Hi all...

Ok I have decided it is now time to tackle a job I have been putting off for awhile...

Since day one of getting my baby, she has always been rough idle and a little rattly upon startup.
and sometimes erratic idle..... it seems to rev up and then die down, sometimes even stalling.

I have also on occasion had the check engine warning come up..... it never stays on for long tho.

Once she is started and you are driving under load etc... she runs sweet as... never misses a beat.

there is also a rather strong smell of unspent fuel while idling, and possibly while driving (but I have not stood outside her while she is in motion lol).

I am no expert on any of this as computerized cars are totally new to me..... I have spent my life tinkering with naturally aspirated non ecu cars.

I recall seeing a post somewhere where they showed step by step removal and cleaning of the AFM.... and IIRC it is located under the air intake pipe between the air filter case and the throttle body.
I think this would be a good place to start, so if anyone can point me in the right direction to that post it would be a great help.

Also I am wondering if the throttle body sensor may have any bearing on this and info on how to service that would also be good....

My main concern, and reason for putting it off for so long is that I believe everything is set to specific positions and I do not want to risk knocking anything out of alignment as I am also limited as far as diagnostic tools are concerned......

My tool kit basically only contains a multimeter and circuit testers..... besides the normal tools of course.

Is this a job I should be tackling myself or do I need specialist tools to do it?

 

Red,

I'm wondering what you mean by "AFM", based on your location description, are you not talking about the "MAF" (mas airflow meter)?

I'm not sure there is much you can do to it other than clean the body exterior/interior and ensure the connector contact points are clean. Perhaps someone else knows better.

As far as the throttle body is concerned, I know in the past week or two at the most, Don B has posted links on this forum site, to his photo gallery of cleaning the TPS. You need not remove it from the throttle body housing to clean it. Further, the XJ6 Haynes Repair Manual located in the sticky section for download contains instructions setting the clearance for the throttle plate and the throttle body wall, if they are found to be out of spec. You could go to Don's photo gallery on jag-lovers and browse for the pictorial in his albums.

I suggest you start with the two items you mentioned, then if the idle doesn't improve, report back and we'll conquer the next likely cause after these are eliminated.

 

Ok, job one is to replace the air filter and remove the big rubber hose just back of the throttle body and clean out the muck. I guarantee that it will be full of sludge.

Computerized cars like these differ from yer ol carburetted versions in that the intake system is basically just a metered air system - the fuel just gets squirted in at the last moment and the amount fuel is delivered based on engine temperature, exhaust oxygen content and what's happening along the air flow, i.e. amount and temperature of air etc - the air coming through the intake is monitored by several sensors on it's way to the cylinders and the exhaust is monitored the same way. The various sensors report current operating conditions to the computer (ECU) and fuel is delivered through the injectors based on the results sent by the sensors.

Eventually, as Rob says, you'll have to do a full intake cleanup as the throttle body and butterfly WILL be carboned up and gummy. Although it is possible to clean it up (somewhat) in situ, the best method is to take the throttle body off and really clean the beejezus out of it. If your model has an exhaust gas recirculation (EGR) system fitted, this is also the time to clean the EGR ports which you will find to be very carboned up. These EGR inlet ports are located below the Throttle body. You'll see them when you remove the throttle body.

With time, all of the components of the intake system will become familiar to you. We all had to learn!

This is a step by step description with photos of the intake cleanup I did on my car:

https://www.jaguarforums.com/forum/x...leanup-109079/

good luck

Larry

 

Hi Bob,

The rattles at start up probably have to do with your timing chain tensioners, or possibly the timing chains themselves. Search the archives here and at the Jag-Lovers forum for lots of info.

The rough idle could be due to a number of issues, and Rob and Larry have given you some great advice on things you should do to help your car idle and run better. In addition, I might suggest that you look for air leaks in your intake air plumbing, which are a classic cause of rough idle and high idle. Also, you should remove and clean your Idle Air Control Valve (IACV) - see the photos at the link below.

Welcome to Jag-lovers - Members Photo Viewing Page

The computer may have stored a Diagnostic Trouble Code that you can read and which may provide clues as to what is misbehaving. Turn the key to position II (ignition ON but do not start the engine), then press the VCM button on the trip computer panel to the right of the steering wheel. Watch the display on the dash for a code such as FF7 or Fuel Fail 7 or such - I can't remember how the '88 and '89 codes are displayed. Let us know of any code that is displayed. There may be more than one code stored and that may take a special procedure in order to read them all. I'll have to look that up for the early XJ40s unless Rob knows it off the top of his head.

