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

[swissarmychainsaw]

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


EAS had failed (on bumpstops). I rebuilt the EAS valve block, pump and replaced one failed airbag. Fixed.
Failed Smog. I replaced the fuel injectors, and intake manifold gasket and it passed smog. Fixed
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!




This is a summary of a RR thread (https://www.rangerovers.net/threads/rough-idle-passing-smog-lions-and-tiger-oh-my.360066/)





Theory

Test
Notes


Spark Plugs
New from PO
All Look good – see pics in thread link above


Distributor
New from PO



Distributor Air gap
Not tested
New stye does not seem to have the “air gap” so i did not set it (.010)


Plug wires
New from PO



Fuel filter
New from PO



Air filter
New from PO



Compression
Tested by PO’s shop
1: 140; 2: 140
3: 140; 4: 140
5: 145; 6: 135
7: 145; 8: 145


Ignition coil
New from PO
Looks to be a year old?
Not tested other than verifying spark.


Ignition coil grounding
Cleaned



Coolant Temp Sensor
New from PO
There are three?
1. Upper rad hose
2. Intake manifold
3. Water pump neck


Vacuum leak
Tested with propane
Tested with carb cleaner
Inconclusive - Replaced Intake Manifold gasket
Created a leak! Ran like ****.
Re-did intake gasket seal, now it just idles rough, same as when I got it.


Fuel Injectors
Replaced
Passed smog!


Head gasket
Tested Coolant for hydrocarbons (pass)
Tested clean


Head gasket
Pressure tested cooling system
Passed


Head gasket
Borescope cylinders
All looked good, no ‘extra clean’ cylinders


Exhaust Leak
Small leak on even side collector?
Smog guy noticed a leak. I think it’s the header-to-collector gasket.
Would that cause rough running?


Timing
Tested
6° BTDC - pass


Weak Alternator?
Not tested
No other supporting symptoms


Stretched Timing chain
Not tested



Idle Air Control Valve
Cleaned
RoverGauge shows this working, opening and closing.
Cleaned when Plenum was off.
Removed and cleaned again to be sure.
Tested, no change to idle.


MAF Sensor
Cleaned
Tested voltage
In spec (~1.87v)


MAF Base air adjustment
Nope
This is a sealed item and feels like a last resort



Base Idle setting?
Not tested yet, etc.
Sealed cap has been removed by someone.
Currently idles around 700


throttle position sensor
Tested: passed
Rover Gauge show this seems to be working.
Adjusted to spec.
~.350 at idle & 4.5 at WOT.
Voltage correct through range of throttle


Fuel Pressure
Not Tested
No test port on the fuel rail, don’t want to cut the factory fuel lines.


inertia switch
Not Tested



02 Sensors
Not tested
However range rover.net feedback was that the 02 sensors don’t control idle?
Likely candidate due to the code "Lambda Sensor (even)"

[Tins]

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

[V8Ian]

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.

[RANDLOVER]

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.

[Mercguy]

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.

[350RRC]

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


EAS had failed (on bumpstops). I rebuilt the EAS valve block, pump and replaced one failed airbag. Fixed.
Failed Smog. I replaced the fuel injectors, and intake manifold gasket and it passed smog. Fixed
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

[DoubleChevron]

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?

[Mercguy]

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 [thumbsupbig]

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

[Tins]

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.

[350RRC]

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

Familiar with both............ if given a choice I'd take 240.

DL

[swissarmychainsaw]

Can't believe it's been nearly a year of trying to chase down this problem.

Last bits I've done are:
fix the exhaust leak (even bank), by replacing the manifold gasket and Y-pipe gasket (which was definitely leaking). This made is run better, but still not perfect.

Set the timing properly.

Re-checked for vacuum leak.

Replaced 02 sensors with new ones. This was my first "throw parts at it" in a year, so that's not terrible.

Still has a misfire, a slightly rough idle, and throw the cod 45 Lambda (even) & a check engine light.
It's pretty clear from Rover Gauge that the even bank is not running properly.

I'm going to go back and make sure there is no exhaust leak (check with some water yesterday). Maybe double check the snugness of the Y pipe.

Maybe swap the 02 sensors, to confirm the new one is good.

It's been very consistent that its on the Even bank throwing a code, so what is exclusively on that bank?
Electronics, wiring, 02 sensor, plugs, plug wires, exhaust, fuel injectors.

But I'm kinda at a loss here. Any thoughts of a test to do would be helpful!

