Fuel injector issue... or something else?

[Nenad]

Filling up fuel some weeks ago, at a new petrol station (my usual place was closed for renovation – here in Malaysia I only use Shell V-power Racing but this time I had no choice and got plain V-power), soon after I could feel, and hear, that something wasn't right. The engine started getting hiccups, as well as producing more pops and bangs than just on overruns. Pushing it 'a bit' did seem to clear the engine so I assumed that it was just a case of bad fuel and waited for the next fuel top-up.

But I still have the same problems – the engine not running cleanly. And recently it's started behaving strangely at cold starts. Once it starts up, it's getting up to 1600-1700 RPM (not good, I know, so I start driving immediately to keep the RPMs down), but once warmed up, the idle drops to the usual 800-900.

I've had the tappets adjustment done recently, maybe a couple of months and a few hundred miles ago, and also had the HT leads changed, just in case. So, unless the guys screwed up the adjustment, that can't be the problem.

One more thing, now I think about it: Over time, the idle RPM drops (it's done that since I got the car some five years ago), and following the last adjustment, it was getting down to barely 600 with A/C so I adjusted it manually, to 800 with/900 without A/C.

Any suggestions? Anyone familiar with the engine rushing on cold starts? Time for injector cleaning, or worse?

[TimLux]

Have a read through these, some of them seem applicable:

http://www.mytuscan.co.uk/problems_main.php

[dvs_dave]

Worn, or out of adjustment throttle bodies causes this. Could also be a throttle body/head gasket air leak, or a bad oil pack. Fuel probably just a coincidence.

[mk1fan]

Easy to check if the throttle bodies are out of balance - in you have a flow meter. Would be my first check as this was the issue with my very poor running. It is also non-invassive.

Coil packs are mounted on the side of the engine below the airbox so get cooked easily. Again swapping out for a known good one is relatively easy.

Idle can be adjusted and the ecu base idle reset accordingly.

After that it's undoing things - the spark plug cover is sealed in place with mastic so checking the plugs and leads means redoing this. That would be my next check.

[Nenad]

Thanks for the suggestions, guys. Admittedly, I've not yet done any further investigation, partly because the engine seems to be behaving much better now… kind of. Particularly when the air temperature drops a bit, in evenings and during rain. It still happens now and then – I can feel it stutter slightly on the motorway, but opening the throttle clears it out every time. And surely worn throttle bodies and/or a bad gasket would behave more consistently?

But there's also the other, strange, issue of the engine revving on cold starts. Not immediately when it's started, but as soon as I depress the throttle to drive off, it goes way up to almost 2000 RPM. It did it in November, when the whole thing started, then it went away for a while, and now it's back. Once the engine starts getting warm the RPMs drop to normal. Has anyone come across something similar? Weird electronics/sensors?

I so wish I could get the diagnostics software to work; have located the plug under the steering column, am using a cable bought from TVR Power, the software is running fine and detects any of the USB (serial) ports that I connect to, but it just won't detect the ECU. Tips gratefully appreciated!