V8 - cylinders 2 and 4 are cold

[mad_pete]

Right I have

4.2 V8

Megasquirt doing EDIS spark and fuel

New plugs

A big spark from 2 and 4 leads

But the exhaust manifold from 2 and 4 is cold. The back reads 170 the other side reads 180 but the branch from cylinders 2 and 4 only reads 90

Also it is blowing water out the top of the expansion tank but I'm hoping that's the misfire making the rest of the cylinders run lean as there is too much oxygen in the exhaust.

Any ideas where me missing bang has gone ?

[Bowie69]

First things first, pull the plugs out and take a look, I suspect they are very wet, given the symptoms you describe, which is causing your misfire.

Water blowing out the expansion tank will unfortunately be nothing to do with your misfire (aside form maybe a related symptom), this is coolant, bubbling, which means there is more than likely combustion gasses working their way into the water ways. Does the water system pressurise quickly? How hard are the hoses?

This can happen in a couple of ways, head gasket, or the dreaded slipped liner.

Do a search, you will find lots about both, and don't condemn it, the above is guess work on limited information.

HTH.

[mad_pete]

Well I was hoping to fix the misfire first and move onto the water escaping.

The car had new plugs fitted today and still didn't fire on those cylinders. I understand that misfire causes the fuel to wet the plugs but that's effect rather cause isn't it ?

[Bowie69]

Wet as in water...

I'd also triple check the plug lead positions.

[Hybrid_From_Hell]

Do a compression test on 2 and 4 for a start and report back

Nige

[mad_pete]

compression is fine on all cylinders ( sorry forgot to mention that ) Range 110 - 130 and I don't think 2 and 4 are the lowest.

I only doubled checked lead positions 2 and 4 are correctly plugged into coil pack 2 left hand side.

[Hybrid_From_Hell]

Swap coil packs ?

Check Injector Plug onto injector is clean / not poor connection

What colour is the plugs ?

Nige

[mad_pete]

I'll check what colour the plug was and injector contact. The spark from the lead looked pretty meaty on a HT lead to engine block test.

Is there a way to test injectors ?

[FridgeFreezer]

Pete, am I right in saying that this engine has always had a thing for losing coolant / pressurising the tank?

[mad_pete]

Yes ever since it's been in it's liked to throw it's coolant out of the expansion tank. The garage was looking at that today and said " you know it's not firing on 2 and 4 don't you ?" and I'm like "um no". So I thought I'd try and get it back to a V8 and then go back to the problem of coolant tantrums :-)

[mad_pete]

"Wiring faults on the injector circuits (and within the injectors) can be tested for at the ECU connector. Turn the ignition off and disconnect the ECU connector. Check the right bank of injectors by measuring resistance between terminals 2 and 11. Check the left bank of injectors by measuring resistance between terminals 2 and 13. In both cases, an Ohmmeter reading of 4-4.5 Ohms is expected. If the reading is 5-6 Ohms, suspect one bad fuel injector. A reading of 8-9 Ohms could indicate two bad injectors, and a reading of 16-17 Ohms could indicate three bad injectors. In any case, if the overall circuit resistance isn't 4-4.5 Ohms, proceed to checking for wiring faults or for open-circuit injectors. "

Anyone know if this still works post megasquirt ? and if so which terminals it now is ?

[FridgeFreezer]

It'll be pin 35/34 (Bank B) or 33/32 (Bank A). The pairs of pins are joined in the ECU but I can't recall the exact details of your loom. It's possible that there's a loose/dirty connection as 2 & 4 are next to each other it's conceivable they'd get paired up and connected to a pin.

[mad_pete]

So should I check for resistance / open circuit between 34/35 32/33 and 28 ?

[mad_pete]

okay looks like the connections to the injectors are shot, pulling the connector plug off one of the pins came off the injector.

The question is how likely is running as a V6 ish likely to be causing the overheat as well ?

[bluespanner]

If a vehicle came to me with a misfire and coolant problems, I would 99.9% of the time say head gasket or liner. Have you had the coolant tested for exhaust gas?

Roland

[mad_pete]

It was negative.

[Hybrid_From_Hell]

OK

Runningas a V6 won't make the engine boil its head off,

I know this from all the "Fun" I had when I had the engine

with its frigin misfire for months

SO, there are poss 2 probs here

1 - The engine misfiring

2 - the engine overheating

1st the misfire

You say you have good compression on the 2x cylinders in Q

and you have good spark too

On the simple basics of 4 strokes therefore (Suck, squuze, bang, blow)

you have the Squeeze, and Blow but not the bang, so the missing item

is most likley the suck - ie fuel

CHnage both injectors for know good ones, and also check the plugs for any

corrosion and decent joints / wiring issues

THis may sort out the misfire, additionally lower than the req pressure of fuel can cause

this too, if the above doesn't sort it rig in a fuel pressure gauage and check when running the rail

pressure - I have the kit you can borrow if you need to, you know me number

As to the overheating, what radiator are you using, do you have fans

if so which / what sort, do you have a fan cowling, and what themostat

temp are you using ?

As I said, I doubt the 2 issues are related

Nige

[mad_pete]

That's a pity. Injectors and connectors 2 and 4 and maybe the rest are going to be replaced. Hopefully the misfire is down to that. The radiator is a na 90 and is new. The thermostat is 88 I think and new. The heater matrix has been replaced and it has a new rad cap. The fan is a viscous fan and I recently put the right cowl to go with it on.

Doesn't the extra air in the exhaust from the 2 cylinders not burning anything mess up the oxygen fueling as the sensor over reads oxygen?

[Hybrid_From_Hell]

The Lamda in the zorst will read wrong, but the effect on the ECU MSQ is minimal if set right, and

the reading are "Lost" when engine is switched off, re start and it begins again, and the changes are not "Written" to the MSQ unless via MLV

90 TD Rad may not be enough - does it overherat all the time, or when just working hard off road, or in heavy traffic, or only on hot days and not cold days etc, or will it just boil its B******s of it left standing on tickover ?

Nige

[mad_pete]

I would have done my logging runs with the misfire so I'll assume it's probably saved. On tick over it won't boil, but any sort of driving tends to get some out. I think a good prod of throttle when driving results quite quickly in coolant out the overflow. So anything above a few miles or any full throttle will cause some coolant loss.

[FridgeFreezer]

Easy way to check, bump up your REQ_FUEL value in Basic Settings -> Engine constants by about 10-20% (makes the whole map richer) and turn EGO correction off.

[mad_pete]

It was faulty injector connectors. New injectors and connectors and hello V8 again. I upped total fueling from 20 to 23 and it still loses water.

[Hybrid_From_Hell]

Yep

As I thought seperate issues between misfire and cooling

So, misfire sorted, now can concentrate on cooling

Please explain when it does / doesn't overheat

ie stationary and running Tick over 30 mins yes no, booting it about

cold days hot days both at speed only when I ....etc etc

Nige

[mad_pete]

It might not be overheating. The temp gauge ( which may be wrong now due to gauge / sender mis-match due to 3.5 carb -> 4.2 EFI ) goes up to normal and stays there.

Megasquirt thinks it gets up to 105 C which is a bit hot but under pressure still maybe not boiling.

So water never comes out on tickover but will come out after a 15 minute drive or more at normal speeds. A good bit of right foot seems to cause more to come out. None of the days I have tested on have been particularly hot or cold.

So anytime under load with more load seemingly pushing more water out.

[FridgeFreezer]

105 C is still well hot (for a truck with an 88 deg stat). As I said further up the thread, this engine has always done this since you've had it so I'm afraid to say it could well be something fundamentally wrong with the lump.