1.6KSS cutting out at idle - possibly fixed - or is it?

[JP]

One for the wisdom of BC please.

For the first time my 1999 EU2 1.6KSS spluttered and almost died when idling as I coasted up to a junction today.  Managed to save it by blipping the throttle and got home.  On arriving home and lifting off the throttle, it simply died as the revs dropped.  Engine has verniers, recently timed by oily, and a 52mm TB, but is an otherwise std 1.6KSS.

Managed to restart by blipping the throttle on the starter - usually it just starts up on the button.  Switched off again and checked inertia switch - all fine it seems.  Restarted on throttle but died again.

Then tried the "reset" by opening throttle 5 times with ignition on .  This time it fired into life, but then cut out.  Restarting required throttle again. 

Then thought I'd check the plugs.  As I did so, I felt that the HT plug leads could have been better seated on the spark plugs.  None seemed loose, but the tops of the plug leads seemed to sit proud of the plug hole whereas the previous HT lead plugs tops sat down flush with the top of the plug hole.  Plugs all look fine and HT leads pushed further home on refitting.

It then started on the starter and a test drive for about 20 minutes was faultless.

Could loose HT leads cause the cutting out at idle or was it coincidence that it started working again and should I be looking elsewhere for a failing component?  The Rover Haynes manual for the 216 suggests checking HT leads for such symptoms...

Also, can anyone point me to a good general resource for understanding and trouble shooting engine management issues.  Having spent the last decade + on old Series Land Rover engines, I need to get my head around the various sensors etc on the K-series engine, what they all do and the effect of failing components on engine behaviour.  A loose plug lead on a Land Rover would have given a misfire / less power, but perhaps when there is an ECU involved, it just gives up instead?

Many thanks for any guidance...

[SM25T]

Usually a sign of battery on the way out.

[JP]

Thanks, would that also explain it seemingly being intermittent?

Battery is not that old.  Bought in spring 2022, but only used briefly and then removed and kept in the shed (not on charge) from late summer 2022 to May 2023, while the engine was out of the car for my rebuild.  The battery has recharged on a charger and will start the car without help, but it hasn't exactly been kept in ideal conditions!

[PaulRainsford]

Have you checked the idle control valve. If i remember correctly on the K series they have 5 wires going in to the connector so check all are seated correctly in the pins and none of the wires are fractured /shorting. If so your idle control valve wont function correctly - It allows air in to the intake when your throttle is closed to prevent stalling so could be stuck in the closed position. 

[JP]

Sorry for the numpty question, but is this the idle control valve?

If so, other than visually checking the wiring, is there a way to test it other than by buying a new one and fitting it?

[revilla]

Sometimes tweaking the cam timing changes the air flow at idle and necessitates an adjustment of the throttle stop screw. On a managed engine this doesn't control the idle speed, which is managed by the ECU. If it is too far closed, the revs can tend to drop too low as it returns to idle and can stall before the IACV has chance to react and catch it. If it is too far open you can have an idle that struggles to settle. The stalling issue tends to be worse after coasting slowly down to a junction; the ECU sees the closed throttle and as the revs fall into the target range, the ECU sees it as idling too high and tries to pull the RPM down by closing the IACV. Then when you drop the clutch it dies before the ECU can wind it open enough. If you've got a 52mm TB on it could make the issue worse. There's a procedure for setting the idle stop right, based on the number of IACV steps needed to maintain idle with a fully hot engine. You tweak the screw until it settles it a specific number of steps (26 from memory). You can see the number of steps on a PScan device or a Rover T4. With some experience it's possible to set it by feel alone, watching the idle return, which should just hover and hang ever so slightly at 1500rpm-ish before settling. If you get it slightly too far open, you tend to get a bit of an on-off step when just touching the throttle, it's hard to transition between on and off power without shunting a bit.

But, a warning: On the 52mm TB the idle screws are set at the factory and a black thread lock compound is applied (along with a black plastic anti-tamper cap). The thread lock is so strong that the screw will often shear and snap before it turns! The best way I've found is to apply heat to the end of the screw to soften the thread lock, but then you need to use protection to avoid accidentally melting the throttle quadrant. Layers of aluminium foil work.

On mine, after softening the thread lock I took the screw right out, cleaned the thread lock out with a tap, and then fitted a longer stainless screw with the end ground to a smooth round ball. The longer screw allowed me to use a lock nut instead of thread locking compound.

Where abouts are you, anywhere within stiking distance of the Midlands?

[revilla]

I made this video a while ago to show the kind of idle return profile to expect when the throttle stop screw is correct. This is on a VVC 160 but it should be similar: 

 

[JP]

@revilla - thank you.  Food for thought. I've had to watch the video a few times, but I think I get it - there is a momentary pause as the revs drop at 1500? 

