What is wrong with my car? Help!

[JR Hartley]

This may not be the best place to ask but atleast you get a fast response.

I have a classic Subaru Impreza turbo, went along the motorway and in 5th gear, when i go over a certain speed it's almost like the engine stops and i jolt forward in my seat like i have jabbed the brake pedal. This only happens for about a second, then when i back off abit it runs smoothly again.

So i thought they may be some kind of limiter on it, but it happened again later at slower speeds in 2nd and 3rd accelerating

I do not have a clue what is going on and would greatly appreciate any help!?

[Dave_]

Hard acceleration?

Fuel cut possibly.

[Flintstone]

More details? For how long has it been doing this? How often does it happen? Had any work or modifications done recently?

[sunbeam_alpine]

If it also happened in 2nd & 3rd, does it happen at the same revs, rather than speed?

Please post as much detail as possible.

[JR Hartley]

No work or modifications done recently. It has only done it once in 2-3rd gear, it is only really consistant when i am on the motorway and reach a certain speed. Roughly around 4000-4500rpm not even under heavy acceleration?

[JR Hartley]

sunbeam_alpine said:

If it also happened in 2nd & 3rd, does it happen at the same revs, rather than speed?

Please post as much detail as possible.

Thinking about it, it may be roughly around 4000-5000rpm when it happened

[mybrainhurts]

It's got the Heaves...

You need turpentine...

[Don1]

Is it around 112mph? It's a Japanese import and you have the spped resrictor on it still.

[rottie1972]

Hi had the same thing happen on my old one, when it happens it feels like a speed limiter being hit, rather than a rev limiter. Sorry I cant remember exactly what the fault was. When I explained the problem to the dealer, they knew what was up,seem to recall a valve was clogged and needed cleaning, and it was a quick and cheap fix.

[JR Hartley]

Don1 said:

Is it around 112mph? It's a Japanese import and you have the spped resrictor on it still.

No it's not 112, happens at 95mph on a private airfield

[mybrainhurts]

Is your book stuck under the accelerator...?

[JR Hartley]

mybrainhurts said:

Is your book stuck under the accelerator...?

If only it was that simple!

[Ricky_M]

Worked with a bloke who had a similar-ish problem with an Impreza turbo. Rough idling and running, he seems to think it was the airflow sensor.

[Jebi]

I take it that will probably have coil packs?

[carl_w]

Is it modified in any way? Sounds like you're hitting the boost limiter.

[JR Hartley]

carl_w said:

Is it modified in any way? Sounds like you're hitting the boost limiter.

Just has a Blitz exhaust and Bailey dump valve as far as i know!?

[Waugh-terfall]

carl_w said:

Is it modified in any way? Sounds like you're hitting the boost limiter.

This, or maybe the MAF sensor?

[carl_w]

JR Hartley said:

carl_w said:

Is it modified in any way? Sounds like you're hitting the boost limiter.

Just has a Blitz exhaust and Bailey dump valve as far as i know!?

Is that a vent-to-atmosphere dump valve? Can cause no end of confusion to the ECU when it dumps metered air. ECU thinks it's getting x amount, but y amount has already been dumped.

[JR Hartley]

carl_w said:

JR Hartley said:

carl_w said:

Is it modified in any way? Sounds like you're hitting the boost limiter.

Just has a Blitz exhaust and Bailey dump valve as far as i know!?

Is that a vent-to-atmosphere dump valve? Can cause no end of confusion to the ECU when it dumps metered air. ECU thinks it's getting x amount, but y amount has already been dumped.

Yes i think it is. What is happening if i'm hitting the boost limiter and can anything be done?

[MMTWRX]

I have WRX and it was doing this and it was the MAF. Expensive to replace, about £300 I think, but has been fine since.