doesnt apply for gti 6, but thought perhaps a wiring diagram might help. on one of the diagrams it shows the rear heated screen relay as part of the lambda sensor, heated throttle body and coolant temp sensor circuits.

is there much similarity between the xsi wiring and gti6?

[Niall]

No fuse. Heater is powered from the ECU. With the car running just tap the wire with a multimeter and check the voltage. Just because the lambda is new doesn't mean the wiring to it isn't damaged.

After that I'd be looking at a new ECU
The Sagem 1.8 ECU is notorious for being spiked by broken down coil packs. Most of the time it would just mean one day the car just wouldn't start and it needed a new ECU. Sometimes it would mess with it and you would get lumpy idles, hesatant acceleration until a certain rpm, blown sensors ect.
The gti ECU isn't known for this at all but doesn't mean it's not possible.

[Popeye_6]

according to the diagram im looking at (i think it might be for xsi because it shows individual coils, but go with it) page 12.45 of haynes manual, it shows one pin going to f11 in engine bay fusebox and according to the diagram key, its one pin from a resistor. the other 3 pins go to ecu, with one of them spliced to earth 3.

think theres any truth to it?

[Niall]

Gti has separate coils. Xsi has 2 coils in a single coil pack.
Take your multimeter and check all the ECU fuses (don't just check by eye. Sometimes they can blow and you can't really see it) although if a fuse is gone, it should bring up the EML

[Popeye_6]

hmm... there is no eml, just the same code being stored every time i plug it in.

another avenue to explore. will keep me busy tomorrow thats for sure thanks

[Niall]

Probably a stupid question but you are clearing the codes arnt you? Some codes don't disappear for ages after the fault is fixed.

[Popeye_6]

yes mate cleared codes and reset ecu every time, after about 5-10 mins of idling whether hot or cold the fault code comes back

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f*ck ive just realised something that shouldve been obvious....earths......

can anyone tell me where theyre supposed to be in the engine bay? i know earths can cause allsorts of gremlins i cant believe i overlooked it. my car has what looks like a bodge, its got a wire from battery negative to slam panel and looking at engine bay pictures on google, i cant find any earth on the slam panel.

[Niall]

There is definitely no earth on the slam panel. The earth from the battery goes to the top of the box below the thermostat. From there it either goes from the same bolt to the engine bay fuse box or it goes from a separate bolt that's about 1cm from the first.

[Popeye_6]

There is definitely no earth on the slam panel. The earth from the battery goes to the top of the box below the thermostat. From there it either goes from the same bolt to the engine bay fuse box or it goes from a separate bolt that's about 1cm from the first.

right, thanks for clearing that up for me....could explain it then if the earth is in totally the wrong place.

its been bolted just behind the drivers side headlight. do you have access to a diagram or anything because it looks like ive got some rewiring to do in the morning.

there are 2 yellow and green wires down there under the thermostat housing, never thought much of it tbh.

if this fixes it il be happy as larry

[Niall]

I do but it's on autodata which is on my car computer which Scott has at the moment!

It should just be a black earth from the battery. The green and yellow if I remember correctly Is from the loom under the inlet manifold which I would assume is for some sensors

[Popeye_6]

do you know where theyre meant to go from the negative terminal? ive looked and service box and it shows 2 wires, but mine has one with the other added later going to the slam panel.

does this need to go to the gearbox and could it cause running problems going to the wrong place?

[Niall]

It's supposed to go straight from the - terminal to the top of the gear box.

[Popeye_6]

thanks that the first thing il do then and check the green and yellow earth cables while im there.

would an earth in the wrong place cause this kind of problem?

[Niall]

Faulty earths can cause all sorts of weird and wonderful problems.
Even if there securely fixed, take them off (10mm bolt iirc) and give both faces a bloody good clean with some sand paper.
Where abouts are you based? Will you be coming to ace day next Saturday? I can get pug planet plugged in then and see what sort of readings your getting.

[Popeye_6]

im in northampton bud.

wouldnt really trust it to drive the distance the way it is atm, barely trust it around town but thanks for the offer.

edit: the guys at a local garage have a bosch diagnostic tool thats able to communicate with the ecu, im going there tomorrow to pick up the coolant temp sensor so il get them to plug it in again

[Popeye_6]

So lambda is getting 12 v, checked and cleaned earths, replaced coolant temp sensor and replecated the problem and disconnected each injector in turn, still no clue to the cause. Still doing exactly the sane thing. Officially clean out of ideas now. Compression test was fine, coolant system was pressure checked, also fine

any other ideas?

[lewisdmz]

Have you unplugged the power steering sensor from between the inlet manifold and the rad? Known for these to cause funny issues?

I think this was suggested recently in a different thread can't remember if it was you or not?