This may be an important safety issue so you need to track this down soon. First I would suggest opening the trunk and smelling for fuel odors. If present, they would indicate a leak somewhere around the fuel tank, such as in the rubber hose in the fuel filler neck, the breather hose attached to the fuel filler neck, the seal around the fuel level sender, or the evaporative emissions flange on the top of the tank.

If you don't smell any fuel odors in the trunk, open the hood and smell around the fuel rail, fuel hoses and fittings. A fairly common issue on XJ40s is for the diaphragm in the fuel pressure regulator (FPR) to fail, which allows fuel to be drawn into the vacuum system, primarily into the intake manifold, but it is possible there is some communication into the Climate Control system that is drawing fuel vapors into the passenger compartment.


In XJ40 terminology the Air Flow Meter is the Mass Air Flow meter or sensor. It is mounted in the large pipe between the air cleaner/filter housing and the plastic elbow that bends toward the throttle body. See the photos at the links below for all the parts of the air intake plumbing.

Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page

As Rob mentioned, the Throttle Position Sensor (TPS) is known for developing a couple of problems. One is oil contamination of the electrical connector, the other is oil and gunk contamination of the sensor itself. See the photos at the link below for how to carefully drill drain holes in the corners of the TPS housing so you can flush it out with zero-residue electrical contact cleaner spray.

Welcome to Jag-lovers - Members Photo Viewing Page

You've probably got 90% of what you'll ever need to maintain your XJ40.

Let us know how it goes and if your work leads to additional questions, and YES, you can do this work yourself!

Cheers,

Don

 

Red,

I can't recall if you mentioned how many km's you have on your odometer? This will help some in diagnostics.

I agree with all the other comments in this thread but I'll also add that servicing the engine is more a case of replacing consumables like plugs, leads, filters, fluids and the like. This is the best place to start before jumping in to the other components and don't forget to change your transmission filter and fluid while you're at it.

Then I would start cleaning out all the "breather" hoses associated with the various engine components. Cleaning out all the accumulated muck from all the various pipework in the engine bay including the throttle bellows and body.

The main one to check is the crankcase ventilation (CVS) hose that attaches in part to the oil fill tube. For the CVS See section 6-8 of the Haynes Manual. Be careful as you remove the lines (this one in particular) as in most cases they are very brittle from years of operation and will probably break on you as you remove them, or disintegrate on you during cleaning. I would highly recommend having a new CVS hose on hand before you start.

Something not mentioned yet, but very much worth checking. Take off the exhaust manifold cover (the big pretty chromed plate) and then check your manifold for any cracks. I'm thinking that you may have a cracked manifold which may explain your start up and fuel smell issues.

 

Ps. A little trick that a very competant Jag tech once told me..... Keep a bottle of Morey's Upper Cylinder Lube handy and add half a bottle to your fuel tank every 6 months. Yes, it works and will protect your engine in the long run. Or, if you like, add a full bottle every 12 months.

Also, try and avoid E10 crap wherever possible when you fill up. Try to always fill up with premium 95 or better. It helps keep everything clean, burns better, and does give you better mileage in the Aj6 engine

 

Hi Jagfix38,

Your posts raise some questions I hope you'll explain so we can help Red with his actual symptoms, without getting him too far off track.

It's a 1988 XJ40, so how few miles would it need to have in order to change the diagnostic procedure?

Red's symptoms are a rattle at start-up and a rough and sometimes erratic idle, but that once driving at speed the engine runs "sweet and never misses a beat." Doing a full tuneup is always a good idea, but his symptoms point to very specific possible causes, none of which is the transmission fluid or any other fluid, so help us understand why you suggest that he should change the fluids before "jumping into other components?"