I should say that the mods to the engine were done many years ago and it had always run without any problem before.  Until today, it has also been running well since its return to the road about 6 weeks ago after 14 years of hibernation .  And it seems to be running well again now, but I'll take it for another spin when I get a chance in a few days...

I'm going to look into a PScan - I think it would be helpful to see what's happening with the engine - am I right in thinking a PScan plugs into the black large plug that hangs free behind the dash?

I'm not in the Midlands, I'm afraid.  I'm SW London. 

Edited April 21 by JP

[revilla]

@JP yes that’s it.

But as you say, if its been running well them something has changed, so maybe not the problem. Still worth having a quick look at the stop screw though, if someone has previously adjusted it, it might not be tightly thread locked and could have worked out a bit with vibration.

The symptom of needing throttle to start, and then a bit of throttle for a few seconds to keep it going after start, is often a battery issue as Ian says. Its a funny one as the starter still spins the engine over quickly, but the battery voltage drops in a spike for a few milliseconds as the motor starts, and that confuses the ECU into thinking the ignition was switched off, so it starts the routine of recycling and indexing the IACV and it won't idle until that is finished. It can also be caused by some aftermarket starters with larger inrush current transients, particularly some Brise units. Neither of these will lead to it stalling at junctions though.

The IACV can get a bit gunged up. You can take it off and clean it. Be very careful if you dismantle it though as there's a little spring inside that tends to exit across the garage never to be seen again! This will also happen if you operate the IACV by turning off the ignition with the IACV removed from its outer housing but still connected. Because its a stepper motor with no servo feedback, the ECU finds the closed position by winding it closed until it hits the seat. If it is disassembled there's no seat to stop it, it winds right out until the spring fires it out again.

The PScan is the most comprehensive ECU interrogation, diagnostic and maintenance tool available for the EU2 and earlier. Those earlier ECUs are not OBDII compliant so don't work with regular diagnostic scanners (or my MEMS3 Tools), but the PScan lets you see fault codes, view extended live diagnostics data and set service adjustments etc. And yes it just plugs into the OBDII-style 16-pin connector if you have that on your car (some very early cars didn't and needed an adaptor). I've used one to diagnose cars successfully on a few occasions.

[JP]

@revilla Thank you again.  I've had this car since 2001 having bought it with 900 miles on the clock.  The starter is original and the TB came from Oily - fitted fresh out of the box, so there shouldn't have been any tinkering.  I'll double check behind the dash to see if I have the "OBD" plug. I seem to recall noticing it when I pulled the dash for the rebuild...

When I came to refit the battery, it was dead, having lived in the shed over winter and not on charge.  I have "revived it" with numerous charges so that it holds enough charge to start the car without help now...but I doubt it's in very good condition. 

I'll fire the car up again today and see what happens...it had run OK again after reseating the HT leads yesterday - could misfires from loose HT leads cause this or is that unlikely?

[JP]

Found a picture from when the dash was out of the car.  Is this the PScan plug?

Edited April 22 by JP

[Miker7]

Yep - thats the one.

[Jonathan Kay]

49 minutes ago, JP said:

When I came to refit the battery, it was dead, having lived in the shed over winter and not on charge.  I have "revived it" with numerous charges so that it holds enough charge to start the car without help now...but I doubt it's in very good condition. 

I'd test the battery before doing anything else. That's both to see if that's the cause and because you'll be relying on it in diagnosing other faults.

1 If it's the type that you can top-up then check the fluid levels and top-up if necessary.

2 Measure the battery voltage:
• At rest
• Minimum during cranking
• At 3,000 rpm.

Jonathan

[JP]

@Jonathan Kay Thank you.

The battery is a std Banner.  Checked the cells and all  were slightly down on water so topped up (3-5mm at most in each)

Voltages - tested on a cold engine:

• Everything off, FIA off: 12.65V
• Everything off, FIA on: 12.65V
• Lights on for 10s, then switch off: 12.44V

Cranking: initial momentary drop to around 7.55V, but then settled cranking at around 9.10V while cranking for a few seconds.  (Cranking with king HT lead unplugged from distributor.)

Engine then started first time on the button only (no throttle required) and idled happily while cold at around 1300-1400rpm.  Voltages:

• At cold idle: 13.85-13.90V
• At 3000rpm 13.95V.

Does that shed any light on matters?

I am wondering if this was just a loose HT lead issue, unless that doesn't make sense.  Haven't test driven today.  May try to do so tomorrow.

Edited April 22 by JP

[Jonathan Kay]

That voltage during cranking is far too low.

Did you charge it after topping-up? If not I'd do that now and retest... but I expect that you'll get a similar result.

Jonathan

 

 

[JP]

Thanks @Jonathan Kay.  I just topped up and tested.  I'll whip the battery out tonight and charge overnight.  What should the cranking voltage be? Do the other voltages look OK?

