Engine Cutting Out Intermittently

[Dom Williams]

Good afternoon all,

 

I experienced some unusual engine cut-outs whilst enjoying some (very light) road driving a short time ago.

Cut-out was intermittent, often occurring at the most helpful of times (most notably when giving it a tickle entering a roundabout to slot into a gap in traffic 😑).

Power does return (without needing to turn the engine over again), it is usually absent for a couple of seconds and in the meantime blipping the throttle had no effect.

 

The engine is a 1600K running MEMS 1.9.

I imagine it will either be fuel-related or electrical, however I would expect the ECU to take more than the couple of seconds for it to reboot and start firing etc. after having lost power. Power to fuel pump?

I believe it unlikely (but not impossible) that there is an issue with engine-bay wiring. The loom was opened up, cleaned and resleeved before putting back in a refreshed engine from DVA. The car then completed a drive to and back from Curborough for the introduction to sprinting day (plus the event) without any problems.

 

The car is currently on axle stands doing a load of other small jobs so cannot go and do any “testing” for a while, but can have stuff off/apart for an inspection.

 

If you have any theories, please let me know!

Yours,

 

Dom

[TomB]

Could be Throttle Position Sensor - TPS - and its not picking up those small light throttle inputs. 

It would be worth taking off and seeing if the spindle is clean and is free to turn.  Also look at resetting the TPS using the 7 full pedal deflections with the ignition on.      

Edited April 17 by TomB

[Skipper555]

Worth checking all the major earths and power connections for corrosion/dirt?

[Mick Day]

Had this problem on & off for some time. 1.9 DVA K. But mine was a complete cut. No hesitation just complete shutdown. Give it 30 seconds & engine would start again.

At 1st it was occasional then ok for months.  But in the last 5 years it made the car undriveable. I changed all the usual suspects: coil, crank sensor, TPS, distributor cap & rotor arm, plugs etc.

In the end had the fuel pressure measured which was low. So tank out to remove the pump. The gasket had melted forming a goo around the pump inlet partially blocking it.

So after a new pump, gasket & filter I'm now back in the game.

 

[Shaun_E]

Electrical: I'd start with the coil - if it's the one bolted to the engine block then they get a hard life in a Caterham and I went through about 3 of them before going wasted spark with a remote coil pack. Otherwise the usual rotor arm, distributor cap, leads.

Fuel: fuel pump is a possible culprit. I'd been chasing a similar issue for months - swapped all the ignition components out with no success but checked fuel pressure which was fine at idle but dropped rapidly under load. A new pump resolved the issue. TPS is also a possibility.

Edited April 17 by Shaun_E

[Englishmaninwales]

Hi Dom,

In addition to the other checks suggested, take look at the main engine loom power supply - there is a brown to purple spade connector in the loom bundle just behind the dry sump tower. Well known for being loose and causing engine drop in/out.

Malcolm

[Jonathan Kay]

Hmmm... 

Lots of possibilities, and it's intermittent, and there's been recent work on it... 

Do you have the appropriate wiring diagrams and a multimeter?

Has it been drowned recently?

When it happens does the ignition warning light come on, and do the electrical instruments change what they're showing?

When it happens and you restart does it immediately run well, without coughing or similar?

Jonathan

[Jonathan Kay]

In addition to suggestions upthread:

• Check all relevant connections, feed and earth to the battery, ECU, and engine earths. Inspect, wiggle, disconnect, clean, reconnect.

• Check battery voltage at rest, minimum during starting, and at 4,000 rpm.

• Check ECU fuse contact and connections. (And what's the fuse rating?)

• Check spark plug wells for water and spark plug leads for positive engagement. (But sounds like all cylinders losing power, not one.)

Jonathan

[Klunk]

In addition to the above,  do you have an FIA switch?  Intermittent cut out can be a sign of it starting to fail.

Giles

[Dom Williams]

Good morning all,

thank you very much for your feedback.

@TomB I will check the TPS - however I would have thought that this would result in the engine stalling as I engage the clutch without revs - I wouldn't expect it to "regain power" a few seconds later(?) It's an easy check though...so I will definitely have a look.

@Skipper555 I will have a look but I doubt the problem is earths/power supply as I went over the entire electrical system last year and cleaned it all up.

@Mick Day that's very interesting - I know the fuel pump is on the list of "consumables" for this car. I don't fancy this job, but think I might have to check this.

