Yet another car trouble thread...

nooshinjohn

My 2000 Jaguar XJ-8 with 87xxx miles on it has begun giving me all kinds of grief. It began with an evap code(p0446) and not I get two codes, P0172 and P0175. These codes are for run-rich conditions ofr the left and right banks of cylinders. In addition to this, the car enters restricted performance mode and stalls, shuts down, sputters, randomly accelerates and a myriad of other symptoms.

The fuel pump is new as is the mass-airflow sensor. All connections have been checked and rechecked as have the vacuum lines and all are clean and properly connected. Any Ideas as to what is happening here and what I can do to fix it?

Any and all help is appreciated.:)

Jstas

Didija install the Mass-Air sensor backwards?




Seriously. I watched my boss troubleshoot a similar issue on a Volvo for an hour and a half. When he threw his wrench and cursed at it, I walked over, look at the mass air sensor, pointed to the flow arrow and said "It's backwards." He swapped it around, ran like a champ.

nooshinjohn

It is installed correctly. The MAF fits only one way on the car and the wire harness will not make the connection if installed incorrectly. The MAF has been in the car for a year and a half now. It has been tested and cleaned properly.

My gut is leaning towards a fuel pressure regulator, but there is a possibility that O2 sensors may be involved.

Jstas

Well, the P0172 and P0175 codes are likely caused by the restricted performance mode.

However, I don't think the evaporator code is to blame. Usually a p0446 code comes when the system can't get a vacuum on the gas tank. That's caused by a leaky gas tank, a clogged fuel filter or a bad seal on the gas cap. Typically.

However, it could be indicative of a bad or worn fuel pump which might also cause the rich condition and low power because fuel pressure is too low. However, it's odd that the fuel pump would not have an associated code as well. But if the pump is drawing proper power and the pumping mechanism is what is worn out, the pump might not throw a code. But, again, fuel pressure should have a code with it too. That's a little weird. then again, it is a Jaguar. It took Ford a good 5-10 years to exercise all of the Prince of Darkness' demons from them.

I would clear the codes and reset everything and give it a drive. Also, check that the gas cap is all the way on before you pull out. If it still sputters with no codes, you have a fuel delivery problem. That could be a bad injector, a bad fuel pressure regulator, a bad fuel pump or a bad/clogged/improperly installed fuel filter.

Polkersince85

These car problems of late seem to be connected to people who have visited the Polk Audio forum. Hmmmnn.

Sounds like one of your system sensors have gone wild or you have a short or bad connection. Go with the codes and look up the diagnostics.

LessisNevermore

Polkersince85 wrote: »

These car problems of late seem to be connected to people who have visited the Polk Audio forum. Hmmmnn.

Damn you man,....damn you.:D:D

Face

Sell it, it's only going to get worse.

nooshinjohn

I have already reset the codes and cleared the computers. The pump is new (three weeks old) and has proper output. Gas cap is also new... The car will sputter and die out until the restricted performance lite comes on and the codes reappear. The P0446 codes always come on before the other two.

jrgoswick

Someone said check MAF direction. I'm saying HO2 sensors and cats(should be like a dozen of them-seriously like 6 though).

treitz3

When was the last time the fuel filter(s) were replaced?

nooshinjohn

Fuel filter was replaced the same time as the pump...

treitz3

Let me ask you this....and this is a long shot. When was the last time you replaced the battery? Was it recently and/or did the car sit without any power from the battery at all for more than 4 or more hours [lately, or since the symptoms started?]?

nooshinjohn

The battery is in great shape. The car starts quick and the starter cranks with authority. I did disconnect the battery AFTER the troubles began to clear the computers. The car acts exactly the same after clearing them as it did before.

After power was restored, the car idled for about 20 minutes before it was driven...

treitz3

John, I understand that you disconnected the battery after the issues began but you may have compounded the issues by disconnecting the battery. Basically, what happens is the computer resets itself to stock or "original" factory settings and and at this point, will not recognize what changes the computer has set the vehicle settings at as the vehicle has aged.

If your injectors are dirty or any other changes in air/fuel mixture have been adjusted as the car has aged in order to keep the vehicle up to optimal operating specifications, disabling the battery will [as mentioned] reset the computer to factory defaults which results in poor engine performance, stalling when coming to a stop and rough idling/sputtering.

You may have to have the fuel injectors professionally cleaned and the fuel system changed to reflect changes that has happened to that system since it was purchased.

treitz3

treitz3 wrote:

You may have to have the fuel injectors professionally cleaned and the fuel system changed to reflect changes that has happened to that system since it was purchased.

Allow me to clarify, not changed........but the spec's altered to reflect the changing environments of an aging engine. I did not mean that you have to have it replaced, just adjusted and thoroughly cleaned. Sorry about that.

nooshinjohn

According to Jaguar, allowing the car to "idle-in" for 15 to 20 minutes after reseting the computers is sufficient time for the car to adjust and re-learn the operating parameters and make the needed adjustments. The car ran just as bad, if not worse, before I followed their guidlines.

