I'm completely lost. Hoping for some help here. It's a 2002 xkr convertible. Has smaller pulley and 3in exhaust for mods. But, I'm completely lost into fixing the hidden misfire and fuelling problems.
issues are: random misfires and fuel trims in ranges I've never seen before, 150% both banks
Attempted fixes: New catalytic converters, 02 sensors, injectors, fuel pressure regulator, fuel pumps, feul filter, coul packs, spark plugs, timing chains, tensioners, rebuilt supercharger, new gaskets on entire top half of motor, new map, maf, intercooler pump, vacuum lines, throttle body.
Replaced, not related: radiator, power steering, hoses( including under blower hoses), ac compressor and condenser, top, top hoses, and forgetting more.

I give up. I don't want to sell it, if it isn't obvious, but I'm at the point where I might. It's been to Jag dealer 3 times, gave up with them and took it to an Indy. He gave up, and so now I'm here. Car is salvage titled, but it was an accident, I've repaired it and now we're here. Help lol

 

Forgot to add, what happened to cause this. Had an injector on cyl 1 break, erupt and melt. Fuel rail and injectors were list. Replaced both. Fueling issues since. Went through 7 injectors, both rebuilt and new. Current ones are good and flow tested.

 

Good grief. Sorry to hear you're pain.

As I'm sure you know, the aberrant fuel trims indicate your ecm thinks you are running lean. I gather you aren't throwing any lean bank codes?

​​​​​​​If it really is lean, it would explain the misfires, but at the same time if the ecm is dumping excessive fuel (really excessive) you could also get a rich misfire, but that would be pretty evident by the exhaust smell and plug condition.

​​​​Any chance you might have errantly swapped the O2 leads at the junction block? That would cause chaos.

 

Beaterbeliever,

You obviously have done a lot to try and fix things. Have you got any DTC codes from the OBD2 port?

How long have you had this problem and can you confirm it appears to be on both banks.

Running rich can be bad O2 sensors on the CATs, or even a bad ECM module. The DTC codes will help isolate the issue.

The ECM cooling fan can die due to age of our car and the ECM can overheat. Rare but not unheard of.

 

Given all the other issues are you confident in the MAF sensor?

Have you ruled out some kind of intake leak after the MAF? Replacing injectors means taking the whole intake apart and lots of gaskets and opportunities for leaks.

 

​​​​​​​No codes, but it's actually dumping fuel from the plug condition. O2 leads are good, I tried swapping them to see if it was a mistake on my part, but no avail

 

I got the problem about 8 months ago, and hasn't really been driven since. It is for sure both banks, but it won't throw codes.
ECM, what would be any telltale signs of that going out?

 

I kinda lost confidence in everything on it lol, but the maf was pulled from a xjr in working condition.
As for leaks, I'm certain of none, since I've pulled it off about 6 or so times, and replaced gaskets each time to double check myself. It was what I assumed, but passed a smoke test. It's why the dealer told me to "kick rocks", in polite terms lol.

 

Open up the ECM case and inspect with a magnifier the ECM for damage to the circuit board from leaking electrolytic capacitors. This is usually seen as brown stains, corroded areas or moist areas on the circuit board.

 

Allright, allright, calm down.

This car can be fixed.

We need to start with a vacuum gauge, get some readings. See if there are any valve train issues. Valves not closing, burned, sticking, etc.

A vacuum gauge WILL ALSO tell us if you have a clogged catalytic converter or muffler. Not @#$$#ing likely, but...who knows. Maybe your old
cats blew their guts into your mufflers. I've seen it happen, albeit on a Subaru turbo wagon.. IF you're not getting sufficient vacuum (engine not breathing well) PERHAPS due to
a clogged cat or mofla, we'll pull out the 02 sensor, let it roar, and see if the misfire(s) go away.

At idle, we need to spray some carb cleaner / starting fluid in to see if ENRICHING the mixture cleans up the idle.

A misfire is either A) valve damage B) lean misfire or C) Ignition misfire. First we have to ascertain which.

Pull the spark plugs. See if you've got one or more that's "too clean" from a head gasket failing and allowing coolant into the combustion chamber. It'll look like brand new, shiny.

I don't care what you've done previously on injectors, get ahold of AUS in Tempe Arizona and stab 8 rebuilds from them in that motor. I trust them, no one else. Esp not
Ebay injectors.

I'd swap in a new fuel filter to make sure anything in the tank doesn't contaminate the new injectors.

You MIGHT have fuel contamination. Water, diesel, who knows. Maybe someone sabotaged you. Let's try and siphon out the tank and refill with Premium. Or at
least take some fuel samples using a fuel pressure gauge with a release valve IN THE ENGINE BAY to see what it looks like, smells like, and how it burns when poured
on the concrete driveway.

After that, you got a scan tool? If not, get the $79 Harbor Freight one, or the $119 one if you want to be able to read ABS codes as well.

Reading codes and/or using $Mode6 we should be able to determine WHICH cylinder(s) are misfiring.

