16v KR 9a ignition timing issues

Spent time swapping plugs, leads, distributor cap etc - no difference.

Decided to switch investigation to fuel so took the top off the carbs, the carb supplying cylinders 1&2 has a broken float support (where the pin that holds the float goes through - see picture), so I swapped this with the one from the carb supplying 3&4 and their good one to cylinders 1&2 carb and the running issue moved to cylinders 3&4 ie pulling HT lead off making no difference, but it now does with 1&2 misfire like I was getting on 3/4 previously.

I put everything back so this was my only change - could this be the issue it points to it and I am sure the break would mean the float/carb is not working properly?

I have found someone who can repair it, but it takes 2 weeks so on the hunt for a Dellorto DHLA45 carb top piece.

 

I have ended up sending the carb top off for repair - apparently this breaking is quite common.

Will update once its back - pleanty of other jobs to do in the meantime.

 

So its back from repair and fitted - engine runs much better and has passed the MOT emissions. Its still not 100%, but at least I can now take it for a good drive and somewhere for a proper tune/setup.

 

Ok so car does run better but still is not right there is hesitation when under load circa 3K RPM, could this be the ignition timing issue? There is a spark and fuel, seems to rev up fine when no load? I have a timing light and have checked the static timing on both the crank pully and flywheel this is correct and markings move when engine is rev'ed and return to their original position leading so would seem ignition advance is working, but is there a specific way to check this?

Any ideas welcome. At least I can drive it on the road now so getting it somewhere for attention is a bit easier.

 

So I have attached a pipe from the vacuum off the intake to the connection on the ECU (this was previously blanked off) the car seems to run a bit better but is still not right, can the vacuum be anywhere in the servo pipe or does it need to be a specific side of the one way valve?

 

You may need to up the vacuum to your brake booster unless you have improved pedal pressure ,don't think you mentioned after pipes fitted ? could be ok but the factory setup takes vacuum from a plenum manifold which in effect pulling that from 4 cylinders .
Your engine sounds flat , thinking maybe the vents are too big hence the "hole" from idle to main jets on transition ,yes it will rev great but under load ? ,it could also be idle jets too small or mains too big this will also create the same "hole" but no matter what you do unless you have carbs specs that are within basic sizes of components for a 4cyl engine they will never be 100% .
Only a guess but expect your carbs you have 36mm vents but for a car that you are driving on the street they aren't really ideal ,any reduction in size will improve transition and driving in town and on the motorway with the added bonus of reasonable fuel economy.
You should be making great power with this combo if dialed in ,perhaps the past owner may have some details ?,make sure your float levels are to spec and you have a good regulated and metered fuel pressure ,reckon you will hit near to the sweet spot soon ,cheers.

 

Thanks for the reply - the pedel pressure feels much better after adding the vaccum pipe to servo and brakes are good, I appreciate, as you say its only pulling vacuum from one cylinder.

Yes flat is a good description - it felt a bit better with the vacuum pipe connected to the ECU, but still not right and its hesitating under load. The issue could well be the carbs, I have taken the jets out and looked and the sizing, but am no expert so it may well need a proper setup on the carbs. I will look into the 'vents' you mention and see if I can get some help with a carb tune.

 

Ok will try without again as I took the cabs off last night stripped them and cleaned them everything seemed ok no major dirt, damaged seals etc. I have made a note of the jets and tube sizes. Will see how it drives.

should the static timing be 6 degrees BTDC regardless of cams fuelling etc or should it be bespoke with my setup?

 

Sounds like a jetting issue to me, if that were a motorcycle it would be around the transition from pilot to main jets.

You can normally feel a lean hesitation as "bogging out" so to speak, far to rich will give you a rich misfire (feels like hitting a rev limiter).

Plugs should give you an indication.

 

Thanks yes been keeping an eye on the plugs and they are pretty sooty so rich, will look at the jets now I have an idea of the markings on them.

 

It would be well worth investing in a Wideband AFR meter if you are planning on tuning it yourself.

I have one on both my cars and find them invaluable really.

 

Thanks any recommendations welcome for an AFR meter.

I checked the main jets - weirdly 3 are 170 and one is 168 so I have ordered another 170 so at least they are all the same (idle jet is 60). I am struggling to find any guides on the correct jetting for my setup as its far from standard from a block/cams/carbs perspective, any pointers welcome I am happy to change the jets but would rather not guess....

 

I personally use Zeitronix (ZT-2 with LCD display) and have not had any problems with them.

AEM seem popular as well.

The Zeitronix comes with datalogging software and a serial cable which is handy if you don't have an ECU to log from.

 

Thanks assume you had to weld a port in the manifold for the O2 sensor? On mine nowhere to fit this.

 

Have you tried throwing in a bit more initial idle advance , thinking you may want to try that ?
Anyway back to your jets , your idles and mains are pretty "fat'' idles should be in the range of 50-55 and your mains @ 145 ish , these are based on the carbs having 36mm vents (or chokes as they say ) which are most commonly supplied off the shelf , the whole PITA part about tuning carbs is buying jets that you may only use once for testing but you need to swallow the cost to help establish a base line .
Have you set the air idle mixture screws to 2 1/2 turns out ?,your airbleed screws will need to be closed before applying a balance vacuum test to get the carb throats even, do you have the correct gauge ? the best is the Redline Synchrometer as they read better than all others and only way to do it .
Set your engine to rpm up on the throttle screws to between 1200-1500 and use the meter to check even balance @ each throat ,the air bleed screw should only be adjusted a small amount to correct readings ,if you can't balance you may have external vacuum leaks .
My experience with carbs go's back a long way mostly with air cooled VW's and have fitted Webers and Dellorto's ,always found the Dellorto's better to tune from the start as they are a more modern design than the Webers .
Good luck ,cheers.

 

Thank you yes I did add some idle advance and the engine sounded better but I have not driven it yet and need to before fiddling with anything else. I did suspect with my setup the static of 6 degrees BTDC may not be correct.

The new main jet is coming today so at least then I will have all 4 the same and use that as a baseline. I have not touched the idle mixture screws it did pass the MOT on emissions if that’s anything to go by but smells rich. I also need to get a gauge so thanks for the recommendation. This is all new to me so the help is welcome as I don’t profess to know what I am doing. As mentioned i probably need an AFR gauge to check my changes on the mixture. Jets are not massively expensive but as you say you need to buy some to see.

 

I have ordered some 145 main jets so will see if they make a difference, although I am thinking I will get it to a specialist with a rolling road as I could waste loads of time and money chasing something I don't understand,