HELP guys! ´83 911 SC

[Billiracing]

Hi guys!

I have a friend with a 1983 911 SC that has got the following problem:
Engine runs good when cold, but when it gets warm and under acceleration from about 2000rpm the engine does not respond well - runs like a kangaroo (sorry, not sure of the english word for this, but hope you understand).

The problem was not there last year, but its like this after winter storage...

Hope someone has a good answer to this problem

thanks!

[tirwin]

Will need more info.

Let’s start with some basics.

Euro or US/North America version?

[proporsche]

Hi ,....the only thing you have to start with is ..to put fuel press.gauges into the system and find out what the fuel pressure is.....
Also was there any backfire.?.that would knock of the sensor plate of its position and the problem would start there...

Ivan

more details would help

[Billiracing]

chassis no: WPOZZZ91ZDS101440
3.0l
150kw /204hp

[Billiracing]

Not my car so dont have too many details...
Can the CDI box behave this way? I mean bad spark under acceleration when the engine is warm?

[Bob Kontak]

Originally Posted by Billiracing

Not my car so dont have too many details...
Can the CDI box behave this way? I mean bad spark under acceleration when the engine is warm?

Yes, if a spark is escaping to ground. Not a CDI issue. Just basic primary and secondary ignition.

[toddetch]

@billiracing - I'm chasing a similar issue right now. Working through a checklist of issues between myself and my mechanic. I'll try to remember to reach back out to you once I solve it to in case it can be of help. (FYI I'm working on an '80 SC.)

[john walker's workshop]

Might want to see if the lambda system's frequency valve is working.Unplug the small lambda relay under the passenger seat at idle and see if the idle drops off.

[proporsche]

here is a list of basic procedures to check.......

[MBEngineering]

HI Billiracing

have a look through this and see if it can help;



and a check list to run through, as it sounds like the rnging is running to rich when warm/hot



let your friend with a 1983 911 SC that I have a SC 1983 sport with a chassis No'

101410, only 30 away on the factory line from his.

regards mike

[SkiVT]

Check the fuel pressures (ccp through wcp) and for unmetered air/vacuum leakes. I dont think you have a Lambda on the 204hp engine. There are several components that aid in cold start/running but once warm, it would seem problems would be tied to the WCP or unmetered air.

[Billiracing]

Originally Posted by SkiVT

Check the fuel pressures (ccp through wcp) and for unmetered air/vacuum leakes. I dont think you have a Lambda on the 204hp engine. There are several components that aid in cold start/running but once warm, it would seem problems would be tied to the WCP or unmetered air.

Sorry but have to ask. What is wcp?


Sent from my iPhone using Tapatalk

[MBEngineering]

HI Billiracing

the WCP is warmup control pressure, this needs to be checked with a Cold/NON run engine and check the cold fuel pressures and then start the engine to see if the warm up reg is chainging the fuel control pressure to the Spec' of the regulator fitted.

there is a graph of the regulators, if you can check the no' on the regulator I will dig the graph out for you

regards mike

[tirwin]

Originally Posted by john walker's workshop

Might want to see if the lambda system's frequency valve is working.Unplug the small lambda relay under the passenger seat at idle and see if the idle drops off.

John, does a RoW motor have an OXS relay?

[tirwin]

Billiracing,

Lots of people have chimed in. I will offer my advice for what it's worth.

It is really hard to troubleshoot these vague problems over the Internet. Your friend needs to follow a systematic approach. There are lots of things that it could be and without a systematic approach he will just be guessing. Fuel, air, spark - I would check each systematically.

Proper function of CIS fuel injection is highly dependent on fuel pressures - system, cold control (ccp), warm control (wcp) and residual pressure. This is the fundamental starting point. Always a good idea to make sure everything is in spec. If you need more help on that, let us know. There are lots and lots of posts here about how to do this.

Next I would check the ignition system. CDI, coil, plugs, plug wires, rotor & cap. How old are the plugs, plug wires, etc.? Is it time for them to be replaced? Is timing properly set at idle? Is the max advance correct? I'm only familiar with the US version and I suspect the distributor is different, but I wonder if the distributor weights are moving freely? Also, the green wire coming out of the distributor is a common failure point. The green wire signal controls when the plugs fire. An inductive timing light is a good tool to make sure there is spark at each cylinder. The symptom related to RPMs makes me think timing which makes me think distributor. The distributor also has bushings that can fail and then it needs to be rebuilt. There are quite a few things related to the distributor that could be easily checked.

CIS is very susceptible to vac leaks and it is common for them to creep in over time. There are several places where rubber connectors can get hard and brittle from age and heat cycles which creates a lean condition. A lean backfire can crack the air box. If a pop-off valve is installed, the glue could be cracking and preventing a good seal. There are a few different ways to check for leaks. An easy test is to start the car and let it idle. Take off the oil filler cap and listen for the RPMs to change. If they do not, there is a significant leak somewhere. You can spray something like carb cleaner around the intake runner boots, fuel injectors, etc. and listen for RPMs to change.

Finally, consider that there could be more than one problem. Another good reason to have a systematic approach.

[Billiracing]

Thanks for many good tips
One thing that I keep thinking of is that the car worked perfectly before storage this winter.
Personally I thing that the problem is rust on the needle inside the CIS (K-jet).
Or maybe a fuelpump.
The problem is only when the engine is warm, and under full throttle from about 2000rpm..

[MBEngineering]

HI Billiracing

how much fuel was in the tank when the car was laid up, as the URO fuel will not stand for to long before going off, and will give the engine bad running, it is not to bad in the UK, but still will not stand for to long over hear, around 5 to 7 months on a full tank,

regards mike

[Bob Kontak]

Originally Posted by tirwin

John, does a RoW motor have an OXS relay?

No O2/Lambda through 83/ROW. Pretty sure but I have been wrong before.

[pampadori]

My cracked airbox had another symptom or crackling and popping noises when engine-braking / decelerating. Does his car exhibit that?

[Bob Kontak]

Originally Posted by tirwin

How old are the plugs, plug wires, etc.? Is it time for them to be replaced?

Need more info.

If you have tired wires they could be hammering spark onto the air conditioning bracket when under load. There are other culprits but Kangaroo means jumping. Hit miss. Hit miss. If you are bleeding spark it can be fine at low speeds then raise it's head under load.