Fuel Trims

[ChrisHolmes]

If you look at the Rockingham Track day thread you will see several posts about what happened to my car. viewtopic.php?f=100&t=78021&start=200

The car now idles but its not the smooth 1000rpm that it was before yesterday.

The fuel trims at idle are as in the photos below but I don't know if the variations are normal or not. Also I don't know if the fluctuation is caused by a fuelling issue or an ignition issue so any pointers will be greatly appreciated.

[ChrisHolmes]

Have you checked the air meshes in front of the MAF?(I haven't read the other posts)

[ChrisHolmes]

Not checked the meshes. We had the airbox off yesterday and it was dry.

The engine died 3/4 way down the start finish straight and I pout it down to fuel starvation, even though that has not happened since I upgraded to an S2 pump about 2 years ago! I finished the lap and went into the pits for fuel and when the engine revs dropped to idle the engine would go rough and stall. Upon trying to start it just spin and spun with little kicks and eventually would run at very low revs as if on one cylinder and then with a little throttle would gradually build revs and run smoothly right up to the red line.

We swapped the plug leads round and it started a bit better but still would not idle smoothly and sounded really bad but then sounded normal when revved so we eliminated anything mechanical having failed.

When started this morning it was slow then we drove immediately back to Cheltenham on the motorway with the engine sounding and pulling normally. Once home I let the revs drop as normal to idle and the engine kept running but the revs fluctuated slightly but not in a consistent way. Sometimes rising to 1100 then falling back to under 1000.

I have my old OEM coils back which I will swap in tomorrow to see if that makes any difference and will of course check the meshes etc: whilst doing that.

[SeeJay]

The MAF seems to be showing a higher reading than normal for idle - it's usually about 5g/s I believe

The elevated fuel trims show extra fuel being added - perhaps to compensate for an airleak

[350matt]

I'd agree
sounds like a vacuum / airleak to me
if you spray some lighter gas / brake cleaner around all the rubber hoses / possible leak paths with the engine running and listen for it revving up then you've found your leak

[ChrisHolmes]

Hmm! I may have disturbed or broken something when I removed the airbox to get at the coils.

[Juey]

Eccentric shaft position sensor been knocked?

Disclaimer - I am 100% clutching at straws and have no idea of the symptoms of this.

[warpc0il]

There was no mention of the EML flashing, otherwise I would have been all over the ESS - either the sensor itself, or the wires, or something magnetic stuck to it.

The problem could still be the latter, especially as there's often a lot of metallic debris around a track and the higher speeds often create strange airflows under the car, that could suck something up the front of the engine.

[V8 Power]

Chris
Do you have a catch can fitted and is it more full of oil than normal?

[ChrisHolmes]

All sorted engine now idles smoothly, starts straight away hot (after 15 minutes) or cold.

Solution was to remove the D585s and fit my old origin unknown coils!

Clearly one of the plugs on the rear rotor, 3rd from left, was not firing, see photo.

@Dave I have had no flashing EML or any codes appear when the car faltered yesterday.

@Graham I don't have a catch tank and have never had an oil burp. The bellows of my inlet is virtually dry.

[warpc0il]

Have those plugs been recently "cleaned"?

Cleaning rotary plugs, either with a sandblaster, wire brush or sandpaper is a big no-no.

The plating of the metal surfaces is critical to preventing corrosion while the surface of the centre electrode insulator is engineered to prevent "tracking"; any mechanical cleaning will damage these surfaces and cause ongoing issues.

@Chris if your plugs were just changed recently and had not been "cleaned" then please take the above just as advice.

Plugs can be "cleaned" by soaking in Seafoam or Cataclean and scrubbing with a soft (e.g. tooth) brush, but don't be surprised if the brush handle melts.

[ChrisHolmes]

They are new plugs fitted probably around 1000 miles ago. I appreciate the detail regarding how traditional plug cleaning damages the plugs.

[350matt]

So this is another failure of D585's then

seems to be catching, are you going to go for some of the new rotary rev's 'big' coils?

[ChrisHolmes]

I presume you mean Ryan Rotary Performance. Depends on the result of the tests on my coils

[BigPete]

Well at least it’s an easy fix hey Chris

[ChrisHolmes]

Certainly hope so Pete. Compressions seem to be through the floor though so its not all good news at the moment.

[BigPete]

Um strange but may be nothing as it starts fine. Mine is now in bits and looks fooked