Hi all, I have a '97 XJ6 4.0 which I have just bought. It has a flat spot/ hesitation when pulling away from junctions when warm. It is fine when cold & six air pump is running. Someone has fitted a replacement airflow meter & I tried a throttle body (pot luck) but it is still the same. I was debating a dead oxygen sensor (as these are overridden when cold start injector & pump run I believe ) & wondered if anyone can throw more light on this & point me in the right direction for tech data too.

Thanks in advance

 

First thing is WELCOME aboard.

Please do your intro in the "New members area" when time permits. It keeps the Moderators all warm and fuzzy, and is a good thing to do.

Many items come to mind, some you have attended to.

The rubber bellows trunking thing from the airflow meter to the throttle body can/does split with age.

The TPS {Throttle Position Sensor) under the throttle body is a prime suspect.

The CTS (Coolant Temp Sensoe) is also a suspect.

We dont have air pumps or EGR, so NO help with that nonsense.

I also throw in this one, coz I can.

Is the engine hesitating, OR is the transmission slipping??. How long since the trans fluid was refreshed??. The hesitation factor is very similar and takes some sorting sometimes.

 

Hi thanks for the comment. I will reply to new members when I get to a computer. I am on mobile via app & looked but could not find how to do this.
The throttle position switch was also replaced with second hand body (although condition not known) the fault can be septic acted stationary so in theory should eliminate transmission & also changes up & down cleanly.
Thanks for the input though ,oh & the bellows are good too

 

Any CEL Codes?

 

Good question, please tell me where the diagnostic plug is & how I can read them if you can as I don't have a great deal of experience on these models (more with the later X & S types with ford engines) but would like as much info as possible as this cars a stayer with me.
Thanks

 

Gotta admit I really don't know where the OBD socket is on your car, since your steering wheel is on the "wrong" side! On mine, the OBD socket is at my right knee when I am in the driver's seat.

If you have a code, the engine diagnotic lamp (CEL) should be illuminated on the instrument panel.

 

On my 95 X300, it almost never illuminates the check engine lamp. I have had to investigate a number of misfire issues and my scan tool would show a P0300 code for instance but no CEL.

The OBDII seems to be very hit or miss on the MY95 cars

 

Great thanks, diagnostic plug by my left knee (should have looked first as it's obvious) just read the codes & as mentioned no light on but had p0101 & p0102 stored airflow faults they both cleared & it now idles better but still hesitates pulling away. Someone had fitted a replacement airflow meter in the past so may be old codes.
I noticed when revved to 2500 rpm data showed 18% throttle pos & 12% at idle. That doesn't sound right to me but again has has pos switch changed too

 

12% at idle sounds ok to me. TPS output should be around 0.6v at idle. max output is 5v, so that's right at 12%

 

Ok thanks for the info. So I will keep on hunting, temp sensor is reading fine too on data list but it sounds & smells weak when it plays up. Back to oxygen sensor testing I think. Can anyone point me in the direction to get full tech data for this model please

 

Check out the sticky "X300 'HOW TO' quick links" at the top of the X300 section.

There are links in there to the factory manual and wiring diagrams.

 

Thanks I will check that out. Gotta say this is one of the best forums I've been on for organisation.
Very helpful & fast responses too :-)

 

For lambda sensor diagnosis, you want to look at the STFT and LTFT for each bank. And, the O2 sensor voltages, which should cycle between low (.2v or so) and high (1.5+v) about once or twice par second.