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996.1 engine woes

Haalex

New member
Joined
6 Jul 2023
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45
Hey guys,

I mentioned this issue in my introduction post, but this section is probably a better place to discuss it.

I recently acquired a 996.1 with a smidge over 40k mile, late 98 build. For peace of mind, I elected to have the IMS & clutch replaced immediately after purchase. IMS was a dual row in perfect condition, so not sure this was very useful.

Shortly after my purchase, the car developped a massive ticking noise which turned out to be a stuck lifter on bank 1, that "sorted itself" with an oil change. The car pickup, transportation, labour, oil and filter were all taken care of by the shop that did the IMS, as they felt it was the right thing to do on a car that had an issue shortly after leaving their premises.

In the following 3-4 months, I drove the car for another 800-900 miles, and noticed it was sometimes a bit shaky on idle, and had a light cold start tick that would go away within a minute. No oil consumption, codes, it had good power delivery and got around 25mpg. Then, all of a sudden (and, as irony would have it, right as I was driving to pick up supplies to make a 911-shaped wooden toy car for my child), driving 50mph on an off-ramp, I downshifted into 5th and cylinder 2 stopped firing. Limped the car home (which was close), check codes, of which it had P300 + P302, tried to swap coils (to no avail), and had it flatbedded to the shop that did the IMS. They found an exhaust valve on cylinder 2 isn't closing all the way, and some traces of water in the oil in that cylinder.

The engine is slated to come out in the next couple of weeks. The head mechanic hopes the issue can be solved without removing the head, which I doubt.

This was a seldom driven car before I acquired it (6k miles in 10 years), so I think my more frequent and taxing use might have awoken an existing issue.

Does this sound familiar to anyone here? Any advice / opinion?

I'll keep you posted as I get more info.

Alex
 
hey Alex
welcome to the forum
how soon after the rebuild have these issues surfaced ? and who did the work
 
hey Alex
welcome to the forum
how soon after the rebuild have these issues surfaced ? and who did the work
Has it had a rebuild? OP hasn't said that.

Personally, I'd guess at messing around doing the IMS in situ has caused an issue on bank 1, either jumped a tooth or broke the chain tensioner guide..........hence why the like of Hartech and any decent outfit wouldn't go near replacing the IMS bearing in situ. Being cynical, that's why the place that's done the IMS bearing are covering all this work. Good luck resolving it.
 
Misread the rebuild

To the op, low mileage aside, with what is a 24+ year-old engine age will still be a factor
 
The engine hasn't had a rebuild that I'm aware of. And being it still had a dual row IMS, I'm pretty sure it's on its original engine. Also, FWIW the car was under PA for the first 10 years of its life.

I agree I wouldn't do the IMS again were I given the choice. Live and learn. That being said, I'm not sure messing around with it could have led to this issue.

I was also hoping it would be a timing issue, but only one of the exhaust valves on cylinder 2 isn't closing. So that pretty much rules out timing or Variocam issue.
 
Last edited:
Hello and welcome -sorry to hear about your issues, hope they get resolved with minimal expense.
 
Lee Jenkins (Chief engine rebuilder at Hartech) posted this on facebook a couple of weeks ago:

1708615650642.png
 
Cracked head seems a possibility though I struggle to see how it could prevent the valve from closing. Unless the crack extended to the valve seat? Also, cracked head is supposed to be strictly a 00-01 thing, and this car is a late 98, which apparently don't suffer from the issue.

The IMS was changed with the engine out, FWIW. And since the issue appeared all of a sudden, 1 000 miles later, and since the car had good power before (170+ on a short stint on the Autobahn), I'm still not sure how it could be linked to bad IMS work (yet). Unless I'm mistaken, the issue showed by Lee should have been -noisily- apparent on first startup.

The shop just told me they've pulled the engine yesterday and will remove the cam cover Monday, so I should know more shortly.

Provided that engine isn't a clusterf*ck, what are the while-you're-in-there's I should consider? AOS is on the list, oil cooler & pipes are recent, I was thinking of having them check the starter cables and engine / Gbox mounts. Also the DMF as I had doubts about its health. Clutch's new, so I don't need to change it.

Anything else?
 
Engine in / engine out, same thing - it's still done in situ, i.e. extracting the bearing from the engine, rather than stripping the engine, removing the shaft and removing the bearing from the shaft on the bench. Doing it in situ means you have a likely possibility of damaging or moving anything connected to the shaft, so chains, chain guides, sprockets. Once something moves or gets damaged, the valve timing on that bank can change. Bank 1 valves are driven by the ims bearing end of the shaft. If anything goes wrong doing the bearing, it wall virtually always be bank 1 valves that suffer. Yes it could be a coincidene, but I know many would hedge their bets on it being related.
 
Hey Alex,

I get what you're saying, but this scenario would affect all valves on a cam, wouldn't it? And in this case it looks like only one of the six exhaust valves on bank 1 isn't closing. Which, to me (and the shop) rules out timing.

So far my indie thinks it's a broken valve spring. I had my money on a bad lifter but can't fathom how it would prevent a valve from closing. Broken valve seat is another contender.
 
Not sure. I get what you're saying and that would be the case when running, but if the cam wasn't locked when they did the job and somethings moved during the extraction of the bearing, whether it's possible for a piston to be at TDC and the cam has turned slightly pressing the valve against the piston? I suppose all will be revealed once its opened up.

Sorry, I'm not meaning to be negative toward you problem but just off experience, coincidences are far too familiar on here after someone's had some work done.
 
So I just received some pictures from the shop, and the cause it NOT what I expected...

Apparently, someone had mounted the exhaust gasket on bank 1 the wrong way around which led to some of the gasket protruding in the exhaust channels. With time, heat and airflow, those protruding bits tore off and got sucked back into the cylinder, where in this case the bit lodged itself firmly between the valve seat and exhaust valve.

Interestingly, this happend on all three cylinders but only #2 seems to have gotten its gasket piece stuck into the valve.

The head surface is a little worse for wear, but nothing terrible. Cylinders seems intact and so do the valves.
 

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