1974 Saab 99LE

Hello!

I am an owner of a brown Saab 99LE - djet and automatic - 4 door. I use it as my daily runner for the family in London.

It has only 34,000 miles on it, but a previous owner has really butchered the electrics. Even the wiring colours to the fuel pump (at the relay) are wrong! However, it runs.

 

Lately, when engine is loaded but the car is not moving (gear selector in `D` at traffic lights with footbrake presses) the car sometimes stalls. It is this problem I am trying to solve.

Below is a video of how the tachometer behaves when stalling. If it gets worse than in the video - the car stalls. It also "splutters" when accelerating, as if there is not a lot of power/fuel being fed, or electrically the injectors are missing a beat.
Once I am cruising beyond 1500RPM then the car is sweet and drives all day. On the school run I sometimes use two feet on the pedals - one foot to keep the revs higher (and the throttle slightly open) and one foot to keep the brake on !

youtube.com/shorts/IR3JcU-Mp1E

I've replaced my MAP with a NOS one - which didn't fix the problem, and when inspecting my TPS, there was dark 'burnt dust' along where the track runs.. as if there is too much current? Does the TPS have a considerable current going through it? I have a NOS TPS to install as well but haven't had time yet. It seems rather basic.

When I took apart my Borg Warner 35 automatic "start inhibitor" there was also this dark burnt material where the copper contacts meet. Other's I've seen just have "normal" corrosion from 50 years of exposure. Which leads me to think...

I definitely have some bad earths somewhere (everywhere?) which is maybe causing an increase in current - and therefore burning. Could this be a problem? Or does it sound more like a fuelling issue?

I noticed that I set my fuel pressure to 32 PSI over a year ago but it's crept up to 40 PSI (I will correct this later this week). Could higher fuel pressure be the problem?

Any sage wisdom accepted, and hopefully I can continue to document my journey with this car.

  Charlie Pickles (@photosofpickles)

Hi Charlie,
Welcome to the forum with your car that is quite rare here!

I looked at your video and don't think the hesitation at idle is very spectacular... but I heard a noise like you would open the throttle a little bit just befor the hesitation occurs.
Did you check for vacuum leaks, maybe a broken hose?

The fuel pressure should not get higher without any changes in the adjustment of the regulator - or there is a problem with the fuel-return-line that could be blocked.

The TPS has to switch only very, very low current. Yes, there is some wear and black markings where the contacts run. But this could be polished away. Don't grease or oil this. Even contact spray could hinder correct contact.

You should check these points... waiting for hearing from you again.

Regards
Norbert

Hi Norbert,

> Did you check for vacuum leaks, maybe a broken hose?

I have replaced the hoses just last week - and I think the stalling has lessened - but it hasn't gone away. The recent cold snap ended the last meagre life left in some old rubber.

I have a smoke leak detector I will try (I will disconnect and block the line to the MAP first as it won't like positive pressure AFAIK).

> Even contact spray could hinder correct contact

Do you mean Deoxit D5 could be bad? I was planning on going through a lot of the car with this.

One question I have on the TPS is where should the resting/idle pin be without any accelerator pedal? at rail 1 or 2? (see pic)



Charlie.

Hi Charlie,

welcome to Jetronic.org . I have seen many D-Jetronic cars in my workshops but a Saab would be a first timer. Too bad you are so far away.

Now an unstabile idle can have a number of reasons:

1. Vacuum leakge. Best is a fog tester to find out where it might leak
2. Engine mechanics - Leakage of valves, cylinders etc.
3. Ignition with hanging timing adjustment, spark plugs, ignition cables
4. TS (no it is not a TPS) which does not signal idle to ECU

Your TS looks dirty. Polish contacts and also continuity switch.

And too bad that you are outside of EU. I would love to take a refrence of your MPS. But with customs that gets too complicated.

Hello Doctor, thank you for the welcome.

That would be easy re: customs. Private Message me about the MPS and I’ll send one over.

That pic of the TS is one I have in a spare parts box! The one on the car is much worse!