Engine Cut Out & Failure to Restart Problems

[NSX30L]

Hi All,
I've a problem with my 90 Auto with 150k klms. Perhaps some listers can offer some suggestions.
I was on a long trip, did 900 klms on day 1.
Occasionally the engine would hesitate a little bit. Sometimes this was due to the TCS system when the light would come on but this has been happening for years (perhaps because I run 17in/18in with the next model tyre sizes). (De-activating the TCS makes no difference, the orange light will still come on). Occasionally when it hesitated I noticed a flicker in the tach needle indicating an electrical problem. Slowing down and blasting up to C150kph was faultless.

On day 2 it got 40 klms and cut out altogether and wouldn't restart although it turned over vigorously. Eventually it did but stopped again shortly later. I put hazard lights on and left it. Service man came and by then the battery was flat. We jumped started it and I drove a shorter distance and it stopped. Got it to a country QLD dealer (never seen an NSX before) who tried to trace the problem unsuccessfully. They think it is an immobilizer, which was one of my suggestions. There were also faults connected to the TCS and Transmission recorded although I'm not certain they had all the right diagnostic plugs.
I think I'll retrieve the car by trailer next week but would appreciate any suggestions in the following areas:

Through my stupidity and paranoid insurance companies it has had several iterations of alarms, the factory one and 2 at the insistence of the insurance companies plus the Sat tracker.
1. Factory alarm with 2 buttons working the central locking etc..
2. A Moss security MS735. (on reflection this could be the above as it has no separate interface).
3. A Brant Transponder proximity engine immobliser.
4. A Black Widow/ Car Watch satellite tracker including "Start Inhibitor".
Working on the basis this is the problem I'd like to start by removing or total disabling all these then installing a new device. In particular where does the immobilization occur? The Moss booklet says "Preventing starter motor operation, what about the others?
I imagine there a few $2.00 relays which open or close circuits. where would these be found and if they failed would they be in run or disable mode?

What does the TCS operate to partially shut down the engine and is this possibly failing due to overuse?

Are there any other suspect components with a history of these types of faults?

Would a weak battery have anything to do this while running? Probably when it cut right out it was doing <2000rpm but it always turned over well.

Who in NSW would be qualified and equipped to look at this? So far it has never been to anything but a dealer (I've had it from new), last time Sports Honda at Petersham but they didn't really know the car.

Any assistance will be really appreciated,
Thanks,
Gos

 

[NSX9]

http://www.nsxprime.com/forum/forumdisplay.php/36-NSX-Electronics-(1st-Gen)
Suggest you also put this question in NSX Electronic section.

As a guess...
It could be the main relay which is on the rear bulkhead of the cabin behind driver right shoulder.

 

[Old Guy]

On a stock car with as many years on it as yours, the first things I would take a serious look at are the ignition switch and the main FI relay. Sometimes you can diagnose the ignition switch by gently wiggling the key in the switch when the car is operating to see if this causes the problem. Failing that, the test procedure in the on-line service manual is pretty straight forward. The test procedure for the main FI relay is also pretty straight forward, although most people test by replacement!

On a DBW car, TCS operation causes the ECU to close the throttle. I am not sure about pre DBW cars. I suspect that it might cut fuel delivery and or retard ignition timing which are common strategies for rev limiting.

I have limited experience with after market security systems. The ones that I am familiar with, when activated, energize an interposing relay which opens the circuit supplying the starter or the ECU. This 'immobilizes' the engine when the alarm is active. This provides a fail safe mechanism in that if the security system fails or the interposing relay fails, it does not prevent you from starting the car. It also means that failure of the relay while you are driving should not stop the car. As such, I would assign a lower probability to the security system causing the problem; however, it is possible that where the relay cuts into the existing car wiring you could have a loose connection screwing you up. However, the fact that you were able to engage the starter motor; but, the engine would not start suggests other problems than the security system.

 

[whrdnsx]

if the Car Cranks, It just needs fuel & spark. I don't think It's the Main relay or ignition switch.

the Clue is with the Tacho needle flickering, like you say indicating an electrical issue, maybe a bad ground. Have you checked all the fuses?

The TCS will not prevent the car from starting, however to stop the light coming on you can disconnect it all together. It's behind the Passenger seat panel.

Sounds like an electrical issue waiting to happen with all those different alarm systems!

