New clutch - jumpy throttle when starting
 

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?

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

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.

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

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/tr709...1k5ys3r12&dl=0
https://www.dropbox.com/scl/fi/tr709bg8pbz4o1nrzszyw/clutch-work_Redacted.jpg?rlkey=htjae6igo3a7o97g1k5ys3r12& dl=0

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

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.

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

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

http://forums.pelicanparts.com/uploa...1711146464.jpg

http://forums.pelicanparts.com/uploa...1711145587.jpg


Cross shaft ?

yes ,old style cross shaft
.. they did not update it and used this kind
http://forums.pelicanparts.com/uploa...1711147646.jpg
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

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!

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.

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.

Pay special attention to what JW (and Ivan) said prior. Saving the extra $1K or so is understandable but ...
http://forums.pelicanparts.com/uploa...1711753306.jpg

... 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.

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 will definitely investigate this as primary culprit, thanks!

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

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

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.

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).

Awesome! Congrats.

NEW issue?
 

I'm hearing what sounds almost like debris when the clutch is being engaged (in gear). I think it's a bit worse when cold, but can't be certain as I hear it most when the sound is being echoed off walls or in the garage.

Mechanic said that it could be new style of clutch vs. the old, but I'm feeling like something is amiss here. Normal, abnormal, red flag?

Here's a video to hear what I'm hearing: https://www.dropbox.com/scl/fi/268dcel8dxzqm95pevgaq/IMG_8243.mov?rlkey=x71d0uaqliatz2zx6idnn9hos&dl=0

I just did mine a few months ago and it doesn't make sounds like that - I didn't use a performance upgrade tho. Sounds like there is something loose or loose material in there. Maybe a defective part. Odd

Thanks for the info. Do you have the part number of the clutch kit that you used?

For my 1986: Part#: 915-116-911-00-M38 from our host.

I had my flywheel resurfaced by a trusty air-cooled shop and I bought new bolts all around (not supposed to re-use old bolts).

Just to close this case out (and help anyone in the future)... turns out that a flywheel bolt head had broken off and was rattling around in there. See pic attached.

Not sure if it's a freak happening or if it's an installation mistake, but hopefully it's smooth from here-on-out!http://forums.pelicanparts.com/uploa...1729718620.jpg

good find..either wrong torque on installation or old bolts.Have you replace the others?
Ivan

Clutch shuddering --> Flywheel issues --> O2 sensor --> idle valve --> Loose connector on fuel pump.

Did we go around the world?

That is an installation fault BY THE MECHANIC. During installation of the flywheel, if there is any doubt, you always use new bolts. Some people / mechanic out of sheer laziness would use impact wrench on the bolts and stress them to the point of breakage.

I know that SC and Carrera flywheels bolts are supposed to be re-use-able. But, really, when it's that deep in the belly of the beast, just spend the $20.

My machine shop now charges $300 to grind a flywheel, and I have to wait a week. Between that and $600 for a new flywheel, I would just buy new and be done. Get the car off the lift, and on to the next.