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1990 RRC SWB
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Discussion Starter · #1 ·
I have a barn find 59k mile 1990 SWB in Colorado Silver. Some days when driving for 1 to 2 hrs the engine drives like a dream. Excellent acceleration. No power issues. Other days, it will drive fine for 1/2hr and then start bucking. like the power is on, then dead and buck, on, dead and buck. It will buck when the accelerator is pushed. If I let off the accelerator it is fine. Today, 10 minutes into my drive at about 75mph, it was bucking very hard and constant. When I let off the accelerator there was still now power, then it came on, then constant bucking, then dead, I thought I was going to have to park it. Then it was fine for the last 20 minutes of my drive with no power issues no matter how hard I accelerated.

It reverberates through the whole driveline and I'm afraid it would do damage to the differentials. Doesn't matter what gear the trans is in so i don't think it is a transmission issue.

I am half way through my 2nd full tank of gas. I don't think it is water in the tank.

I am tending towards the ignition and have ordered a new coil, capacitor, Distributor Amplifier module, wires and plugs. Was going to start here and then have the Distributor rebuilt later.

Has anyone had similar issues? And what were findings? or what are your thoughts?
 

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I have a barn find 59k mile 1990 SWB in Colorado Silver. Some days when driving for 1 to 2 hrs the engine drives like a dream. Excellent acceleration. No power issues. Other days, it will drive fine for 1/2hr and then start bucking. like the power is on, then dead and buck, on, dead and buck. It will buck when the accelerator is pushed. If I let off the accelerator it is fine. Today, 10 minutes into my drive at about 75mph, it was bucking very hard and constant. When I let off the accelerator there was still now power, then it came on, then constant bucking, then dead, I thought I was going to have to park it. Then it was fine for the last 20 minutes of my drive with no power issues no matter how hard I accelerated.

It reverberates through the whole driveline and I'm afraid it would do damage to the differentials. Doesn't matter what gear the trans is in so i don't think it is a transmission issue.

I am half way through my 2nd full tank of gas. I don't think it is water in the tank.

I am tending towards the ignition and have ordered a new coil, capacitor, Distributor Amplifier module, wires and plugs. Was going to start here and then have the Distributor rebuilt later.

Has anyone had similar issues? And what were findings? or what are your thoughts?
Some things to check.

Fuel pressure regulator.
Ignition amplifier.
Failing fuel pump.
 

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2016 TD6 and 2018 SCV8 Range Rover Sports
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In addition to the above check for a possible loose/corroded electrical connection somewhere in the ignition system.
Bad fuel is also common in vehicles that sit a long time so maybe a new fuel filter. Storing a vehicle without a full tank allows condensation to form and cause rust. Gas can get stale and form varnish. Maybe also add an injector cleaner. Fuel additives are cheap, easy and can't hurt.

WATER REMOVER
The Best Way to Remove Water from Your Gas Tank | Gold Eagle Co.


FUEL SYSTEM CLEANER
 

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1990 RRC SWB
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Discussion Starter · #4 ·
Some things to check.

Fuel pressure regulator.
Ignition amplifier.
Failing fuel pump.
I have the Amplifier on order and may send the whole distributor out for rebuild.

I would think this would happen even at idle regardless of load but it seems to happen only when the engine is on load when the accelerator is pressed. Even slight pressure on the accelerator under load creates the issue. When the trans is in neutral and the engine is rev'd or held at a higher RPM there isn't any noticeable skipping.
 

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1970-1995 Range Rover Classic
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159 Posts
check all battery connections, alternator, and coil connections. on/off/on/off sounds very electrical. maybe fuel pump connector, mine got loose/bad.
geneo
 

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I had a similar condition on my 93 LWB and it ended up being a failing alternator. Wouldn't show up at idle and it tested good at the parts store. Found out the diodes were failing to regulate current only after they got hot and had a substantial load placed on the electrical system similar to cruising on the highway. Removed and cleaned electrical connections on alternator and no change. Replaced unit with a rebuilt one and problem solved. Hope this helps. Good luck.
 