@Shaun_E Hi Shaun, it is the one bolted to the block - I can't go wasted spark with the MEMS (unless @revilla knows differently) - when the engine came out last year to go to Dave everything obviously came off and had a damn good clean - it didn't look "old"/"worn" but who knows what it looks like inside. I can recheck the connections just in case. As per my comment to Mick Day, I will check the fuel pump and see what that looks like.

@Englishmaninwales Hi Malcom, when I re-did the engine loom before Curbs last year I redid that line completely - new spade connectors on both sides that slot together with a nice amount of friction and the whole thing was then heatshrinked so it can't come undone - thanks for the tip though!

@Jonathan Kay I have all the car/engine loom diagrams yes; no drowning (it lives in the garage and never sees the rain); I must admit I didn't check the dials to see what happened when I lost engine power (I was too busy trying to see what might drive into me); I didn't ever "restart it" - engine power would come back of its own accord a couple of seconds later.

Re: your second message...thanks for the tips. I will re-check all connections just in case however everything is definitely clean (I did this job thoroughly last year and the car has done maybe 250 (sunny) miles since then); I will check battery voltage too, however I have a voltage reading on the dash and I don't remember seeing anything strange in normal driving (both on and off load); ECU fuses are the standard/originals, situated underneath the ECU - I gave this all a clean last year...but there could be something loose. I still can't imagine that if the ECU lost power due to a dodgy connection it would then come back to life and start firing cylinders after a couple of seconds? Spark plug wells are definitely dry; I can check for seating...but as you say, it is definitely not just 1 cylinder causing an issue!

@Klunk The FIA switch and its many kgs of wiring all came off last year!

[7 wonders of the world]

Check the loom at the fuel pump they go hard and crispy and the connections on the connector there to the short pump lead. 

[Mick Day]

Dom: if you do suspect the pump get the pressure checked before removing it.

My problem was more to do with the poor quality aftermarket gasket. 

But there again the original Rover pump quality has been suspect.

[revilla]

A couple  of things I can think of worth checking that haven't been mentioned:

Does the HT lead from the coil on the side of the block up to the distributor run close to the crank sensor wiring? If so it can cause noise pickup, effectively "jamming" the crank sensor signal. Try to space them well apart.

I had a car parked here for days while I tracked down an engine drop out. In this case I would rev to almost exactly 6000rpm then abruptly cut, but it could be similar. In the end it had an FIA switch, so the main 12V supply wiring had been extended down to the starter motor solenoid terminal as a junction point. One of the wires had fractured where it joined the ring terminal, but the joint had been insulated with heat shrink so it was impossible to see. At 6000rpm the vibrations in the wire resonated and the power started dropping out.

An ECU reboot actually takes a split second. It is designed to recover gracefully from e.g. a software fault. But I have seen with MEMS3 that occasionally powering the ECU off and on with the engine running at much more than idle speed (on an engine simulator rig) can leave it in a terribly confused condition where the ignition and injection firing are chaotic and random looking, from which it recovers and gets "back in sync" as soon as the engine stops. So a very brief loss of electrical supply from a bad connection somewhere could be leaving your ECU in a similar state.

How repeatable is the issue? Is there anything in particular that is likely to trigger it?

[Toby S]

I had a similar problem a few years ago on my 1400 SS and in the end I tracked it down to the key ignition switch - change to a dash mounted and solved the problem - was a lot of trial and error as it was intermittent which is the real pain and also usually cut mid junction or roundabout were you didn't have the opportunity to inspect the problem properly - just needed to get the car out of the way.

P.S. Tracked down finally to ignition switch when it cut on a dual carriageway and I was on outside lane overtaking and found I had no indicators so went hunting under the dash - try flicking your indicators on when it next cuts

[john milner]

I had a similar thing. It was the first sign of a failing battery isolator switch.

[Dom Williams]

Good afternoon all,

thanks for your further feedback!

