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I really doubt it you would probably only notice it when under acceleration let's recap when everything is plugged in it runs but the idle surges is that correct? Or it doesn't stay running when everything is connected?
With everything connected, it starts up and dies within a second. It does not idle. If you start it up and snap the throttle to WOT it will rev up. If I accelerate gradually it stalls and wants to cut out like theres a fuel starvation
With the map sensor unplugged, it will start and idle, but the idle will fluctuate and it runs very rich.
If i plug in the map sensor while its idling, the idle will increase to about 1200rpm for a second and it cut out.
Definitely tomorrow.. I was incorrect in what I mentioned a few posts earlier..
This vehicle KOEO is measuring 1034mbar - thats barometric pressure.
I can barely take a measurement around idle because the car is basically stalling at low rpm.
At 1800rpm its measuring 268 mbar (0.7bar vacuum) at 8.5 degrees(T.B angle). Fully closed T.B angle is around 2.5 degrees on this car. So what I am thinking is the car is running too lean based on incorrect map readings and thats the reason for poor performance with the map sensor plugged in.
So what I plan on doing is, hooking up a vac gauge to the intake manifold, disconnecting the output wire of the map sensor and measuring the output voltage at different intake pressures.
Hmm we need to get a measurement with throttle plate closed we should be able to get at least 500 mbar and more also we want to look for the vacuum needle to be jumping or smooth a boost gauge might not be sensitive enough for this test but it's worth a try
Ok i hooked up a vacuum gauge to the car, at idle im getting 0.6bar vacuum. On snap throttle, the gauge zeros out and on deceleration it goes into 0.8bar vacuum and then back to 0.6 at idle (working like it should), the gauge is about 95% smooth, if you look at the gauge very closely theres a very little vacuum fluctuation at idle, but i guess that is because of the idle fluctuation caused by the overfueling.
I did disconnect the map sensor output wire only and checked the voltage at idle, it jumps around 0.8v to 1.4v. I also checked the output wire voltage from the ecu (the 1 that i disconnected from the sensor) it measures around 2v with it disconnected. Suppose to be 5v as its the drop down type..? With the meter still connected to the output wire, i join the wires back together the meter jumps to 0.3v and the car dies. To me this seems as a faulty ecu.. any suggestions?
I also checked my friends car today who has the mp9 system on his car.. his vacuum readings from the gauge matches the readings from the car that I am working on.
I then checked friends car on vcds, the sensor is working in the correct way.. at idle 550mbar (0.6bar), when revving it reaches the barometric pressure (Zero vacuum) on deceleration it drops to the 300mbar range (0.8bar) and goes back up to 550mbar.
With my car using vcds, it works the opposite, when revving, it goes into max vacuum instead of Zero vacuum. But when i disconnect the signal wire from map sensor and read voltage from the sensor output it reads as it should. I just want to be 100% sure before i call for another ecu
For reference what number were the wires on your diagram that you measured your voltages at so I can verify that is incorrect before condemning the ecu . Maybe I missed it somewhere in this thread but your map sensor says your vacuum raises when you snap throttle? You should go to near atmospheric pressure with throttle snap and vac should peak when closed throttle and deceleration
Map pin 1 - ground to pin17 on ecu
Map pin 2 - air temp sensor to pin43 on ecu
Map pin 3 - map sensor 5v ref to pin37 on ecu
Map pin 4 - map output wire to pin18 on ecu
Yes when i snap the throttle the scantool states that vacuum increases. But if i disconnect the output wire, the voltage that comes out the map sensor is somewhat correct, its only when the ecu is connected to the map output does it read too low voltages and makes the car cut off
So when you disconnect pin 4 while leaving the rest plugged in you can measure the voltage coming from the map and it corresponds to the vacuum of the vehicle but once you plug it in in pulls that voltage number lower ? Can you verify that it is connected to the right pin on ecu and that someone didn't have there fingers in there and have the pins in the wrong place ? If the ecu really is changing the voltage that seems like a problem with the ecu as long as the map sensor output is correct when pins 1-3 are connected and measuring pin 4 voltage I would suspect the ecu but to verify you don't have some sort of short I would remove the pin from ecu connector and measure your voltage there from your map to be sure that it's the same at both ends of your wire. Ecu problems are fairly rare so don't jump to that without thoroughly testing everything else . Is the map sensor a good quality part?
I checked through everything a few times just to be sure - all good with wiring and no shorts..
I bit the bullet and took the ecu for a remap for a 2.0L tune. In order to tune for a 2.0 some chip needs to be replaced.. anyway when the guy was doing that, he spotted a problem with the map sensor circuit (dont know what exactly the issue was, a burned track or something) but he sorted it out for me..
I brought the ecu back, put it into the car, realigned the throttlebody and fired it up.. And 100% smooth idle, no overfueling, no fluctuations. I was the happiest person on earth for that moment, his car has been a pain!
Decided to take it for a drive, just rolled down my driveway and it cuts out on me. I try to reverse it back up into the garage and it cannot move without cutting out.
Starts, idles, revs up fine but theres a problem when moving.
So something struck me that something is wrong with the speedometer circuit so i unplugged the speedo plug from the gearbox and the car moves without dying.
After further inspecting the speedo plug wiring i notice that a wire was spliced open and its the +12v wire (probably shorted out somewhere as caused another problem)
Anyway I took the car for a drive, it has kind of a fish bite at light throttle.. i checked plugs, plug wires and the coil. No problems with that. I now suspect it has something to do with the speedo circuit.
This car is really frustrating me wish I could burn it. Lol
Yeah, Thanks for all the help Ben. The fish biting / jerking stopped as soon as the map sensor was unplugged and car drove 100%. Soon as its plugged in the car misbehaves again.
After all the hardwork and stress, i had to send the car away with the map sensor problem. I think the map sensor component (chip or whatever its called) inside the ecu is faulty. I did send it for checking up along with a tune for the 2.0L engine, but i dont trust the guy 100% hence i sent the owner of the vehicle to a qualified auto electrician who is a friend of mine to diagnose further.
I dont like to release a vehicle if its not fixed but the customer needed to use the car and honestly it was wasting my time.
I hope to learn more about wiring and electronics so, if and when i do get another troublesome vehicle like that one il be able to sort it out.
