nikkoa

82' 911 SC, ROW

About to take it to a real wrench. Wanted to stop by here first and give it go over before i fork out the dough for someone else to do it.

Description of problems: Hard start (it's rich) sometimes not starting at all. Once started the idle osculates between 350rpm to 1000rpm in cold loop. Given a little gas it fires rough under 3K rpm, bucking violently. Sometimes it wont accelerate at all (with a random fire to keep me rolling) until i take my foot off the gas and ease it in with less fuel. No said symptoms over 3K rpm.

If i rev it hangs at 1500 RPM then slowly lowers to 350 then back into the bounce.

Once i drive it for a few miles and temp elevates even slightly no bucking no osculation, idles great runs like a champ. Even when warm I still feel as if im loosing a bit of HP under 2.5K rpm.

The symptoms are only present when the outside temperature drops below 50F. If its moderately warm i suffer mild effects. I have an exhaust leak but doubt it relates to this problem.

Attempted solutions:
Set proper idle.
Replaced O2 Sensor
Replaced Oxygen Sensor Relay
Replaced Cold Start Valve

Could this be as simple as setting the lambda curve on the control pressure regulator??

Any insight is valued. Thanks

Houpty GT

Below 50 deg F the system will not reference the o2 sensor. When it does reference the o2 sensor it may be correcting whatever fuel mixture problem you are having. If you disconnect the o2 sensor when it is warm, how does it run?

How did you set the idle?

Have you checked you system pressure and hot/cold control pressures?

Don't get stuck in the cycle of just changing parts.

rusnak

I tred lightly into this thread. First question: did you check your system and control pressures? I am not sure how to check the WUR, but I would try to figure out if it's working properly.

whalebird

First eliminate all external things. vacuum leaks, air box(pop off valve installed?), basic tune, timing etc. Then nothing will be right until you hook up the fuel pressure gauges and look at the system/control pressures. This is easy for an experianced tech. Make sure you find the right wrench for the job. The right tools and procedure is critical but really easy.

TroyN

I would also guess vacuum leak, maybe a misadjusted CIS air meter plate or something as simple as incorrect mixture/CO (you didn't mention having set that).

rusnak

help us to understand.

You guys say vaccum leak (false air), which lets in unmetered air. When the system is in open loop, that means it is running lean. When the engine temp rises, the system goes to closed loop, and the mixture is corrected?

If the mixture is off, then that would account for an incorrect mixture all the time? Or just in open loop? Is the co a baseline adjustment as in L-Jetronic systems? Thanks!

Nikkoa, have you tried setting up an air fuel meter? Perhaps you can rent one? This will tell you how rich or lean the system is running. If you have a test pipe with a second O2 bung, then you can actually see how well the O2 sensor is working.

whalebird

All good advice, but the fuel pressures are going to tell the story if there are no gaping holes in the intake track. Run of the mill test on these cars. being a ROW car - make sure that part numbers and test values of the components are the right ones. ROW cars may have a slightly different fuel curve. There is an expert around here that could tell for sure. My memory can't remember.

nikkoa

Thanks for the quick responses!

I only have 5000 miles on the rebuild, recently timed. Oil tensioners and pop-off valve installed. Brand new fuel pump and vacuum lines.

A plume of white smoke is ejected after being started so it made me think its running rich when i turn the key. During the initial minutes while running it struggles to stay alive, sometimes dying. This morning it took several tries to get started, once started it sounded horribly rough (not enough air, too much fuel?) It also idles around 300 rpm, until it warms up then it idles at 750.

As far as tools i have limited access so i think i will let a pro handle this one. Franks Automotive in Sacto has a great reputation and knows this model. He had mentioned my last visit it was a matter of setting the curve - which - i have a feeling is the problem seeing how under 2500 rpm it drags but over i get a boost of HP like no other. As whalebird mentioned my ROW car has some after market pieces installed to accompany the fine emission regulations we have here in the states, so it may be a matter of a faulty part that I couldnt recognize.

An interesting note about the o2 sensor being engaged when the engine temp heats up, i will unplug the o2 sensor after it's warm to see how it runs. I dont think it's a vacuum leak but based on the erratic behavior anything is possible.

Kevin Michael

Does the ROW models even have an 02 loop or lambda? Also the white smoke indicates lean not rich, but that puff is common upon start up. I am glad to say I am back in the 911 air-cooled game and am looking forward to brushing the dust off my old skills here on this forum. I currently have a 79 euro with a modified 3.0. The engine has 964 cams, SSI's, turbo lowers, modified CIS, pop-off, and a bunch of other things. All my other 3.0's seemed to run as yours till they were properly set -up. This current 3.0 has little power till around 3500-4k and then it comes on hard and fast. good luck with your running issues friend.
Kevin

whalebird

My partner in crime has an 81 euro we built to a 3.2. Mahle high compression, Andial ported (euro)heads and match ported intake, 964 Webcam, SSI/Monty dual-out, case relieved(windage mod), Dopke Rockers, and all of the proper machine work(ollie's crank, case, rods). That CIS motor releases a furious wail all the way to the red. With big brakes and copious suspension mods and stripped interior/lexan windows, no 3.6 car is safe at the track. It has a deep funky lope at idle not much unlike a V8. The warm-up regulator is a different part number IIRC for the euro cars and there was no lambda system originally. It doubles as a street car and now has about 50k miles on it. We drive it to the track often. A euro SC can be a remarkable driver.

nikkoa

Well.....

Don't flame me - 200 dollars later they found i never connected the Lambda control wire....

Live and learn i guess

theiceman

thanks for letting us know. Where is it ( the wire ) and is it running well now ?

nikkoa

Still osculates ever slightly, could be do to a small vacuum leak. Other than that it fires right up, more responsive, increased MPG, i could swear a have more HP... it's like a new car!

The box was located directly under the seat behind the driver

nikkoa

next stop... electrical!

I plan on taking it into audio innovations in roseville to have all the wiring replaced, door switches, window switches, etc....

oh yeah and tranny mounts, and exhaust, and window tinting, and speakers.... almost there!!!

nikkoa

Well - it resolved the cold idle but not much else. If anything the Lambda controler made things worse...

It likes to die after reving/engaging clutch. I will be driving around, as soon as i engage the clutch pressure is not sustained and the engine dies - sometimes, pressure is kept and the rpms drop to about 100 before rising to proper idle. This seems to be exclusive to my cold start problem. I turn the key to start it up again but even so it hesitates to idle until the lambda control adjusts accordingly.

Still hard starts when cold. Engine sometimes fires, smell of gas, but no go. When i finally get it started it sounds like its running under water for about 20 seconds before it can sustain it's own pressure and the engine runs without my foot on the throttle. Once started it continues to ocelate rpms until ever so slightly warm....

Could this be due to my Aux Air Regulator shutting closed and staying closed therefor not allowing proper air flow during startup?

How approach this dying issue?

As always, thank you in advanced