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from your symptoms I’m thinking fuel delivery problem not from fuel pump. Excessive fuel consumption and steady psi on fuel pressure. No fuel smell? Fuel pressure should increase with more RPM. Do snap throttle test. PSI should go max then dip and level off. Pull the pressure regulator vacuum hose, PSI should go up (same as max throttle snap PSI). If fuel present in vacuum hose or nipple of pressure regulator you have a bad pressure regulator. In any event you should not have any drop in fuel pressure, that would be a bad pump but you replaced that so you should not have a drop.
EGR open at low RPM will cause problems as well. This could be secondary problem. Do fuel first.
You can use DVOM to watch 02 sensor movements but its hard and does not give the results/data you’re asking for. With excessive fuel consumption, 02’s are going to be reporting rich condition PCM is going to respond by trying to take away fuel to compensate.
replied on the 4 02 sensors post… do the fuel pressure test first and verify no system leak down and correct pressure. we will get to that EGR as it sounds suspicious. you can have both problems or one leads to the other. both can give you the rich condition. if you work on both problems at the same time you will not know where the problem was and your fix could be temporary.
Ok… good on the right track. If you get a loss of pressure in the overall fuel pressure, next step is to check each injector. If you have a bi directional scanning program, you can test each injector one at a time. So first thing is to check for a loss of total fuel pressure and correct pressure readings. 38-46psi. Charge the system (keyOn) then let set for 15-30 min (keyOff). Note loss is any. No more than 1psi loss.
your AF’s appear to be working fine… the engine is still getting too much fuel. Even though the fuel pressure is normal at idle you can still have a fuel delivery problem. That’s why it clears up a higher RPM. Do a leak down test of each injector. Rule out that an injector is leaking. You can do all at once by charging the fuel system then turn off the key off and let the system rest for 15min. If pressure drops more than a couple of PSI, you have a leaking injector. I re read you posts, but I don’t see where you listed a code fault. Are you getting a P1172?
Import is correct. The 2001 Jag uses Air Fuel Sensors (AF). They work differently from the narrow band 02 sensors.
You’re not going to get much data from using a DVOM as the AF sensors measure in mV changes(current). You will have a stoichiometric reading in voltage for your car. You need to have a scan tool which will give you an equivalent ratio reading. That will tell you what voltage reading is stoich. 14:7:1 for your car (each is different for makes and models). A reading of less than :1 is rich and greater than :1 is lean. That’s just the opposite of a 02 sensor.
Both upstream AF should be reading a steady voltage. You say you’re getting a rich condition code. That is the reason for the -trims. The computer is taking away fuel to compensate. Without knowing the stoich number I would have to reason that the 3.4v reading is below stoich.
Your engine is getting to much fuel by a bad pressure regulator or a leaking injector, bad EGR or EVAP problem. These are a few things that can cause too much fuel. Find the fuel delivery problem and I bet the trims, AF and CAT problems will go away.
Credit goes to Matt of Schrodinger’s Box and Paul Danner of ScannerDanner. They are the real teachers. Thanks Matt and Paul.
you have access to real time data then… working with the P0171/P1133 codes, you are looking at a problem with the bank 1 02 sensor, most likely the heater circuit.
You have several 02 sensors, but only focus on B1S1 and B2S1 02 data for now. The two sensors are the upstream sensors located just below the exhaust manifold in the head pipe on each side of a V engine. The P0171 code is the B1S1 and P0174 is the B2S1. Bank 1 on GM is the driver side.
Using live data, select a graph mode for the B1S1 and B2S1 STFT and LTFT as well as the voltage for both. On start up your 02 voltage will be high then quickly drop as the heater circuit brings the 02’s into operating/closed condition. Once in close loop, the 02 voltage will oscillate between 150 and 800mv… if they do not drop in voltage or remain high that indicates a problem with that 02 or its wiring. Your STFT and LTFT should show a high (above +10) reading for the B1S1 02. This indicates the lean condition and a P0171 code. A defective heater in the 02 will not allow the 02 to operate correctly and give the P1133 and P0171 codes. Swap the B1S1 and B2S1 02’s and see if you now get a P0172 code. Don’t forget to clear all codes before restarting.
Coolant temp is important. The engine needs to be at correct operating temp. You reported that the STFT and LTFT are always at 0. Either your not reading the data correctly or the engine temp is low which will cause the system to remain in closed loop.
You have a very good scanner and I do not have any expertise in that device, so I could confuse you with attempting to use the scanner for anything more that the basics for now.
If the problem moves to the bank 2 sensor after swapping, I would change the 02. I say this because of the P1133 code. If it was just a P0171 I would do more testing. Remember, the reason for this site is to NOT be a parts changer.
negative fuel trims on both banks would indicate a fuel delivery problem. stop throwing parts at the problem. Check fuel pressure. Now that you changed the O2, what are the STFT and LTFT at idle with engine hot.
If your still in open loop with engine at full operating temp… the O2 sensor heater circuit is not functioning correctly (P1133). You cannot have 0 STFT and LTFT with a PO171. A PO171 is a lean condition, your trims will be positive as system is adding fuel to compensate for extra air. Because of this I would check for proper signals to the O2 sensors. Rough idle when warm would indicate an intake manifold gasket leak. When cold idle is Ok because gasket seals itself but as engine gets hot, the intake manifold and head expand causing the gasket to leak. Don’t work on the gasket leak yet, get the O2’s in closed loop and reporting trims first. O2 signal will oscillate high and low in a wave pattern if working properly. Sounds like a wiring problem.
P0442 is usually a small vacuum leak in the evap system. With Chevy most times its the gas cap or purge valve… if you have replaced the valve, did you test it before installing? Many times new purge valves are defective. If you do not test it, you will believe its OK and it still may be the problem. Recheck the purge valve. Hook up a vacuum pump to the valve (Ok to be installed on veh) and insure its holding vacuum.
You’re throwing a lot of parts at this problem. You have a vacuum leak somewhere, you have to test every piece before replacing. Putting grease on the seal of the gas cap can test that part. Smoke testing is the best way to find a stubborn vacuum leak.
I’ve read your previous posts on this problem. The reason for this site is to learn not to replace parts without cause but to learn to use deductive reasoning and our test equipment to establish why and where something has gone wrong. It has taken me some time to resist the urge to replace parts, but the satisfaction has been that when I do, the problem is resolved.
In order to fully understand your car’s problem/s it would be best to start with the exact codes you are getting and the STFT and LTFT for both banks of the engine.
From what I have read, your car is running rich for some reason. The STFT and LFTF from both banks will establish a basis for figuring out where things have gone wrong. As you have found out, replacing O2 sensors does not correct the problem.
Your car has four O2 sensors as most do. Two are located in the exhaust head pipe one each on either side of the engine and two down stream. One ahead of the cat and one after the cat. The two at the head exhaust pipe are the ones that tell the computer how to manage the fuel injectors to supply fuel to run your car. The computer receives data from other sensors to know how to control fuel.
bank 2 is getting too much fuel… stft is -35 which means the computer is calling for less fuel to bank 2 because your ltft is +35. P0430 is the post cat sensor reporting an improper cat condition. your engine is getting too much fuel from one or more injectors on bank 2. to know for sure if the problem is specific to bank 2, check the stft and ltft on bank one. if both sides are showing – on stft and + on ltft the engine is getting too much fuel. this would be a fuel delivery problem. check the fuel pressure at the fuel rail. if only one side is having the problem, check the injectors on bank 2 for leaks.