 

[Old Guy]

if the Car Cranks, It just needs fuel & spark. I don't think It's the Main relay or ignition switch.


Sounds like an electrical issue waiting to happen with all those different alarm systems!

The starter circuit is separate from the main FI relay circuit. The starter motor will still operate with a faulty main FI relay. The tell tale will be that the fuel pump will normally not prime when the ignition key is turned to run position if the main FI has failed. I agree with whrdnsx that the mix of security systems sounds like a toxic cocktail.

With respect to the tach needle flickering when the engine hesitated, I also agree that could be an indicator of an electrical problem. If other things such as the radio or lights were momentarily interrupted, you could have a common 12v supply issue (such as a faulty ignition switch or bad ground or ....). However, if only the engine hesitated and the tach needle flickered, that could again point back to the main FI relay. The ECU is powered up by the main FI relay and the tach gets its signal from the ECU. If the ECU temporarily lost power the fuel pump turns off, the ignition quits and the tach signal would disappear.

 

[rollie]

Hi NSX30L

Were you driving through extremely wet weather or did you wash the car before driving out?

Sometimes excess water would leak through the spark plug cover and into where the spark plugs are located.

 

[Jinks]

I would start at the battery and it's connections. Relay, coil packs, and traction control have nothing to do with the tach going crazy. You sir have a voltage issue it sounds like. Good luck!
I love forums such as these. Always great to read and try to help people out.

 

[NSX30L]

Thanks for suggestions.

I would start at the battery and it's connections. Relay, coil packs, and traction control have nothing to do with the tach going crazy. You sir have a voltage issue it sounds like. Good luck!
I love forums such as these. Always great to read and try to help people out.

Thanks Everyone.

I've arranged for a trailer and will go and get it next week, a 2000klm round trip. I'd be too concerned using commercial carriers who would move it to Brisbane first, then to Sydney and then to Goulburn, especially if it wasn't running. I think the cost of a specialist carrier would be unaffordable.

The dealer established there was nothing happening at the coil packs when it was turning over, so that confirms the electrical theme.

It was a fine morning no wipers or lights being used although now I think of it I did put on the lights (to see if it could be a low voltage problem) and it did hesitate as they came on.

The earthing situation bears investigation. It recently (in terms of klms) had a full service - belts, cam clearances etc. which might have involved this. Could someone advise me of where the main earth to the engine is located please.


I don't need to be told about the alarms and I'll be sure to reduce it back to one now the insurance companies aren't so paranoid. I've got wiring diagrams on all of them and can see it is unlikely they are the problem. One only isolates the starter, another works on voltage drop alone, so there is only one which has cut the power feed off the ignition switch and looped it through the unit. I hope that is close to the switch so I can find it alternatively, as I know the colours, I can join these at the unit.

Gos

 

[Jinks]

I think the earth group to the engine is between the fuel pump resister and the coolant reservoir tank mounted on the rear firewall. But I could be wrong.

god I hate iPads and spell check! Earth ground* not group...

 

[Old Guy]

I don't know where the engine ground is; but, if the starter motor is turning over fine then the engine ground has to be good and in fact your battery connections are probably OK, although those are easy enough to check.

Not meaning to beat the main relay problem to death; but, if the ECU is not powering up then there will be no action at the coils as the ECU switches the coils through the igniter. While on the topic of the igniter and poor grounding, there have been reports of poor grounding of the igniter module causing ignition failure. Again, something to check.

 

[NSX30L]

Main Relay

Thanks again,
I'm off to retrieve the car tomorrow so am psyching myself up to see what I can find when I get back. I'm assuming you refer to the relay on the bulkhead next to the ECU and it would be tested simply by checking voltage in and voltage out when ignition is on - it looks very simple in the book. The workshop manual doesn't seem to give any test procedures on this, at least not under the Electrical Section. Replacement isn't possible unless I take a shot that this is the problem and get one ordered which would take a couple of weeks. In a way having an intermittent problem is worse than a total failure. I'll work out the failure pattern as soon as I get the car in my workshop I don't want to drive it out and have it fail to be trailered home as the repeated process.
I'll certainly check the igniter earth though.
Gos

 

[Old Guy]

Correct - the main relay is on the bulkhead. The main relay is actually two relays in one package along with some isolation diodes. As such, testing is not exactly straightforward! I seem to recall that the test procedure for the main relay is in the fuel injection / emissions section of the manual, not the electrical section.

