Like buses, 2 faults arrive at the same time

[Northern Banana]

2019 Sigma 1.6 vvt

Car starts and idles ok. 
When warmed up and you increase revs engine stutters and dies. 
 

At the same time the taco needle wildly flares around.  Thought maybe crank sensor, but when I plug in easimaps barometric sensor error is reported. Also unknown error in ecu box on easimaps.

 

Can't see why  MAP sensor would cause taco needle issue.  
 

Any ideas?
 

 

[Jonathan Kay]

And two posts!

; - (

Jonathan

[Jonathan Kay]

Any recent work on it?

Other instruments working OK?

Has it been drowned recently by weather or washing?

Check ECU connections including earth.

Please let me know if you'd like a wiring diagram.

Jonathan

[K7 VCT]

https://www.caterhamlotus7.club/forum/techtalk/map-sensor-0

 

 

Might be linked to this

[Northern Banana]

Link to YouTube clip of easimap screen highlighting issues. 
 

 

[aerobod - near CYYC]

The baro reading is normal for a Caterham tune, when there isn't a baro sensor fitted (not sure if any models get one), as it defaults to the "failed" value of 1.040 Bar. Even if there is a baro sensor fitted, in the UK it won't make much of a difference unless you're in Snowdonia or the Scottish Highlands.

The two values that are problematic are the battery voltage measured at the ECU that is all over the place (from 7V or so to normal voltage), so there is a lot of fuel being added when the voltage drops, I would suspect a bad ground or supply line somewhere. The main ECU ground is somewhere under the dash not too far from the ECU, I would look for any ring terminals attached to the scuttle and see if they are clean and tight and also check the engine to chassis ground is good and has low resistance.

The other issue is the air temp at -6C or so, unless you are in a chilly climate at the moment, this is way out and would also cause a mixture adjustment problem with more fuel added. This may be a reflection of a bad earth, too.

I would work on finding the issue that is causing the measured battery voltage to vary so much (assuming the battery voltage itself is confirmed as good using a voltmeter across the battery with the engine running).

[john milner]

Not where I live. Two routes one of each every fortnight on separate days on alternate weeks.

Now I think about it that is a bit like the faults I get.

[Northern Banana]

Thanks useful stuff. 

The voltage drops were when the engine was hunting for revs/close to stall.  It is normal voltage when idling properly and when further up the rev range.  I've ordered a new crank sensor and need to get the scuttle off to allow a proper check of earths and connectors.

When the racecars move up the ladder and windscreens are removed, the wiper mechanism simply gets pushed down under the scuttle and the wiper head holes plugged.  Not great having that wobbling around with a good chunk of the loom cable tied to it!

The minus temp value and pause in the live data is as you suggest concerning, will unplug the air temp sensor to see what default value it throws in or if it shows an error.  From speaking to others the live data values should be reporting seamlessly.

[aerobod - near CYYC]

You shouldn't get such a voltage drop when near stall as the battery should be providing the right level of voltage itself when the  alternator isn't. The only time you should see the voltage drop below about 11.5V is a very brief spike when the starter motor is engaged during starting, even then less than about 8V is problematic. Voltage measured at the ECU should normally stay in the 12.5 to 14.0V range all the time when the engine is running. The stalling and hunting may just be an effect from the wildly fluctuating fuel injector time value due to the wildly fluctuating voltage seen at the ECU, not the other way around.

It is also worth logging as many values as possible into a file and graphing the output (up to 32 is the limit I think), as things like the Reset Counter may be incrementing. It is then easier to look at any interaction between specific sensors and events, using for example, a 50ms output time resolution.

[Northern Banana]

Thanks James spot on

logging it the issue occurs when the voltage drops the ecu seems to shut down and easimap pauses. 
 

need to work my way through the electrics but only seems to occur when warmed up so possibly a cracked main cable possibly a duff master switch. 
 

will try a replacement air temp sensor but it seems to run the same connected reading minus 8 or disconnected.