| Author | Message | ||
     Paul Cringle (Manxi) New Member Username: Manxi Post Number: 1 Registered: 04-2003 |
Can anyone help with this problem? I have a 1995 Range Rover 4.0 SE Auto 40K Miles the engine starts OK and runs fine when cold but when it reaches operating temperature it starts to misfire so badly that it is completely undrivable this problem has been so bad that the cats have had to be replaced and I do not want to have the expense of replacing them again here is a summary of what has been checked already. 1. Ignition leads have been replaced 2. Fuel Filter has been replaced 3. Cats and rear exhaust system have been replaced 4. Spark plugs have been replaced 5. Both Cylinder heads have been removed all valves have been cleaned and the heads reassembled with new gaskets and bolts. 6. I have an Oscilloscope and have checked the Crank Shaft sensor, Camshaft Sensor, Temperature Sensor and Injectors the traces look fine while the engine is running, when the misfire starts the engine stalls. 7. The resistance of the sensors and injectors have been checked hot and cold also checks for shorting to ground have been carried out and they all seem OK. 8. Fuel pressure is OK I have now spent a lot of time trying to sort out this problem the English spec Range Rover does not have the diagnostic LED readout so I cant relate to any fault codes the only way to retrieve them is through a dealers test book. I suspect the engine is running rich the misfire is effecting the right hand cat temperature (looking from the front of the engine) and it begins to glow red, at which point I have shut down the engine. When the plugs were removed the were all sooty. But I am not sure if this is from running rich or because the engine never gets further than operating temp. This problem has gradualy got worse it started as a slight stumble which cleared itself after a good run to the point where the engine is now crippled when it reaches operating temperature all the symptoms pointed to sticking exhaust valves which is why I took off both cylinder heads to clean the valves and stems. Any help would be appeciated before I have to resort to a land Rover dealers test book | ||
| LEON KEDZIERSKI (Rovertech) New Member Username: Rovertech Post Number: 13 Registered: 12-2002 |
O2 SENSORS ? | ||
| Paul Cringle (Manxi) New Member Username: Manxi Post Number: 4 Registered: 04-2003 |
Hi Leon I have removed and tested the o2 sensors I only have 2 on my range rover before the cats the heater resistance is within the tolerance specified in the workshop manual and when i connect the scope to them off the ecu box they switch on and off as they should, have even tried running with them unplugged so it should then run on default value (or will it?)have you seen similar problems with 02 sensors as I have mentioned this is so severe the vehical is undrivable when engine has reached operating temp. since the last post cleaned all the plugs replaced them ran the engine a few times, removed them again and all were sooty and wet with fuel, so the problem seems to be effecting all 8 cylinders. | ||
| LEON KEDZIERSKI (Rovertech) New Member Username: Rovertech Post Number: 21 Registered: 12-2002 |
HOW DOES THE VEHICLE START UP AFTER SITTING FOR A WHILE IS THERE AN EXTENDED CRANK? | ||
| LEON KEDZIERSKI (Rovertech) New Member Username: Rovertech Post Number: 22 Registered: 12-2002 |
I HAVE SEEN LAZY 02 SENSORS CAUSE RUNNING PROBLEMS .TRY TO REMOVE AND PLUG HOSE COMING FROM CHARCOL CANISTER TO INTAKE PLENUM. CHECK FOR RAW FUEL IN LINE(THIS MAY SET CHECK ENGINE LIGHT FOR EVAP SYSTEM FAULT) | ||
| Paul Cringle (Manxi) New Member Username: Manxi Post Number: 5 Registered: 04-2003 |
Hi again starts up from cold instantly and runs fine untill the engine gets warm. I will try your suggesion with the evap the evap solenoide valve is ok I have tested it. | ||
| Paul Cringle (Manxi) New Member Username: Manxi Post Number: 6 Registered: 04-2003 |
Fault Found!!! THe tip of the Crank Shaft Sensor was touching the flywheel timing ring when the engine got warm metal expansion made it worse I made a spacer about 1/16" and fitted it in front of the sensor mounting flange, engine runs perfectly now. must have been a combination of bad machining tolerance on the bell housing face and possibly float on the end of the crankshaft although at 40K miles the latter seems unlikley, still a mystery as to why but I dont care as long as it runs OK | ||
| Rob Davison (Nosivad_bor) Senior Member Username: Nosivad_bor Post Number: 272 Registered: 02-2003 |
DAMN! who the hell tracked that down? | ||
| Jon Santana (Mustache) Member Username: Mustache Post Number: 41 Registered: 09-2002 |
DAYUM! i gotta bump the question. how on God's green earth did you figure that out? | ||
| Paul Cringle (Manxi) New Member Username: Manxi Post Number: 7 Registered: 04-2003 |
Hi Jon & Rob I have now run up about 400 miles after the fix and everything seems OK. In answer to your questions "how did I find it". When I had the scope on the crankshaft sensor the signal looked OK, when the engine reached operating temp and the misfire started I lost the signal but that was because the engine had stalled. when the the misfire started I noticed the taco kick back, on the 1995 Range Rover the taco takes it's signal from the crankshaft sensor so I started to suspect the sensor was faulty even though the signal looked OK. Ordered another sensor �34.00 checked it against the old one and noticed the new one was slightly longer about 1/16" I did not think much about it untill the new one was fitted and I started the engine It ran worse than ever misfiring straight away. Stopped the engine and removed the sensor to check it and noticed the tip of the sensing rod had bare metal showing it was originaly cadmium plated. I looked ot the old sensor and that was the same. Took the bottom bellhousing cover off so that I could see the timing ring on the flywheel and could see a slight score mark where the sensor tip had touched it. The new sensor had the optional 1/2" spacer supplied for the 4.6 RR so I cut it down to 1/16" and fitted it in front of the new sensor I had fitted. Checked with the bellhousing bottom cover removed that it was clearing the timing ring and it was, started up the engine and it ran perfectly and has done since. So it seems the old sensor was actualy OK just touching the timing ring when the engine reached operating temp. The only explanation I can think of is perhaps bad manufacturing tolerances on the flywheel/ crankshaft area together with end float on the crankshaft, when I have time I will setup a dial indicator to measure the crankshaft end float but at the moment I am just enjoying driving it after 3 months off the road. |
