Gti6 Misfire Between 1500 And 2000Rpm

[macaroni 17 1 Cars]

Hi,

this subject has been covered before, but I can't find a solution so wanted to open a discussion again.

 

My GTI6-equipped (actually Xsara VTS) 205gti has a stuttering misfire exactly between 1500 and 2000rpm. Below that it pulls strongly and above it screams towards the redline.

 

My initial thoughts were lambda probe, so I disconnected it. This made the car run much better, so it is clearly knackered, but still this misfire persists.

 

I've put a multi-meter on all the sensors and compared the values to book and they are all OK.

The engine dies when I remove the MAF sensor connection and runs horrendously rich when I remove the water temp sensor connection. All normal I think.

 

The misfire clears when I come off the throttle or boot it, but is very noticeable at part-throttle.

 

My thoughts are;

 

Lambda - Would a new lambda solve it as it should adjust the mixture to compensate for this?

Cam timing - when the engine was rebuilt and fitted, the timing was advanced a little to give a bit more top end. Would that cause this effect and should I revert to standard timing?

 

Any more ideas I can try please?

 

Antony

[welshpug 1,657]

is it actually missing and popping/banging or just a flatspot?

 

if just a flatspot at part throttle lower speeds then sounds like the VSS is dead.

[welshpug 1,657]

p.s, no maf on these engines, its a MAP sensor.

[macaroni 17 1 Cars]

Thanks for the reply. It is more of a flatspot, but with jerking and stuttering. No pops or bangs.

 

OK, I'll replace the VSS and give that a go, thanks.

 

Yeah MAP sensor, I meant that...

 

Cheers,

 

Antony

[macaroni 17 1 Cars]

There is this one available from GSF, or a real cheapy from ebay.

 

http://www.gsfcarparts.com/929pc0400

 

http://www.ebay.co.uk/itm/171503903893?ssPageName=STRK%3AMEBIDX%3AIT&fromMakeTrack=true

 

OEM is £90, which is fine, but wondered if the aftermarket ones were ok.

Edited November 5, 2014 by macaroni

[welshpug 1,657]

GSF one should be fine, I would be wary of the cheapo units, incorrect one on your link anyway.

 

I managed to bag an o.e unit for £20 last week from LCS louth but was the last one

 

 

 

this one from Neat Auto's may be ok, doesn't state the brand they have, o.e was valeo or sagem.

http://www.ebay.co.uk/itm/CITROEN-AX-XM-ZX-C15-XANTIA-SPEED-SENSOR-RPM-CABLE-TYPE-EARLY-MODELS-616024-/360608737436

 

 

and they do have genuine boxed here

 

http://www.ebay.co.uk/itm/CITROEN-AX-XM-ZX-C15-XANTIA-SPEED-SENSOR-RPM-CABLE-TYPE-MODELS-616024-GENUINE-/371026110358

[macaroni 17 1 Cars]

Excellent, I'll go for the Genuine part from Neat. Thanks.

[camgti 56]

Sounds also like tos if its part throttle? Is it the same position of the throttle thats causes the mis?

 

Cam

TPS sensor not tos!

[macaroni 17 1 Cars]

Its not always the same position, as it is the same revs in each gear.

 

I'll look into the "tos" after I've tried the VSS.

 

Thanks for the suggestion,

[macaroni 17 1 Cars]

OK, well I fitted a new, genuine VSS and the problem has kind of been solved. It seemed absolutely fine this morning, but 20 miles into my commute it started missing again right in between 1500 and 2000rpm.

 

Could the fact there is no lambda sensor being used have an effect?

 

It is definitely improved, but there is still an issue. Also, the idle speed seems to have dropped to about 600rpm, so maybe an ICV reset is in order.

 

Antony

[welshpug 1,657]

why no lambda?!

[macaroni 17 1 Cars]

I unplugged it as part of the diagnostic process and the car ran better without it, so I assume it is knackered.

 

I can replace it and replug it in if there is any benefit. I don't have a cat fitted.

[welshpug 1,657]

should run a lot better, dont need a cat to run a lambda, the ecu doesnt use it when cold, ecu does use it to trim part throttle fuelling a lot.

