Car won't drive until it's warm

[rs6er]

My car will start with one turn of the key when it is cold and hasn't been driven for a few days. It will idle fine (goes up to about 1200RPM, then drops down to 850 after a while.) However, until the oil heats up, the car will not drive. It bucks and pops. If I let it idle in the driveway for about 5 minutes, it will drive away just fine.

Is this a WUR issue? Other possibilities.

[saxen]

sc? mine does the same, I would love to hear an answer to this

[rs6er]

Originally Posted by saxen

sc? mine does the same, I would love to hear an answer to this

Yes.

[Nickshu]

Sounds like WUR. Do a search on how to test it.

[Paulporsche]

It's quite possibly WUR related, but there could be other factors.

Is the popping out the exhaust or back through the intake?

Have you had your CO% (mixture) and fuel pressures checked?

Have you checked for vacuum leaks?

[spuggy]

Sounds like your CCP (cold control pressure) is too high, thus too lean when the motor is cold. Mine is the same way just now. I have to break out the CIS pressure gauge and go mess with the adjustable WUR

Idling the car when cold; the handbook specifically says not to do this (mine does, anyway). It doesn't say why - probably poor oil/air flow at idle.

[rs6er]

Not having any of these gauges, sounds like I need a trip to the mechanic.

[schumicat]

is frequency valve working? makes buzzing sound if working. or unplug relay under passenger seat and see if that changes anything. you can' t diagnose fuel related problems on these cars without fuel pressure gauge.

[rs6er]

I thought I'd update this thread, because there was a very simple solution to my problem: Car wouldn't drive until warm, low idle when warm, backfiring on deceleration. Stopped by Speed Sport Tuning in Danbury. Spencer Cox told me the car was too lean. Adjusted mixture in fuel distributor. Five minutes later all problems solved!

[ossiblue]

Originally Posted by rs6er

I thought I'd update this thread, because there was a very simple solution to my problem: Car wouldn't drive until warm, low idle when warm, backfiring on deceleration. Stopped by Speed Sport Tuning in Danbury. Spencer Cox told me the car was too lean. Adjusted mixture in fuel distributor. Five minutes later all problems solved!

Just a word of caution.

Unless they checked the fuel pressures and tested for air leaks, they likely just masked the problem by adjusting the fuel mixture. I don't know how experienced they are with early CIS systems, but adjusting the fuel mixture screw is the very last thing to be done when diagnosing/fixing a lean running problem. I suspect you still have the same issue but it is now just covered up and it will return in the near future. If the shop did a complete diagnoses on the fuel system and vacuum system, found it in spec and then adjusted the fuel mixture screw with a CO meter, then it was done correctly. Anything short of that and you're driving on borrowed time.

[boyt911sc]

Originally Posted by rs6er

I thought I'd update this thread, because there was a very simple solution to my problem: Car wouldn't drive until warm, low idle when warm, backfiring on deceleration. Stopped by Speed Sport Tuning in Danbury. Spencer Cox told me the car was too lean. Adjusted mixture in fuel distributor. Five minutes later all problems solved!

If the mechanic adjusted your fuel mixture without testing the integrity of your vacuum system, there is a good chance that the LEAN condition was due to unmetered air!!!!! There are 3 conditions where you get the LEAN/Rich conditions:
1). Change in fuel flow (pressure) or
2). Change in air supply (air/vac leak).
3). Both fuel and air supply changed which is unlikely but possible.

The first question you should ask the mechanic was 'why did it go lean?'. Unless you have done something to the engine before or something happened unknown to you.

Tony

[rs6er]

They are very experienced. He told me to bring it back for a smoke test to check for air leaks. Noted that the air box was in good condition and the pop off valve secure. Will follow up.

[Kemo]

yeah...what ossiblue said.

the CIS pressure kits arent that expensive if you decide to do some further testing. Try the oil cap removal test...if the idle drops, you have a somewhat air tight system. if the idle stays the same, you got an airleak. Innovate makes a reasonably priced A/F ratio system. for me, I set my A/F at about 13.5 or so when warm. I do notice a difference in winter A/F vs Summer. Only a fraction of a turn makes a pretty big difference. there are lots of other things that can affect the smooth running of CIS. It took me a while researching things to get a halfway decent grip on all the different parts of the CIS system and how they all work together. Good luck with this. I do wonder how the adjustment screw got "out of adjustment". they usually stay put unless someone puts a tool on it. Just something to think about.

[ossiblue]

Originally Posted by rs6er

They are very experienced. He told me to bring it back for a smoke test to check for air leaks. Noted that the air box was in good condition and the pop off valve secure. Will follow up.

You've gotten a bit of an "ear full" since your post and this last one tends to confirm the quick fix the shop did. Being an experienced shop does not necessarily translate into thorough knowledge of early CIS issues, just sayin'. Clearly, they did not thoroughly check for vacuum leaks--the primary cause of lean running--and unless you left it over night or for an extended period, they probably couldn't have tested the cold control pressure either. Not really criticizing the shop, maybe they wanted to get you on the road quickly and didn't have the time to do a complete diagnosis--we really don't know the circumstances.

Since you will follow up, I'd suggest you ask Tony's question, ask them to perform the smoke test, ask them if they intend to check the fuel pressures, ask them if they intend to reset the mixture using a C0 meter after all the other testing has been done. Let us know your results.

[rs6er]

In all fairness to the shop, I stopped in without an appointment. Owner did me a favor by making the car run much better. He told me to make an appointment to get it worked out properly. I guess I posted out of exuberance that it was running so much better. As far as his experience goes, he has been one of the best 356 and 911 guys in CT for many years. I will follow ossieblue's directions in a manner that will not insult their Air cooled 911 mechanics.

[tirwin]

Quote de rs6er

I thought I'd update this thread, because there was a very simple solution to my problem: Car wouldn't drive until warm, low idle when warm, backfiring on deceleration. Stopped by Speed Sport Tuning in Danbury. Spencer Cox told me the car was too lean. Adjusted mixture in fuel distributor. Five minutes later all problems solved!

Just a word of caution.



Unless they checked the fuel pressures and tested for air leaks, they likely just masked the problem by adjusting the fuel mixture. I don't know how experienced they are with early CIS systems, but adjusting the fuel mixture screw is the very last thing to be done when diagnosing/fixing a lean running problem. I suspect you still have the same issue but it is now just covered up and it will return in the near future. If the shop did a complete diagnoses on the fuel system and vacuum system, found it in spec and then adjusted the fuel mixture screw with a CO meter, then it was done correctly. Anything short of that and you're driving on borrowed time.

^^^ What he said. Can't emphasize this enough.