Instant high revs on start up = damage?

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Fri 9 Jan 2004 18:22
Instant high revs on start up = damage? - SjB {P}
I now kow that a drive by wire throttle = no user control over how an engine behaves on startup, other than switching it off again if you are ready and quick enough (I wasn't).

1) Leave car for two weeks over Christmas and New Year
2) Let oil truly drain out to the sump and get thick and cold
3) Insert and turn ignition key
4) Observe engine fires absolutely instantly (ie before oil pressure establishes), and then revs hard to nearly 3,000 RPM for several seconds, before dropping to normal gentle idle

This has been a one off (so far!) but the tappet rattle was truly, truly, horrible until the hydraulic lifters pumped up, and I dread to think about piston and bore contact and a turbo running quickly up to boost speed.

I assume that the crank, journals, and other bearings would still have been nice and oily, but in the experience of those who know, is this brutal treatment likely to have damaged anything that will manifest in many miles time?

V70 2.4 petrol turbo.
10k miles.
No oil change or service performed yet.

TVM
Reply | Report as offensive | Link
Fri 9 Jan 2004 19:58
Instant high revs on start up = damage? - Victorbox
I know how you feel. Unless it is off tune, my Cavalier starts instantly summer or winter from cold on the slightest turn of the key. I immediately remove foot from throttle so revs are sufficient to get oil around but with minimum rattle from tappets etc. My neighbour on the other hand with his contract hire 5 Series BMW's (replaced every 18 months) guns the throttle and then revs the engine mercilessly several times at each cold start. Great at 5am! He does this to his wife's two year old Picasso too and that smokes nicely now! There have been occasions when starting on a freezing cold morning the rattle from the Cav's engine seemed horrendous until the oil light goes out (2 to 3 seconds) but it has passed 170,000 miles now and touch wood is still going strong.
Reply | Report as offensive | Link
Fri 9 Jan 2004 20:16
Instant high revs on start up = damage? - Marcos{P}
Why does the car rev to 3,000rpm?
Is that a fault or a design flaw/feature.
Reply | Report as offensive | Link
Fri 9 Jan 2004 20:56
Instant high revs on start up = damage? - SjB {P}
Current petrol Volvos on the P2 range of floorpans are designed to rev instantly to a moderate extent on startup, to help reduce emissions and extend the life of the cat.

My V70 typically spins instantly to 1400 RPM, holds for a second or two, drops to 900 RPM, then drops to the normal tickover of 700 RPM. This is consistent with every other one I know, and with what I have found on the web. Being drive by wire, the driver has no influence on this, try as you might such as by subtly and very very quickly 'blipping' the throttle like I used to do to nudge the cold tickover down on my (injected not carbed) Rover 420 a few years ago.

In the case I wrote about, methinks either:

1) A 'glitch' occurred.

2) (More likely) the ECU responded to the fact that the engine was used five times times for a few seconds each immediately prior to being parked up for two weeks, with fuel left swimming around:

Leave car to get thoroughly cold after work.
Start up and drive in to garage.
Leave until next day.
Start up and reverse out of garage to wash car.
Commence washing.
Start up and move car to make room for SWMBO's Pug.
Carry on washing.
Start up and move car back to original place.
Finish washing.
Start up and drive back in to garage.
Park for two weeks (Yes, with the handbrake off BTW!)

All this was done using only the idle control circuit and clutch to control speed. The throttle pedal would not have been touched once.

Will watch to see if it happens again, and if so take a trip to the dealer, but in the mean time it is simply a case of wondering what damage may have been done, even though "It's too late anyway".
Reply | Report as offensive | Link
Sat 10 Jan 2004 20:04
Instant high revs on start up = damage? - Jonathan {p}
Leave car to get thoroughly cold after work.
Start up and drive in to garage.
Leave until next day.
Start up and reverse out of garage to wash car.
Commence washing.
Start up and move car to make room for SWMBO's Pug.
Carry on washing.
Start up and move car back to original place.
Finish washing.
Start up and drive back in to garage.
Park for two weeks (Yes, with the handbrake off BTW!)


I'd be more concerned with the damage to the car from doing the above than moderate revving after startup.
Reply | Report as offensive | Link
Fri 9 Jan 2004 21:55
Instant high revs on start up = damage? - kithmo
My 2001 V6 Mondeo does this every morning although not quite as high, only 2500 rpm. Apparently it's normal as part of the emission controls.
Reply | Report as offensive | Link
Sat 10 Jan 2004 06:11
Instant high revs on start up = damage? - Roger Jones
I guess this is all consistent with the advice I have found in all the handbooks for the cars I have driven: start up and get moving, don't let the car sit with the engine idling cold. But initial engine speeds beyond 1500 rpm do seem a bit excessive. I imagine that your suite of five fleeting start-ups was an aberration. If it wasn't, I feel sorry for the car.