I have attached the test procedure along with the internal wiring diagram for the relay, the pin out for the relay and the section of the wiring diagram showing where the relay connects to the ECU and the fuel pump.

Good luck with the testing!

 

[venomous42]

mine would do this every so often, then one day, it would not start at all. just crank over. pulled the main relay, and sure enough the solder joints needed to be fixed. got out the iron and presto, it was fixed. never a problem again. that was 2 years ago.

 

[Old Guy]

mine would do this every so often, then one day, it would not start at all. just crank over. pulled the main relay, and sure enough the solder joints needed to be fixed. got out the iron and presto, it was fixed. never a problem again. that was 2 years ago.

You are correct that fracturing of the solder joints seems to be the most common failure mode and that reflowing the solder can provide a temporary and perhaps long term fix. If the actual relay coils or contacts fail (really rare) it is possible to cobble together a temporary fix using some simple SPST relays to replace the existing relays. Excellent quality 30/40 A automotive class relays from Tyco are available for less than $5 from electronics vendors. Anybody who is moderately proficient with electronics could figure out how to do the patch. It won't look pretty since you will have jumpers from the main relay out to the external replacement relays; but, it will provide a patch until you can get a new replacement .

 

[NSX30L]

Main Relay

Got the car home and of course it is running perfectly, which in one sense is good since it drove on and off the trailer and into my workshop.
Had a quick look at the igniter module earth and it seems OK. the next step will be the main relay removal and examination and testing plus bypassing the alarm that cuts into the ignition supply.
Thanks for the documentation I was looking at electricals.
The mention of ECU failure makes me weak at the knees, I'll continue eliminating the other options as per suggestions.
No one suggested anyone in NSW who could service it, apart from a Sydney dealer where it has been but where I didn't get the impression they were capable of this job. Anyone have any suggestions?
Thanks,
Gos

 

[Stefanos]

I had a similar problem and was my ignition barrel switch, try it its a very common problem with nsx's over 100k should be done anyways.

 

[Old Guy]

The mention of ECU failure makes me weak at the knees, I'll continue eliminating the other options as per suggestions.

Gos

If the engine runs fine (when it runs), then it is highly unlikely that the ECU is the problem. ECUs do not normally fail intermittently unless its a intermittent terminal connection which can be a pain to track down;but, easy to fix once you find it.

The high probability suspects are the main relay and the ignition switch (as Stefanos suggests). If you are unlucky enough that it is not one of those then it becomes a grind in terms of tracking down the problem. At that point you start wishing that it would fail permanently so that you could find the problem!

I share your pain about good dealers knowledgeable about the NSX. The solution is to purchase a shop manual and read it in your spare time! If you had the approximately 5 months of snow cover that I enjoy, you would have lots of spare time to read the manual!

 

[NSX30L]

Main Relay Access

A little more advice please...
I tried to remove the rear trim panel to access the main relay. I expected it to release with moderate outward pressure but felt I was going to break something so gave up. Is it just a matter of applying the necessary force until it yields. Again I couldn't find a specific instruction in the manual although it gets a mention in the Body section.
Thanks,
Gos

 

[Stefanos]

Remove the 10mm bolt from the bracket and remove gives you a lot more room to take it out

 

[jwmelvin]

I think he's talking about the trim panel? Just pull near each of the three clips along the top.

 

[NSX30L]

Resolved?

It looks like the fault is the main relay as pointed out by your helpful suggestions.
I removed it and checked the solder points. One had been repaired about 10 years back, I retouched that one, however noted that pungent smell of an electrical component in its death throes.
I reinstalled it and the car started (as it had before removal), however if I tapped the unit it faltered and if I tapped it enough it stopped altogether. This seemed to replicate the circumstances of failure on the road. Although I didn't associate the failure with a bump on the road I was travelling on a fairly rough secondary road.
I've surveyed the alarm wiring which is atrocious.
I've ordered a new relay and will ensure that is the source of the problem before I then start on that mess.
Thanks for the suggestions and advice, it is a very valuable forum.
Gos

 

[Old Guy]

Good stuff! Hope its truly the fix.

Makes me think that I probably should order a spare main relay for my 2000 to have on hand since they seem to be one of the failure points in the NSX.