Mechanics

RANGE LOSS OF POWER, MISFIRE

1997 Rover Range Rover

Engine Performance problem
1997 Range Rover V8 Four Wheel Drive Automatic 168000 miles

I have a range rover that has a sudden loss of power. When I try to accerlate it is very sluggish and doesnt matter if the engine is cold or warm. I step on the gas peddle and it seems to be clogged. I have error messages that state there is a misfire on #2, 4, and 7. Also have an engine oil pressure sensor high voltage input greater than 4.5 volts. I have recently replaced the plugs, checked the coil on all 4 packs, all read within range, checked that I have spark. At a loss. Going to replace the iginition wires.
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Moserobledo
April 12, 2010.




If it is missing that many cylinders, it is never going to accelerate. Since the coils are good, I assume you have good compression. The injectors are all that is left since you are already replacing the wires. Measure the resistance across the suspect injectors and compare with known good ones to se if there is a diiference

Tiny
Jack42
Apr 13, 2010.
I have replace the wires and still have the same issue. How do you test the resistance across the injectors. Is it possibly a fuel filter clogged? The car idles rough and it smells like it is running rich.

Tiny
Moserobledo
Apr 13, 2010.
Clogged fuel filter will usually lean them out, not richen them up. Since you verified spark on the offending cylinders, use a meter to measure resistance across the injectors that are showing misfires and compare the readings to cylinders that are known good. How do the plugs look in the cylinders that are msifiring?

Tiny
Jack42
Apr 14, 2010.
Wires replaced, fuel injectors tested and all good. Spark plugs look good all the way around. Had the misfire codes erased. What about a catalytic converter? Motor sounds good other than running rough and a loss of power. When you try to accelerate you dont get power.

Tiny
Moserobledo
Apr 14, 2010.
Usually a bad cat will give a random misfire code, not particular cylinders. You can try loosening the exhaust before the cat converters to see if it runs better. It will be loud, but if the exhaust can get out it will run better if the cats are the problem. May want to start at square 1 with th emisfire and do a compression test on the offending cylinders. Also if theinjectors are accessible, you can try swapping one from a cylinder that is missing to a known good one and see if themisfire follows it. Sometimes they will Ohm good but be sticking

Tiny
Jack42
Apr 15, 2010.
Usually a bad cat will give a random misfire code, not particular cylinders. You can try loosening the exhaust before the cat converters to see if it runs better. It will be loud, but if the exhaust can get out it will run better if the cats are the problem. May want to start at square 1 with the misfire and do a compression test on the offending cylinders. Also if the injectors are accessible, you can try swapping one from a cylinder that is missing to a known good one and see if the misfire follows it. Sometimes they will Ohm good but be sticking
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Tiny
Jack42
Apr 15, 2010.
Hey.

Hope you don't mind me adding 2 pennies worth.

I would be rechecking or replacing the coil pack for cylinders # 4 & 7 .. I would also be checking the camshaft and crankshaft position sensor are not dirty or reluctor teeth dirty/gunked up ..

Ignition and spark distribution are controlled by DIS. DIS uses 4 double-ended ignition coils located at the rear of the engine. ECM provides internal switching of ground circuit for each coil, which operate on a waste spark principle. A spark is delivered simultaneously to 2 cylinders, one on its compression stroke and the other on its exhaust stroke. Coil No. 1 feeds cylinders No. 1 and 6. Coil No. 2 feeds cylinders No. 5 and 8. Coil No. 3 feeds cylinders No. 4 and 7. Coil No. 4 feeds cylinders No. 2 and 3. Failure of any coil will cause a misfire in 2 cylinders.
Ignition timing is controlled primarily as a function of engine speed and load. Engine load is sensed by Mass Airflow (MAF) sensor. Engine speed is sensed by a Crankshaft Position (CKP) sensor. ECM determines correct firing sequence and timing of ignition coils from input provided by Camshaft Position (CMP) sensor. An ignition coil fault is indicated by illumination of the MIL.

Camshaft Position (CMP) Sensor
CMP sensor is a Hall Effect sensor located in the engine front cover. CMP sensor produces 4 pulses for every 2 revolutions of the engine (one pulse is slightly longer than the others). CMP sensor signals are generated from 4 gaps on cam gear (one gap is smaller than the others). CMP sensor signals are used by ECM to correct fuel injector timing for fully sequential operation and for active knock control.
If CMP sensor fails, default strategy is to continue normal ignition timing. Fuel injectors will be actuated sequentially based on top dead center timing. Injection timing will either be correct or one revolution out of synchronization. A fault is indicated by illumination of the MIL.

