Unusual behaviour

[Blu3R]

I have what feels like a misfire at only occurs at around 3.5krpm in third/fourth/maybe higher, haven't checked - the car feels fine and has lots of boost building with WOT before this point and then coughs. If I keep my foot in, it clears and pulls right to 5.5k ish where I'll typically change anyway.
Now ordinarily I'd look at plugs, coils, fuel pump plus associated wiring, filter etc. BUT the od thing is when it's coughing, the rev counter drops to 0 and flicks back and forth between the correct rev and 0.
What's that all about? Crank sensor?
I've recently resealed the floor and am wondering if I've inadvertantly managed to trap a wire, is this possible given the symptoms?

Any ideas where to start would be great.

[sundance002]

Blu3R said:

I have what feels like a misfire at only occurs at around 3.5krpm in third/fourth/maybe higher, haven't checked - the car feels fine and has lots of boost building with WOT before this point and then coughs. If I keep my foot in, it clears and pulls right to 5.5k ish where I'll typically change anyway.
Now ordinarily I'd look at plugs, coils, fuel pump plus associated wiring, filter etc. BUT the od thing is when it's coughing, the rev counter drops to 0 and flicks back and forth between the correct rev and 0.
What's that all about? Crank sensor?
I've recently resealed the floor and am wondering if I've inadvertantly managed to trap a wire, is this possible given the symptoms?

Any ideas where to start would be great.

Hello mate., could it be the lamda sensor? also i had this problem that turned out to be the ecu .

[TIGERSIX]

Start at the plugs and work your way out imo .

[GTO600]

Check the bulkhead relays & holders.

[worty]

I had something very similar. After checking plugs coild ht leads chamging the map and swopping the ECU Dave at Jetstream tracked it down to a dodgy injector.

HTH
worty

[dave sutton]

It must be something that is sending duff signals to both the rev counter and engine management. If it is also rpm/vibration sensitive, it suggests a sensor that is loose or has a dodgy connection or something in the fuelling system. These are the clues, I leave it to the experts to narrow it down to the likely candidates.

[Hollowpockets]

the same symptoms for me was one coil breaking down and not able to create a strong enough spark at high boost

[Blu3R]

Thanks for all the suggestions, I think the best course of action is to start at the beginning and rule out the obvious, as Tigersix said.
Only thing is.....

dave sutton said:

It must be something that is sending duff signals to both the rev counter and engine management. If it is also rpm/vibration sensitive, it suggests a sensor that is loose or has a dodgy connection or something in the fuelling system. These are the clues, I leave it to the experts to narrow it down to the likely candidates.

That's what I started thinking, the rev counter is making me doubt any of the obvious ideas and why I initially thought I should look at maybe crank sensor - is it a red herring?

[mgbond]

Is the car well warned up when this happens. Didn't a few people get a similar symptom and it was the fuel pipe collapsing?

Bondy

[GTO600]

Blu3R said:

Thanks for all the suggestions, I think the best course of action is to start at the beginning and rule out the obvious, as Tigersix said.
Only thing is.....

dave sutton said:

It must be something that is sending duff signals to both the rev counter and engine management. If it is also rpm/vibration sensitive, it suggests a sensor that is loose or has a dodgy connection or something in the fuelling system. These are the clues, I leave it to the experts to narrow it down to the likely candidates.

That's what I started thinking, the rev counter is making me doubt any of the obvious ideas and why I initially thought I should look at maybe crank sensor - is it a red herring?

Rob, that's why l suggested checking the bulkhead relays & holders as this can be the cause of your fault with indentical symptoms. Remove the relays & blow out the bases with an airline then spray with a switch cleaner, also clean all the relay connections & make sure they are making good connection in the holders or even better fit a new Ecu & fuel pump relay ( Note though that these are not your normal 5 pin changeover relays).

[Ash 996 GT2]

GTO600 said:

Check the bulkhead relays & holders.

This!

If your relays, behind the driver are upside down, check for water damage.

If yes, remove, replace, take the relay holder out, turn upside down, preferably move into cabin.

Sorted.

Of course, thats if it is that

[Gadgeroonie]

is it overboosting in the cold weather ?

[Nickellese]

Blu3r did you ever get to the bottom of this issue?

Mine started doing exactly this whilst out today. No other symptoms execpt the cough (rev counter drops) then back to normality.


Advice would be welcome!


Cheers

Nick

[Blu3R]

Nick, being completely honest - the car hasn't moved since I posted about this problem. It's in the garage and tucked to one side so I can get around without bumping it, so I can't even lift a clam to check anything. When the weather improves I'll get onto it.

Rob

[Nickellese]

Thanks for the quick reply Rob,

A bit more progress my end, I took mine out again yesterday and it starting stuttering at tickover at junctions/ whilst stationary. It sounded like a fueling issue, to my inexperienced ears anyway!

Hope you get to the bottom of yours soon chief.


Thanks

Nick