XJ6 & XJ12 Series I, II & III 1968-1992

More throttle less power!

 
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Old 11-07-2007, 02:35 AM
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Default More throttle less power!

I have a 1983 XJ6 that I recently bought and have been working out the problems on. The engine starts fine, idles fine and at slow speeds on flatlands there is not problem. But as soon as I go past half throttle it looses power. Seems like it may either be flooding or being starved of fuel. Could it be the fuel filter? Are there any adjustments anywhere I can make? Need help. Thanks.
 
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Old 11-07-2007, 09:03 AM
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Default RE: More throttle less power!

could be anything in a lot of places.

1) clogged catalytic converters, (yes there's two)
2) deffective coil, (test by substituting with another).
3) deffective/unadjusted Throttle Position Sensor (TPS),
4) old injectors, power resistor packfor injectors,
5) Fuel Pressure Regulator out of calibration, (high mileage),
6) Intake Butterfly gummed or out of adjustment, clean and adjust to .002,
7) clogged fuel filter. Use the Jaguar Bosch filter only. No aftermarket.

Important Note: these Series 3 XJ-6 (1980-1987), will Pass State Inspections without catalityc converters.BUT it is illegal to tamper with emissions controls, but if the car passes inspections without cats, it is technically not illegal.So you canremove the front convertor, pry it open, empty it, re-weld it and pressure test it, paint it with hi-temp engine paint copper, and re-install it empty.Install new onion seals too. More power.Better mileage. For the second cat, you can replace the "Y" Cat pipe with the European "Y" pipe without a cat. More power, Better mileage. Please note I am not advising anyone to do this. You do so at your own risk.

In my car, I sent the Y pipe and the over-the-axle pipes to Jet-Hot Coatings. they were coated with their Ceramic and Silver "Sterling Coating" inside and out. This reduces exhaust system temperatures and produces better exhaust flow. I would not go back to the way it was. My car runs clean, passes inspections,and the exhaust system has a lower temperature overall. Theseare the same coatingsapplied tojet engine exhausts for maximum efficiency.

For more power, fast starts,and better gas mileage:
1)install a K & N Air filter, Part Number: E-2350
2) install Splitfire spark plugs, Part Number: SF6E
get the above at AutoZone.

3) install a Ground Strap to the 1-wire oxygen sensor (you can contact me for those, I manufacture them, for 1980-1985 and some early 1986 only). Engine idles better, more stable signal to the ECU.

Jose
 
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Old 11-08-2007, 02:49 PM
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Default RE: More throttle less power!

That is a long list. I will be replacing the furl filter and plugs today and will have the cats looked at soon.

I will also clean the butterfly today. How do I go about adjusting it?

I will have to find a substitute coil to test it out.

The rest I am not even sure where to start. Are there this you recommend I check before others. Things that are more prone to failure?

Where I live we are not even required to get emissions tests. So if the cats are bad i will just remove them. Thanks for the advice.


 
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Old 11-08-2007, 03:50 PM
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Default RE: More throttle less power!

to checkthe intake butterfly, use a .002 gauge filler,if out of adjustment, undo the screw until you get it to .002.

here's a pic of the Y pipe I use in my 1984, I got it from Motorcars Ltd. back in 2000.

Test the coil first, then the fuel pressure regulator. don't buy any replacement parts until you know for sure yours are bad.

[IMG]local://upfiles/1235/5338E6EB29CA439EB76E713B38E23CE3.jpg[/IMG]
 
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Old 11-09-2007, 02:24 AM
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Default RE: More throttle less power!

I changed the fuel filter today. Plan to do the spark plugs and clean the intake and adjust it tomorrow.

Where can I find a coil and fuel pressure regulator just to test things without buying?

I drove it again today and it accelerates slowly with sudden short spurts of power. Could that suggest something?
 
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Old 11-09-2007, 07:10 PM
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Default RE: More throttle less power!

it's all trial and error Val, unless you are a Trained Technician and I am not.It suggests to me something electrical or electromechanical, but the way I manage similar problems in my cars, is by being a "Taenician". (Trial and Error
Nician).

Check all the large hoses from the Air filter housing back to the butterfly intake.
A cracked hose can produce strange symptoms.

So can the Coolant Temperature Sensor,

the Coil,

the Fuel Pressure Regulator, (you'll need aspecial gauge and the Shop Manual).

The throttle position sensor/switch. located right under the mouth of the air intake, below the butterfly.This last one is a good place to start. Disconnect the large black rubber plug and see what happens.

Where can you get a good coil for testing? I don't know. Easier to find out how to test the one you have.
 
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Old 11-09-2007, 09:25 PM
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Default RE: More throttle less power!

Thanks again Jose. I will keep working on it.
 
 
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