Cylinder 5 problems - Opinions please on what to check next

[hadtstec]

Hello everyone, I have a Tuscan MK1 with a 4.0L Speed six and cylinder number 5 is not happy.
When idling, I can feel with my hand over the passenger side exhaust that the exhaust is not steady like the other side.
I also used a temperature gun to measure the temperature of the manifold right by each cylinder and cylinder 5 is about 100 degrees cooler.
I pulled all the plugs and they were all good, apart from cylinder 5 which was brown.

My problem is that I've done all of the following, but the issue persists and I need advise on what to check next.
(These are all brand new quality parts)
- Replaced Spark plugs
- Replaced HT Leads
- Replaced Coilpack
- Swapped Injectors (1 and 5) and confirmed that the issue is still with Cylinder 5.
- Checked the wireing from the Engine bay harness plug to all Injectors and I have continuity for all.

What else is there to check?
Is this a common issue?

I assume that the next step is to check the wires from the ECU to the Injectors, but I am confused as to why I have continuity accross both terminals of the Injectors from the Engine Harness.

I have looked at the TVR Wiring diagram, but does someone have an ECU Pinout so I can check the fault from there?


Many thanks for any suggestions

Edited by hadtstec on Tuesday 28th July 18:19

[Modrich]

MBE ECU harness pinouts

Edited by Modrich on Tuesday 28th July 20:28

Edited by Modrich on Tuesday 28th July 20:29

[Modrich]

Have you checked the throttle body side? When running check for pre-ignition in the inlet/backfires etc which suggest poor AFR. After that whip the cam cover off and check the valve train and valve clearances...

[mrniceguy351]

Compression test.

[stlol]

mrniceguy351 said:

Compression test.

Yes, agreed.
You may have bad compression due to closed up valve clearances, when were they last checked.

[Snaaakeey]

I had exactly the same symptoms on cylinder 6 except it was just the injector plug had popped of the injector. If you have swapped out the injectors and the problem persists then its compression or signal. Its probably thrown a shim. I imaging your AFR is in alarm too.