IPB

Welcome Guest ( Log In | Register )

2 Pages V  < 1 2  
Reply to this topicStart new topic
> Rough idle after engine rebuild
donutty
post 3rd May 2019 21:07
Post #21 | Print


1.4 16v
**

Group: Regular
Posts: 115
Joined: 27th November 2018
Local Time: 13th December 2019 23:06
Member No.: 13,545
Driving: 145 2.0 '96 Cloverleaf
From: Sheffield, UK



Well, crossing fingers wasn't enough to stop my 145 from failing the MOT today. Emissions. Its could be a faulty lambda but the tester also said it could be a slight timing issue...

The cam cover will get whipped off again tomorrow.
Go to the top of the page
View Vehicles
+Quote Post
donutty
post 10th May 2019 07:46
Post #22 | Print


1.4 16v
**

Group: Regular
Posts: 115
Joined: 27th November 2018
Local Time: 13th December 2019 23:06
Member No.: 13,545
Driving: 145 2.0 '96 Cloverleaf
From: Sheffield, UK



YUSSSSS biggrin.gif Passed MOT after changing the lambda sensor. Got a genuine Bosch one too for a good price.
I will probably wrap this topic up with a condensed recap to help others who have similar issues
Go to the top of the page
View Vehicles
+Quote Post
JeremyG
post 11th May 2019 10:12
Post #23 | Print


1.6 8v
***

Group: Regular
Posts: 547
Joined: 19th August 2016
Local Time: 13th December 2019 22:06
Member No.: 12,797
Driving: 166 3.0 Sportronic, GT 2.0 JTS
From: Oxford



QUOTE(donutty @ 10th May 2019 08:46) *
YUSSSSS biggrin.gif Passed MOT after changing the lambda sensor. Got a genuine Bosch one too for a good price.
I will probably wrap this topic up with a condensed recap to help others who have similar issues


Great news, you must be well chuffed!

Are your idling issues fixed now, too?
Go to the top of the page
View Vehicles
+Quote Post
donutty
post 12th May 2019 17:07
Post #24 | Print


1.4 16v
**

Group: Regular
Posts: 115
Joined: 27th November 2018
Local Time: 13th December 2019 23:06
Member No.: 13,545
Driving: 145 2.0 '96 Cloverleaf
From: Sheffield, UK



QUOTE(JeremyG @ 11th May 2019 11:12) *
Great news, you must be well chuffed!

Are your idling issues fixed now, too?


Yes.. but two different issues I think. I do plan on making a more thorough recap and summary when I can be arsed but here is what I have come to think:

1. The idle issues were not caused by the lambda. That sensor *did* cause the MOT failure and I can see the difference in reading on multiECUscan. Basically the old lambda was dead or approaching that.
2. I believe the idle issues would have had me tearing my hair out if I had not 'stumbled' across my assumed solution:

Remember that the engine was idling fine before the head gasket blowout and subsequent head re-build work.
After trying all connections, cleaning throttle body, idle valve, trying the 'throttle reset' procedure, monitoring the parameters with multiECUscan and still getting nowhere I thought I would try the Actuators tests in mECUs. With engine off I toggled all the actuators that I knew had some connection with the running of the engine: ICV, VVT, Evap. One of them.. the VVT (camshaft variator) I think only did a half-baked click the first time then clicked strongly thereafter. I think it was that one, I might be wrong.. but one of them was certainly 'stuck' or 'half-cocked'.

Thereafter, the idling was back to normal but it still failed the MOT for the emissions. I did a bit of logging with mECUs and saw very erratic and low readings from the lambda sensor and no sign of an oscillating control loop.. just stuck high or low and no change in the lambda status. Also, DTC reported lambda open intermittent.

On fitting the new Bosch lambda it passed the MOT and then I did another diagnostic run and saw that after the engine warmed up (about a minute) the lambda started cycling as it should do through lean, rich, upper limit. I also noticed that after about three minutes the RPM reduced and the tickover was very smooth. With the bad lambda the idle RPM never slowed.


So, in summary this is my 'theory': I think that during the head rebuild one of the actuators, seemingly the phase variator solenoid, was not fully disengaged or there was an 'oil lock'??? that caused incorrect setting of the VVT. This may explain why under acceleration there was no problem, as this is when VVT should be engaged, but if it was 'stuck on', this may explain why the idling was rough as VVT should not be used at this low RPM and power demand. Manually 'exercising' this solenoid caused it to fall back to the correct position and idling was fixed.


Thoughts? ....
Go to the top of the page
View Vehicles
+Quote Post

2 Pages V  < 1 2
Reply to this topicStart new topic

 



- Lo-Fi Version Time is now: 13 Dec 2019 22:06