I have to say, I think I'm just putting off the inevitable with the battery - although not old, it was flat as a pancake when I got it out of the shed after sitting outside over a cold winter...

I saw the thread on batteries, but I'll review again.  I do want something that fits in the battery cradle so it needs to be the same dimensions as a Banner or smaller...

[Jonathan Kay]

"This is a quick DIY method for testing how the battery behaves under load and whether the car's charging system is working.

"The minimum voltage while cranking (the convenient DIY load) should be greater than 10.5 V. As well as measuring the condition of the battery this may help to explain what's wrong with the car as electronic components, including the ECU, can drop out below this. (The surprising thing is that this can happen although the cranking speed seems fine.)

"The voltage at 3,000 rpm is a test of the car's charging system, and should be greater than 14 V."

Jonathan

[JP]

Thanks again @Jonathan Kay - I suspect time for a new battery - let's see tomorrow...

I'll also check my drive belt tension.  I really don't fancy changing my alternator...

[Jonathan Kay]

Checking the drive belt condition and tension is a good idea. I wouldn't worry about the 13.95 V beyond that.

Jonathan

[JP]

@Jonathan Kay - Following charging the battery overnight, I now have these numbers:

Voltages - tested on a cold engine as soon as charged battery re-installed.  No driving between charging and testing:

• Everything off, FIA off: 13.24V
• Everything off, FIA on: 13.23V
• Lights on for 10s, then switch off: 12.68

Cranking: initial momentary drop again to around 7V, but too brief to be sure.  Settled cranking at around 9.60V while cranking for a few seconds.  (Cranking with king HT lead unplugged from distributor.)  When stopping cranking I noticed, what I guess, is a stepper motor sound from the IACV, so I guess that is working - or at least doing something.

I didn't recheck voltages at 3000rpm as it was a little early in the morning for my neighbours!

From the figures above, I guess I need a new battery?  I'll trawl the thread above again, but I suspect a std banner will be in order...

[Jonathan Kay]

Thanks for the figures.

I'd fit a new battery.

I try to keep that "Best battery" thread up to date. All additions welcome.

Jonathan (Sealed batteries only in my cars)

[revilla]

7V during cranking is very low. But the real killer will be the inrush current spike as the motor first starts, which will drop a lot lower. You can't see it on a multimeter, it's too short lived, maybe 0.1 seconds - you need an oscilloscope.

I recently did some work for a tuner who wanted me to include a low voltage warning in my tools when programming an ECU. I have a very good digital programmable power supply for my bench harness that lets me adjust the supply voltage in 10mV steps, so I have a play around to just how low a steady state power supply voltage the ECU would run normally on. The answer is a surprising 6.6V! I think it's the point where the internal 5V regulator drops out. Anywhere above that, the ECU was running normally, including for programming purposes. At 7V you are very close, and any inrush current spike is going to take you well below.

If you're hearing the IACV after turning off the ignition key, that's normal. If you're hearing it just after releasing from cranking, that's not, and it's a prety sure sign that the ECU is dropping out during cranking.

I'd definitely replace the battery.

However ...

I don't see how any of this could contribute to it dying at junctions, expecially as the alternator seems to be charging reasonably well so the batery voltage should be quite acceptable under normal driving conditions.

[JP]

@revilla - thank you.  I will replace - looks like a decision between a Banner and a Powervamp PC535. I understand that AGM batteries require a different charging profile from standard acid.  Is that an issue on a 7 or is it only an issue for cars with an ECU that manages the charging pattern?  I replaced my LA battery with an AGM one in my Boxster and was advised that I should have stuck to regular LA as the charging would not be properly suited. 

As for the cutting out and failing to start and stay started on the starter button without throttle, it does seem to have resolved after removing and firmly reseating the HT leads. Would it make sense for that to be an explanation?

I'll listen again to the IACV and make a note of when I hear it...

Edited April 23 by JP

[Jonathan Kay]

2 minutes ago, JP said:

I will replace - looks like a decision between a Banner and a Powervamp PC535. I understand that AGM batteries require a different charging profile from standard acid.  Is that an issue on a 7 or is it only an issue for cars with an ECU that manages the charging pattern?  I replaced my LA battery with an AGM one in my Boxster and was advised that I shoudl have stuck to regular LA as the charging woudl not be properly suited. 

I haven't heard of any problems with this on the many Sevens that have Powervamp/ Odyssey AGM batteries.

If you use a smart conditioning charger it's probably sensible to use one that has an AGM mode. (But I don't know what would happen in practice if another setting is used.)

Jonathan

[aerobod - near CYYC]

With a brand new battery that has been charged to full capacity before use, the initial voltage before start on my Duratec drops to 8.5V for 80ms, before cranking at 10.5V before starting. The ECU logging captures this, but it is a bit quick to see on a voltmeter.