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Hello all,
I've been having a helluva time tracking and sorting a serious idle issue, with slight stumble/hesitation at cruise. I've also had a local Rovers-Only shop take a cursory look and they came up empty. I'll try to remember everything that I've done.

New parts within a year, not all for this issue:

Fuel pump
Fuel temp sensor
Coolant temp sensor
Dist. cap/rotor (Lucas)/wires/plugs/coil
Idle valve
Idle valve to throttle body hose
Breather hoses
Crankcase breather filters
MAF sensor
Oxygen sensors (NTK)
Fuel pump relay (5-plug, Metal case Bosch)
Replaced ECU with proper P/N (was fitted with a Disco 1 ECU)
Wiring associated with the MAF that had internal resistance due to corrosion -

Checked:

Vacuum leaks (no brake booster, ABS pump type)
Dist. amplifier resistance (3.4 ohm)
Timing chain, within new specs
Wiring to the key switch (new switch 2 years ago)

Cleaned:
Idle valve chamber and upper intake manifold
Throttle body
Associated grounds in the engine compartment

Startup, runs better cold. Slowly runs worse. One of the last times I ran it (Friday) the left side injectors stopped operating. Never seen that before. Verified with an IR temp gauge.

One thing that'd be nice is to know the spec for the coolant temp sensor (this is my second new sensor). I have the factory manual and have searched a lot to no avail.

Any thoughts would be appreciated. As these machines get older, I have a feeling the wiring will become a real issue. I'm sure there are small things I've forgotten.

Regards...
 

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Hello all,
I've been having a helluva time tracking and sorting a serious idle issue, with slight stumble/hesitation at cruise. I've also had a local Rovers-Only shop take a cursory look and they came up empty. I'll try to remember everything that I've done.

New parts within a year, not all for this issue:

Fuel pump
Fuel temp sensor
Coolant temp sensor
Dist. cap/rotor (Lucas)/wires/plugs/coil
Idle valve
Idle valve to throttle body hose
Breather hoses
Crankcase breather filters
MAF sensor
Oxygen sensors (NTK)
Fuel pump relay (5-plug, Metal case Bosch)
Replaced ECU with proper P/N (was fitted with a Disco 1 ECU)
Wiring associated with the MAF that had internal resistance due to corrosion -

Checked:

Vacuum leaks (no brake booster, ABS pump type)
Dist. amplifier resistance (3.4 ohm)
Timing chain, within new specs
Wiring to the key switch (new switch 2 years ago)

Cleaned:
Idle valve chamber and upper intake manifold
Throttle body
Associated grounds in the engine compartment

Startup, runs better cold. Slowly runs worse. One of the last times I ran it (Friday) the left side injectors stopped operating. Never seen that before. Verified with an IR temp gauge.

One thing that'd be nice is to know the spec for the coolant temp sensor (this is my second new sensor). I have the factory manual and have searched a lot to no avail.

Any thoughts would be appreciated. As these machines get older, I have a feeling the wiring will become a real issue. I'm sure there are small things I've forgotten.

Regards...
First Please describe the idle issue? will it idle? does it die when idling?
Is there any connection with outside temps being high when this happens? say 95 degrees and going uphill?\
You checked for vacuum leaks--did you check the cruise control vacuum line that goes to the brake pedal? in my 94 it was broken in 3 places!
The plastic vacuum "t" that is in front of the throttle area near the throttle position sensor? the throttle position sensor?
Did you check your coolant level? the two lines that go from radiator to underside of throttle body? these prevent icing.. though you problem is fuel related it seems to me.
Fuel filter?
Do you have a code reader display box under the passenger seat? move seat forward flip back carpet from the back, and look for 3 inch wide box with (texas instrument calculator style numbers) lit up on it?
I will guess the fuel pressure regulator has decided to retire. I replaced 3 in 10 years on my 94 4.2..
But the other demon is often the ignition amplifier module? they fail when hot. I carry one in the tool box. sometimes just opening the hood for 5 minutes out on the freeway would cool it enough to run okay..It's hot mounted to the distributor, right behind the hot radiator flow, my acted up on hot days with A/C on...I need more information describe more details..lol

john kemple94 RRC LWB
 

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First Please describe the idle issue? will it idle? does it die when idling?
Is there any connection with outside temps being high when this happens? say 95 degrees and going uphill?\
You checked for vacuum leaks--did you check the cruise control vacuum line that goes to the brake pedal? in my 94 it was broken in 3 places!
The plastic vacuum "t" that is in front of the throttle area near the throttle position sensor? the throttle position sensor?
Did you check your coolant level? the two lines that go from radiator to underside of throttle body? these prevent icing.. though you problem is fuel related it seems to me.
Fuel filter?
Do you have a code reader display box under the passenger seat? move seat forward flip back carpet from the back, and look for 3 inch wide box with (texas instrument calculator style numbers) lit up on it?
I will guess the fuel pressure regulator has decided to retire. I replaced 3 in 10 years on my 94 4.2..
But the other demon is often the ignition amplifier module? they fail when hot. I carry one in the tool box. sometimes just opening the hood for 5 minutes out on the freeway would cool it enough to run okay..It's hot mounted to the distributor, right behind the hot radiator flow, my acted up on hot days with A/C on...I need more information describe more details..lol

john kemple94 RRC LWB
I have had mine for 10 years the wiring was never an issue. Though I am concern why it had a disco ECU in it, and then why did you change it? was it because of this?
 

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Registered
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57 Posts
Hello all,
I've been having a helluva time tracking and sorting a serious idle issue, with slight stumble/hesitation at cruise. I've also had a local Rovers-Only shop take a cursory look and they came up empty. I'll try to remember everything that I've done.

New parts within a year, not all for this issue:

Fuel pump
Fuel temp sensor
Coolant temp sensor
Dist. cap/rotor (Lucas)/wires/plugs/coil
Idle valve
Idle valve to throttle body hose
Breather hoses
Crankcase breather filters
MAF sensor
Oxygen sensors (NTK)
Fuel pump relay (5-plug, Metal case Bosch)
Replaced ECU with proper P/N (was fitted with a Disco 1 ECU)
Wiring associated with the MAF that had internal resistance due to corrosion -

Checked:

Vacuum leaks (no brake booster, ABS pump type)
Dist. amplifier resistance (3.4 ohm)
Timing chain, within new specs
Wiring to the key switch (new switch 2 years ago)

Cleaned:
Idle valve chamber and upper intake manifold
Throttle body
Associated grounds in the engine compartment

Startup, runs better cold. Slowly runs worse. One of the last times I ran it (Friday) the left side injectors stopped operating. Never seen that before. Verified with an IR temp gauge.

One thing that'd be nice is to know the spec for the coolant temp sensor (this is my second new sensor). I have the factory manual and have searched a lot to no avail.

Any thoughts would be appreciated. As these machines get older, I have a feeling the wiring will become a real issue. I'm sure there are small things I've forgotten.

Regards...
I have had mine for 10 years the wiring was never an issue. Though I am concern why it had a disco ECU in it, and then why did you change it? was it because of this?
john kemple 94 RRC LWB
 

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for what its worth.....i spent the better part of a year chasing code 44, 48 and 50 on my 95. My list of repairs and upgrades was very similar. Finally, ready to dump the thing, I took it to a friends shop where he basically rechecked everything i did but with better tools, as well a bunch of other things and after all that, it was a loose ground cable. 1 yr, countless repairs and money and an exhaustive professional search and it was a bad ground. Weird stuff will come from bad ground.
 
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