New clutch - jumpy throttle when starting

[atownusa]

I just got the clutch replaced (it needed it) in my '89 911.

There is an odd issue, however. When letting the clutch out quickly (for a quicker start) the car gets very jumpy, almost stuttering, before smoothing out and taking off. This is only when letting the clutch out quickly. It happens mostly in first gear, but I have also gotten it to happen once or twice in second, again, when attempting to accelerate quicker and letting the clutch out quickly.

Obviously the clutch was what was replaced, so that's the likely culprit. However, if I didn't know what work was done, I would have guessed a fuel/oxygen issue as it feels more like it not getting a smooth supply.

Any ideas on this magical challenge?

[stownsen914]

Anything different about the new clutch vs. old? I.e. different pressure plate, same style clutch disk, etc.

[john walker's workshop]

Did they replace the flywheel along with the clutch assembly? It's part of the clutch assembly. Shudder can happen when a partial job is done, like disc only or using the old flywheel.

[proporsche]

as John said about the replacement.....
This would help-let`s see your repair order -no names needed...
Ivan

[atownusa]

The flywheel was resurfaced and it should be full replacement of OEM clutch kit. I'm attaching the work order that was done.


https://www.dropbox.com/scl/fi/tr709bg8pbz4o1nrzszyw/clutch-work_Redacted.jpg?rlkey=htjae6igo3a7o97g1k5ys3r12&dl=0

[kevbo]

Had the same issue and it was a bad "new" o2 sensor. put the old crusty one back in and it was fixed.

[john walker's workshop]

I gave up on resurfacing flywheels years ago. New only now. Depending on who does it and how accurate their grinder is, it's hit or miss.

[proporsche]

i am blown away with the prices? just the guide tube for $150?...basic cost is 50.
Looks like they did not do the update to your cross-shaft for fork,they used the old style bearings?
What is the clutch kit with R/B..anybody knows?
Regular price is $750
the prices are besides the problem point here..

This 911 should have rubber clutch disc , did they used the regular spring disc??....the quality of these sachs kit are lately questionable.The spring disc makes a lot of noise in the car but if it is a crappy made, that could be the problem.
As stownsend914 said above....
one more thing, are the nuts of the trans-to the engine tight?

Ivan
rubber disc
https://www.europaparts.com/media/catalog/product/cache/abf26066ecd46d435ee2486b4a5aee03/9/5/95011601252.jpg

[pmax]

Originally Posted by proporsche

i am blown away with the prices?

From our host though it includes the slave cylinder ...

Looks like they did not do the update to your cross-shaft for fork,they used the old style bearings?
What is the clutch kit with R/B..anybody knows?
Regular price is $750
the prices are besides the problem point here..

This 911 should have rubber clutch disc , did they used the regular spring disc??....the quality of these sachs kit are lately questionable.The spring disc makes a lot of noise in the car but if it is a crappy made, that could be the problem.
As stownsend914 said above....
one more thing, are the nuts of the trans-to the engine tight?

Ivan
rubber disc
https://www.europaparts.com/media/catalog/product/cache/abf26066ecd46d435ee2486b4a5aee03/9/5/95011601252.jpg

Cross shaft ?

[proporsche]

Originally Posted by pmax

From our host though it includes the slave cylinder ...







Cross shaft ?

yes ,old style cross shaft
.. they did not update it and used this kind

up date kit is usually done when doing clutch job
https://www.pelicanparts.com/More_Info/101518090.htm?pn=10-1518-090-M157&SVSVSI=911M&DID=3008

[atownusa]

Thanks all for the replies. Just wanted to update the post with the final work done which include replacing the temp sensor and oil line.

https://www.dropbox.com/s/nldzght3bpf7n12/Screenshot%202024-03-29%20at%2012.08.27.png?dl=0
https://www.dropbox.com/s/7dl5uupv3ivtnni/Screenshot%202024-03-29%20at%2012.08.37.png?dl=0


Prices are high to me too, and I wish I trusted myself to do the work, but alas I don't have the skill! I price compared a bit with reputable shops and this was inline with others.

So working theories and things to check:

1. Resurfacing flywheel - I haven't heard any issues around about this and shop knows what they are doing, but will still check. Anyone else had issues with this?
2. Bad O2 sensor
3. Ensure rubber clutch disc like original
4. Update cross-shaft instead of standard
5. Check nuts are tight from trans > engine

I will be heading to shop today or Monday so all the ideas/fodder I have is very helpful. Thanks!

