Engine stops in heavy stop/start traffic

[Dammit]

Something (I think) is overheating, what's the most likely thing for it to be?

I did a track day earlier in the day and the car was perfect - but driving past Oval at rush hour and abruptly I am having to push it into the bus lane and wait 10 minutes for it to cool down before I can drive the rest of the way home.

This is what I would characterise as sub-optimal, all helpful suggestions gratefully received.

[TheEnd]

I'd say it's the engine overheating.

[anonymous-user]

If you turn the cabin heater on to full hot and full fan, does this stop the "Overheating"?


(ie, is you main cooling fan goosed and not coming on?)

[stevieturbo]

Temperature gauges usually give a clue as to whether it is overheating.

[Dammit]

Temp gauge stays in the usual place, which is why this is confusing.

[stevieturbo]

So history ?

It has run good for how long ? What vehicle ? Any tampering recently ?

Symptoms. Car just stops ? totally dead ? dash lights etc ?

Will it wind over, fuel pump run, make any noises etc etc ?

[andyiley]

Had a coil do exactly this a few years ago, leave it for 10/15 & it was fine, always happened when there was little air under the bonnet.

[Dammit]

Stevieturbo - a lot of changes, rather too many to point the finger at one I suspect:

- Aircon compressor clutch shimmed so it now works for the first time in my ownership (electromagnetic clutch that requires a maximum clearance between plates, which it was far beyond)
- Stock intercooler replaced with do88 intercooler, all pipework replaced at the same time
- New airbox with new 90mm MAF housing (replacing 63mm), new MAF, new air filter element etc
- New Kinugawa 20T TD04HL turbo
- New heater matrix

Since then the idle has been ~200 rpm above what it used to be (now 1,000).

What happens when the engine dies:

- Sat idling in traffic, aircon on, in neutral with handbrake on, engine simply stops
- To give an idea, I'd just driven from Castle Combe down the M4, to A4, over Vauxhall Bridge and the engine cut out at around 17.40, so traffic was very heavy
- Oil light and check engine lights illuminate as the engine dies (just as if you'd stalled it)
- Starter spins, engine doesn't catch at all
- Push car over to curb, pop bonnet, wait 10 mins
- Car fires on the first spin, performs like nothing happened

[stevieturbo]

By tampering I meant recently, days, maybe weeks before the problem started. As potentially the problem is caused by the tampering.

I'm presuming you cannot replicate the stoppage sitting stationary with engine running etc ?
When it has stopped, this is the ideal time to perform some tests.

Could be ignition, could be fuel pump, could be a relay, could be a crank/cam sensor, could be many things really.

Without some access to information when it has stopped, fixing will be a pain.

[Dammit]

All of the above changes were made in the last couple of weeks. It may be coincidence, but it never cut out like this before the latest round of changes.

I've tried leaving it idling, it just idles - you need to be in stop/start traffic when it's warm outside for it to cut out.

[Dammit]

Ok, this is my theory:

- The MAF, enlarged in order to accommodate the much higher than stock airflow is not great at low air flow any longer
- This is ok when temperatures are low to medium - when the car is in motion, basically
- In 10 miles of typical London traffic jam on a hot day the under bonnet temperatures climb significantly
- The hot, low speed air isn't within the MAF's ability to read
- It's the MAF sending "no air flow" to the ECU, which then cuts fuel, that is causing this problem

Sound plausible?

[stevieturbo]

Dammit said:

Ok, this is my theory:

- The MAF, enlarged in order to accommodate the much higher than stock airflow is not great at low air flow any longer
- This is ok when temperatures are low to medium - when the car is in motion, basically
- In 10 miles of typical London traffic jam on a hot day the under bonnet temperatures climb significantly
- The hot, low speed air isn't within the MAF's ability to read
- It's the MAF sending "no air flow" to the ECU, which then cuts fuel, that is causing this problem

Sound plausible?

I would highly doubt it.

[Dammit]

Boo. I had read of large MAF housings leading to poor idle/stalling, so thought this might be a good theory as my MAF is very much larger than the original.

Back to the drawing board.

[bearman68]

I was going to say it sounds like an ignition problem, but assuming it's a BMW or something, then 6 coil on plugs are not likely to go down at the same time. Same argument with a fuel injector Therefore I would be thinking a crank or cam sensor, or worst case scenario an ECU (but doubt that TBH).

[Dammit]

Single coil - '96 5 cylinder petrol, turbo Volvo engine.

[Sardonicus]

Crank sensor? if its faulty you have to wait for the temp to reach failure threshold what comes up when you scan it? all your changes may just be a red herring and unrelated ...... maybe

[Dammit]

No codes, which is annoying - and lends weight to the cps theory as that would not throw a code, unlike fuelling which should do.

[Bertrum]

I would suggest Cps as well, had a bmw that would do the same thing when it got hot.

[TheEnd]

BMW Crank sensors (and cam sensors) would break up and drop out when hot.
Cam sensors usually make it run rough, crank sensors make the ECU think the engine has stopped or stalled, and it's tricky for the ECU's to figure out if it's a fault or just a spotted engine.

[Dammit]

Correct range for the CPS is 200-500 Ohms apparently, and mine is showing 294 across the pins.

This is with the engine cold, but would this change with the engine up to temp/very warm?

If no, then it's not that.