It's good advice to check all the breather hoses for cracks since they're all exposed to similar engine heat. Red can check those while checking the rest of the air intake for leaks, as previously suggested (with links to photos). There are many possible places for air intake leaks to develop, including cracks in any hose, the junctions of the elbow fitting (where an over-tightened hose clamp can cause the plastic elbow to collapse, creating a leak), at the accordion hose or bellows that connects the elbow to the throttle body (which if not correctly fitted on its bottom ends can create leaks and can also split between the corrugations), the gaskets for the IACV and coolant-heated restrictor, the gaskets for all 12 ends of the 6 intake manifold elbows as well as the intake manifold itself, the EGR plumbing, the hose from the carbon canister purge valve (if fitted), etc. The point is that you can't just check one breather hose, you have to check the entire intake plumbing because there are so many places an air leak can develop and cause rough and erratic idle.

Red described the smell of "unspent fuel," so I'm not quite following why you would first suspect an exhaust manifold crack as the source of the fumes. If Red has unspent fuel in his exhaust, wouldn't that point to issues that would be inconsistent with the engine running "sweet and never misses a beat?" And wouldn't he be smelling both fuel _and_ exhaust?

Finally, are you suggesting that rather than diagnosing the actual causes of the start-up rattle and the rough and erratic idle, Red should simply use a top cylinder oil and higher-octane gasoline and the problems will go away?

Looking forward to further education.

Cheers,

Don

 

Rob, Larry, Don and Jagfix.
thank you all very much for your insights, suggestions and remedies.
I am so happy to have found this forum, it truly is a wealth of information for all Jag owners.

ok firstly I think I need to clarify something of confusion.
when I mentioned there is a smell of unspent fuel, I probably should have said she is running rich and there is a strong overpowering fumy smell coming from the exhaust.... there does not appear to be fumes escaping from any other area..... this is why my first thought was to check the AFM or MAF as it may be caked up with gunk. Apologies for any confusion.

As for the rattles at start-up, again yes I concur this maybe attributable to wearing of tensioners or stretching of chain, however as soon as the revs stabilize, the rattles stop.
Some of the rattle is attributed to the manifold cover plate... when the car is idling rough it shakes about.

When I first start her.... the revs will pick up and drop down to almost stalling. this depending on how cold it is outside will only last several minutes and then stabilizes.
As I mentioned.... once the car is in motion, it runs sweet as a kitten, not missing a beat.

I did notice when I first got her, that she would sometime give a little ping when navigating a corner (ie: when resuming normal speed after reducing speed to turn) I originally put this down to timing.

As mentioned by Jag fix
I found that once I started using ultimate fuel in her (97 octane) this removed all pinging and I also add the fuel conditioner occasionally.... as for the Moreys.... I too swear by this and like to keep a bottle handy.

Back to the problems at hand..... I tend to agree with the diagnosis presented by all of you and will infact be performing a total cleanout of the AFM, Throttle body and also look into the EGR ports....
again thank you to all.

will let you know how I get on and if this improves things.....
either way it will not hurt and will only save me problems further down the track

 

Red,

A few other things to consider based on your clarification:

As I mentioned, the diaphragm in the Fuel Pressure Regulator can fail and allow fuel from the return (front) end of the fuel rail to be inhaled through the vacuum hose directly into the intake manifold, which results in unmetered fuel and a potentially rich running condition, so I would recommend pulling the vacuum hose off of the FPR and checking for the presence of gasoline/petrol at the vacuum fitting (you may need to crank or run the engine to see it).

Thinking about your rough idle, another possibility is that the EGR valve is stuck open (which is a common issue). It would be worth checking to be sure the diaphragm moves up and down freely and that the valve will hold vacuum.

Another component that could come into play is the Coolant Temperature Sensor (CTS), which mounts on top of the coolant thermostat housing and on our car has a Bosch EV1 electrical connector just like the ones used for the fuel injectors (the smaller, single-spade connector fits to the sender for the dash coolant temperature gauge). The Engine Control Module (ECM) uses the signal from the CTS to determine how much fuel enrichment to apply when the engine is cold, gradually tapering off the enrichment as the engine warms up. If the CTS never tells the ECM the engine is fully warm, the ECM may run the Air-Fuel Ratio (AFR) too rich.

One final component to check is the O2 sensor, which gives the ECM feedback on the oxygen content of the exhaust, and based on that signal the ECM adjusts the AFR rich-lean-rich to maintain a target AFR of 14.7:1 except when engine load, acceleration, ambient temps, etc. dictate a richer mix is required. If Haynes doesn't give the method for checking the O2 sensor, check the archives here and at the Jag-Lovers forum.

