Hi I have a 1999 Land Rover Discovery SD (1) I'm pulling code p0451 which has something to do with fuel tank pressure and im also getting p0300 which means random misfire. I changed two coils, plugs, cleaned MAF and changed a busted O2 sensor. I'm also pulling codes P1316, P1366, P1314, and P1313. Could this be a faulty or clogged injector? What should I do?



Tags: fault codes, random, misfire, p0300, p0451, fuel pressure leak, sensor, injectors

 

What's the engine idle at and how many miles on the engine? The Idle Air Control solenoid probably could use a good cleaning and the ECM's coolant temp sensor (smaller one) probably could be replaced as well. Clean the PCV oil separator on passenger valve cover - check hose that comes from it to the plenum for signs of wear, cracks, loose on fittings..... These can have an effect on the pressure sensor readings received through the ECM. Check the fuel cap as well, non-vented, check purge valve to charcoal can to fuel tank hoses for signs of wear. All the other codes are emissions faults or cat efficiency that will clear once you find the source/sources of the misfires. I would run some injector cleaner through too to make sure they're not a problem. My main targets are the P0451 and P0300 codes first.

 

Thanks for the help . The engine is at about 1000 or 1100 rpms. But sometimes takes 2 cranks to get there. I have about 185,000 miles on the engine and the idle air control solenoid didn't even cross my mind even though I know what it is. So thanks for bringing that up. I definitely will clean the PCV oil separator and check the hose. I already replaced my fuel cap just frogot to mention it lol. I bought some injector cleaner and plan to run it through next time I top off. Thanks for the help

 

*forgot

 

1k is getting up there in rpms, should be 625 - 650, 700 max with A/C on, absolutely get to the IAC. Another big thing that goes overlooked is make sure your intake is tight, bolt torque is pretty light like @ 30 in/lbs, snug em up along with checking for hose leaks. If you can't get the idle to settle down you probably have a bunged up IAC, you can remove the cover, check the wires for breakage. I had all four wires broken, soldered them and idle was back in the computers control. They're very fine, thin. If you change out the IAC you'll most probably need a reset which is not easy unless you know some mech with an Autologic.

 

Ok definitly will torque up the air intake bolts and screws. Thanks for telling me about that. Now that I think about it, it does idle rough so the IAC probably could use a check up and a good cleaning. I hope I wont have to change the IAC.

Also forgot to mention that when the truck idles there is a strong odor of fuel possibly unburnt.

Thank again

 

You might have an injector stuck wide open. Easy way to tell - the spark plug will be soaked and really strong smell of fuel. You can pull the injector lead to disable and idle should be better, not perfect but you'll hear it.

Fuel tank venting. This tank shouldn't ever vent to atmosphere. Vent line busted back to charcoal can.

 

Yes when I took the plugs out some of them were pitch black even after a short test drive. I think your right on the $ about the misfire caused by the injectors. So I'm going to clean my IAC, PCV oil separator and take out the injectors. Who knows maybe one or more of my injectors is stuck wide open and thats causing my high idle.

Any advice on how to take off my injectors. I think I need to take off my fuel rail but that's all I know.

Thanks xD

 

found the D1 workshop manual pgs corresponding to the IAC, fuel injectors and rail, and engine coolant temp sensor. Here they are

pg 288 = fuel injection SFI

pg 295 = IAC

pg 285 = ECT sensor

 

There's no super duper easy way to remove injectors. I remove the plenum, trumpets, coil pack, undo fuel lines, 4 rail bolts/nuts and lift with a rocking motion. That's everything in one shot. Singles is about the same without removing plenum.