hi all - I have been scouring the forums for anyone who is having an issue similar to mine. I have read all the surging etc threads.

here is my scenario:

1. RPM varies about 100-200 RPM at low RPM in traffic or at a stoplight.
2. it mostly happens when the fuel tank is at about 7/8 of a tank or 75 miles used from full.
3. it generally happens after driving about 25-30 miles to work. letting the car sit for a an hour or two and then driving again. About 10 miles into the second drive (usually on my way home from work in traffic) is when it happens. Car is always warmed up and at operating temperature.

• doesn't matter if a/c is on or off
• surging lasts for about 2-3 miles, or if I can get it up on the RPM.
• I have had it happen in both in traffic and in town
• I have had it surge when in park so I am suspect about going down the path of the torque converter.
• coil packs and spark plugs are about 1500 miles since being replaced.
• there are no DTC codes pending or stored
• once the surge happens, it won't happen again until I fill the tank again. it does not happen, at least yet, with a partial re-fill

I think the strangest part is it only really happens while the tank is 7/8 or so full. I don't think it's debris or contamination in the tank as I have serviced filters and this can happen a week after I fill it, so anything would be settled again. I put a new gas cap on the car too thinking it was a venting issue and I have checked the two vent lines at the filler.

I have not inspected the vapor canister, however I do not smell any gas as most of the posts suggest.

I am wondering if there is something else in the fuel system (valve, vent etc) that is plugged or is not opening etc under this 7/8 tank condition.

I got this car from a guy in my car club who had a stroke. I can't get a lot of information about the car. its my understanding the motor in it was replaced about 15,000 miles ago. total mileage 135K

I am wonder if there is a service bulletin for the AJ27 motor like this one for the AJ 26 "Hesitation, Surging, Detonation, Poor Throttle Response/Acceleration –Diagnostic Flowcharts – AJ 26 Engines TSB 303-47"

 

Just out of curiosity, have you tried it with fuel foller cap removed?

 

No I haven’t tried that. At this point I willing to try about anything. Wish I had the WDS software. I just bought a snap on modis to start analyzing the individual components and relays

 

Only thing l can think of to tie the filling of the tank and the certain fuel level at which problem occurs, is somehow something on in tank sender/ pump assembly is dislodged and fouling something else at that point.
Good luck

 

Yes, maybe the primary fuel pump is on its way out and this somehow manifests itself under those condtions. You could check the fuel pressure if you have a gauge and check both pumps are working or even swap the wires for the primary and secondary to see if anything changes.

https://www.jaguarforums.com/forum/x...el-pump-85882/

 

It sounds like it could be something to do with the EVAP system. Canister or purge valve perhaps. It should show up on a scan.

Richard

 

I didn’t know there were two pumps.

 

I too thought about the evap canister it’s on my list to check, along with the fuel pumps. i got the scanner so i could activate the relays and check for operation.

i did recently find out this has been going on for a while with the car

 

The X100 only has one pump. The X150 has two. The fuel pump on the X100 is prone to failure but I would be surprised if it produced worse symptoms with a nearly full tank than with a nearly empty tank.

Richard

 

X100 AJ27 XKR has two pumps, XK8 has one.

 

Ah, I have an X100 AJ26 and an X150 AJ33 so the AJ27 is a foreign land to me.

Richard

 

Maybe click on the links provided before giving totally incorrect information?

 

Maybe think twice before giving making totally superfluous comments? 😉

Richard

 

Exactly. Think before posting. 👍

 

let's keep the commentary civil and related to the topic at hand

 

As a follow on and maybe help solve this for someone else. I had an intermittent and failing mass airflow sensor. Replaced it with a NOS Jaguar part that was the sensor and housing. It was $350 but well worth it at this point. I’ve driven the car roughly 400 miles with no issue, when I was getting the problem every 50 to 75 miles before.