1988 911 3.2 155k miles CA car from new

[996AE]

New to me

Car is stock

PPI showed good leakdown numbers and compression for 30 year old car with these miles

Issue is wont pass smog CA is brutal

Light grey blue smoke after warm

idle is smooth

I put new oil in, fresh sparks, cleaned air box and new air filter, double check oil level.
Techron and fresh gas. Ran it hard after warm up. Checked plug wires and for vacuum leaks no found.

Starts first click, idle as it should.

Symptom, very occasional pop at idle, light smoke and smog fail is a miss just off idle like its running on 5 cyl. Pulls strong above 3k rpm but hesitates off idle. not terrible but like its under powered or starving for fuel or timing. Plugs looked good coming out.

Thoughts?

[faverymi]

Redo compression and leak down.

Something doesn't add up.

Not the first time I've seen worthless PPI

[996AE]

Yes.

I am thinking about a second opinion.

Hoping it may be a simple item I overlooked.

Shop wants 450.00 for leakdown hoping to avoid that

[76FJ55]

What are the actual smog results? if we can see the numbers we may be able to help direct you towards possible solutions. Just take a pic and upload it if you've got the printout in front of you.

[da Vinci Dan]

Try cleaning idle control valve?

[da Vinci Dan]

https://m.youtube.com/watch?v=MRZG-s_55CU

[996AE]

Ill post the smog numbers later today

thanks for posting the youtube

Cars starts and idles perfectly with little to no smoke on start up only thing at idle is very occassional popping exhaust

[darrin]

Check out this thread and be sure that the brown dme wire is connected --

Failed smog, high NO, help!

[Jdub]

Can the CO2 be adjusted in the Carrera as it can be for the SC? You may have already done this so excuse my ignorance, but this is standard operating procedure for me when going through emissions (always passes well within the spec.).

[autojack]

As a data point, my 1988 car with similar miles, bought from Atlanta and shipped to CA, would not pass smog. The brown DME wire was connected as required. I ended up replacing the cat on the advice of my Porsche mechanic (it was original), and it then passed with flying colors.

[996AE]

Update
cat and o2 sensor are good
car is running rich

I will try to post smog results

I looked for brown wire and couldnt find it

Found brown wire. Its connected.

[996AE]

Second opinion shop time for top end. Likely valve guides. Fouling cyl 3, high hydro carbons wont pass smog.

I'm going to bite the bullet and have top end done. At 155k its time to freshen this ride up. Any suggestions on ARP or for new head studs or __________? Hoping I wont have to touch P&C just do valves...

[Techno Duck]

Post the smog results before you rebuild the top end. Ask the 2nd shop how they came to that conclusion, they better say the spark plug was wet or covered in carbon.

Running rich could be a few things. Bad fuel pressure regulator (or vacuum line to it disconnected), air flow meter CO adjustment out of whack or the cylinder head temp sensor is bad (so car stays in cold start enrichment).

[996AE]

ill try to post results. I have two now. Fresh oil, cleaned airbox, fresh gas, techron, ran it hard 100 mi and had improvements but still high. Car was over filled with oil from original owner. PPI didnt catch that. Not happy with first shop. Second said based on 155k mi and smog results I showed them and how it was running its likely valve guides. Didnt want to keep throwing money at diagnostics so at these miles figured time for top end.

[76FJ55]

Has anyone test the fuel pressure regulator and fuel pressure damper, by pulling a vacuum on the vac line and verifying that the vac holds and that no fuel or vapor is pulled through the diaphragm. if either of these diaphragms are bad the engine will pull fuel under vacuum through the diaphragm and cause a rich condition especially at idle where the vacuum is the highest.

Would be really good to post those results as we are currently all making random guesses on limited info.

[76FJ55]

Originally Posted by 996AE

Didnt want to keep throwing money at diagnostics so at these miles figured time for top end.

So you don't want to throw money at it to diagnose the actually problem, but you're cool with throwing enough money at it to rebuild the top end of the engine, which may or may not fix you problem since you don't know what the problem is?

[Tippy]

Try checking your intake manifolds nuts. They come loose easily. If it pops and stumbles, you might be getting unmetered air.

Just snug them up a little.

The black insulators under the intake deteriorate over time and flake and crumble. Might be a culprit.

[SalParadise]

Guess you should have purchased a '75 or older...

[996AE]

good tips guys thanks

with the fouling plug cyl 3 I am thinking as the two shops are its mechanical valves guides not vacuum leaks or unmetered air.

motor coming out Wednesday

stayed tuned

[996AE]

Originally Posted by 76FJ55

So you don't want to throw money at it to diagnose the actually problem, but you're cool with throwing enough money at it to rebuild the top end of the engine, which may or may not fix you problem since you don't know what the problem is?

Two shops have done leak downs and compression both shops say time for valve job.

Not sure where youre coming from?

Cat good. O2 sensor good, no vacuum leaks, fresh gas, fresh plugs, fouling cyl 3 lots of oil leaks time to refresh at 155k.

Makes sense and as a lay person I am at the mercy of experts.