I just had the throttle body replaced on the SuperV8. There is a great amount of carbon build up. see pic below, which makes me wonder what the rest of the motor looks like on the inside.

I asked my service advisor and all he could say is it probably looks like that in the rest of the engine.

The Jaguar tech did not notice the carbon and had nothing to suggest.

The advisor said I should do an engine cleaning for about $300.

I would like to add the car still vibrates on cold start up and when the A/C compressor is running otherwise it is whisper quiet and smooth. Dealer says everything is operating as it should but I know otherwise as the car never did this before.

Feedback would be greatly appreciated.

 

Ditto on the engine cleaner but first things first.

Run a pint of Techron thru it before you spring for a $300 pro cleaning job. After that, if it were mine, I would be getting to the bottom of that carbon build up. My car has 65K miles on it and the throttle body (TB) is spotless.

I would think there is a relationship to the TB carbon issue and the rough idle condition. But if that's true - why didn't the Tech diagnose it and tell you about it?

Are you dealing with a Jag dealer service provider? Either way, it sounds like time to get another service tech involved.

O yes. With this kind of carbon build up - do not attempt to burn it off with high rev driving. You will glaze the plugs for sure to the tune of another couple hundred.

Come to think of it, replacing the plugs may be a good move but only after you find out why the carbon build up.

 

Thats normal, you do realise that oil vapor from the crankcase is vented into the intake tube in front of the throttlebody. So what youre seeing is nothing more than dried oil deposits. I wouldnt waste anymoney on trying to clean inside. Now if you have injectors that are dirty and have a poor spray pattern thats a differant story

 

Brutal--interesting indeed. It would be wise to regularly clean off those dried oil deposits from the TB, would it not? Would TB's last longer if they were regularly freed of the gunk?

I used to regularly clean deposits out of my 5 liter mustang's TB and surrounding areas. This was known to be a wise maintenance step on those vehicles.

 

On my (non Jaguar) supercharged vehicle, I added an inline oil separator on the line between the crankcase vent and the throttle body. It captures the oil before it goes back in to dirty up the intake and the blower rotors/seals. If you are concerned with the oil buildup then the separators are on ebay. I'm not sure if they offer a Jag specific one however.

FWIW, if Brutal says it's normal, it is. If anyone should know it's him. I also second his suggestion to look at removing and getting the injectors cleaned. I did mine and it made a big difference.

Ken

 

And i use a oil vapor seperator on my supercharged nissan too. Its helped alot to reduce oil buildup in the intake.

 

Do a search in the General Tech Help Forum for Oil In Air Intake. There are any number of posts that that appear to address your problem.

One guy described it as a common problem in Jag SC engines. Do let us know how this sorts out.

 

I think it has more to do with the EGR (hot Exhaust Gas Recirculation) , so only way to get rid of it long term is to disable that one, or get an alky kit as that will help in cleaning.

 

Well why the EGR does definitly help to dry and cook the oil vapor by the throttle since its port is right behind the throttle on the 4.2 NA. It is still the oil vapor that runs through the intake system. Avos I know you dont have the NA engine (I know youve probobly been in them though knowing you) but that "bathtub" style normally aspirated engine intake collects alot of oil down in the bottom in the base of the intake. Ive never measured, but it could easily hold a qt of oil and many engines have alot of oil in them there. I see it everytime I replace the t stat housing and have the metal intake elbow off and throttlebody. You can see right in the intake

 

For clarification, the carbon is on the motor side, the intake side is spotless.

I don't have a lot of confidence in them and yes it is the Jag dealer I have bought all of my Jags from.

 

How would I know? One of the diagnostics pages from the dealer mentioned cylinder misfire on two of them, but said it wasn't anything important.

 

The injectors are way down stream from the throttle body and are not the cause of this carbon build up. Whether they need to be cleaned or not is a separate issue.