Thanks guys for all the help so far, but keep the ideas coming. I am going to pull and inspect the O2 sensors this weekend.

Mike Kozak

Check the flux capacitor (sp)

nooshinjohn

^^^Thanks Mike! I forgot all about that.:D

nooshinjohn

Polkersince85 wrote: »

These car problems of late seem to be connected to people who have visited the Polk Audio forum. Hmmmnn.

Sounds like one of your system sensors have gone wild or you have a short or bad connection. Go with the codes and look up the diagnostics.

Maybe it's time for a new POLL. How many SDA owners have had car troubles...:eek::p:D

Mike Kozak

I had to replace the fuel pump and filter on my 92 caddy, 600.00 Ugh, but not it runs great. 69000 miles

wz2p7j

John,

Your engine is running too rich and the engine control module is doing all it can to compensate by backing off on the fuel mixture but can't compensate.

So it's not a clogged fuel filter or bad fuel pump as those would result in lean mixture problems.

Could be leaky injectors but that would suggest the unlikely scenario that injectors in BOTH banks suddenly went bad at the same time.

I'm not familiar with Jags, but is there an equivalent of a MAP (manifold absolute pressure aka vacuum sensor)? If so,it may be reading improperly and telling the engine control module the engine is under load ("I'm accelerating, add fuel") when it's not.

The ECM then looks at the O2 sensor(s) and says, oh crap, we're way too rich and tries to back off but can't compensate, hence the codes you're getting.

Just a thought, I used to see this on GM cars but again am not familiar with Jags.

Chris

joeparaski

I'm not familiar with Jags either. But I would suggest you try a professional fuel injection service as was suggested. You need to get that possibility out of the way, either way it would be good to get it done.

Joe

nooshinjohn

joeparaski wrote: »

I'm not familiar with Jags either. But I would suggest you try a professional fuel injection service as was suggested. You need to get that possibility out of the way, either way it would be good to get it done.

Joe

Flow rates read on diagnostics appear to be spot on(within 5%) of each other. The STFL readings are off the charts and fluctuate wildly at idle and even more so under load. With the cruise control set, they swing from -12.8 all the way out to 26.2. The LTFL numbers remain more constant, but also fluctuate...

Any ideas on what those numbers are all about?

wz2p7j

Don't know much about Jags, but I'm sure STFL is "short term fuel something" and LTFL is "long term fuel something" kinda like "integrator" and "block learn" on older GM cars. I would expect STFL to fluctuate more than LTFL.

Some sensor is fooling you're engine management system making it add/subtract fuel causing this problem. Look at any value on the scan tool related to engine load/acceleration. i.e. MAF MAP TPS.

On older cars, MAP used a 5v reference. Low voltage of about .5-1v was a car at idle. Shouldn't see a MAP voltage of, say, 3v with a car at idle. Same with TPS. Can't remember about MAF, seems like that was usually pulse width modulated or something, can't remember.

Chris

wz2p7j

nooshinjohn wrote: »

According to Jaguar, allowing the car to "idle-in" for 15 to 20 minutes after reseting the computers is sufficient time for the car to adjust and re-learn the operating parameters and make the needed adjustments. The car ran just as bad, if not worse, before I followed their guidlines.

Thanks guys for all the help so far, but keep the ideas coming. I am going to pull and inspect the O2 sensors this weekend.

John, it could be the O2 sensors saying "I'm lean, I'm lean" resulting in your rich codes. But right and left bank would both have to go south at the same time to generate your right bank, left bank rich codes. Not likely.

There's usually only ONE TPS, MAF and MAP and BOTH banks are reading rich. Again suggest starting with MAP, MAF and TPS.

Good luck!! :D

Chris

nooshinjohn

The MAF is spot on spec-wise... the O2 sensors are a 4 wire type that transmits readings back to the ECU and tells it to make adjustments to the fuel/air mix. If the wrong data goes back to the ECU, would this cause the wild readings I am seeing?

wz2p7j

I would expect STFL and LTFL to vary based on load, etc. And STFL to vary more than LTFL.

Is there a voltage reading you can provide for MAP (vacuum) and TPS at idle and, say, WOT?

Also, I'm not familiar with Jags - how is MAF spot on, can you please elaborate??

Thanks! Chris

wz2p7j

John,

OK - I Googled "2000 XJ8 MAP sensor" and found some part numbers, so I suspect you have a MAP sensor in your vehicle. Please verify and provide readings, if applicable.

Thanks!! Chris

nooshinjohn

The MAP sensor and the MAF sensor are one and the same. I believe we are just using american vs. european lingo here. The MAP/MAF is new. There are 4 O2 sensors on my car, and the first two are used to adjust the air/fuel mix. The back two monitor efficiency of the catalytics. It appears the two in front of the cats have the ability to play all kinds of havoc with regards to fuel flow.

What I have learned also opens the possibility of bad catalytic converters.

You guys are great!

nooshinjohn

Any other ideas out there?

Face

Drop the car off to someone who knows what they're doing?