I have a 1993 XJ6. It has been stored winters. It has 71000 miles on it. I have to do a few things like replacing all of the shocks and probably the upper and lower ball joints. No problem. The check engine light is on and the VCM is saying it is failed fuel 44. The book says that is the O2 sensor circuit. One time the VCM read failed fuel 46 which the book says that is Idle speed control valve. I have not tested with a meter the sensors. The book says that if you are at an Idle and you turn on the lights and the rear window heater the idle will lower if it Idle speed control valve is bad. For my car the Idle is fine no matter what I turn on. The Idle goes all the crap when I put it into gear. It just started doing this even though at 52000 the check engine light came on with the failed fuel 44 which was the O2 sensor, and I just never changed it. But just recently it started idleing funny. Really low and sometime will not keep running and die out. Please can someone help as I don't have all the money to replace both sensors right now. I don't know if the O2 sensor is causing the Idle speed control valve to be acting up.

 

Any ignition or fuel metering fault that causes a missfire and incomplete combustion can trigger FF44. That code doen't necssarily mean that the sensor is bad, just that the O2 reading is out of range.

Disconnect the battery to clear the code, and see if you get another warning in its place. It's much more likely you have a basic problem, spark plug or ingition wire as an example, that is resulting in unburnt fuel to fool the oxygen sensor and a decaying idle speed. The idle speed control valve is not a common fault and won't cause a rough idle.

 

I have disconnected the battery to the car clearing the codes a few times. And after driving around which sometimes it is a few weeks the code comes back. I changed the plugs but I have not changed the wires. Maybe being nieve as the wire I replaced when I first got it back in 2002 were life time plugs. The check engine was on then for the FF44 and has remained on since.

 

I meant life time wires not life time plugs sorry

 

I don't know what else to tell you, playing "Maybe it's the..." gets expensive and doesn't usually get you an answer. I was trying to point out that condemning the oxygen sensor is a good example. You need to identify and correct the missfire/ rough idle, and the O2 sensor will probably stop resetting the code. The fact that no other codes have appeared eliminates alot of possible causes, but you still have to identify the ignition or fuel problem that is the cause.

 

Thank you!!

 

I now replaced the plugs and plug wires. I've installed NGK plugs and Bosch wire set. The plugs I replaced were still good as I changed them only 3000 or 4000 miles ago, they were Bosch platinum plugs, but I changed them anyways. The old plugs were white at the electrode and a little oily as the valve cover gasket is leaking a bit. Engine started up a lot better and ran a lot better. I do not feel it misfiring any longer. Exhaust smells a little like fuel, but not anything like before I changed the plugs and wire set. While in Park the car seemed at first to idle perfect, as it did before but with out the misfires, idled at 800 to 850 rpms. When in Reverse or Drive idled down to 700 rpms and sometimes to 600 rpms. At 600 rpms it was not enough to keep the alternator charging at its normal 13.2, but did not dip below 12. I let it idle in park for about 10 minutes just sitting in it listening to what I could hear and it lost it. Very eratic idle, seemed at first it went to 1500 rpms and stayed there until I hit the pedal and it spit and spuddered back down to below 600 rpms until the Check Engine light came on reading failed fuel 44. O2 sensor rich or lean condition which explains the unburnt fuel I smell comming out of the tail pipe. Since I got the advise to fix the misfire on my last post I have realized that the O2 sensor does not cause the problem. Is there a Relay or something linked to the ignition system that could be causing this? Or is it possible that too much gas is being injected into the cylinders which is causing there to be unburnt fuel? Can anyone please tell me the next logical step in fixing my problem. By the way I changed the front shocks this weekend too, and I put KYB's on and it is a world of difference. This next weekend I am doing the rears. Hopefully it will raise it some because now that I replaced the fronts it looks a little low in the back. They were on the front and are on the back factory orginal shocks. The motor has 71300 orginial miles. Hope someone can help.

 

Get your battery tested first, then the charging system output. Low voltage= rich running, eliminate the basics first.

 

I put a brand new battery in it about 3 weeks ago and I put a new alternator on less than 1500 miles ago.

 

That still doesn't mean your charging output is OK, but if you're telling me it is then that's fine.