[macaroni 17 1 Cars]

OK,so a lambda is useful then, even without a cat.

 

That will be my next job then!

 

Thanks.

[dobboy 231 2 Cars]

No sure if this is correct or not, but i read somewhere you can reset the GTI6 ECU by keeping ignition on for 15sec (iirc) then switching off, then starting it.

 

Supposidly the ECU clears itself and then learns all the sensors/tolerances etc again.

 

I did it with mine a while ago after replacing my Lambda and removing all sensors and cleaning them. The car didn't run as nice for a few miles (presumably as it re-learned the sensors at different loads/temps etc etc) but then it ran as sweet as a nut.

 

Or it was my imagination

[Anthony 1,003]

I get this issue to a small degree on my GTi-6 under a specific circumstance.

 

It will do it around 1500-2000rpm under light throttle when the engine is started from cold and beginning to warm up (it's fine stone cold). Press the throttle a little harder so that you're accelerating rather than holding speed and the slight hesitation will disappear, and it disappears completely once the engine is up to temperature. Certainly doesn't feel like an ignition misfire and it's quite different to the VSS flat spot issue - subjectively feels like lean surge.

 

In my case I've put it down to the increased overlap from the Petert inlet cam I've got fitted messing up the fuelling slightly as the ECU isn't mapped to suit, which would make sense why it disappears when it's warmed up and the ECU is correcting the fuelling using the lambda sensor.

 

Might be barking up the wrong tree of course...

[macaroni 17 1 Cars]

No sure if this is correct or not, but i read somewhere you can reset the GTI6 ECU by keeping ignition on for 15sec (iirc) then switching off, then starting it.

 

Supposidly the ECU clears itself and then learns all the sensors/tolerances etc again.

 

I did it with mine a while ago after replacing my Lambda and removing all sensors and cleaning them. The car didn't run as nice for a few miles (presumably as it re-learned the sensors at different loads/temps etc etc) but then it ran as sweet as a nut.

 

Or it was my imagination

 

As far as I am aware, unplugging the battery just resets the ICV. Anything is worth a try though.

 

Anthony, my gti6 lump is standard apart from a lightened flywheel and slightly advanced cam timing.

Also, my issue seems to get worse as the engine gets hotter.

[Paul_13 212 1 Cars]

I can't run vss sensors, my engine has an appetite for like a fat kid and eclairs.

 

I had a horrendous mis fire line yourself I replaced absolutely everything apart from vss sensor. I unplugged the vss sensor and it's fine, no misfire

 

Now I sourced a replacement plugged it in and something was wrong with it. I've given up trying to find it now after it destroyed 4/5 speedo drives.

 

I just run a 8v speedo cable housing minus vss and it's fine. I don't get any hesitation or stalling

[macaroni 17 1 Cars]

Interesting...I'll try unplugging mine tomorrow and see if that makes a difference.

Got a lambda sensor on order anyway.

[welshpug 1,657]

must be something quite wrong with your diff bearings or you're using the wrong cogs paul, or get a new mechanic!

 

can't figure how you say it runs fine, I get a VERY pronounced flatspot at low RPM and a noticeable drop in torque, no stalling, fixed with a working VSS.

[Paul_13 212 1 Cars]

It shorted out and burnt one of the pins in the plug. I replaced the loom and since then it just kept melting the insides of cog.

 

I'm using the correct cogs etc

 

I'm at a loss to what's wrong.

 

Runs fine without the vss

[Anthony 1,003]

It's curious Mei - I've been in his car and can confirm that it behaves itself without the VSS connected.

 

Like yours, mine is an utter pig with the VSS not working - massive flat spot just off idle and prone to stalling too.

[macaroni 17 1 Cars]

Mine runs OK with the VSS unplugged, but definitely feels flatter.

 

The previous flatspot is still there, with the new VSS, but very much reduced.

 

Getting a new lambda today, so I'll try and fit that at the weekend and report back.

 

I'm getting an easy 32mpg per tank with some fairly spirited driving, so things can't be very far out.

[macaroni 17 1 Cars]

New lambda seems to have solved the flatspot problem properly.

 

It runs very much smoother too.

 

Thanks for all your advice chaps.