[Dans-ta-benz]

Hello,
Bought this car 2 weeks ago. It clearly needs some more attention than previous owners gave.

The car runs fine except there is this annoying point that breaks a bit the dream.
When approaching to a stop, letting the engine and transmission manage slowing down, the ecu attempts to correct lean condition i suppose.
It runs like imagine a saw teeths or waves, there is a very slightly accelerating and then letting down rpms and so on until it reaches values under 1000 rpm where the idle is stable. Very strange.

I've been struggling a long time with potential vaccum leaks, attempting to read on obd some faulty components but there's nothing to see. I removed the throttle body but nothing to see there as well. I cleaned it but nothing showed as remedy. Inspected the air ducts, filters, nothing. Unplugged the MAF without more success.

I checked each and every injector in situation by removing their power, they are all alive, same for coil packs.

It's a very very weird trouble.

 

[darbysan]

It may not help, but many have found that the Throttle Position Sensor needs to be re-calibrated often. Seems that the computer gets confused as to where the throttle is, and tries to compensate. There is a simple procedure to do it. I did this to mine and found a significant improvement .

1. Turn the ignition key to the on (not start) position.

2. Press the gas pedal to the floor and hold for five seconds.

3. Turn the key to the "off" position (don't remove the key), then release the gas pedal.

4. Wait at least two minutes for ECU to reset.

HTH

 

[Dans-ta-benz]

Thank you Darbysan,

I forgot to enumerate i tried this as well. I also left the key on without starting the engine to let the throttle body do it's job few minutes, whinning, clicking etc but nothing spectacular from these procedures. When i detached the throttle body, i also opened the black plastic cover to check the tracks state but no oil contamination nor graphite dust. Clean as new. I added a bit more pressure to the tiny tips with slight push towards up, at least it should offer better contact without scraping tracks. Closed back with original clamps, mounted and tada... Nothing better 😵‍💫

 

[Dans-ta-benz]

My next move is to do it in old school mode when obd was not even a project. I'll take some gasoline, a paint brush or carb cleaner spray to check if petrol changes engine speed at idle.
After that i have no idea of what it could be. Forgot to mention that emissions failed when inspected back to France but it was a real pleasure to drive it on German Autobahn 😋😆

 

[Dans-ta-benz]

So i think i found what is wrong with it. Sprayed carb cleaner on vaccum lines, nothing, around egr and throttle body nothing, brake booster nothing, breathers from valve covers, around valve covers nothing...but when spraying carb cleaner on each injectors feet, two of them made the engine changed it's idle speed and started to be irregular like if it was slightly misfiring or stalling. For me this means, carb cleaner enters the manifold just as additional unmetered air.

I ordered 16 seals to replace them all for each injector. I suspect that some must be cracked allowing unmetered air to enter the manifold through these damaged seals. It seems logical, that's why the ecu attempts to correct by adding more gasoline then lambda says too much enrichment, then cuts off injection, becomes too lean and again adding fuel and the cycle goes on and on.