Next thing I would check if fuel pressure, with a gauge you will have to buy and plumb. My high mileage '92 was loading uo at idle because the fuel pressure regulator failed, not a common problem but easy to diagnose with the proper tools and another system to eliminate when trouble shooting.

 

Thank you for your help. I will check out the voltage by putting a volt meter on the battery cables with it off and then with it on. Would I be correct by saying it should read 12 volts off and what the dashboard gauge reads running, which is normally just past 13 volts. If it does then I will check the fuel pressure. I will get a fuel pressure gauge. Not sure exactly how to use one but I will figure it out. I will do this soon and get back to you. Once again thank you for your help.

 

Something that might be relevant here is the reason I changed the alternator 1500 miles ago is because while driving down the road it shut down on me. A lot of lights came up on the dashboard. I drove the car about 3 to 4 miles with out the alternator working before I shut it off and replaced it. Could that have been the reason this problem is happening? I can not remember if the car was idling funny prior to this or not, which would be very relevant here.

 

I replaced the air filter altought the one that was in there was still pretty good. Better idle but still does not hold at 800 to 850 rpms. It goes down slowly during deceleration and when comming to a complete stop the idle continues to drop until 700 rpms or 600 rpms and sometimes starts choking at 550 rpms. Idling at 800 rpms I do not smell gas in the exhaust. I checked the charging system and it checks out a little over 12 volts off. and was at 13.9 idling and jumped up to 14.1 with the lights on, and with lights on and in drive rested at 13.9. I bought an Actron Fuel Pressure Tester. I will be testing the fuel pressure in the next few days.

 

I have access to a diagnostic computer so I am wondering if I hook my car up to the computer will the computer be able to help me chase down this problem I am having. I don't have much experience with hooking a car up to a computer and whether or not this will be a waste of my friends time. He wants to charge me $50 so if anyone has experience with using these computers will it diagnose my car?

 

I would say it depends on which variety of computer your friend has. If he has an OBDII reader, then go to Auto Zone and they will read those codes for free. If on the other hand he has access to a dealers code reader that can read all the on board computers, then $50 might be cheap enough.

 

Not applicable to 1993. OBD II readers, and Jaguar PDU's, only read codes for 1995 and later Model Year vehicles.

 

My friend who is a UTI student looked at it and said it needs an O2 sensor, and the fuel system is dirty, and needs to be flushed out. The engine light came on this morning reading fail fuel 14 which is the coolant temp sensor. So I will change that Saturday. But that was all he found and the fuel pressure he said was fine, but it needs a system flush. I guess a machine does it. The guy I bought it off from years ago said he had that problem and he mixed the premuim gas with the regular and reset the codes and to would run better for a while. I've had it since 2002 and have put 20,000 miles on it and it just recently started this. I normally put Shell or Speedway mid grade in it. Seem to me like dirt is the fuel system could cause a low ilde with the injectors a little pluged. I don't see how the coolant temp sensor is related to the idle? Could it be dirt in my fuel system and the wrong fuel octane? What would be the right octane? What do you think?

 

Maybe the MAF that are failing you . Try to clean it whith CRC MAF cleaner.

The most common reason for O" sensor faults on Volvo is almost always the MAF (Manifold Airflow Meter) I would also check if the car tok in some false Air ( Air taken in after the MAF) This is easyeist checked whit motorstart gas . Spary the motorstart gas around the intake manifold and throttle housing while the enginge is running if the revs go upp then you have a leak.

 

Still chasing low idle. The only thing I have not done is to change out the O2 sensor. The engine check light is not on. New plugs, wires, cap and rotor, and air filter. I just had the fuel system cleaned out and although it idles smoother at a stop with the car in gear the idle still drops to around 550 rpms? The charging system is reading as it is supposed to and it has proper fuel pressure. Can and/or is the O2 sensor causing a problem like this. A couple of days ago the VCM read fail fuel 14 coolant temp sensor and I changed it the next day. But like I said no lights are on now and the O2 sensor needs to be changed. To JagtechOhio thank you for the help you have already given me I really appreciate it.

 

I also appreciate all the others that have responded to my post. Thank you everyone