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First time posting, on my first Porsche! I just bought an 85.0 944 for what I think was a decent price after it had been sitting for 2 years. It's a bit of a project car, but in general seems to run (mostly) well. I live in the CA SF/Bay Area and I am trying to get it to pass Smog. The seller was confident it would pass, but I was a bit skeptical and ran it to Smog directly the next day after buying. No surprise, it did not pass on the NO at both 15 and 25 mph, but otherwise it was passing with really low numbers in all other categories (see below). After that I took it to a reputable mechanic for a PPI. They said it was mostly in ok shape, though it needed new tie rods and the oil pan was leaking a bit. They also noted it had the stock ca which was likely the main reason for my Smog woes. I had the cat replaced with a CARB certified cat at a muffler shop, and changed the oil and filter the next morning and ran it around for about 25 minutes on the highway before going into another Smog test (results below). Good news is that I'm passing at 15 but still failing at 25, though the results are less egregious for both! The technician mentioned that there is likely something else wrong as, even at 15, with a new cat my numbers should be much lower on NO.
I'd appreciate any tips you guys may have based on my numbers. I'm new to this, but from what I've been reading here, I figure my next step may be to replace the O2 sensor and spark plugs? Am I on the right track? Is there any other non-major work I can go through before taking it in for another test? Thanks for the help!
I agree with V2Rocket that the engine is running lean. I question an exhaust leak but could have air leaks between downstream of the throttle body to the intake of the cylinder head that is not compensated by oxygen sensor, failed oxygen sensor, or fuel injectors need cleaning and testing. Normally the fuel pressure regulator fails closed, producing a rich mixture.
First time posting, on my first Porsche! I just bought an 85.0 944 for what I think was a decent price after it had been sitting for 2 years. It's a bit of a project car, but in general seems to run (mostly) well. I live in the CA SF/Bay Area and I am trying to get it to pass Smog. The seller was confident it would pass, but I was a bit skeptical and ran it to Smog directly the next day after buying. No surprise, it did not pass on the NO at both 15 and 25 mph, but otherwise it was passing with really low numbers in all other categories (see below). After that I took it to a reputable mechanic for a PPI. They said it was mostly in ok shape, though it needed new tie rods and the oil pan was leaking a bit. They also noted it had the stock ca which was likely the main reason for my Smog woes. I had the cat replaced with a CARB certified cat at a muffler shop, and changed the oil and filter the next morning and ran it around for about 25 minutes on the highway before going into another Smog test (results below). Good news is that I'm passing at 15 but still failing at 25, though the results are less egregious for both! The technician mentioned that there is likely something else wrong as, even at 15, with a new cat my numbers should be much lower on NO.
I'd appreciate any tips you guys may have based on my numbers. I'm new to this, but from what I've been reading here, I figure my next step may be to replace the O2 sensor and spark plugs? Am I on the right track? Is there any other non-major work I can go through before taking it in for another test? Thanks for the help!
[/QUOTE] I figure my next step may be to replace the O2 sensor and spark plugs? Am I on the right track? Is there any other non-major work I can go through before taking it in for another test? Thanks for the help! [/QUOTE]
Change the plugs n O2 sensor but also pull the injectors and soak them in some Berryman's carb cleaner for a day or so and order the injector O-ring kit and put new O-rings on the injectors also change the Fuel filter the car has been sitting for 2 yrs so you just pumped 2 yrs of varnish and trash into your injectors. also a couple of days before you take it to get smogged half fill the tank with mid or premium and then top it off with E-85 then take the car for a couple of spritted runs in excess of 65 mph. The E-85 will help to lower combustion chamber temps which should help with the NOX. plus chase down any vacuum leaks and if you can leave car with the defroster running during the smog check helps cool the head. injectors out of my 88 Turbo when I bought it not running after 3yrs
Thanks everyone for all of the tips! It sounds like I've got some homework to replace 02 sensor, spark plugs, and clean the fuel injectors as a start. Even if it doesn't help my smog case it's probably good practice, especially for a car that has seen a lapse in maintenance for this long. Hopefully it does the trick though.
Regarding running lean vs some sort of leak: I pulled out a spark plug to check their condition (pictures below). I'm a newbie, but from what I can tell they seem worn more than anything else? If it were lean I'd expect them to be more white? Also if it is fact running lean would calibrating the mass flow sensor help at all (assuming the above maintenance does not push me over)?
With regards to a leak are there any methods to diagnose?
