Hello All: I searched the forums but couldn't find similar. Last night after a 200km (125mi) drive in my I was climbing a one km 5% hill at about 95kmh when the CEL came on and the message panel over-rode the odo with "restricted performance". I stopped and turned the car off then restarted -- the CEL light remained on but the message didn't. I proceeded 100km home at a modest rate and all seemed okay. It ran quiet and smooth and fuel usage seemed normal.
I know I have to take in to get the codes read but wondered if anyone has had this "restricted performance" message?

 

I wonder how high is the hill you were climbing.

Never heard of a “Diminished Performance” warning but the obvious culprit is a vacuum leak somewhere.

Car needs air and there are O2 sensors to check engine operation. Wonder if you have a broken plastic accordion in the air tunnel or bad/dirty MAF sensor

 

If the CEL is on, you need a code reader. Start with a cheap ELM327 (eBay, Amazon) and a phone app for a few $. You will get specific codes you can then search with.

 

Sorry David: My wife says the message was "Restricted Performance".

 

Good news is that the car seems to behaving itself .... for now. Restricted performance is commonly known as the dreaded “Limp home” mood for our car.

However for peace of mind, as said above, you’ll need an OBD2 reader to find the root cause. Could be a whole wide number of issues, vacuum/air leaks, engine, spark plugs, emissions or just a bad O2 sensor somewhere.

Post the P0xxx codes here and someone will help you.

 

Thanks guys. Will get the codes read and post the fault(s).

 

Follow on the CEL fault codes -- there were three:
P0171 - System too Lean (Bank 1)
P0174 - System too Lean (Bank 2)
P1111 - System Pass

My interpretation is that pulling up the hill at 99kph (reader indicated car speed) the engine ran slightly lean (indicated 18%) for a moment but then went back to normal, hence the P1111 System Pass code. The CEL stayed on but went out when the codes were cleared.

The Innova 3120 reader --nice unit -- showed all green lights at the top indicating no problems with oxygen sensor, cats, exhaust, etc.

Anyway, thanks to members who responded to the initial post.

 

One of the causes of those codes can be misfires (because they leave unused air i.e. O2 in the exhaust) and uphill is a classic time misfires show up.

Commonly the kind that show up like that are due to failing coil(s).

Expect more trouble or go hunting.

 

These codes come up for fuel trims above 25%. These should ideally be under, say, 5%. You likely have a bunch of air leaks, or a failing air flow meter, possibly both. Best is to do a smoke test because there are so many possibilities for air to get in besides the proper intake. FWIW, an engine running at 5% trim feels very different from the same engine running at 15%. It is a lot more responsive and feels so much more powerful. Chasing this problem down will likely reward you handsomely.

Best of luck, keep us posted.

 

This is very interesting, I too have had this issue. Last fall climbing in Rocky Mountain National Park in Colorado the "Restricted Performance" came on and the accompanying limp mode. I was able to pull into the Visitor Center, let the car rest and when we resumed all was good.

Today while climbing up to Powder Mountain ski area here in Northern Utah (16% grade) I had the car in 2nd gear and was pulling pretty hard when it came on again. I will pull the codes and see what comes back.

My car is a 2000 XK-8, with about 82k on it. I occasionally get the DSC/ABS issue, but other than that the car has been fantastic. Replaced the secondary chain tensioners last summer.

 

Mine has not had the problem since I cleared the codes. I did fill up with Chevron 94 (no ethanol in Canada) and have done some spirited driving/climbing with no issues (crossed fingers). Hope you can overcome the issue quickly.

 

Have a 2000 XK8. My Innova 3100 won't pull codes. May be the wiring to OBD port? Reader does power up.

 

If you've never replaced the intake hose (with the accordion section), it may have cracks in it - especially the accordion section. This is very common. Cleaning the MAF with MAF cleaner wouldn't hurt either. CRC makes one that's available in most auto parts stores. Try another OBDII reader. I believe the protocol should be ISO 9141.