From there we swap around Coil packs to see if the misfire follows a particular (bad) coil pack.

You also need to get yourself or a friendly auto tech to get on iatn.net and enter a Techhelp request. Some of America's BEST auto techs are on there. And that's what you need is a guy who's HIGHLY competent instead of the Yahoos you've dealt with up to this point.

Give some serious thought to renting an auto-hauler and driving it out here to the British place in Scottsdale (AZ) and have them fix it. They're as good as it gets. Or put it on a truck and ship it. When they tell ya it's done come out and road trip home in your FUN, BEAUTIFUL, FIXED JAGUAR XKR CONVERTIBLE. Be the envy of every other guy on the road!!! So what if your wallet is Zippo --- a little lighter!

Good luck and if you need any more of MY advice feel free to email me your phone # and a convenient time to call at "gmail @ myfirstname mylastname.com" Substitute Wade and Nelson

You owe me a cold beer!

 

opened the case, didn't see anything of that nature, but an interesting thing happened. After placing it back and starting it up, fuel trims drastically changed? In realistic, workable ranges. So maybe it was partially unplugged?? Don't really know, but renewed my interest into keeping the car!
But as of now, currently it's sitting as follows
At idle, in park bank 1: 17.32-19.69%
Bank 2 : 18.11-19.73%
Zero misfires, just rough idle.
One code B1313 Battery circuit?
In drive, at 1500rpm
Bank 1:3-7.45 %
Bank 2: 7.99-11.34%
At 2500 rpm
Bank 1 : -0.73- .69%
Bank 2: -0.21- 1.3%
So, looks to me it is some kind of vacuum leak. As to where yet, I don't know. I'm thinking it's such an obvious leak, I just can't see it lol. Though I would think it would affect both banks almost equally??
I'm probably going to tear it down again, and specifically look for vacuum leaks. Anybody has any diagrams for the vacuum line routing? Anything else I'm missing?

 

Fuel trims are a function of load and rpm, in other words, there is a trim value for a range of rpm, and a range of load, per bank. Are your crazy trims at idle, or under load at high rpm? I'd focus on long term trims first, then check the short term after that. To my knowledge, trims went only as high as 25%, positive or negative, and then threw a code. You see yours as high as +50%?

FWIW, best shortcut to get to these trims is to get a cheap ELM327 tool and a mobile app. Would give you OBD codes, too, including misfired cyl.

I know air flow meters for an XKR are not as cheap, but I would definitely cross check the part numbers to make sure. AFMs are sort of at the base of this whole trim feedback thing. If they read wrong, nothing good follows. Make sure the o-ring at the base of the AFM is there and in good shape. Remember, these AFMs only sample the air flow, so they are not necessarily interchangeable between models, depending on the design of the air box. Do you run a normal paper air filter? Is the flap/actuator in the air box operational? People here tend to trust Denso parts.

I am sure you have physically gone over these things a dozen times already, and a hundred more times on your head.

Best of luck, keep us posted.

 

I'd say do a smoke test. There are so many ways air can get in. A good injection point is the fuel pressure regulator vacuum line for a direct fill of the intake.

You can get smoke testers on eBay, or make one with a old soldering iron burning oily rags in a jar, and plumbed to a bicycle pump for pressure.

 

Yea, I assumed so reading as much on here from previous threads for fuel trims, which is why I've been so lost. I ended buying a fairly expensive reader that also does airbags and abs functions, so I'm covered there I believe.

I have two different intake setups, the stock, which is on now until issues are fixed, and a true cold air setup I had fabed up whenever I had the fenders and inner fenderwell repaired. Filter right now is a stock replacement paper filter

For the MAF, yes, I read that the densos seem to be the ones to get. I ended up pulling one from a running xjr, got tired of buying them and not knowing if they were good or not. I know for sure it's good, since it works fine on the xjr. It's like with Volvos, what I'm familiar with, only the Bosch brand are good to last.

But these ideas are what I need, lol, since I've been lost on it.

*Update, the long terms fuel trims, after running for an hour and about 15 miles driving, are sitting in the ranges posted above.

 

Valves are good, from what I can tell. When I did the timing chains and tensioners, nothing stood out since I thought the timing chain may have jumped a tooth. I ended up replacing the number 1 cyl valves from the initial fire, thinking that a valves issue may have caused the fire.

I definitely thought about the gas tank, and ended up pulling it out,( I despise the location of the fuel lines by the heat shield), draining it. I did a trick I learned a while back on restoring had tanks, drained it completely. Cleaned it, and treated it. It had rockauto brand fuel pumps, replaced them with walbro 255s to. As it sits, I get about 50 psi idle in fuel rail.

I ended up going through a little over 24 coil packs on this car, lol.

I'm tempted to, I'll definitely save their info.

The whole reason I bought this car was that I wanted an automaticV8 cruiser to replace my Vette( had a 99 FRC 6 speed that was totaled by a red light runner). I have enough standard transmissions to last a lifetime, since everything else I own is a standard, including my daily (04 S60R)
i fell in love with these for as long as I can remember. Such a great looking car.

