QuestionQUESTION: Aloha Nigel,
Jeff from Hawaii again. 2002 LR Disco 2. Thanks for the driveshaft info. Went
in like a dream! Now I have a flashing check engine light accompanied with
what feels like fuel starvation. Cutting out intermittently under acceleration.
Bought a code reader (CanOBD2) and it gives me a fault code P0174(System
too lean bank 2) It seams this is usually a Mass airflow sensor issue. I took it
apart and it was clean with no visible air leaks down stream to the engine.
I have about 60K on the rover. Any suggestions? Should this be the culprit?
ANSWER: A flashing check engine light normally indicates a severe misfire, causing catalytic convertor damage. P0174 is normally present with another lean code and a transmission gear ratio fault. This combination indicates a mass air flow sensor fault. But an air flow meter does not normally make the car stutter or cut out.
From your description of the symptoms, I would say it sounds like a misfire from a coil or the crank sensor breaking down. Persevere and see if some other codes appear. let me know what you find.
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QUESTION: Thanks Nigel. I recently had all coils, plugs and wires replaced so I'm thinking maybe the Mass airflow sensor? It doesn't cut out bad...Just enough to notice as an owner.
It's more like a subtle misfire...Not drastic. I was under the impression that a faulty MAF sensor causes misfires due to it not providing correct /consistent air fuel mixtures.
Any way to test trhe MAF sensor? I ordered the 700 page shop manual the other day so hopefully I can stop bugging you soon. Any other help is appreciated!
ANSWER: Mass Air Flow Sensors on these vehicles do not normally cause misfires. If they did, they wouldn't be on only 2 cylinders. There would be random misfires on all 8 cylinders. According to the codes you presented in your second e-mail, however, you do need an air flow meter, however.
Cylinders 4 and 6 on this year are notorious for random misfires due to loose cylinder liners (sleeves). If there has been any overheating, this could be the problem. Check for coolant contamination on the plugs.
Alternatively, check for consistency of spark on cylinders 4 and 6. Finally, you could try a proprietary oil additive to free up any sticky valves, rings, etc. which could also cause misfires.
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QUESTION: Hi Nigel,
Replaced Mass airflow sensor today....Same misfire problem on cylinders 4
and 6. as well as a P1300 code (Catalyst damaging misfire multiple cylinders)
drive cycle C: signal out of range-above maximum. The P304 fault code
freeze frame data says : Fuel Sys 1 OL-Fault Fuel Sys 2-OL Calc. Load %
22.75 ECT (f 98) 4 and 6 plugs have black soot on only 1 side of the plug
bases. Uneven firing? I'm replacing those 2 plugs tomorrow and then
checking for spark. I'll let you know the outcome. Any thoughts? I have not
witnessed any overheating although I have only owned the vehicle a year
now. Who knows about it's past.
AnswerThe black soot on one side of the plugs is pretty common. It can be caused by sticky inlet exhaust valves, poor injection spray or an ignition problem.
You still need to check for consistent spark on those cylinders and check the plugs for coolant contamination.
