Hey, been searching for possible answers but can't find anything specific. My 1997 5 speed I brought in December 2024. Well serviced vehicle with 260km. Recently it started spluttering at highway speed over 80 kmph, slower was fine. Changed the fuel filter, then drove fine for 4 days (100 mile ish), splutter returned. Removed fuel pump, minimal debris, fuel tank all clean inside, good again for 1 day, spluttering returned, idles perfect. It had new plugs and HT leads last August, 14000 km ago. I have checked vacuum lines under the hood,all good, the ones in and out the valve covers can blow through no problem with the oil cap off. The MSF was replaced just before I got the vejicle. Disconnected speed sensor, made no difference, drove fine for 15 minutes then spluttering.
No engine light comes on, there is one P1179 code stored, which I cannot clear, however the fuel line split by the filter and was replaced, just after filter was replaced, so that code makes sense at least to me. I check resistance on the 7 injectors I could get at, 16.6 on one, 16.9/17.0 on the other 6, which from the video I followed sounds ok? I tried octane boost and Seafoam in gas, no difference. Pulled all spark plugs all are good, same brownish coating as they should have. I wonder if an injector is faulty, but would that not throw a code? I checked fuel rail pressure 30psi when idling, climbs to 36 ish when engine switched off and stays above 30 psi for over an hour.
Don't know what to do next, can anyone give me some idea what to look at/ for please....
thanks Dave

 

Sounds like you need troubleshooting tools. I would be monitoring O2 voltages and fuel trims, real time, with an OBD app such as Torque. Voltages should modulate high/low in a rhythm. Fuel trims should be middle of the road, not to extreme values. Also try resetting adaptive values, especially since the MAF was replaced. The tools needed are an OBD dongle (OBDLink LX for example), and and app on a smartphone or table (Torque for example, and GEMS Lite for resetting adaptive values). These are basic tools that work for any vehicle with the OBD2 protocol (required since 1996), except GEMS Lite is Land Rover specific.

If crud in the fuel found its way to an injector, that could potentially clog the screen of a fuel injector. That could show up as unbalanced fuel trims from one bank to the other, or unbalance O2 voltages, changing between idle and highway driving. I have been happy with the 19#/hr 4-hole injectors I installed from Accel. Maybe the fuel pump motor is getting weak? Probably best to dive into the troubleshooting vs throwing parts at it, but new parts can be a good thing too.

Maybe try a clean air filter. Need to get that 1179 code cleared. Try unplugging the MAF and drive. If MAF is bad, the truck should drive OK with it unplugged. The ECU compensates for the MAF being unplugged. Good luck. Let us know how it goes.

 

Had problems with my '98 cutting out and it was the speedometer sensor giving flakey signals to computer. Swapped it out and problem went away. It would drop down to about 35 mph, then go back up to 60, I used a OBDII monitoring live data and saw the speed sensor cutting out.

 

Much appreciate the response, I went borrowed an OBDii reader, notvery familiar with reads but did find the O2 voltages are not good on I beleive one side of the engine,did not go low/ high in rhyme. Will try upload picture of the graph. Does this mean likley injector issue?
What did change when reader was attached the spluttering got really bad,but when trying to pull away,still idled good. Then driving home (15 minutes) the spluttering got less and cleared and I was able to do highway speed no problem. Total opposite to before when slow was fine and highway bad. I thought maybe the fuel cleaner was helping,so took the disco for a run to the city, drove ok at speed, got.to city and was terrible at low speed and pulling away, driving back was almost 100% the odd minor hesitation. When spluttering at low speed, smells like cat bad, but good at speed. It did throw code 102 twice, which said Mass airflow low voltage, I believe.
Will try unplugging Mass airflow and see what is does.
Not sure what to try next?





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I tried the Mass airflow disconnect, it would not start, reconnected to start it, then disconnected, had hesitation from idle to accelerate, as it did in the city earlier today. Ruled another option out.
Really appreciate the responses helping me. Thank you

 

Have also tried the speed sensor possible issue, is not the problem with my discovery, appreciate the tip though! Thanks

 

No need to monitor the S2 (Sensor 2) O2 sensors, only S1. That is B1S1 (Bank 1 Sensor 1) and B2S1. Those control the fuel adjustments to the injectors, so control how well the engine runs. Bank 1 is the left bank with odd numbered cylinders. Bank 2 is the right bank with even numbered cylinders.

Also take readings for Short Term Fuel Trim (STFT) for each bank, and Long Term Fuel Trim (LTFT) for each bank.

Noticed a ? beside the MAF reading 0.00. Looks like the MAF could be bad. Need to clear up any MAF codes first, before looking elsewhere. Code P0102 also suggests the MAF is bad or very dirty. If you know a friend nearby with a Disco that runs good, maybe try their MAF. Or get one from a wrecked truck. They were usually running when they wrecked. The MAF reading should not be zero when running. Lower numbers at idle, then higher on freeway.

 

Your sensor readings are odd. I suspect that somehow the downstream and upstream sensors are backward though not sure how that happens.

O2B1S1 - Bank 1 Sensor 1 - generally refers to the Upstream (aka Pre-cat) sensor of bank 1 (left - driver).
O2B1S2 - Bank 1 Sensor 2 - generally refers to the DOWNstream (aka Post-cat) sensor of bank 1.

Downstream (post -cat) sensors generally show readings at/near 1.0. They don't (and shouldn't) bounce around very much at all. If they do bounce too much it suggests your cats are shot.

Upstreams bounce around constantly as the air-fuel mix is adjusted by the Engine Control Unit (ECU).

In your case, it looks as though the 'Sensor 1' sensors are hovering around 1.0 which is absolutely NOT what should be happening.

So either your reader is a little wacky in how it labels things, or the sensors are somehow hooked up incorrectly.

 

I will look further later this week and get the fuel trim readings etc. Your help is much appreciated, thank you

 

bad fuel - try Shell