I've noticed that after high revs/long runs when i come to stop at traffic lights the engine 'wobbles' the car more than it normally would. So i've been thinking of either doing an engine flush - using detergent you put in your oil, you then run the car for 10 mins and change the oil. Or - use the product you put in your fuel to clean the engine.

Any thoughts on the 'wobble' or either of the two products?

Also advice on oil would be good, i'm thinkinh 5w30

Thanks guys

 

Sounds like your idle control needs cleaning.

Flushing an old engine is a bad idea, you might circulate some junk and block or loosen something. You could inadvertently cause a stroke.

I have been running 20x50 in my XJ since I got it and now have over 200,000. Change your oil every 5000 and the AJ16 will run well for a very long time.

 

I must confess I'm struggling to see this having the desired effect.

If the engine is failing to drop down to a smooth idle, Air Filter condition and checking if the Throttle Body needs cleaning would be my first thoughts. US members sometimes report issues with fuel quality and use an additive but this is rarely a problem with fuel in the UK.

If the engine is actually moving then condition of Engine Mounts has to be suspect.

I've never been a fan of engine detergent and have always preferred to do a couple of quick succession oil changes instead.

Graham

 

I am betting you have a vacuum leak and the engine is winding up the LTFT to high positive. Then when you come to idle, the mixture is overly rich. Look for cracks in the entire induction system, especially the full and part load breathers. It wouldn't hurt to put a scanner on it and trend chart the fuel trims.

 

Think this may be a vacuum leak Ross. Only just bought the car but noticed a little bit of tape on the induction system. Will properly invesitgate tonight and report back.

 

Update on the above. I changed the oil (which looked very old as I'd only just bought the car) and further taped full load breather as it had oil dripping out it. This seems to have improved things. There is still a slight bit of wobble sometimes. Does anyone know why the full load breather hose would leak oil? Is there to much pil in there maybe?

 

The reason the full load breather would LEAK oil is it has a hole in it. Therefore, it can pull in air and cause your stumble. Now, what I think you really meant to ask is, "why is the full load breather full of oil?" If you have too much oil, I do not believe the part load breather will be your first problem!

The answer to that one is one of two general reasons. Either the engine has a seal or ring problem and has too much blowby, or (with any luck), the part load breather orifice is plugged. Thats the little tube on the other valve cover and there is a TSB on here somewhere describing the method to use a drill bit to clean it out. If you do not see the TSB right of way, I am sure Jim Lombardi or one of the other more organized posters can lead you right to it!

Good luck and let us know your results.

 

^^^

What he said ... and I bet the throttle body is a gooey mess as well, not to mention the EGR, and a dirty MAF.

The plan would be to go through and clean the induction system from air filter all the way to the throttle body as well as the side branches of the breathers.

 

check around intake manifold for a loose or vacuum line off or cracked ,anyway you can bet is air intake some where good luck --Satterfield

 

On that advice I'm going to do a full clean of the induction system. One question.... When cleaning the throttle body should I touch it? IE use a cloth to clean it or just spray with cleaner? I've seen varying opinions on this

 

I've done the full clean now and the engine seems to running much more smoothly. At the same time though i swapped out the spark plugs for new NGK iridium's. There was oil in the spark plug chamber, ahhhh!!! Still running well but looks like i may have to change to cam cover gaskets now...

 

Sounds like the car has not been well looked after.
Mine had similar symptoms when I bought it (not the engine wobble but the general dirtiness, even though the book was stamped regularly.)
The air filter looked like it had done 100k on its own or example...
Do get the valve cover / spark plug boss gaskets done ASAP before your shiny new plugs become fouled, the B-bank cover can then be thoroughly flushed with solvent to clean the part load breather gauze. You will need a drop of RTV sealant on the gaskets.
Some people cut a slot in the dipstick mounting plate to remove the tube from the B bank cover - I just pulled the tube up slightly out of the block.

 

Have had my for a year now bought it after it sat in a garage for 9 years, had a really poor idle, took to local garage who said straight away coils, new coils fitted still rough and lousy Mpg!
Next throttle body changed,Lamba sensors changed, & new plugs!
Next found a garage with the correct Jag know how & they told me a VVT code 1338 was showing and either to get a new vvt fitted or try engine flush so I bought Liqui Moly and whist my Mot was done yesterday I asked the mechanic to do the flush and change the oil and to my amazement the car runs incredibly well now! Toque acceleration and mpg instantly improved what a difference!!

I cant honestly believe it , it's like driving a new car!!! I am a sceptical git and thought it was dangerous to do a flush but she's got only 46k verified mileage so mechanic said it shouldn't be a problem and how right he was.

My fears were blown away in flash or should I say flush, despite having linkages changed rear and all sort of suspension bit done am now finally am very happy.