Everytime I drive the car just doesn't go above 2,500 it doesnt wanna, I have new spark plugs and Ignition Coils, cleaned the TB and MAF and new air filter, new oil. Normal city driving is 1,500 to 2,000 rpm and hwy driving is 2,000 to 2,500. Even when I push to go and its going 70mph its going just 2,500 rps. it will rev very high when its in park.
2001 Jaguar XJ8 4.0

 

Well I guess you have a rev limiter now, don't you.... lol

Ok, so the MAF may be clean, but is it functional?
Did you double check the connections for seating?
What about your fuel pressure, have you checked it?
Have your tensioners and chains been updated?
Check to be sure your MAP vacuum line is connected.
When it revs high in park, is it just after you put it in park and goes back down or is it always high?
Have I asked enough questions?
I'm sure I haven't, but this will get us started. Besides, I'm real sure I won't be the only one with Q's, I have to leave some for everyone else.

 

1. How do I check if it is functional?
2. No
3. Have not checked fuel pressure.
4. Tensioners and Timing Chains are not updated
5. Where is the MAP Vacuum Line?
6. After I leave park the revs drop.

 

Ok, with what you said on #6, I think we should work from there. Because it sounds like a vacuum leak. Which may be connected to #5, which is located on your firewall, center, just behind the throttle body. It will be on an offset, its small and will be upside down from the pic.

 

Fuel trims (see the many posts) will cheaply and easily let you see if it's a vac leak.

Don't rev high for long when parked. Not good for trans!

 

Hi all together,
That's my time to chime in and share the lessons learned from another thread.
@omgimali: your car probably has no MAP vac line, since the MAPS only comes with SC engines, which have exhaust gas recirculation fitted. And your 4.0 N/A hasn't.

Did you just do any repairs to the car before the issue? Or did you buy the car with the 2500 rpm "limiter" and you never experienced it revving higher than that when driving?

Please check the throttle body cable if it is adjusted right. If it has play or slacks, you can floor the pedal without the throttle body fully opened (or rather the butterfly valve inside the throttle body).

Otherwise: +1 on looking for vacuum leaks and reading the trims. You'll definitely notice such a vac leak when looking at the trims.

 

Thanks xjr2014_de, I just read your post in that other thread and came over here to post the link.

I had thought of the throttle cable also, but the rev scenario has me thinking vacuum may be the issue and thought it should be addressed first.

 

Oh, btw...forgot to ask: you don't have any fault codes or messages in the dash and/or the check engine light is on?
Cheers, Alexander

 

No fault codes but sometimes i got a Misfire cyl #7, changed the ignition coil and it went away. Before the car would rocket but after sitting 6 years i don't know what happen. I do not have a OBDII scanner but my mechanic does and he does my repairs. So check throttle cable, Vacuum leak, and fuel pressure?

 

Yes, check those...you can get a Bluetooth monitor/decoder on Amazon for the monitoring, like the Elm327. It will tell you fuel trims, O2's in open/closed loop, engine temp etc...
The Bluetooth kind of coincides with your previous question on the MAF, you can monitor your motor for sudden changes. Be sure to check you seated your connections and no terminals pushed out. I also recommend this video, its a simple process and quick to watch....

 

Ok. So if I tap on it and it stalls or bring up like a Restricted Performance mode then then sensor is bad or needs cleaning? and I will do this once snow clears up in an hour or 2.

 

He said it "...if it does...", I don't want you to be misled that it will fluctuate. The most important part with your diagnostic is the removal of the connection to see if your issue disappears when the ECM goes into backup mode. But that should be your last test since that should send a code. No sense creating a code until you need to.

 

Did you adjust the throttle cable? Clean the throttle bore and throttle plate (lots of threads); this is the issue I had on my last 01 in 2013 - cleaning the bore and plate opened up the breathing. Make sure all of the air tube from the air cleaner to the throttle body is air tight. Change the air cleaner. Renew the plugs.

What is the status of your secondary tensioners?

 

Tensioners never been replaced.
The plugs are Autolite Double Platinum plugs i put in last month with a new ignition coil because the valve cover gasket and spark seals are leaking.
Oh btw once a month the past year (happen 2 days ago as well) everytime I start the car it will be rough, but no codes or messages, I will rev it a little it would get worse but then I would rev it again and then it will go back to normal, BUT one time I revved it and engine stalled.

 

I'd put in iridium's....

 

 

I'd rather go with the iridium plugs too. They're recommended for the AJ27 engines (from MY99 on). My MY2000 XJR would run with the platinum plugs, but not as smooth as with the iridium's. And the fuel consumption is worse too.
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Ever since I changed the spark plugs, I have to push the accelerator pedal more than I use to get to speed.

 

NGK?

 

Ok so the #1 picture is the Iridium plug on rock auto, #2 picture is the Double Platinum on rock auto NGK R, #3 Picture is the OEM Jaguar Dealer Spark plugs
#4 Picture is a closer look and as you see they are NGK R Double platinum's? or are they Iridium with R?..