Running on 2 (of 4) cylinders after head gasket change, tried everything except throwing money at dealer

Help & Advice
1

Update: I think I’ve found the problem: I put back on my original idle control tubes (the plastic piping from the inlets to the idle control valve) that I’d swapped for some better condition replacements and got . . . . . . . 4 working cylinders (well, 4 cylinders where the revs drop when I disconnect each coil).

Fingers crossed that I’m now sorted.

Original:

I’m tearing my hair out in frustration with my bike running on 2 cylinders. Please, help before I lose my temper and take a sledgehammer to her.

In short:
2002 Triumph TT600 22k.I lost all compression on No 4 cylinder with no other signs (no problems with coolant pressure, oil perfect etc) and got a small pressure rise when I put some oil through the plug hole.I took the engine out. The rings, piston and bore were all well in spec so I fitted a new head gasket and reshimmed a couple of the valve clearances that were slightly out of spec.On a compression test all 4 cylinders show a similar pattern and a max of around 145 psi.She started OK, albeit sounding rough and revving to 3000 rpm for a short time.When balancing the inlets I somehow shorted one of the Power Commander leads to an injector (I don’t think this is causing the issues but you never know).I took the Power Commander off and she started but ran rough as before.When I disconnect the coils on No 3 or No 4 cylinders nothing happens but she stalls when I disconnect No 1 or No 2’s coils.There are no fault codes unless I do something silly like leave off an injector connector. Strangely, I don’t get ignition fault codes when I disconnect the coils.I get, as far as I can tell by eye, similar sparks and injector patterns on all 4 cylinders.The compression tests gave the same results as before, hot or cold.I’ve checked and rechecked voltages, continuity and resistances on the battery/alternator circuits, ignition circuits, injector circuits, fuel pressure, crankshaft position sensor and just about anything else I can think of.I’ve checked and rechecked that the camshaft timing marks are aligned correctly, the valve clearances are OK and the opening, closing and centre of lift of each cam matches the figures in the maintenance manual.I’ve swapped plugs, coils and injectors and fitted different ECUs (with or without the Power Commander), crankshaft position sensors and cables, all to no effect.I’ve ordered a leak down tester to double check compressions.I have an OBDII interface and used the free ScanTool to find anything out of the ordinary but nothing showing.
I hate to throw money at a dealer but I’m running out of ideas.

Any advice please?

2

Coil plugs in the right coils?
Depending where you are, I can have a look for you.

3

ps: I had a Daytona 600 for 2 years, spent most of its life in bits, so I feel your Triumph related pain :wink:

4

Scorch, thanks.

The coil plugs are to the right cylinders. The connectors are staggered along the loom so its’s hard to get them wrong and I’ve checked the wiring colours. I’ve also checked that they go to the right pin on the ECU connector.

Thanks for the offer. Alas, I’m in Redhill so at the opposite end of the M25 to you.

5

Yes, bit of a hike on 2 cylinders. Let me have a think about this, you’ve provided plenty of detail so I suspect after a couple of post-work tinnies I might have a brainwave :slight_smile:

6

When you first started it after the rebuild, it revved to 3000rpm? You haven’t knocked the tps out of line during your engine refit?

7

And the timing wheel on the left has an I on it, and the one on the right has an E…? Just checking :wink:

8

Found something!

I put back on my original idle control tubes (the plastic piping from the inlets to the idle control valve) that I’d swapped for some better condition replacements and got . . . . . . . 4 working cylinders (well, 4 cylinders where the revs drop when I disconnect each coil).

It looks as if the tubes for 3 & 4 each have a partial blockage. I think that would explain my symptoms: if there’s little air getting in through the tubes and the throttle butterflies are adjusted properly then the cylinders would have had little air going in and hence little power.

Now to put her back together and try her out on the open road.