notfastenough

Valve lift control #4. Engine runs good but throwing this code?
Thanks.

Macster

Would be nice to have more details on car: model, miles, etc.

I don't find a P1374 code in my sources.

I do find a P1354: valve lift control, cylinder 4 above limit.

Diagnosis conditions: Speed between 5280 and 6520 rpms. Load between 125 and 190%. Acceleration with wide open throttle. Possible fault causes: a valve does not switch from small lift to large lift. Several valves (various cylinders) do not switch from small lift to large lift.

The diagnosis/trouble shooting requires the use of a PST2 diaagnostics computer which the tech uses to command the valves remain in large lift mode during running the engine and at the same time monitoring the O2 sensors of the two banks to determne if one or more valves fail to switch over to large lift.

I am not familiar with the Durametric system but it may offer access to or support this test.

Sincerely,

Macster.

notfastenough

Sorry. '02 996.
PST2 was used and faults came up when large lift short test was run. P1354 (valve lift control, sum error) also came up.

Macster

Well, if you have access to PST2 you should have access to the very specific steps necessary in order to perform the tests properly/correctly and the 02 sensor readings that are used to determine the presence of a valve lift fault.

Just to cover some high points:

It is possible if one or more intake valves do not remain in large lift mode the engine can run rough mimicing a misfire condition.

Several cylinders may be flagged as bad even though just 1 valve on one cylinder is bad.

Thus, if you are confident of the test results, if you believe the test was executed properly, then the fix is to replace all flat-base tappets of the intake valves on the failing bank.

If the difference between the two cylinder bank O2 sensors is less than 4%, one valve may be faulty on both cylinder banks and then the fix consists of replacing *all* flat-base tappets of intake valves on both banks.

Replacing these are expensive. (I bought one to disassemble and study and IIRC it cost me around $75. But it is a marvelous piece of hardware!) There are 2 flat-base intake valve tappets per cylinder, 6 per bank, 12 per engine, which I'm sure you already know. Flat-base intake valve tappets parts cost alone can be nearly $1000.

In the machine shop we had a saying: Measure twice. Cut once. (Although one machinist bragged he only did jobs that required he measure with a yardstick, mark places to cut with chalk, and then he used a cutting torch to make the cuts. No close tolerance work for this guy!)

In this case, you want to test twice and remove, open up the engine and replace tappets just once. And my sources - for DME 7.8 -- don't give any but you want to be darn sure nothing else can account for the test results. That is that the test results point conclusively to the flat-base intake valve tappets and nothing else.

Best of luck!

Sincerely,

Macster.

peavynation

Holy cow Macster, awesome! I just like reading every single one of your posts, regardless of the problem. It's like reading a manual with every answer conceivable. I hope I never have any hard core issues, but if I do, I hope you're still on the forum to help diagnose mine!!!

OP, keep us posted. I'd like to know the final outcome to your problem.

notfastenough

Broken right bank chain guide bracket.
Will post pics after damage survey is completed.