Hello Jag Friends,

I frequent the XK8/R forum quite a bit, and am familiar with the 4.0L very well. I'm trying to help a friend that is down on their luck with their car, that works for a non-profit. I'll be visiting tomorrow to check out the vehicle and run through some of the diagnostics I'm aware of.

I haven't seen the car yet but this is what I know: "After driving it for a seemingly random amount of time the Jag starts to stumble and cough and then the engine kills. It smells like gas from exhaust when you try and start it but I cannot start it again right away.Usually it has to cool off 45-60 minutes and then it might start but you don’t know if it’s going to stay running."

I'm going to take my code reader, check codes to see if any emissions related codes, read the MAF Sensor readings and clean it, check for any signs of air leaks, etc. The gas smell almost has me thinking it could be emission related in a closed loop? I've seen my 4.0Ls do some odd things when the fuel filter needed to be replaced and the MAF cleaned, but never a strong fuel smell.

Anyone else run into an issue like this or similar? I'm really trying to think ahead so if there are tools or other items i need to bring to help out, but definitely understand hands on diagnosis tomorrow is key.

Thanks again.

 

It's all about the codes and then following what they say.
No other way.

What codes does the car have?
Have you cleared all the codes and drove the car some more?
What are the current codes?
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I wouldn't be driving it if fuel is getting into the exhaust. It will ruin the cats and they ain't cheap.

 

Okay, so reporting back, I'm sure the downstream O2 sensors have been cooked. I pulled the plug on one and tried to ohm across the terminals, and it would not show any continuity at all, which is confirmed by the scans below. What is the preferred O2 sensor for the 4.2? Denso? (Looks like the OE Manfucturer)

The MAFS was super dirty, so I cleaned it with CRC MAF Sensor Cleaner, along with the throttle body and the car also seemed to idle much better on initial warm up.

The Vavle Cover Gaskets are also leaking like a sieve. Anyone have good luck with the MAHLE Kit?

It was also throwing an intermittent code for a coil on #6, which didn't reappear in the scans after clearing them initially, so going to get a coil. My local NAPA is showing Echlin as the OE for this coil? The 4.2 is slightly different than the 4.0s I've been working on, where Denso was the OE for coils.

Anyway, any comments are preferred but going to try and knock this out on a Saturday with him. If anyone sees anything out of the ordinary with fuel trim data, etc., please let me know.

Scans here:


OBDII Scans

 

maf cleaned airfilter clean ,coil and sparkplug at least have a look at number six.
you might want to change and experience position another original coil from same bank.obd check.
if the o2 sensor is rattling when shaking it is shot .

these have been tested and had the best result but check if these are the right ones. . I do not remember if 4,2 xjx or 4,2 Na.
fuelfilter is underneath B pillar left side hidden underneath the plastic cover

 

Sparkplug Ngk 1496 for na and xjr
coil ngk 48267 na and xjr
Maf Denso Dma 0113 for 4,2 na
maf Denso DMA 0114 for xjr
pre cat o2 sensor either Denso Dox 0428 Na and xjr
Or Dox 0426 Na and xjr
after cat o2 sensor either Denso Dox0427 na and xjr
Or Dox0429 na and xjr

 

Sounds like you have a plan and are knocking out the problems one by one!
Post back as you make progress.

Yes Denso 02 sensors.
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