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[Morrie]

Driving to work, hard acceleration and bumped up against the rev limiter in 2nd gear at about 5500, backed off and upshifted.

Immediately noticed what at first felt like a miss, like the engine was running on 3 cylinders. Car accelerates fine above approx 4K rpms. feels rough from 2k to about 3K at highway speed or idle. Pulls strong at high RPMs and feels normal. Idle seems okay, but was quite rough when cold, more than usual. Once warm it felt fine.

Clutch was done about 2K miles ago, spring center, all new parts, professionally installed and under warranty.

Any thoughts? I am guessing an engine mount? Or maybe hoping is a better word for it.

Morrie

[Rasta Monsta]

How many miles on the car? Have you done a vacuum refresh?

My initial vote on this is vacuum leak. . .AOS, lines, etc.
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[fiat22turbo]

Especially after hitting the rev limiter. You could have spiked the vacuum system and the weakest link may have popped.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Morrie]

Interesting. It is definately in need of a refresh of the vacuum lines. I am short on time and it may need to go into the shop for this. I will have about 10 minutes to check it out in the morning and do have a vacuum gauge. If I pull a line what should happen, and what should I see for numbers at idle, and so on.

THANK you for the responses guys.

Morrie

[edredas]

+1 on what they said above...

However, if it ran fine once the engine warmed up, it could also be the O2 sensor. Try unplugging it first before getting the engine warm and take it out on the road. If it makes a difference, replace it.
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'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

[Morrie]

After checking the obvious, the car went to my favorite local shop. They say that they can depress the valve on #3 with a finger so the head is coming off and going to the machine shop for inspection. Car has approx 120K on it.

Any advice, comments, direction, etc is appreciated. I am used to working on pushrod motors only so overhead cam issues are a new thing for me. Also, if I have the head done, what else should I do while I am in there...

I will know more on Tuesday or Wednesday morning. Unfortunately, I really like this car so scrapping it out is not an option. Still got to be cheaper than lease payments on a new one!

Thanks!
Morrie

[fiat22turbo]

The only difference between a pushrod motor and an overhead cam motor is that the cam has to actuate the valves via pushrods and rocker arms..

Sounds like the valve spring broke, which happens on pushrods motors too. Replace all the valve springs (to be safe), check the seat pressure, valve heights and valve seats. Replace anything else questionable.

Of course the front of the engine will be serviced since it is apart.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[Morrie]

So the reason why its not hitting the piston is that the broken spring is still closing the valve but not with sufficient force to seal it. Correct?

The front end service was done 10K miles ago. I am thinking that in this case the water pump can probably stay but a new belt and adjustment made.

Is this worth getting a rebuilt head or going over the whole head? I am thinking that if it looks okay just do what you said and then reassemble. Compression and leakdown were all in spec before the issue. No racing, it is my daily driver.

Thanks!
Morrie