Assuming your air intake and throttle body need cleaning, as they all do after so many miles, if you add a problem with any of the above components you could easily have a rich-running condition.

And don't forget to check for intake air leaks (a rudimentary test is to mist starter fluid at individual areas of the air intake and listen for the engine rpm to increase - if it does, you've found a leak), and also don't forget to remove and clean your Idle Air Control Valve. Disconnect the electrical connector from the stepper motor before you remove the motor from the valve body because if voltage is present at the connector, the plunger of the stepper motor can extend all the way out of the motor.

Sorry not to be more systematic, but if you check the engine's behavior after each step, you may discover exactly what the problems were (and I'm betting you have more than one problem, not counting the timing chain tensioners).

Cheers,

Don

 

Don,
sounds good.... I think I may just have to go right through everything suggested here....
The way I see it... it is better to do all things mentioned this way you can almost rule out these components for future possible problems.... just to keep things maintained and serviced.

Unfortunately it looks like I am going to have to put it all on hold as it looks like the rainy season has swung into full effect..... it has not stopped raining for the past 3 days/nights, and it has been forecast for more of the same for the next week....
As I do not have a garage, shed or carport.... and do all my repairs in the driveway in the open... this makes it a little difficult.

again thanks for the info and I will get onto it ASAP and let you all know how it goes.

 

Hey Bob, sounds like the car is in average shape for it's age when maintenance has dropped off a bit - I think mine had a lot of the same symptoms when I first got her.

Don has given you the A-Z of what could be up, so that's a good checklist to refer to as you go along.

My advice would be to start with cleaning out the intake bellows and rubber plumbing and if your temperature gauge reads below N when warmed up, I'd have a look at the thermostat. If it's no good, she'll run rich for sure.

I wouldn't necessarily zone in on the timing chain as being the source of your startup rattle noises as belts can cause all kinds of metallic sounding noises at the front of the motor when it's cold. Mine sounded like a I had a bunch of "just married" tin cans hanging under the car. A buddy of mine told me to spray some wd40 around the belt area (not directly on the belts) and lo and behold the noise went away, at least for a while. The noise was actually a belt noise brought on by a failed air pump clutch relay, but that's another story.

As far as additives go, I'm a huge fan of Techron, sure keeps the car carbon free and running sweetly. Driving these suckers every day can also help to keep them going, they really don't like to "sit" too much!

Larry

 

Thanks Larry,
I am getting some really good advice here and will slowly but surely attend to each one regardless of whether it is a problem, like I said preventative maintenance.

Yes I do know of one screech sound I get occasionally, I believe it to be a belt or pulley, but it doesn't last long and not too often and I have often thought "I must give that a spray" and keep forgetting after it disappears lol.

I totally agree the car needs to be run on a daily basis just to keep things spinning freely and fluids etc flowing..... as this is my everyday car, it is pretty much used everyday anyway.
I just enjoy driving her so much, I use her rather than the other car in most situations. The other car (TE Mitsubishi Magna) being the wife's car, was my everyday car til I got the CAT

I am hoping I can iron out all these little gremlins slowly one at a time.... for a car this age and done 33300+ kms.. I think she is holding up well and a testament to the quality of workmanship and how cars used to be made.

I hope I can restore her in such a way that she will survive and can be passed down to my son who is only 15 months old.

 

Don, your opinions are appreciated however I feel that you are introducing argument just for arguments sake for which I am in no mood to offer you an explanation. If you fail to grasp the notion of "preventative" maintenance, which was the basis of my post, then I'm not going to highjack this thread attempting to explain it to you other than to say would you change a tyre without undoing the wheel nuts first?

Anyone with any mechanical knowledge will know that in any diagnostic procedure that it is common to start with the basic serviceable items first before jumping in tearing components apart looking for a gremlin that may, or may not, exist. Removal of the exhaust shield and examining the manifold is relatively easy compared with tearing apart the air intake. Yes, a hairline crack here can be the cause of the symptoms that Red described both initially and in a subsequent post. Yes, the regular addition of an upper cylinder lube/cleaner will result in not having to rip apart the intake every 12 months in order to keep it clean. Yes, the crankcase breather hose does clog up and is a recommended regular service item. And finally, a poorly serviced transmission can cause poor idle at start up.