[QUOTE] injectors out of my 88 Turbo when I bought it not running after 3yrs [QUOTE]
Dwizle, Oh yeah that looks really gummy. I'm sure I'm not any better off. I'll post pictures of mine before cleaning to compare. I'll also give those smog tricks a whirl when I go in.
Also, FWIW, in CA the law says the SELLER is 100% responsible for ensuring a car passes smog, not the buyer.
V2, yeah buying this car before passing smog was a mistake. Short of legal action I'm not sure if I could do much to get the seller to resolve the smog situation? Lessons learned I guess.
The gap on the electrode of the spark plug is out of spec, too larger. For intake air leaks, check hose clamp tightness on J boot, any vacuum hoses disconnected or cracked, cracked J boot, loose bolts at the intake manifold.
SouthBay Fuel Injector Service is very reputable and customer focused, actual experience. Google for info.
There are three hoses, (idle air in, out and AOS) mostly concealed by the intake manifold, that are nearly guaranteed to be leaking false air to the mixture and crankcase.
Replacement involves removal of the intake manifold but it is effort well spent. Combined with injector cleaning, fresh manifold gaskets and "standard" Bosch WR7 DC plugs should have noticeable effect.
Wise to put in new S & R sensors too (much easier with manifold removed) if they haven't been done recently.
would calibrating the mass flow sensor help at all...?
Do NOT attempt to "calibrate" anything. If your car is stock, you have an "Air Flow Meter" calibrated during production with lasers and something you likely cannot duplicate at home. It may, however, be worn out; you can look up how to clean it or bend the little arm inside to track on fresh material, but don't attempt to calibrate it or adjust the spring. You can test it somewhat. Some info here: http://www.clarks-garage.com/shop-manual/elect-22.htm
There is an adjustment for the CO2 but you are so out that I would not try to do that (and you probably don't have a proper measuring device)
Your plugs look a bit lean and as mentioned you should swap for copper (ie. OEM Bosch or equivilent) but that is not your biggest issue. Begin by making sure there are no air leaks and replacing plugs, cap, rotor, air filter, & maybe even wires: a 1980s tune-up. Then, work on looking for air leaks. This will probably involve replacing vacuum lines. Info here: https://rennlist.com/forums/924-931-...86-944-na.html You can test for leaks by removing the piece labelled "AFM" and sticking something you make into the hole of the "J-Boot" and, using a compressor, pressurize about 5psi while spraying bubbly water around all hose connections. Here you can see the piece I made with a plumbing cap and an air hose fitting (my turbo's J-Boot is orientated differently than yours):
After ensuring your vacuum lines are all leak-free, start the car and have someone hold a rag on the end of the muffler while you feel for leaks with your hand around exhaust joints. With a new install, the only leaks I would imagine might be at the manifold.
You can also test the O2 sensor by getting a cheap oscilloscope on Amazon. Probably easier just to replace it though. And since you removed the intake to replace vacuum lines, you now have nice new intake gaskets and you've ensured your injectors are clean & working properly.
After all this fun, try again. If it continues to fail, well... ...in the end, I got mine to pass by removing the head, changing the head gasket, and cleaning all the built-up carbon on the pistons https://photos.google.com/share/AF1Q...9La0NkX21fYU9R
Dan Martinic, you shared a observation that is not intuitively obvious, the carbon buildup on the pistons. On every power stroke, the carbon absorbs oxygen molecules and then glows. This minutely reduces the amount of available oxygen that could lead to a lean mixture for the emissions test. But as you suggested, do all the external things first and then get a retest before removing the head.
If the OP has access to a horoscope, then this device could help to assess any deposits on the top of the piston.
From my research old 944s failing smog with high NO is very common in states that smog test due to AFM aging.
Once you understand how it works you will realize that everything in the AFM, as it ages, tends to cause the engine to run lean. If this is the problem then none of the other things being discussed are going to fix it.
You fix it by using a razor to cut the cover seal as much as possible, prying the cap off, cleaning every contact point, adjusting and bending the wiper to contact a new portion of the track and turning the gear one click more rich. (I don't remember which way that was at the moment.) Really, there's nothing to it. I did it in a parking lot.
Made a huge difference in my 1989 2.7, restoring a lot of lost power.
This was after I'd had the head reconditioned and cleaned all the pistons at 130K miles which produced zero improvement.
edit: I'm speaking above about an otherwise stock engine. If you have done mods that affect A/F ratio, like cat delete, etc. then you may need a bigger adjustment. In that case you will need to have feedback, i.e. an O2 sensor that lets you know the A/F ratio and how the adjustment is affecting it. (A dyno would be great but some have done it via road testing.) The 944Spec guys figured this all out. They are allowed to tune the AFM because they have to to keep the engines healthy but can't mess with anything else. Opening up the exhaust with an old AFM leads to really lean mixtures that they can only fix via this method. Clark's Garage has a write up of how to do everything inside the AFM except does not mention adjusting the gear. I found other, more detailed sources of info on the internet as well.