[kevbo]

I'd be remiss if I didn't mention that replacing my 02 sensor didn't fix my surging problem in 1st and 2nd. After I tested and cleaned my idle control valve my cold start and surging went away.

https://www.youtube.com/watch?v=MRZG-s_55CU
Forward to 8:52..

This is an easy thing to test yourself. Franny does a great job of making this stuff easy.

[pmax]

Originally Posted by atownusa

Thanks all for the replies. Just wanted to update the post with the final work done which include replacing the temp sensor and oil line.

https://www.dropbox.com/s/nldzght3bpf7n12/Screenshot%202024-03-29%20at%2012.08.27.png?dl=0
https://www.dropbox.com/s/7dl5uupv3ivtnni/Screenshot%202024-03-29%20at%2012.08.37.png?dl=0

Prices are high to me too, and I wish I trusted myself to do the work, but alas I don't have the skill! I price compared a bit with reputable shops and this was inline with others.
...

What's the breakdown for the labor charge and how many hours does each line item translate to ? I was wondering if you were charged the book or actual time for the engine drop for instance.

Originally Posted by atownusa

1. Resurfacing flywheel - I haven't heard any issues around about this and shop knows what they are doing, but will still check. Anyone else had issues with this?

Pay special attention to what JW (and Ivan) said prior. Saving the extra $1K or so is understandable but ...


... how are you able to check unless you remove the flywheel and have it independently measured ? I think that's the risk tradeoff here. Given what they experienced, I'll wager that one is better off reusing the flywheel as is, in other words vs one with a possibly botched resurfacing job because the latter means the flywheel is likely toast whereas the former means it is at worst the same as before.

[atownusa]

Originally Posted by kevbo

I'd be remiss if I didn't mention that replacing my 02 sensor didn't fix my surging problem in 1st and 2nd. After I tested and cleaned my idle control valve my cold start and surging went away.

https://www.youtube.com/watch?v=MRZG-s_55CU
Forward to 8:52..

This is an easy thing to test yourself. Franny does a great job of making this stuff easy.

In the video, this is if idle is surging so to me it doesn't seem like this is the issue as the surging ONLY happens when releasing the clutch quickly. That's my hunch, but feel free to disagree.

[atownusa]

Originally Posted by pmax

Pay special attention to what JW (and Ivan) said prior. Saving the extra $1K or so is understandable but ...


... how are you able to check unless you remove the flywheel and have it independently measured ? I think that's the risk tradeoff here. Given what they experienced, I'll wager that one is better off reusing the flywheel as is, in other words vs one with a possibly botched resurfacing job because the latter means the flywheel is likely toast whereas the former means it is at worst the same as before.

I will definitely investigate this as primary culprit, thanks!

[kevbo]

Originally Posted by atownusa

In the video, this is if idle is surging so to me it doesn't seem like this is the issue as the surging ONLY happens when releasing the clutch quickly. That's my hunch, but feel free to disagree.

I hear ya. I relate this to going to the doctor with a symptom and with a hunch as to what the issue is only to find out it was something else. My flywheel was resurfaced too, new fuel lines, new vacuum lines, new plugs, new gaskets and spacers on the manifold, etc etc. For some reason that idle control valve not functioning properly caused surging in 1st and 2nd under load.

I removed that valve, cleaned it tested it reinstalled it. Boom.

I’m learning too. These machines are engineering puzzles - great hobby

[john walker's workshop]

The clutch shudder issue became an enging surge issue somehow. Which is it?

[atownusa]

Originally Posted by kevbo

I hear ya. I relate this to going to the doctor with a symptom and with a hunch as to what the issue is only to find out it was something else. My flywheel was resurfaced too, new fuel lines, new vacuum lines, new plugs, new gaskets and spacers on the manifold, etc etc. For some reason that idle control valve not functioning properly caused surging in 1st and 2nd under load.

I removed that valve, cleaned it tested it reinstalled it. Boom.

I’m learning too. These machines are engineering puzzles - great hobby

Ha, yes! OK, that's more clear, thanks for that.

Yeah, the odd thing is it's just when the revs drop a bit low and letting the clutch out quickly. If I do a little throttle blip to start and match revs a bit, it's clean.

[atownusa]

Hey all, looks like IT'S SOLVED!

Turns out that it was just a loose 4 pin connector to the fuel pump. We were able to replicate the problem, tighten the connector and all is running smooth as butter.

I'm grateful for all the helpful ideas here and thankful it was something so simple (and not a botched resurfacing).

[kevbo]

Awesome! Congrats.