- This topic has 19 replies, 8 voices, and was last updated 3 years, 5 months ago by
.
-
Topic
-
Hi guys,
I have a problem with my Fiat Bravo ’08, 1.4 turbo T-jet 120hp( similar engine as in the Chevrolet Cruze, Dodge Dart, and Fiat 500).
The problem:
Every time i do a cold start ( the car has been sitting for more that 3-5 hours) the car starts up just fine, idles for 3-5 seconds and then it sputters and dies. It does this 2 or 3 times and then it won’t die anymore, but for the first 1-2 minutes the car is very jerky/ lacks power.After it’s warmed up there’s no sign of any problems: idles ok, runs ok. The problem started about 1 year ago and it got increasingly worse, at the beginning it would just sputter for a bit and then it was fine.
I had a scanner on it:
-it has no stored codes.
-coolant and air intake temperature sensors report ok.
-did not find a vacuum leak (tested as Eric has shown)
-the MAP sensor reports reasonably close to the ECU expected amounts.(and since it’s a MAP i would not expect a vacuum leak to cause problems)
-tested the fuel pressure in the rail at cold start: 3.5 bar with engine off or without the vacuum hose connected, pretty stable, it drops to 2.5-2.8 at idle .. so that seems to be ok.
-fuel pressure bleed off seems a bit more than expected.. drops to around 2 bar in 10 minutes.. but it goes right back to 3.5 in 1-2 seconds with the ignition on… so not that bad.
-no blockages in the intake system.
-replaced the spark plugs.
-replaced the fuel filter.
-checked the EVAP solenoid- works fine.
-had the injectors out, tested the with an ohmmeter and they are all really close in readings( don’t remember the exact figures. but i remember looking up the official figures and they were close)
-tested the injectors (using the two-way obd2+laptop combo I’m using) spray pattern looked fine and uniform across all four.
-cleaned the throttle body that is ok.-It has a coil on plug system. don’t know how i could test them.
-With starting fluid added to the intake it no longer sputters.
-LTFT was only about -7% at one time, i then reset the ECU and the LTFT to ZERO to see if that would make any difference- it did not.
– What makes a difference is the level of fuel in the tank, when full it only sputters; as it drops it sputters and dies, even tho the pump is still completely submerged in fuel( and altho fue pressure is still ok)Any suggestions are welcomed!
-
Replies
-
I don’t have access to an oscilloscope, but i might do a DIY soundcard/laptop oscilloscope but i will only be able to measure up to max 12v ( would rather apply max of 2-3v).. but that should be enough to see the patterns of the crank and cam sensors. I will not be able to measure the secondary ignition.
It’s not a vacuum leak, it uses a MAP so it will adjust fuel to the pressure in the intake manifold. Also i’ve pressure tested it while i was testing for boost leaks.
Eric, I do agree that the sensors should measure closer.. i will take another measurement, one morning before it gets any sun, so the temperatures should be much closer.
If that is still 8 degrees C, off than i will try to make it closer to what the other two sensors ( climate control and intake) are reading; i will add the necessary resistors in parallel or series till i can read a closer temp on the obd interface. I think this should be ok, since the coolant sensor is basically a thermistor (temperature controlled resistor)Hi,
I’ve measured the temperature sensors in the morning, they are closer, only 5 degrees difference as opposed to 8.
Tried playing around with resistors on the temp sensors ( got them almost identical – close to the actual temperature) but there was no change in the behavior when starting the engine.
So..it’s probably not the temperature sensors.Also I’ve checked to see if it’s loosing injector pulse or spark when it’s starting to die. It’s not loosing spark and it’s pretty strong. As the engine starts to die the injector pulses get longer( maybe trying to supply enough fuel to keep it alive).
Had a look in the repair manual at the fuel pressure testing procedures:
Supply pressure check:I don’t understand how it would have more pressure with the engine started idling, since the intake vacuum would make the pressure regulator open sooner. What do you think? is that part correct? -maybe it should be tested at full throttle not idle (when the boost would force the regulator closed to make more fuel pressure in the fuel rail)
Anyway my results are 3 bar after 1-2 seconds after i turn the key to the on position, 2,7-2,8 bar at idle, and 3,5 bar at full throttle.Return pressure check:
Why would there be any pressure on the return line after the regulator??? since it’s a straight pipe directly to the fuel tank and there it just dumps inside, and an even bigger volume of fuel is being sucked out of the fuel tank by the fuel pump( it’s bigger because some of the fuel is burned in the engine)
Is this some crude way of measuring volume??My measurement on this was a big ZERO bar pressure.
I would take it to a professional, if i could find someone who i could trust.
Here they are all about reading fault codes and replacing parts, Nobody does diagnostics.
Last time i had a problem with this car(it has a feature called “Hill Hold”- holds the brakes for 3 seconds after you release the brakes, if you are on a hill… mine would hold the brakes indefinitely ) i took it to a Fiat dealership and they couldn’t even reproduce the problem( even tho i gave them all the info) so they decided that i should replace the entire braking system, abs pump,brake pump… and all at a cost of ~3000 euro.
Of course I refused to do that, and after spending 300 euro’s on a second hand ABS pump+controller ( thinking that Fiat might have been right- they weren’t problem was still there ) …anyhow long story short i fixed the problem with a 1 cent washer between the brake pump and the servo!It’s been a while since i last posted, so here is a little update:
At one time i replaced the crank sensor.. that did nothing.
It had gotten so bad it would die 3-4 times after each cold start;
I took it to the Fiat Dealer.. they had it for 4 mornings. They concluded that since nothing was obviously wrong, and the fact that it runs fine after it heats up, that the ECU must be faulty.When i heard that I took the car away and payed for the “diagnostic”
About a week ago I emptied the gas in the tank and put it in a different car.
I then put fresh gas in.. after that it has started each time in the morning.. but it still sputters a little after start.hello! I has the same problem with t-jet. Very bad cold start with 3-5 even 6-7 attempts!
I check all temperatures from ECU and fuel preassure – all OK. Then I checked crunkshaft sensor resistence – 885 omh.
Also I closed evaporation valve and reset self-adapt. parameters in ECU. – In the morning engine started from same 4 attempt((
Please help me with some recomendations – what I should do next?
- You must be logged in to reply to this topic.