Boxster Misfire - suggestions?

[Legba]

Thanks for the suggestions, I have removed and checked the plugs and there is no sign of fouling and there are no other fault codes.

I think I will replace the coils.

Can anyone suggest anything else before I spent lots of money?

[The Radium King]

sniff your oil; if it smells like gas your injectors might be leaking. a cheap test, but still sounds like coils.

[Legba]

Thanks Radium King, I'll try that.

I borrowed a fault code reader and used live data. I found the following but don't know what it means. Can anyone help?
At the time I had these readings I had a fault code showing misfire on 456.
Fuel Sys1: CL
Fuel Sys2: OL Fault
STFT B1 25%
LTFT B1 0%
STFT B2 0%
LTFT B2 0%

At other times I noticed that the STFT and LTFT for B1 and B2 mirrored each other so I suspect that the STFT B1 is probably indicating a fault.

[shadrach74]

Originally Posted by Legba

Thanks Radium King, I'll try that.

I borrowed a fault code reader and used live data. I found the following but don't know what it means. Can anyone help?
At the time I had these readings I had a fault code showing misfire on 456.
Fuel Sys1: CL
Fuel Sys2: OL Fault
STFT B1 25%
LTFT B1 0%
STFT B2 0%
LTFT B2 0%

At other times I noticed that the STFT and LTFT for B1 and B2 mirrored each other so I suspect that the STFT B1 is probably indicating a fault.

You've a fuel system issue.

STFT = Short term Fuel Trim
LTFL = Long Term Fuel Trim
B1 = Bank 1
B2 = Bank 2

0% means that you fuel system is operating in open loop, which is to say that it is not adjusting mixture based on input from the 02 sensors.

Your car is running based on the factory preset fuel program. it is metering fuel based on throttle position for the most part with some input from the MAF and coolant temp.

Something is certainly arrive and I don't think it's the coil pack (at least not as far as the codes provided.

[Legba]

Sorry if this is a bit long but.....

I am trying to interpret some data to track down a misfire and need some help to interpret live OBD data on my 1998 2.5 Boxster (UK spec).

Can anyone tell me what the following means?

STFT (Short Term Fuel Trim) and
LTFT (Long Term Fuel Trim)

At times I have seen STFT vary from 0 to 25%. Presumably the readings for B1 and B2 should mirror each other.

I also have readings for:
SHRTFT
SHRTFT 12
SHRTFT 22

What do they mean? What is the difference between STFT and SHRTFT?

The readings obviously vary depending on driving conditions but a snapshot I got was:

STFT B1 18.75%
LTFT B1 0.78%
STFT B2 18.75%
LTFT B2 0.78%

SHRTFT = 0%
SHRTFT 12 = 99.21%
SHRTFT 22 = 99.21%

I also have readings for O2S which I assume is the voltage of the O2 sensors.

What does the following mean?

O2SL 11 12 21 22
O2S11 = 0
O2S12 = 0.435
O2S 21 = 0
O2S 22 = 0.435

Grateful for any help.

[Bruce Wayne]

i would look at the coil packs too, where they sit, they get a lot of heat and corrosion.

[shadrach74]

Originally Posted by Bruce Wayne

i would look at the coil packs too, where they sit, they get a lot of heat and corrosion.

Why would coil packs cause an issue with fuel trim?