This is really doing my head in!
I recently had a couple of "limp homes" in the last six months and ended up changing the upstream bank1 heated O2 sensor (with Bosch unit)(yes it was tricky) (P1646)
I checked for other fault codes and there was one that related to possibly the throttle position sensor.
I cleared the fault codes and they have not recurred. I did a hard reset and retrained the throttle as per " Redline"
The car is driving perfectly!!! BUT if I sit in park and rev the engine then it starts misfiring at about 2900rpm. ( When driving I have taken it up to 5000rpm without any issue.
I dont know if it was doing this before replacing the sensor as I cant remember sitting revving the engine that high in the past
I have checked the plugs, cleaned the coil connectors, made sure that the air intake after the mass air sensor has not leak to no avail
Perhaps the answer is not to rev the engine at rest lol but I cant unknow it and something must be wrong
There are NO DTCs coming up
Suggestions??

 

The PCM does not allow the engine to rev above 3000 rpm with no load on the engine. DO NOT rev the engine in the 'P' or 'N' positions.

If the engine is revved excessively in the 'P' and 'N' positions without a load, damage to the rod and main bearings may be the result. Thus the PCM does not allow the engine to rev above 3000 rpm.

 

Thank you so much! I will cease and desist!
Im overjoyed to know that I have no problem with my beautiful car 🙂

 

If it limits the RPM in Park by disconnecting the ignition it will miss as you describe.
For a UK roadworthy test they have to run it at 2000 rpm for 2 min prior to an emission test . So what gear do you suggest >?

 

OP, For what it’s worth, the practice of free revving an engine with no load on it can be very damaging. Which is why Jaguar has the rev limiter when the car is in neutral or park.

But many cars do not have such a rev limiter.

On those cars the manufacturer is depending on your common sense not to free rev the engine. The fact that you have tried to do so on your XK leads one to believe that you have done this in the past on other cars.

That would be a good habit to discontinue.

Z

 

If you mean the MoT, I don't recall that being true - but haven't scoured the MoT manual (it's free, online).

The usual way is to run the basic emissions test and ONLY if that fails to try getting the cat(s) hot/hotter by some revving, then if needs be do the longer emissions test.

I doubt serious engine damage occurs in such cases.

 

There’s a big difference in the effects on engine internals between no load 2,000 rpm and no load 3,000 + rpm.

I don’t know of any knowledgeable engineer who recommends high rpm revving on a no load engine, it if there are any out there I’m all ears.

Z