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1970-1995 Range Rover Classic
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Discussion Starter #1
Today to got the first chance to actually drive the rig much since I installed the 14CUX ECU and got the cutting out issue resolved. When I start it up, hot or cold, I get an initial high idle of about 1500 RPM that then settles down to about 750 in 10 seconds or so, is this normal?
I tried twice to go thru the base idle setting as described in various threads, but when I start it after the routine that should close the IAC, I get an idle of about 2000 RPM, with the IAC unplugged. Today, I just removed the IAC and manually extended the plunger, and then re-installed it. I was careful not to pull the plunger out, and I'm sure it was fully seated and closed. I fired the rig, IAC unplugged, and got a smooth idle right at 500. Plugged the IAC in and no idle difference. Shut the rig off and re-started without touching the accel pedal and got the exact same jump right up to 1500, then settle in at 700-750ish.
One other item to mention is when moving, it seems like it does not want to idle under about 1500. It seemed to not want to slow down on downhills with no accel pedal pressure, so I kicked it into neutral and sure enough, the idle was at 1500. If I come to a complete stop, the idle drops to 700.
I know that the speed transducer talks to the IAC and has an effect on idle speed while moving, but again, not sure what is "normal".
Last bit of intel, the ECU I got off of FleaBay has evidence of moisture/rust out of one of the bottom vent/weep holes. Have the RR gods once again put me in a position where I have a partially disabled ECU??

Here is a pic of the vent/weep hole I mentioned:
IMG_1609.JPG
 

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On my 92 the base idle was not right
The plug was removed and someone on the past messed with it
I did the base idle adjustment like in rave
It still wouldn’t idle right
So I adjust it by feel
I did small adjustments till now I feel it is running right
Good idle
Steady idle
Very good power
But a tad rough
I don’t think it will ever be perfect
Just some input
Mike
 

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1970-1995 Range Rover Classic
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Manual or auto transmission?

Have you set the ignition timing correctly and used Rover gauge as the tacho to set the base idle?


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1970-1995 Range Rover Classic
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Discussion Starter #4
Auto tranny. Going to reset again. Just found this from actproducts:

Where the idle speed shoots up to 1800 RPM and takes at least 10 seconds to come down, this usually means that the Base Idle has not been set correctly. For catalyst-equipped cars it may mean that either there is a defective oxygen sensor, or that the basic mixture adjustment is incorrect. Contact your supplier for specialist advice in this case.




Where the idle speed shoots up to 1800 RPM and takes at least 10 seconds to come down, this usually means that the Base Idle has not been set correctly. For catalyst-equipped cars it may mean that either there is a defective oxygen sensor, or that the basic mixture adjustment is incorrect. Contact your supplier for specialist advice in this case.


 

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1970-1995 Range Rover Classic
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Discussion Starter #5
OK, set timing, set base idle via RG following vacuum line unplugging procedure. Still doing the surge high then idle down. Going to drive it some to see if this changes.
How I long for an idle screw and low speed idle mixture screws....
 

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1970-1995 Range Rover Classic
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You did blank both ends of the vacuum hose tightly when you disconnected it?

The behaviour isn’t that unusual to be honest, it normally takes a few days driving to settle down assuming the timing and base idle are set correctly.

It’s not a bad system there is just a right way to tune it up, any deviation from the rules and there will be problems




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Discussion Starter #7
Yes to hoses blanked off. Timing, MAF, TPS and base idle all set (or at least I did it, by the directions and tried to pay attention to detail, no beer involved...)
Going on a bit of a drive to see if she will settle in.
 

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Both my rigs do it the first startup after a new battery. Surge to 1400ish for 5 secs or so and back down to the high 600s.
 

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1995-2002 Range Rover P38A
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The butterfly valve needs an airgap (0.05mm), and the TPS needs a certain Voltage (0.3 Volt), there need to be an restriction in the hose from butterfly valve to the IACV.
after I did that mine idled a lot better..
If TPS voltage isn't correct, make slot holes and twist the TPS till you have the right voltage.

I couldn't adjust my base idle setting, then I made a restrictor in the hose, and since than the idle is good.

I should idle higher after start up, but when all is well the revs should drop real quick.
I think mine went better after I replaced the IACV
 

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14CUX doesn’t need the TPS position set it self learns. Is the throttle cable loose?

As above it may be the stepper motor is tired, if you remove it and plug it into the loom, you can drive it in and out using Rover gauge (engine off obviously). Movement should be smooth.

There is an AC Delco replacement for a GM vehicle available, much better quality and cheaper than the now unavailable LR genuine ones. Don’t buy the cheap pattern ones they are all rubbish


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14CUX doesn’t need the TPS position set it self learns. Is the throttle cable loose?

As above it may be the stepper motor is tired, if you remove it and plug it into the loom, you can drive it in and out using Rover gauge (engine off obviously). Movement should be smooth.

