GTA Turbo - running issue

I have a slight running issue.
GTA starts fine, idles fine and drives OK when cold,
However, when I’ve driven for say 20 miles i.e. the engine is warm (I’m reluctant to say hot as it’s blooming freezing outside) it has a slight hesitancy about it.

Symptoms are;
Driving at steady 60 MPH, the rev needle starts to flicker slightly yet the engine revs stay constant.

If I accelerate slightly, then it pulls ok but not that smoothly – that’s when it feels hesitant.
If I put foot to the floor, the turbo kicks in, but the engine doesn’t feel like it wants to rev freely and again it feels hesitant.

I’ve checked that the HT leads to the plugs and the connectors to the Renix unit and they appear to be OK.
I did notice that the Renix unit seems to be a bit loose, would that make any difference – should it be bolted firmly to the car?

I did have a loose hose to the actuator which I tightened a week or so ago.

Any views would be much appreciated.

Check dizzy and rotor + wiggle the wiring to tdc sensor .Is it overfueling when hot ?Check water temp sensor resitance .

Check dizzy and rotor .

+1, had exactly the same symptoms on mine.

Thank you.

I'll check out the water temp sensor resistance and see what readings I get.

Cap and Rotor havent been changed for a while, so I'll replace both as well.

Coolant temp sensor reads 263 Ohms cold and 396 hot, so that looks to be working ok.

Replacing Cap and Rotor, but the three hex screws holding the rotor on wont budge.
Surely they shouldnt be that tight

The cap is well worn - centre pin almost gone.
Do the Rotors wear out as quick as the Caps ?

Managed to replace the Rotor and it seems to run a bit smoother than before.

A few part nos. if anyone is interested.

Bought the Cap and Rotor from GSF (German Swedish French).
Cap - 921BM0070 £54
Rotor - 922BM0070 £14

Both are listed by GSF for a 1989 BMW 3.0

Both are BERU types and the Cap had the following letters and numbers printed on it;
VK 378 S GX


My old Cap & Rotor were sourced from Renault and Bosch make with following nos. printed on it
7700 267 728
1235 522 388

I'll also add the above to the other PARTS thread.

Rgds
Paul

Usefull info thanks. You say it's better but is it sorted now?

Trevor.

To be honest, I havent had a chance to take it for a proper run yet. It just seems to tick over runs smoother than before.
The old dizzy & rotor had been on the car since 2001 and I didnt realise that these cars eat them quite quickly.

You did well to make it last that long!!!

I carry a spare set having been caught out by the side of the road on a couple of occasions even after fairly recent changes...

You did well to make it last that long!!!

Well now I know they're a weak point, I'll buy another set just in case.

Took it for a long run today and all the previous symptoms seem to have gone, so all good.

Am slightly worried about the three screws holding the rotor on and the fact that they can shear off when you attempt to undo them. Did put a very small blob of copper ease on the threads, but then screwed them up quite firm. Wondering if I should take off cap again and loosen them a little.

.
Good results Paul, good to see another one running sweetly. What plug gaps are you running?

Regards,
Martin

I'm currently using Champion S6YC plugs set at 0.8mm gap.
Havent changed these for 12 months or so, but to be honest I only did about a 1000 miles last year if that.

I'm currently using Champion S6YC plugs set at 0.8mm gap.
Havent changed these for 12 months or so, but to be honest I only did about a 1000 miles last year if that.

I'm not a big Champion fan, NGK through and through, but hey ho. I would run them closed up a little at 0.6mm, and see how you get on at that. It will give your rotor arm and dizzy cap a slightly easier time as well.

Martin

I'm currently using Champion S6YC plugs set at 0.8mm gap.
Havent changed these for 12 months or so, but to be honest I only did about a 1000 miles last year if that.

I'm not a big Champion fan, NGK through and through, but hey ho. I would run them closed up a little at 0.6mm, and see how you get on at that. It will give your rotor arm and dizzy cap a slightly easier time as well.

Martin[/quote

So you recommend closing the gap slightly, does this not reduce the flame front, does this not reduce power due to a less efficient combustion chamber burn?

I am not saying your wrong Martin, I am just keen to learn the reasons behind it, or is this something you have found to be ok through real life experience/trial and error?

Cheers

Si21

I'm currently using Champion S6YC plugs set at 0.8mm gap.
Havent changed these for 12 months or so, but to be honest I only did about a 1000 miles last year if that.

I'm not a big Champion fan, NGK through and through, but hey ho. I would run them closed up a little at 0.6mm, and see how you get on at that. It will give your rotor arm and dizzy cap a slightly easier time as well.

Martin[/quote

So you recommend closing the gap slightly, does this not reduce the flame front, does this not reduce power due to a less efficient combustion chamber burn?

I am not saying your wrong Martin, I am just keen to learn the reasons behind it, or is this something you have found to be ok through real life experience/trial and error?

Cheers

Si21

Hi Simon,

Later.. results on the rollers, and general running. If you are on the OE single coil pack you are on a limited energy budget, better to have a strong short spark than a weak long one... it's all about heat intensity, not that the spark jumps from one side of the chamber to the other. In fact, the orientation of the plug earth strap will have more effect on performance within this gap range than the gap... if you are really serious about it you will index your plugs as well...

Yes if you close it up too much it will expose less fuel air to be ionised, and hence weaken the initial kernel, but you have to close it up a lot. The over-riding thing in this case is the limited amount of energy from the OE coil pack... hence my comment, recommendation and how I run them, works good for me chap

If you have modern coils and drivers, and consequently a good margin of excess energy, then sure widen them back up, but I'll put a full English on it, you won't pick up much worth talking about

Cheers,
Martin