@7 wonders of the world added to the to-do list

@Mick Day thanks for the tip - I have a pretty decent history for the car and cannot see any fuel pump-related purchases (at least since 2003)

@revilla thank you for the suggestions - I will check the spacing; it may be rev-dependent, but I don't have enough data to go on; that's very interesting to know about the ECU-reboot time...I remember the issue occurring at low revs (it also cut out a few times whilst trundling up the hill to my house and when approaching junctions slowing down to a stop/setting off again)

@Toby S the barrel ignition switch was removed last year and replaced with an aircraft-style toggle switch on the dash - however next time I am out I will try the indicators and see if there is some sort of correlation 😉

@john milner thanks for the comment; unfortunately it won't be that in my case as I removed the FIA isolator switch last year (my car is now very stealable!)

[Miker7]

Thread hijack time - on my new to me 51 plate 1.6SS I've had the car cut out three times. Twice whilst doing medium acceleration (3/4 throttle) and once whilst slowing for a junction. This seems to be after about 30 to 45 minutes driving. In all cases the car doesn't seem to want to restart, but will happily spin the starter or light up the hazards. If i switch off the ignition it then restarts after a few seconds of the starter spinning. Reading the above it sounds like the battery master switch (retro fitted, not sure its FIA) and hidden starter button may be prime suspect. Is their a simple way to remove the dash to check this out?

[SM25T]

There's no easy way to remove the dash 😀 .... mobile phone handy for looking behind it.

[Jonathan Kay]

3 hours ago, Miker7 said:

Thread hijack time - on my new to me 51 plate 1.6SS I've had the car cut out three times. Twice whilst doing medium acceleration (3/4 throttle) and once whilst slowing for a junction. This seems to be after about 30 to 45 minutes driving. In all cases the car doesn't seem to want to restart, but will happily spin the starter or light up the hazards. If i switch off the ignition it then restarts after a few seconds of the starter spinning. Reading the above it sounds like the battery master switch (retro fitted, not sure its FIA) and hidden starter button may be prime suspect.

Cutting suddenly... not gradually losing power?

When it happens does the ignition warning light come on and do any of the instruments change reading?

Check whether the starter circuit is independent of that master switch. And the hazard warning lights.

Does the immobiliser work normally?

Keep your list of possibilities open...master switch, original column switch, hidden starter switch, something else...

...

Do you already have the appropriate wiring diagrams? Including Andrew Revill's corrections? Please let me know if you'd like a set.

Jonathan

[JP]

3 hours ago, SM25T said:

There's no easy way to remove the dash 😀 .... mobile phone handy for looking behind it.

Or a vehicle endoscope thingy.  I got a reasonably cheap one off Amazon and it has been good enough to enable me to do a few jobs where I could get a hand but not a direct line of sight..

[Miker7]

Cuts suddenly, no warning hence I think wiring and not a failing coil etc. The fact it's after a while makes me wonder about heat which will be hard to diagnose.

 

Got a USB endoscope - hadn't thought of that. Got one with 5m of cable, hopefully enough 😀

Gauges die - good point, need to work out what circuit is what. I've got the wiring diagrams. Interestingly afterwards the indicators didn't work, but the hazard switch is a bit flakey. Although if my memory is correct I realized I had the dog light on, turned it off and they worked.

 

Immobilizer is disabled (ECU has a k maps map)

 

Just wish it hadn't happened on the a5 in a fast section going up a hill. I couldn't really stop and have a thoughtful play.

[Jonathan Kay]

Just now, Miker7 said:

Interestingly afterwards the indicators didn't work, but the hazard switch is a bit flakey. Although if my memory is correct I realized I had the dog light on, turned it off and they worked.

Have you already found the previous discussion(s) of flakey hazard light switches and what to do about them?

Jonathan

[JP]

I had a flakey hazard light switch.  New one was £9 from Redline - now fine.  One of the side terminals had broken loose on my old one.

[Miker7]

27 minutes ago, Jonathan Kay said:

Have you already found the previous discussion(s) of flakey hazard light switches and what to do about them?

Jonathan

No, but I'll search now. I find a few presses "sorts it out". I keep meaning to try contact cleaner prior to replacing. Will look up the thread now.

 

 

Looking at the wiring diagram, a dodgy ignition switch in position 2 looks like a good candidate for my problem.

[Jonathan Kay]

1 minute ago, Miker7 said:

No, but I'll search now. I find a few presses "sorts it out". I keep meaning to try contact cleaner prior to replacing. Will look up the thread now.

That sounds like the known fault. The surprising thing is that it affects the indicators as well. 

Clean the contacts, replace the switch... or reconfigure the circuit so that the problem doesn't recur!

Jonathan