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Discussion Starter #1
Trying to diagnose a slight engine miss
1998 4.6 HSE 85k miles. Plugged it up and no codes. Replaces plugs and wires. Every plug looked good no oil/ fuel just slightly brow. I hate to just keep replacing things . Any other common problems to check for?
Thanks
 

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Premium Member
1970-1995 Range Rover Classic
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455 Posts
Use a clamp meter to see if there is any difference on a specific cable/ coil output.
Use a standard ohmmeter to check the connection between engine ECU and coil pack.
Still no luck? Test compression on each cylinder.
 

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Premium Member
1970-1995 Range Rover Classic
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455 Posts
start at idle. If you have no luck try at 2000 rpm

PS forgot to say that you also want to check your injectors if you can't find anything else.
at least here fuel quality is not always fantastic
 

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Discussion Starter #6
Hi
Mainly at idle. Motor pulls decent. Sometime it seems to almost go away. Some days it’s worse. I’m starting to lean more tword injector/s vs some spark issue
 

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1995-2002 Range Rover P38A
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167 Posts
Plus an older engine with a little carbon build up, worn throttle shaft and bushings, "worn" stepper motor, cam lobes no longer perfect, injectors that might use a clean, less than factory tolerance valve guides, PCV system that could use a clean, older O2 sensors, a failing IAT sensor, a dirty MAF, a leak in the air induction pipe from air cleaner to plenum, a leak in the fuel vapour canister lines or solenoid, low fuel pressure, high fuel pressure, then there is fuel quality, and that is without really looking at electrics.

Check that the resonator box(es) on the air inlet pipe from air cleaner to plenum doesn't have holes melted in the bottom from manifold heat. It does happen and of course that gives you some unmetered and worse, unfiltered air.

If it were electrical, as in spark, it is likely to get worse under load and not better, spark breaks down under pressure and speed generally.
 
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