Crankshaft Position (CKP) Sensor
CKP sensor is located on the left side of flywheel housing and uses different thicknesses of spacers for manual and automatic transmissions. CKP sensor provides ECM with information indicating that engine is turning, engine speed and crankshaft position. ECM controls fuel injection and coil firing based on signal from CKP sensor. Engine overspeed protection is set at 5500 RPM and is based on CKP sensor signal. There is no default strategy for the CKP sensor. A failure will result in an engine no start condition. A fault is indicated by illumination of the MIL.
CKP sensor output signal is obtained from the magnetic path being made and broken as the reluctor ring teeth pass CKP sensor tip. Reluctor ring has 35 teeth and one missing tooth spaced at 10 degree intervals. The missing tooth is positioned at 20 degrees after TDC.

Hope this helps


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Dave H
Apr 16, 2010.
I had removed the catalytic converter and the car did run better so I replaced the catalytic converters and although it runs better it is still running rich. I then rented a scanner and cleared all codes, restarted the car, drove around block couple times. Still hestitates a little but better than before. When rpm's reach about 3-4 thousand I get a hesitation and sounds like it wants to backfire. Check engine light comes back on. Re-ran scan and now get the following codes: 1316 excess emission misfire fault. P0300 misfire crankshaft period malufunction criteria emissions threshold.P1185 two heater upstream hardware driver o/c both heaters post f left and left back. P1188 inferred open circuit fault both heaters. I tested the oxygen sensor heaters and two of them are not getting a reading on the meter. Two others read fine.

Tiny
Moserobledo
Apr 18, 2010.
Did you replace the H02s, when you replaced the Catalytic convertor ? Also what type of new cats were fitted OEM/Aftermarket/universal ?

DTCS P0130-P0133, PO136-P0139, P0150-P0153, P0156-P159, P0171-P0172, P0174-P0175, P1137-P1139, P1157-P1159, P1171-P1172 & P1185-P1196: HO2S CIRCUIT MALFUNCTION

There are 4 Heated Oxygen Sensors (HO2S) located in the exhaust system. Primary HO2S-1 "A" is located before left side catalytic converter and secondary HO2S-2 "A" is located after left side catalytic converter. Primary HO2S-1 "B" is located before right side catalytic converter and secondary HO2S-2 "B" is located after right side catalytic converter. Secondary HO2S-2 measure oxygen content after catalytic converters to monitor operating efficiency of converters.
Each HO2S is electrically heated to ensure sensor achieves operating temperature as quickly as possible after start-up. ECM energizes HO2S heater using a Pulse Width Modulation (PWM) signal which starts low and increases within 30 seconds to desired heater temperature. Primary HO2S heaters are wired in parallel and secondary HO2S heaters are wired in parallel for synchronous ECM control of each heater pair.
If front HO2S wiring is crossed, vehicle will operate properly until sensors reach operating temperature. ECM will then cause one bank of cylinders to run very rich and the other bank to run very lean. This will cause engine to misfire, idle rough and emit black smoke, with possible catalytic converter damage.

Diagnostic Aids
Indications of HO2S failure may be a strong smell of rotten eggs until default condition is initiated, high CO readings and/or MIL is illuminated. Check for contaminated sensor, poor connections, loose terminals, and open or shorted wires. Ensure wiring to primary sensors is not crossed.
With engine running at normal operating temperature, measure HO2S output voltage between HO2S 4-pin connector terminals No. 1 and 2. See Fig. 7 . Output voltage on primary HO2S should change between approximately 0.2 volts (rich mixture) and approximately 4.7 volts (lean mixture). Using a Snap-On Personal Automotive Computer (PAC), compare wave pattern with known-good wave patterns. See Fig. 8 . Oxygen content of exhaust gases after catalytic converter should be nearly constant, causing little voltage change in secondary HO2S.
Measure HO2S heater resistance between sensor connector terminals No. 3 and 4. See appropriate WIRING DIAGRAMS article. See Fig. 7 . HO2S heater resistance at 68 F (20 C) should be approximately 5.7 ohms.
Fig. 7: Identifying 4-Pin Sensor Connector Terminals


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Fig. 8: Identifying Known-Good HO2S Wave Patterns


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Dave H
Apr 19, 2010.
I took to a mechanic to do the cataylic converters. Not sure what he put in. Replaced the oxygen sensors yesterday after the converters were done. Had a mechanic come to the house and he did an oil pressure test, checks the plugs, sensors, engine looks and sounds good and recommends to replace the timing belt because it runs fine until you accerlate to a high rpm and the engine skips or sputters. Sounds like it wants to backfire. In his opinion sound like a timing chain. Any thoughts on that?

Tiny
Moserobledo
Apr 20, 2010.

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