Thread: Rough Idle help for 1993 USA Range Rover Classic LWB 4.2!

Just a wild thought seeing as you seem to have done nearly everything : is the camshaft standard?

Originally Posted by Tins

Just a wild thought seeing as you seem to have done nearly everything : is the camshaft standard?

My first thought too, or uneven lobe wear.

Wow that is a comprehensive list, I had a few thoughts, but they all appear in the table, I like Tins suggestion of a set of wild cams, the only other thing I can think of is failed engine mount/s as that doesn't appear on the list.

Suggestions that helped me when I had a similar issue (turned out to be a munted cam and rocker shaft, plus some muppet did not clear the oil feed holes... long story
1. Fuel Pressure test - got to find out if it's fuel or spark, right?
2. Ignition - Dizzy cap and Rotor (genuine Lucas only) and these have a tendency to be short lived. Clearance on the hall sensor on a "new" dizzy should be OK, but never hurts to check.
3. dwell angle at idle will also help identify above setting - there is a mod for external HEI type module (bee-utey) here on the forum. It's worthwhile, but you have a new dizzy....so...
4. Vacuum leak - sounds like you have checked all the hoses and replaced the needful, but were they all clean inside (threebond engine conditioner - remove, spray, wait 20, spray again(rinse), drain, refit).
5. Idle air control solenoid (check wiring and clean the solenoid with some threebond engine conditioner(soak)) - the crush washer and thread into the housing can easily strip and the solenoid itself can crack in the root of the threads, leading to leaks and erratic idle. (I doscovered this one from a previous owner "repair" where they used thread tape and loctite...... idiots).
6. fix the collector gasket - this will mess with your O2 sensor and probably threw the engine light
7. set the static timing to 12º BDTC. use good fuel.
8. You have done filters - unlikely, as are injectors (new)
9. Temp sensors - how old are they? have you tested them? Worthwhile checking and replacing as needed (genuine)
10. Camshaft wear and rocker adjustment on these is a notoriously repetitive task of check, replace when worn - so check, and replace worn bits as necesssary. It's not hard for this to cause an issue - and possibly the likely culprit, but you will never know until you check them all, get them all adjusted and then wait for the results - often the results are not what you expect, or no change for a week or so.

and since you have access to seafoam over there, I'll just ask if you think it's ever been used inside that engine or if you have considered it.
Stranger things have been fixed with that stuff - with no apparent explanation (if you read the anecdotal evidence provided by those consumers).

I'm leaning to a timing / valve / worn lobe - but checking is the only way to eliminate this possibility.

So many other 'random' or intermittent contributors are possible - but knowing your own engine, only you are best poised to know if any of those things could possibly be a contributor or not - Remotely diagnosing someone elses problem - especially one that has no obvious indicators, is always a crap shoot.

Originally Posted by swissarmychainsaw

History: Had the car 2 months. Had three issues:

1. EAS had failed (on bumpstops). I rebuilt the EAS valve block, pump and replaced one failed airbag. Fixed.
2. Failed Smog. I replaced the fuel injectors, and intake manifold gasket and it passed smog. Fixed
3. Rough idle. Below is my list of things I’ve attempted to fix.

Symptoms: Rough Idle, hot or cold, very consistent.
I have twice triggered the CEL Rover Gauge says: "(45) Lambda Sensor (even)"

Have a look at what I've tried so far, I could use some advice here![COLOR=#990000][FONT=Arial]

It might sound stupidly simple.............. I had the same issue (rough idle) with a 2 door I briefly owned with a 4.4 race motor.

I thought it was just the cam.

Turned out that 2 plug wires were going to the wrong plugs. The thing really howled after sorting that out.

The safest way to check is WITH THE MOTOR OFF, disconnect one plug and start it up. If it runs rougher that individual plug wiring is correct.

Turn the motor off and reconnect that plug wire and disconnect the next one, and repeat the process for the rest.

It is not safe to pull the wires while the motor is running.

DL

He's had the inlet off to seal it back up ...... So would have check the camshaft at that time? worn cam lobes would be very obvious (and you can easily measure the lift by measuring how high the lifter..... well lifts ).

cam timing it starting to sound good given what has been checked already?

Originally Posted by 350RRC

It is not safe to pull the wires while the motor is running.

DL

Certainly not safe if you're earthed to the chassis and have a pacemaker or a heart condition

Nothing quite like a jolt from the HEI to spark up the neural activity.

Originally Posted by Mercguy

Nothing quite like a jolt from the HEI to spark up the neural activity.

240V AC would give it a run..... Says me who have enjoyed both over the journey.