My MX5 MK 2.5 1.8 VVT is hesitating and sometimes missing a cylinder mostly when cold.
the mileage is low (<50k)
I have done a compression test (all ok)
I have changed the plugs, leads and coil packs (standard advice for this type of issue)
But still the problem persists.
Any ideas?
I had a good look around under the bonnet and found a sensor called a "Boost Sensor", it seems to be a pressure sensor.
The car is not turbocharged
The hose to this sensor has been cut off.
Does anyone know exactly where it should connect?
I suspect that this may have something to do with my hesitation.
Description
[Edited on 28/11/19 by JonBowden]
[Edited on 28/11/19 by JonBowden]
Pretty sure you are talking about the atmospheric pressure sensor - I seem to remember it is labelled boost sensor, it does not have a hose as it is
just sensing atmospheric pressure!
When I stripped the wiring loom for my conversion I discovered that it has an OBDII port - think it was the first one. if you can get live data out
with a scan tool that might give you a clue as with an intermittent problem you are a bit in the dark.
Any one of the inputs to the ECU could have a bad connection or be putting out defective data - Cam,Crank, Temp, MAF, engine speed... or it could be a
faulty injector, an air leak, stuck VVT actuator etc.
For a wild guess, as it is when cold and looking at the time of your post, do you have the right spec, clean, oil in it ? The VVT uses oil pressure
for actuation, thick or very old might give you issues.
As its mainly when the engine is Cold, Coolant temp sensor or its wiring/connector?
It's definitely got fresh correct oil in it.
The boost pressure sensor has a hose attached but it seems to have been cut.
The manual diagrams indicate that it should go to the inlet manifold somewhere - but give no indication of where.
I could do with seeing a similar car.
I have seen it suggested that the pipe may be cut as a temporary fix for something being gummed up from the EGR.
I have a cheap diagnostic unit (EOBD MS309 OBD2 OBDII Car Fault Code Reader from eBay), it indicates no faults
Are you sure it's been cut? According to this forum post the hose connects to a
plastic Y junction and it's very easy to accidentally disconnect it whilst changing the oil filter.
[Edited on 2/12/19 by MikeRJ]