2.0 16v shaking; self-advance ignition timing

[Michal 0]

Hello

Please   forgive me  of wording/ language mistakes as i’m not native  english speaker but hopefully enough to understand the issue.

Year ago I decided to refresh engine in new buyed 92’ corrado 2.0 16v [CIS-E Motronic]. Intention was to keep 100% ori car incl. 9A engine.

Point is that after whole works and some adjustments there is still problem with litlle shaking engine on idle and propably a bit to less RPM. Additionally ignition timing is  adjusted a  bit advance by ECU.

What was done:

- Complete overh. Of head, new timing belt etc.

- New knock sensor x2, new dizzy [aftermarket not Bosch], new leads, new sparkplugs, new temp. Sensor, new ISV

- Old fuel injectors mounted with new o-rings; new fuel filter; „fresh” fuel in tank

- TPS checked;  working

- General cleaning all parts, no vacum leaks etc.

- Airflow sensor potentiometer checked and adjusted acc. To bentley manual [Input: 4,85v output fluctuate 0,75-0,81v]

- Mixture verified and adjusted using readings from Diff. Press. Regulator. Meassured current is fluctuating aprox. between 2 mA  to 4 mA.

 

I’m using VCDS and OBD1 cable to connect with ECU and its working 😊 So, to adjust ignition timing I followed Bentley description- ECU was disactivated [by VCDS] and then I set using strobe lamp on proper mark on flywheel [6degree BTDC].

 

After all this adjustmens, engine:

- Starting without problems cold or hot

- RPM on cold is almost same as on hot. Acc. readings from ECU [vcds Read meas. Value block:3] is jumping between 816 and 888. In fact I do not feel  difference with rpm on idle ; also rpm dashboard indicator is stable

- Ignition timing [ECU back to work when VCDS is off] is a bit advanced and is not stable- is jumping  [visible when using strobe lamp]. Acc. to readings from VCDS [Read meas. Value block: 10] is jumping between +4.10 to +8,67. Average / most time is +7,27 what is aprox. equal to this what I can see by strobe lamp – most time is advanced [orginally is set +6]

 

- Propably due to above fact [jumping ignition] engine is shaking; additionally I feel that RPM is to low [despite of fact that ECU showing min. 818rpm].

- Engine is working quiet without any bad knocking or other strange sounds.

- Resistance of temp. sensor is giving readings aprox. +10degree more than in reality when engine is hot.

 

- Exhaust manifold temp. is about 250-290 C [idle running after ca. 10min].

On the begining when TPS was broken and ignition timing was continiuosly retarted by ECU -> temp. of manifold in short time exceed 350 degree and more so after 10min ex.manifold started to change colour to dark red :/

- Acc. to me smell of fuel from exhaust is a bit to rich but maybe I'm to sensitive ?;) ; catalysator on place.

 

Remain oxygen sensor to check but I do not have fault code from vcds [there is posibility to read faults if occur] and is no matter if hot or not -engine is shaking. Increasing RPM cause shaking disappear [aprox. From 1000rpm and up]

Does somebody meet with such a case? Whats more is worth to check ?

When car was buyed 1,5 y ago engine worked ok but from one hand idling was not so stable as now and was not so quiet but from other hand was no shaking problem

[Dox 23]

I'd start by checking basic timing with the camshaft cover off and sparkplugs out turn the crank bolt until cylinder number 1 piston is at the top of its stroke on the compression stroke, the cams should be opposing one another, ie    \      /

 

I'd confirm the TDC markings on the flywheel and / or crank pulley are correct by inserting something into the plug hole as I turned the crank bolt - a wooden or plastic cooking spoon is good for this as its unlikelt to damage anything should it become jammed.

 

If that's OK you could confirm cylinder leakage with a leak down test

 

 

[Michal 0]

Thank U for quick response Dox👍

Fortunatelly problem is solved! 

I spend half day today for checking again everything and I noticed misfire sound from exhaust. I decided to install some old dizzy which I found in garage (my original was broken and instead of that I bought aftermarket JP Group distributor). And shaking disappeared! I adjust timing using vcds agsin for +6 and ecu work stable with this set point without jumping (+4  / +8) as it was before. So to sumarize topic: do not buy JP Group ignition distributors ! Because of that piece of s**t I lost weeks with unecessary tuning, adjustrinv, checking etc. 🤬

[Dox 23]

1 hour ago, Michal said:

Thank U for quick response Dox👍

Fortunatelly problem is solved! 

I spend half day today for checking again everything and I noticed misfire sound from exhaust. I decided to install some old dizzy which I found in garage (my original was broken and instead of that I bought aftermarket JP Group distributor). And shaking disappeared! I adjust timing using vcds agsin for +6 and ecu work stable with this set point without jumping (+4  / +8) as it was before. So to sumarize topic: do not buy JP Group ignition distributors ! Because of that piece of s**t I lost weeks with unecessary tuning, adjustrinv, checking etc. 🤬

JP have a bad reputation in the Corrado community for all items not just distributors.