VFR800 on 2 litre bus - idle bafoonery - fixed

[oliverisit]

I've recently replaced Dell 36s with a micro squirt on my 2 Litre type 4 engine VW bus.
Specs
*MS2/extra3.4.4
* TS MSv3.2.05
* vfr 800 ITBs, with recon injectors and FPR
* external walbro FB with coarse pre filter and fine post pump filter
* Bosch / VW jetta 4 post coil
* 36-1 timing wheel with hall sensor
* std cam
* no idle valve yet (will fit an on-off type once up and running)
* 14point7 wideband earthed as per best practice
* MAP sensor connected to all throttle bodies, under the butterflies and tee'ed together

Timing set at 10 degrees and angle adjusted using timing light
Throttle stops adjusted to approx 900-1000rpm idle
ITBs balanced with 'snail' meter
all plugs resistor, and tested sparks
all injectors flow tested

I've not got the tuning stage yet, as I've been struggling to get it to idle.

This eventually turned out to be heavily carbon fouled plugs, however only two of them .

Clyinders 1 & 3 have the fouled plugs, 2& 4 are as clean as a whistle.

My synopsis is 2 & 4 are not firing, which has meant the wideband is showing super lean, which I''ve over corrected, and fouled the plugs on 1 & 3.

In order to try and coerce half my engine to join in, I've tested all four injectors ( Tuner studio test mode, holding open the throttles I can see lots of spraying action), and tested each plug and wire (again via test mode), all of which give decent sparks on command. I've swapped wires and plugs round too ( no difference).

Any ideas?

Next plan is to swap the ignition channels and plugs over to see if this makes any difference (to rule out the coil), and start swapping injectors round.

The bus will idle fairly well, however unplugging injectors 2 or 4 makes no difference.

Here are the plugs from 2 & 1 after a cold start to warm idle:

Screenshot_20250406-155855.png

[Bruce.m]

Check the HT lead allocation very carefully. The coil is wasted spark so opposite pairs must use the correct pair of terminals. The coil current passes vai the HT lead to the first plug, through the cylinder head, cylinders & block, over to the opposite spark plug then returns to the opposite coil terminal via the other HT lead.

[Bruce.m]

If you hold the coil with the multi plug socket pointing downwards, the top two HT terminals go to one side of the engine and the bottom two terminals go to the other side of the engine. 1&3 to one side and 2&4 on the other side (left & right).

If 1&3 or 2&4 are opposite corners, it’s definitely wrong.

[oliverisit]

Thank you for helping, coil wiring as below:

PXL_20250407_184119696.jpg

PXL_20250407_184128654.jpg

I've since swapped the channels over ( and leads) and still no joy from 2&4, so I think the coil has is ok.

Next up I've reflashed the firmware, but ran out of time to test. If this is no good, I'll start swapping injectors round.

[Bruce.m]

HT leads are good then.
You are taking a sensible approach (swap stuff).
Since you are batch mode injection there is less to go wrong there (no cam sync).
Any chance the valve tappets are tight on that side? Doubt it, but no compression would explain the situation.

[oliverisit]

Alas the firmware refresh wasn't the issue. Here is a terrible video showing the issue, apologies for the bits where I had to put the phone down to find the noid.

[media]https://youtube.com/watch?v=t73qTarFTUQ&feature=shared[/media]

Have swapped injectors on 3&4, so will test tomorrow

[oliverisit]

Updates...

Swapped non- firing cylinders injector for firing one, and no change.

H'mm so back to sparks. Unplug dodgy cylinders lead, put in spare plug, lay it on the block, run engine - no spark. Put inline tester light, repeat - no spark, but weak flash from the light.

Check same plug / lead with test mode, strong spark

Current thoughts tend to coil and or current power supply?

New coil on order ( the one I have is brand new Bosch), and recheck coil power (it's a separate fused feed from the fuel pump relay), and the coil earth.

Good job I like a challenge, might have to revert to carbs temporarily if I cannot figure this out

[Bruce.m]

If test mode is firing the plug nicely id be double checking all the basic engine settings in Tunerstudio. Although the test mode probably uses a very generous dwell period to charge the coil which may mask a weak coil.

Note, the coil pack has two separate coils inside. One fires 1&3 and the other 2&4. So if one of each pair is having issues and the other is fine, that is very weird.

[oliverisit]

Thanks Bruce,

It is very odd - 1 & 3 always fire, 2&4 do not. I've swopped the two coils round and the same happens, which suggests both seperate coils are fine.

This leaves the connection from ECU to coil for 'IGN 2' , the power / grn circuit for the coil pack, or (as you suggest) the signal from the ECU.

Given I can see an indicator light flash on the 2 & 4 circuit, I think that means the connection from the ECU is OK, and there is a logic pulse getting to the coil (backed up by the test mode).

If the replacement coil doesn't fix it ( as I suspect), I'm going to rejig the timing so the firing order goes from 1-4-3-2 to 4-3-2-1 , (similar to cranking round the dizzy wth a carb'ed engine). I think this will mean I can get the misbehaving cylinders to be on 'IGN 1' , and see if they fire.

[Volky]

Hi,

I believe this is the same coil. See wiring...

[oliverisit]

Thanks volky, that's how it's wired 1&3 on one side, 2&4 on the other, with the appropriate ign feed to each - in the pictures I've got ign feed A feeding the l/h side, which is why it looks different, but swapped round ( and the plug wires) it still misbehaves...

[Volky]

Hi,

I am assuming the Type 4 engine has the same firing order as the Type 1. So, aren't the wires out of order?

[oliverisit]

So the coil is two separate coils in one package, split left and right, with a trigger wire for each. As long as ignA wire from the microsquirt is on the coil connected to 1 & 3, it can be on either left or right coil. Mine is on the left, so the plug leads don't cross over.

I have wired 1&3 to the r/h coil, and moved the ign A trigger so it matches the dub shop picture, and that made no difference ( as seen in my video linked above)

So this suggests both coils are ok, and the fault is elsewhere.

Appreciate the input, normally I'm the cause so need all the help I can get

[Bruce.m]

What have set the dwell to in tuner studio?
And the basic engine settings, firing order etc

[Bruce.m]

What HT terminal are you using at the coil? Should be the M4 style although a GM style fits I think.