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Discussion Starter · #1 ·
95 lwb rrc 4.2l

been trying to diagnose this problem...gets progressively worse. it is intermittent but now occurs more often.

starts up fine. then cant hold a steady idle after awhile. rpm will drop suddenly then recover...ie stumbling. happens at park, and in drive and reverse.

when underload travels fine but maybe the hesitation is still there but you dont notice it until you come off the pedal, and it will stumble again.

new stepper, cleaned intake, new ignition module, gapped distributor, fiddled with idle screw etc.

i did unplug maf to see if made difference....it would idle lower i.e. 750 vs 1200 rpm but hold steady and check engine light on. it would not stumble but just not run right...
 

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I had a similar problem. After replacing the IACV, battery, alternator, and everything else I finally tracked it to one of the alternator lead cables intermittently shorting on the alternator housing. There was just enough wear on the insulated wire to allow for a short.

My problem was intermittent sometimes disappearing for a few weeks before returning after hitting a bump in the road.

I suggest checking all the wires under the bonnet for potential shorts.
 

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Discussion Starter · #3 ·
do you know where grounds are main grounds?

my alternator is putting out good voltage, in my case i dont think its alternator i checked it carefully, i will go back and see what i touched, from base idle screw to distributor and maf.

it might be possible i adjusted base idle screw too low, so it tries to idle at 250 rpm and then the stepper kicks it back up etc and then cycles again.

there does not seem to be any issue under load, its only at idle situations.
 

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Don't mess with the idle screw. It's set at the factory for correct function. If its not idling correctly the very last thing to do is mess with the idle screw. Thats why its covered up with a plug. 9.99 times out of 10 it's something else causing the problem.

Test your TPS. Sometimes they have dead spots or become lazy and that can cause idling issues.

Make sure the small vac lines going around the back of the intake manifold from the IAC to the throttle are clean and unobstructed.

There are grounds all over the place on a RRC. Best to get yourself the factory service manual because listing all them, even if I could remember, would just cause more questions than answers.
 

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1993 range rover lwb - Roman Bronze
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This same issue happened to me and grounded my rover for the whole summer. Heres what you should check..
1. Make sure your timing is dead on
2. Check your distributor rotor ( that was one of the causes for mine ), it might be damaged
3. check your O2 sensors - look on the passenger side seat panel and read off the code ( should be 44 or 45) - that was cause #2
4. check your idle stepper motor - make sure its an OEM not aftermarket

the check engine light is probably coming from the idle stepper motor and the stuttering is probably coming from the distributor rotor.....these are just a guess based on my issues
 

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Discussion Starter · #6 ·
i have a check engine light and the display reads code 45. that is the o2 sensor that was stuck in exhaust pipe and i drilled out.

as a followup i did finally manage to drill out the remainder of the o2 sensor.

fyi it is M12 x 1.25 thread pitch and for those that want to tap ....it is not easy and i did not succeed in tapping at all. the risk here is you could also break the tap in the bung hole and there is no way to drill that type of metal out for be forewarned.

i did get a grade 8 bolt that i managed to thread in there after i got the threads visible.

my stumbling before most likely is due to o2 getting into bung since the sensor was not screwed in.

i still have the check engine light but i need to clear or reset that code i assume.

i did order a new o2 sensor for that side for good measure.

it does seem to run better at idle now.

i do have one question which annoys me....on startup...i notice that sometimes idle is high 1.2k and sometime idle is 750....most times it is 1.2k but occasionally it is 750.

when i cut engine and restart to goes back to 1.2k

anyone know why this happens? the coolant temp sensor on startup? i replaced it and it is new.

thankfully the threads were still there on o2 sensor. again i think it is very hard to tap that thread for a helicoil or any type of repair. now i understand why most muffler shops will just weld on a new bung and start over....
 

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Did you ever fix it. I've done everything mentioned besides the TPS and O2 sensors only because there are no codes thrown. Really curious as to why it hunts down like you mentioned. (Switching from Regular, 87 Ocatane U.S. gas to Premium, 92 Octane U.S. slightly improved the hunting down)
 

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Discussion Starter · #10 ·
i think the stumble was caused by coolant getting into cylinder. after shut down sometimes hard to start. i replaced the head gasket and testing it now. it has nothing to do with electrical issues.

if coolant leaks into cylinder it will stumble the engine.

i had 116k on the odometer.

i would pull the plugs and see if you see any white deposits on them.
 
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