I searched and didn't find anything that seemed releveant, so here goes.

I just bought an 82 5 speed and it runs very well, except.... when I start it, it fires right up, but then won't run unless I give it a little gas and then it runs VERY rough for about a minute and then smooths out. It isn't so bad when it's warm, but it doesn't have to cool off much before it repeats it's routine. I'm in Indiana, so this is weather about 32 degrees.

I thought it was a bad idler valve, but I don't see that as part of the 82 package.

The MAF was swapped out and that didn't make any difference.

The way it runs, it seem related ONLY to first start up. If it was a good old American car, I would think it was the choke, but ??? It sounds like it would logically be what the WSM calls the cold start valve??

Does this behavior ring a bell to anyone? I'm sure I've left out relevant information, so fire away.

Thanks
Rod

 

Rod,

Is the car in tune? Problems can be much worse with a cold engine.

The first thing to check is for the possibility of vacuum leaks. A 928 of this vintage has many fittings, connections, and small hoses that if they leak could result in hard cold-starting; the effect of leaning out the cold start mixuture could be enought to cause your symptoms.

You mentioned the choke - well fuel injected cars must provide an enriched fuel mixuture to a cold engine. Your L-Jetronic fuel injection system has a cold start system and the elements of that could be causing your problems. The components to check are

- cold start valve (add'l fuel source - gives a quick shot of fuel)
- aux. air valve
- temperature sensors

The system needs to know engine temperature, so be sure that the correct information is beign provided.

L-Jet specs are:

Temp II sensor:
10 C / 14 F 7 to 12 k-ohm
20 C / 68 F 2 to 3 k-ohm
80 C / 176 F 250 to 400 ohm

Cold start valve (brown plug):

Note: when the “connector locator notch protrudes inward to the pins from the top, the left pin is Terminal W and the right one is Terminal G.

Terminal “G” and “ground”
below 30 C / 86 F: 0 ohms
above 40 C / 104 F: 100 – 160 ohm

Terminal “W” and “ground”
below 30 C / 86 F: 0 ohms
above 40 C / 104 F: 100 – 160 ohm

Terminal “G” and terminal “W”
below 30 C / 86 F: 25 – 40 ohms
above 40 C / 104 F: 50 – 80 ohm

Since your problem is cold start, you could just look for the proper resistance range for the ambient temperature of the cold engine. If the sensor is shorted (zero ohms resistance) the mixture will be too lean and the engine will not start when cold. For others who may have problems at other engine temperatures, I’m including all of the resistance ranges for higher engine temperatures. If the sensor has an open circuit (infinite resistance), the fuel mixture will be too rich, the engine will not run when warm, and will be difficult to start when warm.

If replacing the sensor doesn’t fix the cold start problem, check the fuel filter, fuel line pressure, injectors etc. Fuel injectors can be removed and tested for flow and flow pattern. There are several shops that provide this service. The problem could also be attributed to bad ground connections. Also, don’t overlook potential weak spark conditions.

 

Rod, I'm having the same problem with my 81 at the moment. Hard to start when cold, but after a minute or so it's just fine. I replaced the TempII sensor because they are cheap. I got one at Napa for ~$20. Didn't help at all though. You may want to check your Aux Air Regulator. It's located under the passenger side intake runners. When I did my engine bay restoration I pulled mine off lubed it up some (they are known to stick). Just pull off one of the hoses and spray some wd-40 in there. To see if it's working correctly, use a mirror to look inside, IIRC it should be open when cold, and will close up when it gets warm (could be the other way around). I believe I have sourced out my problem. As Rich mentioned above, fuel system could be a problem. When the car is running, my fuel pressure is fine (30 psi). But as soon as I shut it off, the pressure very quickly drops back to 0. This isn't supposed to happen, so I belive I have a bad FPR. I just haven't got around to testing them. I had my injectors cleaned last year, so I know they are good. As I figure things out, I'll keep you posted. But the easiest way to start would be to check the sensors mentioned in Rich's post.
Hope that helps.

Chris
81 auto, 63k miles.

 

Thanks guys, good stuff, now to get to work checking.

Oh, I failed to mention that it idles very fast - above 1000rpm - all the time. Somethimes it even goes higher, if that additional information helps.

Rod

 

Sounds like a vacuum leak

 

Rick,

I removed the aux. air valve and checked it under current and it closed. I even opened it up and cleaned the inside, but not much there.

The electrical connector shows no current with the key on or with the key off? Under what conditions should this show current?

I checked the resistance on the temp sensor II and it shows none, so I assume it's bad. I'll replace it and see what happens next.

Thanks

 

I don't suppose you have a NAPA number by any chance, it appear that my Temp Sensor II is bad.

Rod