Hello,
just bought 95 a X300 with 71000mi.
So Now I have a xj6 III and xj6 X300.
Payed $3200.
it has check engine light on. Mechanic inspected it and said it is because regular gas is being used. He told me to put a full tank of premium gas, drive it good at least half tank with premium gs up to 85mph, then come back to him to reset the check engine light.
Does it look reasonable to you guys?
thanks a lot

 

Auto part store will read and reset it for free as they want to sell you some parts . Write all the codes down .

 

Hello, yes the mechanic told me the code (I don't remember it) was meaning bad gas I'll ask him the code again thank you.

 

These cars will run happily on regular or premium gas, so I would say further investigation definitely required. Do you have the specific code number which the mechanic says is present?

 

Do your self a favor and buy a cheap $15 OBDII DTC reader from eBay or some place like that.

https://www.ebay.com/itm/Scanner-Dia...QAAOSwC9VZgzJG

https://www.ebay.com/itm/U480-CAN-BU...UAAOSwImRYdz~l

You won't have to rely on someone else and can actually clear DTCs after diagnosis and repair.

bob

 

I don't recall a code for "bad gas"! And regular unleaded isn't necessarily "bad". Why couldn't he reset the code right then? Looking for repeat business perhaps? And for how long do you have to drive at 85mph?

Welcome to the modern/classic world of the X300. It has first generation OBDII which can be useful for diagnosing problems! You'll want that code reader. Post a picture for us?

 

yeah I am going to buy it really. Thank you.
when I have it I'll read the code and post here.
thank you

 

ok I just bought the KW806 scanner. I'll have it on December 13.
I'll keep you posted really thank you for helping!

 

update: the mechanic smogged the car. So he told me that it was too rich, after smogging it then he put the settings back as before because the car was running much better slightly richer. I did almost 1000mi after putting premium gas and check engine light did not come up again.

 

Something that won't show up as a code is fresh high O2 air being sucked in between pulses ( at idle ) at a cracked exhaust manifold or downpipe donut gasket seats causing the O2 sensor to bias the mixture rich . This would be seen as a short term fuel trim higher the 0.0 and can be observed with a ELM327 adapter to your laptop .

Another thing is the ECT sensor biases the mixture rich by design until the coolant temp heats up . The sensor is a thermistor and can be calibrated easily or the connector can be dirty causing higher resistance mimicking a colder coolant temp . A thermistor works opposite a temp variable resistor as the higher the resistance is a colder reading . Clean the exposed connector

 

Omg if it is a cracked exhaust mainfold I guess it's crazy expensive to replace...

 

Just pull the cover to find out as you run the engine. Mapping out a cheap repair

 

if I remove the cover should I see with my eyes if there is a crack ?

 

Not always but better if it's heated up . Then there's the puffs of black smoke if it is leaking and the mixture is rich not combusted after coolent temp rise above a certain value

 

Ok after 1600mi check engine light showed up again.
I Stopped at O'Reilly and the OBDII scanner read this error:

P0420: Catalyst System Efficiency Below Threshold Bank 1.

is my cat converter gone ?

 

Since you suspect that your running rich the Cat and sensors could be sooted over . The 420 and 430 come from from the aft O2 sensors . I personally would leave it alone until you get the STFT back to 0.0 . The fwd sensors from what I understand are the ones that do the STFT regulation and you can soak in gasoline overnight washing some gas into the vent holes where the sensor is . There is the 2 connectors that can be easily crossed and will cause engine regulation issues from Jacklynthejag's experience . Missing crush washers on the aft sensor biases the signal as they are 12 mm spark plug size

Editing

 

ok, may I have some hint on how to connect a laptop to read the STFT and LTFT ? with dash command and ELM327 wifi would I be able to read those values on a ipad or iphone ?
thanks

 

The software is different for each manufacturer and there are Youtube videos that may help . There may be a default configuration already set up of PID's ( perimeters ) that have the STFT ( you need both banks ) don't worry about LTFT . It's a learning curve thing

PID's important for engine regulation :

RPM

MAF

TPS

ECT

IAT

STFT bank 1 and 2 - this is the end result of the above sensors which includes the O2 sensors but I could never get mine to read before the licence key dropped out

 

I believe it is the downstream sensors that do the heavy lifting. There are threads that confirm this.

I thought it was the upstream sensors until I was corrected here.

https://www.jaguarforums.com/forum/x...ensors-173577/