JDY928

Hello All,

I have a 1983 928S, right hand drive, Australian delivered. It is a K-jet car. When I start the car it starts first turn of the key (battery kept on charger). It idles like it always has, smoothly. However, when I try to rev it, it almost stalls. If I very gently press the accelerator, it will gradually build revs, but sounds very rough, like it is not firing on all cylinders. If I let it warm up fully, it will rev up more eagerly and smoothly, but still not as smoothly as it should. It will also not rev above about 3,500 rpm. Is there anything I can check before I send it to the specialist? It has not run regularly for some time, so the petrol is not super fresh. Could this be causing the issue?

Thanks in advance

Jed in Sydney, Aus
83S Kiln Red

leiplouis79

Did the car sit for a period of time? When I first got mine- it did a similar type of scenario( part of an estate and had sat). After running a couple of tanks of new fuel( 93+ octane US) and adding some Chevron Techron fuel system cleaner to it, it started to run like a champ- the more and more I drove it-- the better it got. Your injectors and fuel distributor can gum up easily if not driven for awhile. Just a thought + a cheap idea that won't hurt.

The Forgotten On

^^ I second this. K jet 928s especially hate to sit. They gum up easily.

Get a nice quality fuel system cleaner and some fresh gas in the car and it should run better after that.

Petza914

Add SeaFoam fuel treatment to each tank - a whole can with the first one, then 1/3 to 1/2 a can with each fillup thereafter. It helps by providing lubrication to the mechanical fuel distributor. If it doesn't get better with time and fresh gas, also check the WUR.

dr bob

Lots of recommendations on the various chems to help clean things that might be gummed or varnished. Responders should note that the question comes from Sydney, so the brands/flavors we know in the US may not be on shelves local to the car.

---

Virtually all CIS K-jet "problems" start with fuel contamination. The "C" in CIS is for "continuous", what it expects for fuel flow in the system. Fuel is used as fuel of course, but is also used to actively manage in the flow control side. Pressures in various sections are delicately modulated based on engine (coolant) temperature, volumetric airflow, and load on the engine via manifold pressure. "Control pressure" is biased based on temp and load, while airflow is more directly factored into the fuel flow at the metering unit. Varnish and corrosion commonly block tiny ports that manage the control pressures, while dried o-rings and varnish like to foul the workings of the fuel distributor metering unit. Fine brass screens are folded into cones for the control ports filtering, screens that corrode into brown powder over time and exposure to air. It may take more than a few bottles of varnish remover to restore correct function to the system, as they won't do anything for the debris from the failed brass screens.

If you have a known-good CIS specialist available, by all means consult them for guidance including a system pressure check. That testing will tell a lot about system condition, and is a much cheaper option than just throwing parts at the system until it works again. Those presure gauges, in conjunction with a CO meter, are critical to getting the system working perfectly after it's all clean again. If you ever find that the car is sitting unused for any extended period (maybe greater than a few weeks), pop the fuel pump relay out and connect a bypass jumper and switch to the relay socket. Run the pump for a minute to refill everything with fresh fuel. Better, drive the car regularly.

jpitman2

I have the exact same model. I have had success in the past with adding techron to the tank and bridging the pump relay, and allow the car to sit for some time(not running) with the fuel circulating through the system to flush crud out of the lines. If this doesnt cure the issue, get a guage set and check the pressures - system should be ~75psi, delivery rate ~1350cc/30 secs.
jp 83 Euro S AT 57k

JDY928

Hi All,

Thank you very much for all the responses. I will drain the existing petrol out, and put in all new fresh 98 octane, and cleaner. I will then run the fuel around as suggested. I will report back and let you know how I go.

Regards,

Jed in Sydney
Now to get about 60 litres of petrol out of the tank!!

jpitman2

Jed, An0ther experience that may be relevant. I had a misfire in mine once, and found that cracking open an injector line to release pressure cured it. My local mechanic suggested that maybe the misfire was caused by a piece of debris in the FD blocking an injector line, and relieving the pressure would allow the debris to fall away.
jp 83 Euro S AT 57k M474 M220

STRIKEMASTER

K-Jet cars don't like to just sit around...Load it up with Seafoam and give it a "Italian Tuneup". Get on a limited access highway and stomp on it....Rev it up to 5,000 in 1St, 2nd & 3rd. CIS cars LOVE being run hard.

GerritD

allan29

Hi Gerrit .

Try this stuff to have a correct CO setting .
It' a very sensitive to make CO setting .
It's a very good solution and not expansif .
I have one .
The shop is near your home !

https://www.matthys.net/fr/gunson-ki...-g4074-1192973

Allan

allan29

Have you the correct air flow sensor position ?

GerritD

GerritD

allan29

To JDY928 .

To make a good response , the only way is to take different pressure on this system .

Probably the WUR is out of tolerance .
We need the nominal pressure ( 5,2 to 5,8 bar) , cold and hot pressure ( with and without vacuum ) of the WUR ...
What is the WUR's reference ? Bosch 0 438 140 ???

Example for a 036 :





And the other ...





Check the vacuum system .






And your engine need fresh fuel !!!

A very very good saler and expert of K Jetronic in Australia :

http://k-jet.biz/www.k-jet.biz/index.html