Uneven idle

boothy150

Member
I have an 02 vec b that has developed an uneven Idle. some days its worse than others. engine pulls fine when accelerating and cruising.

I've changed coil pack, front O2 sensor, Blanked egr valve, checked manifold and flexi with no obvious signs of blowing. I do have fault code appear on the OBD reader that keeps coming back but doesn't put the light on P1686. About 4 months ago the throttle body was given a bit of a clean and was running fine until recently.

would a stretched chain or worn tensioner give idling problems but be fine on acceleration and cruising, or the throttle body code

also would this cause emission issues at MOT time as this is at the end of the month
 

vx-chris

Regular Member
Same problems (apart from the code) as me and that was the chain. Have you tried changing the cts or checked for air leaks around the throttle body?

Tbh I would be more worried about the chains failing then the mot at the end of the month but that's just me ;)

Do you know if the chains have been replaced at any point and what's your mileage at the moment?

@evocarlos and @vocky, have you guys got anything you can add or remove from my comment?

Best of luck with it though
 

vocky

Staff
bad idle is usually dirty throttle body, stuck open egr valve or loose chains, so might be worth checking or replacing the chains
 

boothy150

Member
cheers 4 the replies

I thinks its the worse case scenario, I'm gonna be taking the cam cover off tomorrow to confirm. Just thought there might have been something else I missed. throttle body was cleaned a while ago so it don't think it could be that. although i'll give it another clean tomorrow by taking it off.
 

boothy150

Member
well, took the throttle body off today and gave it a good clean and didn't make a difference so took the cam cover off to expect to see the timing chain sagging, but it wasn't. it was tight with only a tiny amount of deflection when pressed (is that right?). No signs of wear at all and all timing marks in the right place. you could induce a bit of slack if you rocked the car back and fourth (bit like backlash) but it would immediately be taken up. So the findings at the mo are inconclusive. The mechanic friend that helped me said the tensioner may be a bit weak causing the fluctuations.
has anybody got anymore possibilities what could be causing the uneven idle. Its slight, but then seems to ease into being ok them starts becming slightly eneven again.
@vocky
I'll try and take a video clip to show what I mean. but the weather is crap at the mo.
 

boothy150

Member
would the cts give a false reading on the temp gauge. I have had torque pro connected and that hovers around the 90deg area and seems to correspond with the guage. Also on torque pro, the O2 sensor fluctuates up and down in a fairly even manner which I'm lead to believe is how it should be (I have an impreza with an apexi ECU and that does the same)

I'll try and get a vid clip tomoz and show this.
 

vocky

Staff
it is still possible that the chain has stretched with age and the tensioner is still coping. What mileage have the chains done ?
 

evocarlos

Stupid Bollocks
Staff
i was going to say stretched balancer chain done 2 or 3 cars now with lumpy idle and the balance chain was sloppy
 

boothy150

Member
I have no history of the chains as the engine came out of an astra and put in before I had the Vectra. Although I know the person that did it and they were told the engine had done around 80k. I've done approx. 20k in the 2 yrs I've had it. so I would say its done 100k. it's got the tensioner with the the cutouts on, bit no coloured timing marks on the chain. So it may even be the original chain.

cheers for the input guys :)
 

evocarlos

Stupid Bollocks
Staff
The FAI chains don't have coloured markings, so it could be one of those that was fitted if it's been changed.
they do :) just different color from the gm ones it could be the chain is dirty and you cant see the colored links
 

Matt

Administrator
they do :) just different color from the gm ones it could be the chain is dirty and you cant see the colored links
That's what I meant ;) Aren't they just white / beige rather than the bright purple / blue ones on the GM kit? I've never opened a kit up as I'm worried I'll miss something when putting it back in the box.
 

evocarlos

Stupid Bollocks
Staff
That's what I meant ;) Aren't they just white / beige rather than the bright purple / blue ones on the GM kit? I've never opened a kit up as I'm worried I'll miss something when putting it back in the box.
2 copper and 1 black on the main chain the balencer chain is white and somthing
23660_1473591980827225dc6dbba53f55a9fa.jpg
 

carson_sri

Senior Member
I have a lumpy idle aswell. i noticed it not long after fitting a ported tb. @evocarlos i think i mentioned it at silverstone but cant remeber what you said. alto my balance chain may need changed
 

evocarlos

Stupid Bollocks
Staff
I have a lumpy idle aswell. i noticed it not long after fitting a ported tb. @evocarlos i think i mentioned it at silverstone but cant remeber what you said. alto my balance chain may need changed
yeah the ported tb will make it rev more at start up and takes longer to settle down
your car only had the main chain done ,new inlet cam and sump of so it may need doing at some point in the future
 

boothy150

Member
Here are the vid clips I promised. Couldn't get one of the engine itself it just came out as noise. The clips of my phone is using the app torque pro and showing both O2 sensors. If you have some good quality speakers you can just hear the engine in the background Idling (I can when played to my smart TV). Can anybody shed any light on the readings? Also I had changed the throttle body, but the P1686 code has come back (as an inactive code and no lights had come on). what else could cause this and could it have an effect on idling. The idling can only be described as a rhythmic slight miss fire. it seems as though the ecu sorts it for about a couple of seconds then looses it but then sorts it again in a sort rhythmic fashion. :confused:

this one just after start up engine already at temp

ai40.photobucket.com_albums_e233_Boothy72_black_20vectra_th_1_zps0254be3a.jpg

clip 2

ai40.photobucket.com_albums_e233_Boothy72_black_20vectra_th_2_zps11ac42fa.jpg

clip 3
ai40.photobucket.com_albums_e233_Boothy72_black_20vectra_th_3_zpsafab1173.jpg
 
Hmm that sound clips you made the idle is not normal.
I wait for the experts to say something :p


You got a clean Airfilter? Injectors? Fuelfilter? No airleaks, is the little tube that goed from your inlet to your fuel rail stil intact?
Have you tried to reset the Ecu>?

I think its normal for this engine to have a slightly unbalanced idle.
My chains are renewed for Fai chains after that the idle whas a bit better. but somethimes when im pulling away hard or i floor it! and then i stop before the red light it needs to settle the idle down, this ecu is so foking slow lol.

What you can do for a better steady idle is getting rid of that big pipe that goes from your egr valve to the inlet manifold and buy a Vw/audi waterplug and put in in place under the throtlebody in your inlet manifold.
The pipe that goes under your throttle body blocks your airflow big time! Its a nice little mod for little money
https://z22se.co.uk/threads/oe-style-egr-blank-for-inlet-manifold.12915/
 
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