 

I forgot to also mention... an engine with 100k on the odometer is probably a lot less likely to have timing chain issues than an engine that has done 300k. I don't think my question was irrelevant. Do you?

 

red_101au


I see that some members have recommended that you dismantle the whole of the MAF to get at the TPS.
This is not Australias way of doing things by making the whole thing
more complicated than it should. That advice requires unnecessary &
significant work & of course time. To do it in the most innovative way, "
see my post on "TPS. Apart from drilling holes in the bottom of the TPS that is!


Regards,
Michael Prichard
\Melbourne Aus
XJ40 Sov 144,400 kiloms
.

 

Hi Jagfix38,

I certainly don't want to argue, but the reason I asked you for further clarification is that you seemed to be, in the first case, offering some very general "do your basic maintenance" advice, and in the second case, honing in on one particular breather hose and the exhaust manifold.

Red had been offered some very specific possible causes for his specifically described problems, but it seemed that you were telling him that instead of investigating those very specific possible causes of his car's symptoms, he should first do a general ignition tuneup and fluid change. In my 20 years of XJ40 ownership I have not come to associate Red's symptoms with the typical tuneup items (the ones you mentioned specifically or the others usually included in a full tuneup).

I agreed that checking the breather hoses was a good idea, but all of them should be checked, along with all the many other possible points of obstruction or leaks in the air intake. And from Red's description of the smell of "unspent fuel," the exhaust seemed to be well down the list of potential suspects since there is infinitely more unspent fuel present on the intake side of the engine and in the fuel tank.

None of us will argue that basic service items are important, but if a basic tuneup was the answer to every automotive malfunction, this forum would be unnecessary. We could just put a statement on the home page that read, "TUNE UP YOUR CAR" and be done with it. The point of this forum is to help owners find the specific causes of their specific malfunctions with the least time and money invested as possible.

I'm no more in the mood to argue each of your points than you are, but I'm also sure that Red is in no mood to change his oil, coolant and transmission fluid until he has discovered the real cause or causes of his rough and erratic idle.

One point I would appreciate more information on is your thought about the transmission fluid. I am aware that low transmission fluid has been associated with stalling while driving an XJ40, (and low or rough idle when in Drive with the brakes on), but I have never heard that transmission fluid issues can cause a rough idle at start-up where the revs increase and decrease while the transmission is in Park and no other gear has been selected. Any additional information on this subject would be appreciated.

Cheers,

Don

 

Hi Michael,

I must have missed the suggestion that the MAF be disassembled...I wholeheartedly agree that that would not be a good idea. But removing the MAF and cleaning it with an appropriate zero-residue MAF Cleaner spray or Electrical Contact Cleaner spray is a good idea, and is easier than lots of other maintenance tasks such as replacing the air filter (or just one spark plug, for that matter), so it can hardly be considered "making the whole thing more complicated than it should be."

I searched the forum for your post on the TPS but couldn't seem to find it - would you be willing to provide us with a direct link? I'm always looking for new and better ways of servicing our XJ40 and look forward to your tips.

Cheers,

Don

 

Actually, with both of our XJ40s, the timing chain tensioners were already failing before 100K, so I replaced them when I did the head gaskets, which failed in the '88 right at 100K, and in the '93 at 90K....

There are some XJ40s around with 300K, but not many compared to the far larger number of XJ40s with more typical mileage that have timing chain tensioner or chain stretch issues. If Red's car had only 50K miles, what would you consider a more likely cause of a start-up rattle?

Cheers,

Don

 

Larry, That's an excellent point about a stuck-open thermostat causing rich running. On our car, this has happened twice, and the temperature gauge was apparently not sensitive enough to indicate that the engine was not reaching full operating temperature. What led to the discovery of the stuck thermostat was that our fuel economy became noticeably worse, but 2-3 mpg.

Cheers,

Don

 

Don B


I have often read your MANY posts and it seems that you have too much time on your hands. Jagfix 38 appears to be right suggesting you "quibble"a lot. May I suggest that you offer HELP based on an item that you had to repair & the process that you went through even to the point of mentioning a quicker less expensive procedure. In other words, less theory & more practical advice as we do in Australia.
Regards
Michael prichard,
Melbourne Australia