Momentary loss of power

[dgbalfour]

Hi all,

I have owned my 1998 2.8 since March and I think it's a fantastic car. However, I wondered if anybody could shed some light on the following:

Recently the car has had an instant, but very short, loss of power. This has happened five or six times in the past 3000 miles or so and has occurred at many different speeds from about 30 to 70.

The funny thing is how severe this feels - it's almost as if the brakes have been applied very hard for a split second. There are no warning lights on.

I've been wondering whether it's the ASC, so I've tried driving with it off and haven't yet experienced a cut out.

Any ideas what I should be looking for, or what to replace first?

Many thanks,

David

[Justin Time]

Irrespective of the speed you are going, what gears does it occur in, and at what revs?

[dgbalfour]

Thanks for the reply.

It doesn't seem to matter what gear I'm in, I've had it happen in 3rd, 4th and 5th. The revs are probably around the 3 to 3.5k mark at a guess - I'll pay more attention to this one though.

[aj2007]

I'd get the diagnostics checked for fault codes, could give you a better idea of the culprit sounds like bad connection or sensor?

Ade

[Guest]

It sounds like low fuel pressure, due to the fuel pressure regulator not responding instantly when the throttle is pressed. Find a road with a deep dip in it - down and then up hill - go down with no throttle, then accelerate up the hill, and see if the problem returns.

I had this problem on my BMW K100 motorcycle, which uses a similar pressure regulator, controlled by inlet vacuum.

[SpunkyM]

Change the spark plugs before you do anything else (could be coil pack too if it has 1 per cylinder, not sure on your engine).

[Guest]

Coils are a pretty doubtful cause, as there is one per cylinder - you would need a few to fail at once for this symptom - and likewise if it were plugs.

[pop_sausage]

Coils are a pretty doubtful cause, as there is one per cylinder - you would need a few to fail at once for this symptom - and likewise if it were plugs.

I've had 1 coil fail and give me these symptom on a 3.0l - or at least that's what the garage told me they replaced.

[dgbalfour]

I'll get the fault codes checked - I'm thinking of buying something to do this myself, can you recommend anything? My previous car was a 1977 Triumph, so I never needed anything electronic!

When I say it's a momentary loss of power, it really is a tiny fraction of a second. It doesn't feel like fuel starvation or the throttle snapping shut, it's a significant jolt that's sent through the car when it happens. We're talking the sort of time period of a single hand clap! Hence why I'm suspecting the brakes are being applied, but a diagnostic tool should help.

I will try that fuel pressure test though, just to eliminate it.

Thanks again.

[Justin Time]

Autologic provide systems to link up to your car. Have a look at their site.

[SpunkyM]

Definitely sounds electrical to me, but plugs does tend to me more of a prolonged splutter / missing at peak torque when you put you foot down (3-5k rpm).

you would need a few to fail at once for this symptom - and likewise if it were plugs.

..that's exactly what happens when the plugs reach the end of there life mike as the gaps tend to increase pretty much similarly to each other. The spark gets extinguished at and around peak torque.

Similarly if a single coil fails you get unburned fuel passing the lambda which the ECU objects to and cuts ignition. I would expect a fault code for that though.

[Guest]

Good point - I'm still thinking back in the Good Old Days! So much for progress . . .

[Gazza]

Or maybe it's Air Mass Sensor as recently happened to me