[Ronski]

Not much more I could add here, except for a question about idle.
If an automatic, and say, stopped at lights in gear, does the idle speed fluctuate up and down? or stay the same.
Missing to me is where revs stay same, Hunting, where it revs up and down.

Of course if it's not 'hunting' ( as I call it) then disregard.

[DieselLSE]

You know what swissarmychainsaw? I reckon the EFI loom has been tapped into for an ignition powered source. Suggest check where the loom enters the cabin and check the source of power for any user added accessories or repairs.

[swissarmychainsaw]

...snip...

Of course if it's not 'hunting' ( as I call it) then disregard.

No idle hunting, it's consistent at around 650-700 rpm!

[swissarmychainsaw]

Well, I fixed the CEL light issue, and triggering code 45.
The connection of the O2 sensor - at the electrical plug - was not good, and so it was essentially half plugged in. I cleaned up the connector, put a bit of lube for the o-ring and got it to "click" shut.
That seems to have fixed the Check Engine light. Sometimes it IS the simple things.


Still has a stumbly idle, and cranks more that it should to start - cold or warm. So I'll keep after it.
I ordered a fuel pump and filter.
So far I have not thrown any unnecessary parts at the car, so an extra hundred bucks for a fuel pump is something I can live with.

Truth is, I want to start fixing other things, like the shocks and AC!

[swissarmychainsaw]

One thing I forgot to mention:
On the even bank I pulled #8 spark plug wire and tried to start the car.
It started relatively easily and ran fine. Reconnected.
Then I pulled the #6 wired. Started easily and ran find. Reconnected wire.
I did this for the number 4 wire same thing: started relatively easily and ran fine.

All four were the same: pulled the wire off, started the car easily and it ran fine.
How is that possible?

I did the same thing for the fuel injectors:
Disconnected #8 electronic connector to the injector: started and ran fine. reconnected.
#6 Same thing, started and ran fine. Reconnected.
#4 same: Disconnected but it started and ran fine. Reconnected.

Why does this run ok on 7 cylinders?? Maybe even better!

[Ronski]

You won't notice any change in revs stopping and restarting engine with one plug disconnected because the Idle Control Valve will adjust the idle speed up as per the ECU, ie either 650rpm or 700rpm (USA)
You have to check with engine idling, before ICV adjusts revs back up.

I know most say don't do it, but I always do. Get yourself a pair of sparky insulated pliers, Real ones, Make sure to get the ones, yellow and orange color at tool shop, Bunnings have them.
Check that they are rated for 1,000 volts. Sometimes come in a pack with 2 similar rated screwdrivers.
I can pull the plug caps easily while engine idling. No worries about getting a boot. This method is better at checking than stopping and starting.

You didn't mention checking number 2 cylinder.?

I used this method to eventually find a faulty fuel injector, yes, a brand new one. I could actually hear a slight change or difference in sound when pulling one plug.
No way could I have heard this by stopping and restarting engine.

Led me to pull off manifold, undo fuel rail and, with injectors still connected to rail, lift as far up as possible.
Then I placed some paper towels below and Yes, cranked engine. Before anyone yells crazy, The coil/dizzy was disconnected and you must be 100% sure no spark, you can imagine. Hmm.
All injectors on each bank spray at the same time, (I didn't know that). I looked at the wet circle created and all were about 100mm, Except for one. it was no bigger that a 50 cent piece.
Swapped some around, and same injector. If attempting this method, check none are dribbling with ignition on before cranking.

This was with all brand new Bosch injectors. I then contacted Piper eng. in UK and got a new set of later Bosch 4 holes ones, a bit expensive but, Fixed.

Hope this helps.

[PhilipA]

Ford yellow top injectors also were available cheap from the USA about 10 years ago. Not sure now.

One thing noone has mentioned is that the exhaust valves in these can stick due to carbon fouling the stem. Could be an exhaust valve not opening fully.
I would still also be looking at the lifters and cam, as this is a very common problem if oil changes were not regular especially on low mileage V8s.
Regards PhilipA.

[swissarmychainsaw]

Ford yellow top injectors also were available cheap from the USA about 10 years ago. Not sure now.

One thing noone has mentioned is that the exhaust valves in these can stick due to carbon fouling the stem. Could be an exhaust valve not opening fully.
I would still also be looking at the lifters and cam, as this is a very common problem if oil changes were not regular especially on low mileage V8s.
Regards PhilipA.

Thanks!
Yes I put the yellow tops injectors in this one. Worked great and got me to pass smog!