idling problems with her.

It starts up fine, and on short drives to the market, etc. it is great, but the problem starts when I go for a long drive (about 45 min. or more), the idle drops really low (it gets rough but car does not die) when stopped and just idling. If i turn it off and let it rest a while and start it up again, the idling is fine.

Is this a typical problem on these cars?

Any ideas on what it can be?

Your knowledge and advise is greatly appreciated.

thanks,

Lev

Do you have carbs or fuel injection?

fuel injection

Sounded like a carb problem, but I guess not. Really, I don't know fuel injection systems on 914s very well, but I do know that it is natural for the idle to drop a little when the car is warm. That is why it is important to set idle when the car is HOT. What is the RMP at idle when cold, and what does it drop to?

it is around 9 to 9.5

On older cars you sometimes need to set the idle around 12. See if raising your idle a little helps. If not we will look at something else, but sounds like your idle may just be a little to low.

thank you so much, I will try that and hopefully that will end my frustrations with this idling issue. If not, I will post again.

Sounds good. Keep me posted.

Jon

how about the idle mixture adjustment on the ECU? maybe someone could post how to adjust that and see if that has any affect.

It really takes a while to get the whole car hot and heat soaked. I did a R&R on my whole FI system. New or rebuilt everything except the MPS. I got the system pretty well dialed but I had the same problem. Finally, I put a variable resistor on the cyl head temp sensor. I turned the resistor value up until the car idled right when fully warmed up. It idles great and it still passed emissions.

I think if you just dial the idle up, you'll find it will idle really high when cold.

Have you checked Brand Anders site? Its the first stop for all DJET problems.

http://members.rennlist.com/pbanders/

Just to be clear, my idle hunted, it didn't just drop and stay low.

excuse my ignorance, but what is a variable resistor that goes on the cyl head temp sensor and where to I get one? Any recommendations on brands?

thanks,

Before I explain this, you should exhaust most other DJET troubleshooting before you try and fix it this way. I would use this as kind of a last gasp. Its not a bad fix, but with DJET there can be any number of issues that are causing problems. There is no need to introduce another unknown yet. If you have never verified the compatibility of the parts in your system, I would start there. 73 2.0 DJET does not have many parts that are compatible with other years/cars. Its not uncommon to find a mismatch of parts. Also, you should look for vacuum leaks. Vacuum leaks are probably the single biggest source of FI problems. Finally you can try dialing some idle with the air bleed screw on the Throttle body. And then there is timing, too. So you should do the basics first.


There is a cylinder head temp sensor, if memory serves, on the passenger side cylinder bank. Its inside a hole in the cooling tin. A single wire comes off that sensor and goes through a resistor then into the harness off to the ECU. If its the factory resistor, its in a long "hot dog" shaped plastic piece, maybe an inch long. If its not factory, I don't know what it will look like but it will be on that wire. If you still have the factory 73 DJET system, the resistor should be of the value 270 ohms. You can go to radio shack and get a variable resistor between 0 and 500 ohms (or more) and put it in place of the existing one. On the RS variable resistor you will have 3 leads, tie the middle lead to either one of the end leads. Use an ohm-meter and dial the new variable resistor to 270 ohms. Now you can turn up the value on that resistor until the car idles right.

YMMV

This is awsome info. However, I think it is over my head (I am not that mechanical). But I have taken my car to a reputable Porsche mechanic and he did the valve adjustment, timing, new plugs, points, hoses, alternator and regulator. I will try the throttle body next, if that does not work, I will print this out and maybe take it to a mechanic. Do you know anyone around the Los Angeles area that you can recommend to help me with this.

thanks again,

Lev

I don't know any LA wrenches, maybe Cap'n Krusty? (hes a member here)

Theres no shortage of LA folks here than can tell you where to go.

solicate help from the board members before you drop a ton of dough in a mechanic. Most of them will be able to trouble shoot and fix the prob. for a beer........or two

when's the last time you had your valves adjusted?

I have used a guy in Northridge for a long time. From my experience,
he is honest, reliable and refuses to throw parts at a problem (un uncommon trait in a mechanic, anymore). this is a small one man shop, so you know the guy you talk to is the guy doing the work.
Leonard's forgein car, talk to Bernie at 818-349-2900
(Cap'n Krusty is a good suggestion,but geographically undesirable in Santa Maria)

Good luck
Gary

about 3 months ago, maybe couple of hundred miles

Did this problem start after the valves were adjusted? One being a little too tight could cause this problem. I hate adjusting valves but I would check this first.

I had it professionally done by a porsche mechanic who is very familier with 914's

Check the Valve Adjustments first, but then the Cylinder Head Temp Sensor is a good bet...

Could be one of several issues.. On my '73 2.0, the Sensor had come loose from the repeated Hot/Cold cycling of the Cylinder Head, and it was sort of just rattling around in there... These are very easy to strip so don't try to just go Ape on it... snug it down gently! And you need to build a tool to work with... I bought a 13mm deep socket, and Dremeled a slot in it to allow the wire to come out the side. Stuffed the socket with paper until it just fit over the head of the Sensor,, and used a medium length extension to get it down into the hole in the sheet metal. You are pretty much working by feel at this point, but you can tell when it hooks up with the Sensor. Gently break it loose, and back it out by hand... delicate threads, you know! You may need to replace the Sensor... PP had them about a year ago, but I heard they went NLA... don't know for sure... if the Sensor tests good, then try the Resistor thing... Also, check your wire from the Sensor up to the harness... it can also get damaged and not transmit the info! When mine was kaput, it made everything run really rich after fully warmed up, and sooted the plugs until she wouldn't run any more... Not sure that's your issue... Keep us posted!