Not as good at 911s as I thought - need some coaching on what next (please)

[tdskip]

So i ended up buying that 1974 Carrera Targa that you all helped me with How special is a 1974 Targa Carerra?

It wasn't running properly but I used my extensive 2.7L and CIS knowledge (just kidding, I'm a 2.7L and CIS moron, keep reading) to make a leap that the car was solid but was suffering from deferred maintenance on the CIS system and had a bad WUR or cold start or one or more bad injectors based on the work that just been done to it and the symptoms I was seeing.

Turns out I was partially right and mostly wrong: despite being new the fuel pump was only working intermittently. With a new correct Bosch pump installed and a new Accumulator it now starts easily and I believe I have a healthy CIS system.

What I got wrong is that despite not smoking I have low compression in #6, like 80 PSI. Everything else is dead even at +/-150 PSI. I've asked the shop I use to adjust the valves and do a leakdown but this is obviously a bit concerning.

Now as a reminder this car sat for 10+ years so there is a little back corner of my brain suggesting that I not jump off a bridge yet as it might improve due to the rings loosening up and any carbon deposits that have harded on the valve seats moderating.

I was hoping to get your thoughts on just running it for a couple days and heat cycling the engine before making any further decisions. I don't believe that will do much more harm, but that may just be an irrationally optimistic part of my brain talking again.

Thanks!

[Locker537]

I agree with your thinking. Drive it hard after ensuring everything else is safe.

[tdskip]

Originally Posted by Locker537

I agree with your thinking. Drive it hard after ensuring everything else is safe.

I've got brakes (new fluid, old was surprisingly not skunked) and steering is fine, so think I'm OK to get on it?

[Gianni at Pelican Parts]

Hey tdskip,

Do not get discouraged!

If you haven't found them yet, we have a whole section of the site dedicated to "How To" Tech Articles which should be helpful for future projects.

[75 911s]

drive it for a while. Do the next valve adjustment yourself.

[Bill Douglas]

TD, just food for thought...

If the valves have been adjusted onto carboned up valve seats they won't be closing properly. Once the carbon is gone they will be way to tight and compression will be lost through the gap.

I think a good game plan would be a thoroughly good Italian tune then a valve adjustment on #6

Good luck!

[tdw28210]

Italian tune = go drive the snot out of it.

[NYNick]

Wait, people telling you to drive the loving crap out of a 911? Who could resist THAT advice?

[pampadori]

Adjust valves and pay particular attention to headstuds near cyl with low compression.

[tdskip]

Thanks for the encouragement gentlemen, and a special shout out to my 2002tii brother Nick.

It’s dying at stop lights once warm now, so more fuel system sorting to do.

Still very lumpy at idle and under 3500, over that she starts to sing (but know that RPM range is masking the problem).

[thor66]

Originally Posted by tdskip

I've got brakes (new fluid, old was surprisingly not skunked) and steering is fine, so think I'm OK to get on it?

yes, probably

does it have fresh fuel in it?

[fanaudical]

Here's where I would start:

- Verify tires and brakes are good.
- Empty the fuel tank, get fresh fuel, and replace the fuel filter.
- Verify no vacuum leaks or leaky air box.
- Get a CIS pressure gauge set and verify your cold and warm control pressures and system pressure.
- Check cap, rotor, and plug wire conditions. Run it at night with the lid open and look for arcing.
- Verify plug gaps and condition.
- Any ticking noises near #6 when running?
- Italian tune-up.
- Check leak down when cold.
- Check compression.
- Valve adjustment and check head studs as suggested.

[tdskip]

Thanks for all of the ideas and considerations.

She does have only fresh fuel in her at this point, new spark plugs and wires all tested as good.

Tires are out of round from sitting so long, need to double check rim fitment to see if the Fuchs I have on hand will fit properly so I can’t get good rubber on her.

The shop did do a wet compression test and #6 came up to +/- 180 so sure seems like ring(s) based on that, no?

[Joe Bob]

Can of sea foam in the gas?

[tdskip]

Originally Posted by Joe Bob

Can of sea foam in the gas?

Thanks for the response and idea.

Except for the wanting to die at a stop I think I've got a healthy fuel system at this point, I think my big issue is the testing pointing to bad ring(s) on #6 as the wet compression test seems to suggest.

What do y'all think?

[Hi_Fi_Guy]

Sea foam or or Marvel Mystery Oil can work wonders on the top-end of these old engines if they have set for a while. Can it cure a real problem? No, but it can help you identify if you actually have a real problem or not.

[Joe Bob]

After Sea Foam an oil change is recommended as the douche crapola goes in the oil.

[tdskip]

Good morning and happy weekend all.

So the Seafoam / MMO idea is to loosen up any crud and see if it will possibly unstick the ring issue I have I take it. Thinking is that worst case is I’m in it for the additional oil change and cost of treatment?

If that does not do it then, given that it is a 2.7L, looks like I’m on a slippery slope to a full rebuild?

Thanks!

[NYNick]

What's up Skip?
I have a tendency to think the worst when stuff like this happens. Get the Seafoam, drive the snot out of the car once or twice and then change the oil to get all the crud out of it. Then retest the compression.
BTW, driving the snot out of it isn't a 10 minute deal. You want that baby fully hot. 30-45 minutes or more of excitement should do the trick. Twice maybe.
Fingers crossed.
(BTW, I bought an M2CS. My gawd what a car!)

[tdskip]

Originally Posted by NYNick

What's up Skip?
I have a tendency to think the worst when stuff like this happens. Get the Seafoam, drive the snot out of the car once or twice and then change the oil to get all the crud out of it. Then retest the compression.
BTW, driving the snot out of it isn't a 10 minute deal. You want that baby fully hot. 30-45 minutes or more of excitement should do the trick. Twice maybe.
Fingers crossed.
(BTW, I bought an M2CS. My gawd what a car!)

Congratulations! I bet the M2CS is a total hoot, well chosen Nick. Instant modern classic.

Might be tomorrow but I will run her hard and report back...

On the 3.2 there is a microswitch that helps control idle when the throttle is lifted, don’t think the CIS works the same way as the microswitch I am aware of is activated by the cold start handle, right?

Any idea on what the dying at stop light issue may be caused by?