 

If youve ever driven a van or suburban or other vehicle with a squared off back end. You know how dirty and how fast the back gets. The wind curls around in the low pressure area behind the vehicle and deposits dirt all over it. Same happens to the throttle body, also if you know about ac when you drop from a high pressure to low you get a cooling effect. This on a throttle blade can cause icing which is why engines have hot engine coolant run through them. (god i hope i didnt make a mistake in how i stated that and have jagular come in and "lesson" me again on thermal dynamics )
couple that with the egr heat on the back side and the engine heat that is hotter transmitted up from the engine after shutdown on the backside of the throttle and you see why more is on the backside. I cokes and cooks the oil deposits and once you start building up a roughened surface they just stay and stick that much easier...this is one of the reason in porting and "polishing" cylinder heads the ports (mainly the exhaust) are polished is to reduce carbon and other deposits from sticking to the port walls and slowing down exhaust flow. Intake ports with direct injection or multiport are now considered somewhat safe to polish since polishing a wet port(carburated that has both air and fuel in suspension can cuse fuel drop out on smooth walls and a rougher surface aids suspension and distribution) than a dry mpi, or di injection engine. But this all should be quanitfied in aany head, port and intake design because many efficient engines use high swirl, and or tumbling to increase burn in the cylinder which results in more power, less fuel and less emmissions from the same amount of fuel..sorry didnt meen to go so far out to left field.
On the injectors, you stated that you have roughness on cold start which really is typical till and engine gets warmer and goes into closed loop(monitors afrs) it is normal for alittle roughness. Put from a maintence standpoint i change my fuel filter and air and do an onboard injection system flush(both injectors and induction) if i have an issue i feel is injector related that returns or doesnt go away after this i pull the injectors out and get them test for flow, patterns, and sonic cleaning. Then new screen baskets and orings. This is by far the best way to test and clean injectors. The reason we and so many other dealers/shops do not do this even though jaguar wants us to buy the equipment to do it is from a cost standpoint. The equipment and materials to support runs $7-11k and that is alot of iunjector cleaning to do. Not only more time consuming but to turn a profit on it, cost prohibitive in comparison to onboard cleaning.
And why would we when we can pull a set og injectors now and send or take them across the highway to Fuel Injector Cleaning Service : Injector Cleaning Service : Injector Cleaning : Clogged injectors : Injector Flow Testing : InjectorRX.com and have them cleaned for $18ea same day...without the capitol outlay and guys that may or maynot take care of the equipment to do the injectors...ok time to get back to work im leaving early today for my sons 16 bday party tonight

 

thanks for the education Brutal. I now feel like I should compensate you.

 

I have always been consistent with the use of Shell nitrogen gas or Chevron Techron but I bought a couple of bottle of concentrated Techron and some Seafoam. I normally would not do this as I doubt the usefulness of fuel additives but we'll see.

 

Careful Jahummer. Too much of these chemicals thru your engine is a no no. Read and follow the instructions. I have read reports of damaged sensors.
I use 1 pt. of Techron a year but of course I'm not experiencing a problem.

 

Thank you for the info. This is essentially what the dealer said, but I know otherwise, simply because I never had this issue before. How about the roughness when the A/C compressor is on? By the way, engine noise increases too, FWIW.

 

From what I gathered with Brutal's post is perhaps there is nothing to be concerned about and perhaps why the Jaguar tech had no suggestions. Could be the service advisor is just trying to make a little extra money.

As mentioned before, I always use top tier gasolines, don't know if that makes any difference but I have been told Techron and Seafoam are both safe.

 

From the BG website:
BG Company
BG Air Intake System Cleaner
BG Air Intake System Cleaner is an extremely effective solvent/degreaser formulation that quickly removes sticky, heavy deposits which accumulate in the air throttle body assemblies and plenums of modern, multi-port fuel injected engines. Cleanup reduces harmful exhaust emissions and restores engine performance. Catalytic converter and oxygen sensor safe. BG Air Intake System Cleaner is designed to be used with the BG 9210 Inject-A-Flush® Apparatus.
Part No. 206 11 oz. (325 mL) can

What are your thoughts regarding this product? Seems to address the issue and speaks to resolving it.

 

Since the throttle body was replaced under warranty with a brand new, this is a non-issue for me. Others have said that sometimes cleaning the throttle body & sensors is a solution.

I went back through my dealer service history and realized they were using BG fuel additive & oil additive at every oil change.

Have not decided whether to use the Seafoam I bought, but I did put in a bottle of Techron concentrate. Again for clarification, with the new throttle body installed, the motor runs smoother, quieter and faster just like when it was new, the only issue that remains is rough idle on cold start & rough idle when in gear when the A/C compressor is on.