As for neighbours who gun the throttle in the early morning, I'd be inclined to complete the circuit to their brains by way of a pipe from exhaust to passenger cabin. One of my neighbours has a car with 17 doors -- or, at least, that's how many slams I woke up to one morning.
Reply | Report as offensive | Link
Sat 10 Jan 2004 19:33
Instant high revs on start up = damage? - Cliff Pope
If the car has the correct oil filter with a non-return valve, won't oil pressure be virtually instantaneous?
Reply | Report as offensive | Link
Sat 10 Jan 2004 20:55
Instant high revs on start up = damage? - Ben {P}
Dont worry about it- loading on the tappets and cam are highest at idle.
Reply | Report as offensive | Link
Sun 11 Jan 2004 07:05
Instant high revs on start up = damage? - Cliff Pope
Dont worry about it- loading on the tappets and cam are
highest at idle.


Can you explain that Ben? I thought the stress on the timing belt was highest at high revs. That would suggest to me that the effort required to turn the camshaft increases with speed. The resistance to turning the camshaft surely comes from lifting the valves?
Reply | Report as offensive | Link
Sun 11 Jan 2004 09:06
Instant high revs on start up = damage? - DL
No, it's the other way around Cliff. When a new camshaft and followers are fitted, the engine MUST be run immediately to 4000rpm to assist the bedding process. This is because the loadings are so high at low revs.
--
groups.msn.com/honestjohn - Pictures say a thousand words..... Reply | Report as offensive | Link
Sun 11 Jan 2004 16:17
Instant high revs on start up = damage? - SjB {P}
As an aside, I have since found out that in 1999, Volvo switched from hydraulic to solid lifters in their five pot motors, so my 2003 2.4T is so equipped!

I was amazed to learn this fact, in the de-rigeur world of low maintenance engines.

Interestingly, there is no mention of a valve clearance check or re-shim in ANY of the scheduled services according to the detailed list in my handbook.

As another aside, given that there were no valve lifters to pump up, I'd love to know what made the fearsome clatter, and why it faded to silence over a two or three second period, consistent with oil pumping.
Reply | Report as offensive | Link
Sun 11 Jan 2004 17:12
Instant high revs on start up = damage? - Cliff Pope
No, it's the other way around Cliff. When a new camshaft
and followers are fitted, the engine MUST be run immediately to
4000rpm to assist the bedding process. This is because the loadings
are so high at low revs.


So reving a diesel engine during an MOT does not in fact place extra stresses on the timing belt, contrary to popular belief?
Reply | Report as offensive | Link
Sun 11 Jan 2004 17:51
Instant high revs on start up = damage? - DL
Yes, of course it does, but the stresses are greater at low speed (cranking speed) as there is no inertia acting on the valvetrain.
--
groups.msn.com/honestjohn - Pictures say a thousand words..... Reply | Report as offensive | Link
Mon 12 Jan 2004 08:46
Instant high revs on start up = damage? - Cliff Pope
Sorry, say that again. The stresses are greater at low speed, but reving the engine places greater stresses?

The stress on the timing belt arises from the resistance from turning the cam shaft?
Is that resistance greater
a) at low speed
or b) at high speed, as in an MOT test ?

Or are we talking about different stresses?
Reply | Report as offensive | Link
Mon 12 Jan 2004 15:28
Instant high revs on start up = damage? - Ben {P}
Deisel test requires engine to be run to rev limiter. Starting a car and reving to 3k is very different.

I think the stress is greatest on the belt when you are accelerating the drive train very quickly- ie unloaded. Reving the engine to max rpm with it loaded i believe puts less stress on the belt than unloaded.
Reply | Report as offensive | Link
Mon 12 Jan 2004 15:30
Instant high revs on start up = damage? - Ben {P}
the cam shaft doesnt lift the valves, it pushes them open. Valve springs close the valves. More inertia in cam = less reaction through cam belt.
Reply | Report as offensive | Link
Mon 12 Jan 2004 20:28
Instant high revs on start up = damage? - SjB {P}
Back to the thread: I am pretty damned sure that it *was* the five successive cold starts of a few seconds each, with only use of the idle circuit to drive the car, that caused the problem.

In the interests of an experiment, and with similar weather, I repeated the five starts over the weekend. Each time the engine was run for no more than twenty seconds, and the throttle was not touched. Each start was also long enough apart for there to be next to no residual heat left in the engine. The car was then left to stand for several hours.

What happened on the sixth start?

Yup, revs going skywards, though quickly switching off the engine and restarting only triggered 'normal' starting revs.

Looks like it really was simply an aggressive regime in the anti emissions code, as thought.
Reply | Report as offensive | Link
Mon 12 Jan 2004 23:17
Instant high revs on start up = damage? - Ben {P}
Did i get it right about the cam belt then- im not 100% sure , but i think thats right.
Reply | Report as offensive | Link