Felicia unknown problem

[RicardoM]

Code 01249 is "open circuit/short to positive" or "short to ground" on #1 injector. Test wiring then if nothing found replace the injector.

The stuttering you described might be fuel starvation related from #1 injector faulty.

Edited 9 August, 2020 by RicardoM

[matej2212]

I already tested the wiring before and I also tested the injector resistance which was 15 ohms, so I thought it is OK. Can the injector still trip a code if its resistance is OK?

[RicardoM]

Well, you are testing the resistance of the injector when it is not actually working. Moreover the current of your multimeter is way way lower than the actual current used for firing it. It is another thing when the injector is fired and it is exposed to high heat and vibrations.

A proper diagnose involves using an oscilloscope and "reading" the waveform on injector under load. What I mean is that an injector might look well as a coil resistance but it will fail under load. In your case the #1 injector might work 'well' on idle but fail on higher rpm. Remember I can't be 100% sure because I haven't seen a firing waveform as shown below for a generic reference.

 

 

Edited 9 August, 2020 by RicardoM

[matej2212]

Okay, stupid question. Which cylinder is number 1?😅

[RicardoM]

[matej2212]

Checked the wiring again, replaced the number 1 fuel injector but the stuttering remains, the car still stutters when pressing more than 1/3 on gas pedal. What else could be wrong or what else should I check?

[RicardoM]

Could be many issues. Bad timing (distributor), low fuel pressure, bad coil, bad spark plugs.

Show us a video of stuttering / misfiring.

Edited 14 August, 2020 by RicardoM

[matej2212]

Here it is. I hope it helps, beacuse it is a little hard to see because I dont have a tachometer. But you can hear and see the car jerking and hesitating.

[RicardoM]

I can't decide if it is a fuel issue or an ignition issue. Both could produce the same symptoms under load. I am more inclined towards a fuel starvation issue.

You need to check the fuel pressure under load then injectors. Use VAG-COM.

[matej2212]

Ok, thanks for your effort. Is there a way to test or to rule out the ignition issue first? Because I dont have a fuel pressure gauge and it would be easier to diagnose as much as I can myself, before taking it to a mechanic. I also noticed that the distributor cap contacts become dirty (they have grey/black residue which I have to sand down) after couple minutes of driving, is that normal or does it indicate something?

[matej2212]

Also the same symptoms were present the first time the coil was bad (although the car wasnt jerking as much).  But it would be strange if the coil only lasted 10.000 kilometres.

[RicardoM]

Both the distributor dirty cap as the short lived coil are not normal. I can't say more unless I have the car in front of me for a thorough diagnose.

[matej2212]

Ok, its definitely an ignition issue. I had an aftermarket distributor cap on the car, now I put on the old original (bosch) distributor cap and the car doesnt hesitate anymore. So I guess the aftermarket cap was somehow crap. But the bosch one still gets dirty after cleaning and driving a couple of minutes. Well I'll try to change the spark plugs and wires because they have never been changed anyway and then leave it. At least until the next problem appears.😅 Thanks!

[matej2212]

Ok, I'm really fed up with this. Problem came back. It gets better every time I change something, but returns after a few days. I tested the throttle body again with your (Ricardo's) guide, and found out that the voltages between pins 5-6 and 6-7 are around 1.5V, not 5V like you said they should be. I tested all the wiring and it's ok, so I guess I need a new ECU. Now I just want to ask if you are sure that the voltage between pins 5-6 and 6-7 should be 5V? I don't doubt your knowledge, just want to make sure.

On 06/05/2020 at 20:42, RicardoM said:

Let's have a look at the circuit diagram for the TB - throttle body (circled area) for each step below.

Here is what measurements you have to do, in this order:

• Test power supply to TB

1. TB connector unplugged, key on
2. connect a multimeter on voltage scale between pins 5-6, then 6-7, then 4-6
3. voltage should be between 4.5 V - 5 V.

If one or more voltages are not present, you need to check the wiring as follows:

• Test for continuity and/or short between TB connector and ECU connector

1. key off
2. unplug ECU connector
3. connect a multimeter on continuity (beep) scale between TB plug and ECU plug respectively: pins 1-59, 2-66, 3-69, 4-67, 5-75, 6-62, 7-74.
4. there should be continuity on all connections
5. now check for shorts between pins 1, 2, 3, 4, 5, 6, 7 of the TB plug. (pin 1 to each other pin, pin 2 to each other pin, and so on...)
6. there should be NO continuity

If the wiring is good then the ECU is bad.

 

Since your picture says "Simos 2P engine management" I am adding the picture for magnetti marelli ecu. The throttle body diagram is the same, so I just followed your directions for your picture and then looked for the right pin numbers on my picture (so if you said voltage between 5-6 and 6-7 should be 5V, I checked voltage between 5-4 and 4-8 according to my picture which is for magnetti marelli ecu)

[RicardoM]

On 25/08/2020 at 19:36, matej2212 said:

Problem came back. It gets better every time I change something, but returns after a few days.

It is one of those intermittent issues that all mechanics hate because they are hard to identify.

 

On 25/08/2020 at 19:36, matej2212 said:

Now I just want to ask if you are sure that the voltage between pins 5-6 and 6-7 should be 5V? I don't doubt your knowledge, just want to make sure.

The information was taken from service manual. Now, if I look closer the correct voltages are:

• 4.5 - 5V between pins 4, 7. It is the power supply send by the ECU to potentiometers.
• variable DC voltage between pins 5, 7 (range 1 - 4 V or so) when rotating the throttle valve
• variable DC voltage (but in opposition with above variation) between pins 8, 7 (range 1 - 4 V or so) when rotating the throttle valve

[matej2212]

Oh okay, so I guess it is okay to show 1.5V when the throttle body plug isn't connected. So my problem probably lies somewhere else.