Hey all,

I'm getting the P0174 code only. Runs fine when cold. When hot, things deteriorate quickly. Loses power over about a 5 minute span until it's barely idling, and upon throttle will stall. Starts back up each time, although it goes back to barely running. If I let it cool down completely it runs fine until it gets hot again.

Seems like the intake or gaskets to me. something moving under heat. I'd like to hear you all's take on it though. Thank you in advance.

Nick

 

Hey Nick, please update your vehicle information in your profile so we can better assist you.

 

So sorry! I'll do that now.

2001 XJ8 SWB 4.0L

 

Do you have a scanner that can read live data? I would start with cleaning the MAF sensor. I know some people are against using brake cleaner but, I’ve cleaned hundreds of MAF sensors (even on my own cars) and never had an issue. You can of course use MAF sensor cleaner from the parts store. If you have compressed air to blow it dry, that can also aid in cleaning.

 

It says it does live data. It's the Innova 5210. Not sure if it shows what I need to see or not.

 

Change out the coolant sensor it’s cheap no need to drain fluid just put a cloth under it have the new one ready change it quickly only a very small amount of fluid lost

 

This is the freeze frame data.

 

p0174 System Too Lean - Bank 2, and your short term fuel trims 25%, long term 12% and 13% - quite high
Take the starter fluid and spray around the intake all the way from maf to engine, you may have unmetered air leak somewhere

 

I did this. No change.

 

I suspected that it was acting fuel starved, so I went ahead and changed the fuel filter. Now the problem is worse. Same problem but very acute. Could I have air in the lines giving me problems, now? The backwash from the tank side of the filter was filthy.

 

I currently have a P0511 - this also initially looks like a PCM related issue, like your code.
I also swapped the fuel filter - like yours very old and dirty, and this already helped a lot.
But that is not all. I may be an additional vacuum leak - I am still working on that issue.
Maybe you also have a vacuum issue, maybe not.

But if your problem got worse after changing the fuel filter, it sounds a little bit logically to me that the issue may be the same as in below link, were it seemed to be some blocked fuel injectors, the PCM tried to compensate for those, pumped more fuel and those injectors, which were OK, then flooded the chambers...:
https://www.jaguarforums.com/forum/x...solved-105386/

PS: Greetings to the state (Indiana), where James Dean was born...