There is an AC Delco replacement for a GM vehicle available, much better quality and cheaper than the now unavailable LR genuine ones. Don’t buy the cheap pattern ones they are all rubbish
Nevermind you were talking about the IAC
 

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Discussion Starter #12
Stepper motor is new, GM unit.. Per British V8
"
"The valve itself bears a striking resemblance to AC Delco part number 25527077, which was used on all 4.3L GM V6 engines and most 5.7L GM V8 engines. If you need one of these valves, purchasing the General Motors spec part from your local parts counter will be considerably more economical than dealing with Range Rover. "

I had forgotten that 14CUX learns TPS position. Does anyone remember of know what their absolute TPS reading on RG is at rest/idle? Mine was 3%, but in screenshots, I see many at 8-9%.


14CUX doesn’t need the TPS position set it self learns. Is the throttle cable loose?

As above it may be the stepper motor is tired, if you remove it and plug it into the loom, you can drive it in and out using Rover gauge (engine off obviously). Movement should be smooth.

There is an AC Delco replacement for a GM vehicle available, much better quality and cheaper than the now unavailable LR genuine ones. Don’t buy the cheap pattern ones they are all rubbish


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Nevermind you were talking about the IAC
Which is also referred to as the stepper motor, because that is how it positions itself accurately. Do you always feel the need to split hairs and be awkward??

3% TPS position is normal, my car is the same. You can toggle a function to give the reading as 0% position on rovergauge if you want to.




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Which is also referred to as the stepper motor, because that is how it positions itself accurately. Do you always feel the need to split hairs and be awkward??
What? I thought you were referring to an alternative part for the TPS, that's all. My bad
 

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What throttle position reading do you get when in the “corrected” setting?

Does the rovergauge indicate that it is a manual or auto transmission (this will cause funny idle issues if the wrong select resistor is fitted)?

Can you confirm engine timing is set at 6 degrees BTDC with the vac advance removed? Is there absolutely no vacuum leaks? Have you checked the CO emissions? Are both oxygen sensors live and trimming the mixture (rovergauge will indicate)

The idle speed will be held above 750 when moving if you shift into neutral, 1500 is maybe a little high my manual car would be around 1000 when moving in neutral.

14CUX automatically retracts the iac plunger when starting thats why she revved up when you had it unplugged, the ecu winds it back out as soon as the engine fires. 2000rpm on full open IAC sounds roughly right from my vague recollections of the same scenario.

If the fault code generated is TPS then it’s a fair shot to replace it, try and get a Lucas branded one if you can the cheap ones wear out quickly (I got 6 months out one in daily use, big flat spot in the Rev range).





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What? I thought you were referring to an alternative part for the TPS, that's all. My bad
I maybe didn’t make clear I was referring to the post above, not my previous sentence - my mistake. I mis read your post as being pedantic about calling the IAC a stopper motor!




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Discussion Starter #17
No detectable vacuum leaks, timing light confirms timing set at 6 degrees BTDC, RG shows lambdas working and switching, auto tranny mode. TPS shows 0% in absolute mode.
TPS is a newer Lucas unit. FWIW, I unplugged it and drove around. Runs pretty good, no hiccup as yet.
Only code stored is TPS. Going to check it's performance again, but I have done this before and it responds smoothly, no dead spots. Not sure how a bad signal from the TPS could cause the cut out/hiccup when unplugging it doesn't cause something similar, but obviously, I'm not sure about alot of things.
Does anyone know if somehow, the ECU can store/accumulate codes even if it is cleared by unplugging it for a period of time. Seems like the hiccup issue is getting worse, much like the rig behaved after getting it back from the Guru as it finally got into the total 1500 RPM cut out mode, cured (or so I thought) by changing to the 14CUX ECU.
I'd happily throw another TPS at it if I thoguht it had even a fair chance of fixing the issue, but I'm doubtful.
Anyone know how it is supposed to run with the TPS unplugged?
 

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Unplug tps and start your motor
It should throw a code right away
How should it run
Chitty
I’d say
 

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Discussion Starter #19
Just ran pinout reading on TPS. It has irregular total loss of communication in a couple spots. Lord Lucas has cursed me again! Going to order new TPS (another) today. Stay tuned (no pun intended)
 

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1995-2002 Range Rover P38A
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Everything needs to be alright to get a good idling engine.
Check ignition timing, put Champion sparkplugs in her, NO NGK or Bosch!!, check butterfly air gap, check voltage of TPS.
Check if you have a restrictor in the idle bypass hose (6mm hole is ok).
Check for vacuum leaks, and check properly, mine had a vacuum leak at the charcoal canister, try to say that a leak not necessarily is on the engine.
Check temperature sensors.
Check MAF, there's a screw on it to adjust the CO%.

When this is ALL alright, then you set your base idle setting.

https://www.roverparts.com/TechTips/base_idle_setting_procedure.cfm
 
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