IDLE PROBLEM

I have a 1972 911 with a freshly rebuilt motor from a 1965 911s. Everything is either new or rebuilt (less alternator). The problem I am having is that the car idles high at(1500 rpm) and slowly comes down in small unnoticed increments and then it turns off. I will give the observations I have made.
*carb synched at idle and 3000 rpm
*great power throughout
*no flat spots
*not running rich or lean (I use o2 sensors)
*float levels good
*correct jets according to other 911's and charts
*carbs are affected by the slightest adj meaning the carbs were rebuilt correctly
*timing set overall only at about 35 degrees
*assuming good spark

This accurs all the time. I am thinking either that the system is flooding itself at idle but Once the car turns off, it starts right up contridicting the possibility. I did notice the fuel pressure regulator was set at 5 lbs. Is 5 the max or 3lbs? If anyone can help it would be appreciated. This is stopping me from setting the idle correctly. if any help here are jet sizes
main-130
idle-55
airs-180
would a new ignition like MSD be better than the existing 1972 CD unit?

thanks in advance.
louis

There are a couple of 'perplexing' minor details about your '65 engine ... and it doesn't really matter whether you or someone else made 'updates' or changes to the engine, just as long as you know what is currently in or attached to it ...

1) There was no 1965 911S engine, they started production mid-year 1967.

2) All '65 911 engines had Solex 40PI carbs, and were notorious for a flat-spot that cannot be remedied ... except by changing to Webers! Are the carbs Solex or Weber?

Are you saying the engine starts, idles too high, then dies on you after a minute or two?

Who did the 'rebuild' on this engine, and why haven't you consulted them? How long have you had the car and the problem, or was it in this condition when you got it?

------------------
Warren Hall
1973 911S Targa

Early-S-man,

According to the block and its numbers the case I is from 1965. The reason I say 911s is because when I rebuilt the engine myself (less machine work) and the pistons were 9:8-1 2.0 liter. For that reason I say 1965 911s. I apologize if I mislead anyone but what then would you call this engine? The carbs are weber and I again rebuilt these myself. This car was sitting in a garage since 1984 in Texas when I acquired it in 1999. It ran good except that it had low compression and it smoked bad during deceleration. Although it just needed a top end I decided to go all the way. After my initial post, I did play with the engine and realized a couple of things. When the car is idling high, if I put it in gear and let the clutch out slow to put load on the engine, the engine would come done to the right idle of about 900rpm. I am thinking now that it might be that the distributor is sticking Maybe???? Anyway, the second owner whom I bought it from did not know a thing about the car and he claims he only drove it a year before getting tired of blowing $200 every trip to the dealer. As for your question of what is it? well I cant locate the owner that modified the car but what it looks like they knew what combination of parts and years of parts to use.

all aluminum case
S pistons
S cams
updated oil pump
updated cam oiling system (no rifle bore)
larger than stock valves
ported and polished to match intake
updated fan
webers

The car starts quick and runs good except at idle. Ex. I am driving car and I hit a red light. the car will idle at 1500rpm, within about a 10 sec the cars' idle will go down until it stalls. I then have to tap the pedal once or twice and the idle will come back up to around 1500rpm and the process will start all over again. I have operated the carbs without linkage and the problem still exist. I could adjust the idle screws so that it will not turn off but then when the problem occurs, it will be at about 2100rpm instead of 1500rpm. I am starting to believe I have a sticking distributor but as you now there really expensive and I dont have an extra one to try out.

Sorry for it bein so long but I appreciate your feedback thanks again
louis

Louis,

A couple of suggestions:

1. The fuel pressure sounds a bit high, try adjusting the regulatot to 3.5 lb.

2. By all means, get a timing light with an adjustable 'advance' dial, and spend some time to get an idea what the advance all throughout the rev range from 600 rpm to 3500, and see if there is any variation from initial start-up, as it is warming up, and later when fully warmed up. Keep a 'log' book recording your results, with time, oil temp, and whether the engine is running OK, or problematic ...

You may have a problem beacause of age and wear in the distributor, or because it is not the correct distributor for an 'S' engine, or a combination of the two! I strongly suggest removing, disassembling, and cleaning the distrubutor, for starters, with special attention to any wear and play in the shaft and bushings and thrust washers that need replacing. One thing for sure is that cleaning will most likely take care of any 'sticking' problem! If the distributor is a Marelli, and in bad shape, you should plan on getting a replacement Bosch 'S' unit ASAP, used are available, on eBay, for example. Good luck, and let us know what you find out!

Oh, one final thing ... neither a Perma-Tune unit, nor an MSD box will make ANY difference in how the engine runs, compared to a properly functioning Bosch CDI-unit! You don't still have a condenser attached accross your points, do you? It is NOT needed with the CDI system!

------------------
Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 07-07-2000).]