 

The fuel trims you posted are indicative of an air leak after the MAF, - At idle the unmeasured air makes up a lot of the intake so the O2 sensor say's "eek its lean... add fuel", as you increase the rpm the unmetered air makes up less and less of the total so the problem gets less.
HOWEVER that is pretty basic diagnostic so if it has been in a garage that looked at fuel trims then that would be spotted. I would take a good look at the EVAP system as well as that might be the source of the leak.

Oh and check that MAF no. carefully it might not have the same response curve as a similar but different one - they changed on the XKRs but I can't remember when.

 

Will do. I am probably going to remove the throttle body, double check and recheck vacuum lines, ensure the gaskets are sealing properly, and check on the MAF when I get a chance tomorrow.
The advice is very much appreciated

 

+1 on checking you have fitted the correct MAF for the XKR and not the XK8 MAF..

 

I would like to chime in if I may. Diagnostics is something I enjoy and everyone has given some excellent advise.
So here are some generic - all vehicle diagnostics -
Fuel trims, some manufacturers show them differently but if you have the ability to see short and long term fuel trims, you subtract one from the other and ideally you should be at or near "0". Short term is immediate correction and long term is correction over extended time. So if short is say minus 2 (-2) and long is positive (+3) then total fuel trim is Positive 1 (+1). Typically a + or - 5% total is considered a great trim. Once you start edging over 10% +/- then it can cause some driveability issues. GM for years used a 0 to 255 trim count range with 126 to 129 considered the "0" range. So a positive number is fuel being added and a negative is fuel being subtracted.

Fuel Requirements -
An engine is a pump, so it can only move a finite amount of air at any given moment. The computer knows this so at any RPM, engine temperature, throttle opening amount (demand), manifold vacuum (load), air temperature and barometric pressure a certain amount of fuel will have to be delivered. With a MAF, it measures how much air is actually going in and adjusts the fuel delivery accordingly. The computer also looks at other things it is running like EVAP operation, it knows that when the purge operation is operating a certain amount of vapor is being allowed in that the MAF does not know about and adjust acordingly. Like wise the same for the EGR (if applicable) and other items. It also looks at the O2 sensors after combustion to make immediate corrections and adjust long term corrections.

So having any one of those sensors slightly askew can cause fuel trims to be off yet not be bad enough to cause a code to set.

Now comes the tricky part, not all gasoline is the same. Alcohol content (for those who have to deal with it) can cause drastic changes. It takes more than twice the amount of alcohol by weight than gasoline for ideal combustion. Depending on where you live it can vary from 5% to 20% per gallon. So try to avoid if possible. Also gasoline companies use different additive packages and some do not add any at all. Try to stick with fuel that is Top Tier rated if possible and from a reputable seller. I avoid cut rate stations at costs as I have seen wide variations in fuel quality from them. Gasoline life expectancy is another problem. Typically gasoline in a vehicle has about a 2-4 week life before it has degraded to a point that it can cause drive ability problems. I know I just opened a can of worms there but you'll have to trust me on this as I see it a lot.

Engine Mechanical Problems -

This covers a broad range so hold on. A slightly pitted valve face/seat. Remember the engine is a pump so if there is a very tiny amount of leakage at the valves then the engine cannot move as air as it should. It can also cause the fuel to not mix completely with the air or cause exhaust to dilute the fuel/air mixture some time with gaps in the mixture to not have any fuel at all. This can cause fuel burning to be jumpy in the cylinder and can cause it to not complete combustion before the cycle is done thus felt as a misfire. Also problems with intake and exhaust plumbing can cause this to happen. Leaks, bends, restrictions, even an air filter can cause this too. Fuel pumps can cause problem misfires even though it is capable of delivering the correct pressure and volume. A good example of this was Chrysler when they went to w returnless fuel system. It was found that as the pump would wear, it's speed would increase to the point that it would whip up microscopic bubbles in the fuel (cavitation) These bubbles would start to come together at the end of the fuel injector rail (typically near number 8 injector on V8's) This would eventually cause the number 8 exhaust valve face to develop tiny pits that lead to a slight misfire. GM trucks would develop a misfire at idle on their vortec engine due to a slightly loose catalyst bed that at times could be a horrible misfire.

I could go on and on about the various causes but I think you get the idea. Check everything carefully, having diagnostic data available will make it easier but some things require more data than a scanner can deliver. I use my lab scope often when these get tricky, I can see misfires using the O2 sensors, or pressure transducers (sensors) on the fuel supply, intake and exhaust on my scope. And with the program overlay I can even tell which cylinder, fuel/air mixture, ignition, even piston ring problems and cam to crank relationship changes. SO even if everything checks out as being within range, if enough of those items are at one end of the range, their total may add up to the computer delivering fuel incorrectly and causing the misfire.

I might add that I am currently chasing an intermittent misfire at idle/off idle on my 1995 Vanden Plas. I have found a couple of problems and corrected them but not completely corrected the misfire.

 

did you try replacing ECU? Sounds like computer problem.