And turning the gear wheel CCW makes it richer by slightly unwinding the clock spring. In my case, with everything else completely stock except a catback exhaust, 2 clicks richer worked very well for high-rpm power, but I felt it was too rich for normal street running. I feared washing the cylinder walls. I set it back to 1 click richer, which most people have found is all that is needed.
Hey Rennlist, sorry for the lapse on this thread. I was away from the car for the holidays, and then when I got back I was hit with dead clutch hydraulics (they were starting to act up before I left) and then shortly after the starter began showing signs of giving up the ghost too. I replaced the starter, clutch master, and slave, and bled and filled the clutch system and thankfully that's all back to normal.
I jumped on some of the items on the list discussed above:
Replaced air filter
Replaced distributor cap (wanted to replace the rotor too but the set screw was stripped, will come back to this)
Replaced spark plug cables
Replaced spark plugs (and gapped them)
Replaced o2 sensor (that was a bear to get off)
Removed, cleaned, and resealed the throttle body
Replaced temp sensor on engine (when I was mucking around with the throttle body I found it was broken, I don't think it was by me but no way to be certain).
I replaced a bunch of the thin vacuum lines using the Lindsey Racing kit (pictures below). The technician at the smog test actually told me that I could be disqualified for them because they are not SAE certified. Is that accurate?
I also ran through a tank with "guaranteed to pass" fuel injector/line cleaner. I was skeptical, but I figured it couldn't hurt, especially if I would be driving the car around. At near reserve I refilled on mid octane before testing. I didn't add any E85 this time, but maybe as Dwizle mentioned that could help on the next run.
Results:
Well I didn't end up passing (numbers below)....but even more oddly my NOX levels are actually somehow much higher, especially on the 15mph test? That being said, it seems like I may have caught the vacuum leak as the O2 levels look more reasonable (based on the targets V2Rocket's mentioned). My plan was to pull off the fuel rail and manifold next to get at the gaskets and do a real injector cleaning but after these results I'm not quite sure what's going on or what these numbers are a sign of. I doubt this made the difference, but it was a bit colder today (52ish) and I did not run the car very hard before testing like the time before. I don't think that would explain such a large delta though?
Fuel Injector Cleaner is a major cause of fouling the fuel injectors because the solvent strips the varnish from the ID of the steel fuel supply line. The varnish plugs the screen in the fuel injector. Time for a good cleaning and testing of the fuel injectors. Might want to consider installing a fuel filter, 10 micron, near the fuel injection rail, to capture any residual varnish
From the engine photo I will recommend to take a good look at the battery cables and terminals.
Also be aware that aftermarket parts (with the seductive "racing" colors) often do not perform as well as the stock pieces.
The mixture adjustment plug missing from the AFM may be a clue to the emissions problem.
T&T Racing it looks like I shot myself in the foot with engine snake oil. Would that explain the increased NOx compared to the last test? Do the significantly reduced O2 numbers mean that I likely at least caught the leak? If I'm going to need to bleed the fuel lines to get at the injectors to be sent for cleaning and testing should I replace the fuel filter and fuel pump while I'm at it? Are you also recommending adding a second fuel filter by the rail? Sorry for the overload of questions.
Gage, fair point, the battery cables are not in the best of shape, especially the ground. Just added replacement cables to my next cart haha. A lot of the car has been neglected honestly, so I've been replacing and cleaning things slowly as I work through the smog problem. Regarding the AFM mixture adjustment screw, my understanding is that it only affects Idle? The idle is definitely rough until the engine gets up to temperature (I can see the shake in the rear view mirror). Would it affect my numbers beyond idle though?
No need to drain fuel lines to pull injectors, just use paper towels to absorb any fuel spillage. No, I am not suggesting your replace the fuel pump or the fuel filter in the rear. The 2nd fuel filter is a suggestion after pulling the fuel injectors and getting a report back on cleaning and testing.
I would contact BayShore Fuel Injector Service and discuss that you add fuel injector cleaner with the owner. See what is his response. They have a website and I was very pleased with their service. They go the extra mile for the customer.
12-17-2020, 07:38 PM
85 944 NA not passing Smog (high NO)