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I have the same problem in my 1992 classic. It's very intermittent. It's kind of terrifying. It only happens (or at least the time I most notice it) when I'm at 60 or 70mph. I've replaced about everything I can think of....ignition module, cap, rotor, tps, fuel filter, fuel pressure regulator, sta-bil marine in my gas take in case there's water in my gas, and my alternator is about 2.5 years old...it seems fine, but I'm on the fence about replacing that. My fuel pump is from 2017 so maybe that's it?

If I drive for 5 hours it might only happen a couple times and it's typically towards the beginning.

I'm very interested in how this resolves for you!
 

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Alpine White 1995 County LWB
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I had a similar condition on my 93 LWB and it ended up being a failing alternator. Wouldn't show up at idle and it tested good at the parts store. Found out the diodes were failing to regulate current only after they got hot and had a substantial load placed on the electrical system similar to cruising on the highway. Removed and cleaned electrical connections on alternator and no change. Replaced unit with a rebuilt one and problem solved. Hope this helps. Good luck.
Oh man, that might be my issue then! Mine has been doing similar things. Thank you!
 

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1990 RRC, 1987 VW Syncro
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  • Two issues have caused this on my 1990 RRC:
    • the rollover / impact fuel shutoff switch had corroded contacts in the wiring harness behind the front seats and behind the center console. Cut out the corroded contacts, added new wire and solved the problem for a significant amount of time. The engine bucking seemed to be based on the humidity - sometimes contact was good, sometimes bad.
    • if the ECU under the front passenger seat gets to hot, this also happens. If I'm driving on a cool roadway surface, no problems. If driving in the desert on blacktop and the roadway surface is above 100 degrees, the floorboards of the RRC heatup and heatup the ECU. Engine goes erratic with bucking. There are probably multiple factors at play here I haven't figured out yet. Fix - put a fan on the passenger floorboard to keep the ECU cool.
 

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Thanks mtbchriso - I never even know about the rollover / impact fuel shutoff switch. I'll take a look at that.

While I've been banging my head against the wall trying to figure this problem out - I finally ditched my K&N rechargable air filter and replaced it with a good paper air filter. The I cleaned my MAF sensor (with MAF sensor cleaner....in case I need to say that..) and it has made a noticeable difference in my rover running more smoothly.

I'm not ready to say the problem is behind me, but either way it's progress.
 

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1990 RRC, 1987 VW Syncro
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Thanks mtbchriso - I never even know about the rollover / impact fuel shutoff switch. I'll take a look at that.

While I've been banging my head against the wall trying to figure this problem out - I finally ditched my K&N rechargable air filter and replaced it with a good paper air filter. The I cleaned my MAF sensor (with MAF sensor cleaner....in case I need to say that..) and it has made a noticeable difference in my rover running more smoothly.

I'm not ready to say the problem is behind me, but either way it's progress.
...it was years of head banging for me. And now remembering the process, I also installed the remote ignition amplifier kit to move the amplifier off of the distributor and mitigate the heat issues there.

One of these days after driving for a bit, put your hand on the ECU to check the temp. Almost too hot to touch?
 

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1990 RRC, 1987 VW Syncro
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...it was years of head banging for me. And now remembering the process, I also installed the remote ignition amplifier kit to move the amplifier off of the distributor and mitigate the heat issues there.

One of these days after driving for a bit, put your hand on the ECU to check the temp. Almost too hot to touch?
...and I also replaced the in-tank fuel pump via cutting the old hole in the rear cargo compartment floor to access w/o dropping tank.

I think I would:
  • check heat on ECU
  • check roll over switch connections, maybe even disconnect and jump it, drive and see if bucking stops
  • install remote amp kit
  • do fuel pump surgery
 

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Thanks mtgchriso. The PO installed a remote amp kit, and I replaced the module as part of this trouble shooting. I put in a new fuel pump in 2018, but that has been next on my list...(plus your suggestions).
 
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