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Jamesjesse

exhaust popping, fuel smell issue

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Hi all,

It all started one year ago but car is more of a garage queen. Recently I started to drive more and would like to solve this to not damage anything. Whole vehicle description, please see signature.

  • Car starts no problem, nothing wrong with idle.
  • Car drives mostly fine and has all the power it should have.
  • The issue is, when either driving hard or just shifting in higher rpms,  it seems to dump fuel into the exhaust and it is igniting and gives a loud pop. In certain occasions I do smell fuel - this would be mostly when driving slower down the street or in traffic. Not always during all this, but occasionally, the engine loses power for a second - I would describe it like the piston is maybe overflown too much with fuel and can´t ignite. But next second it pulls again like nothing happened and all the power is there.

I have logged few times with Torque Pro android application and was googling what values should be correct, but to understand everything and the relationships, you would need to study rocket engineering. 🙂 Although one thing seems to be aligned with the above - I have read that "short fuel trim" should not get above 25, but in my logs I have seen they do reach more -  I believe to seen in one log even 32, but here an example:

image.thumb.png.3a24453938b431c45f6f0286e7e6ae59.png

Prior to all this started, car received:

  • plugs
  • oil and filter
  • air filter
  • DO88 intercooler and radiator
  • silicone vacuum hoses
  • ecu tune 

During the one year I have checked several times all boost and vacuum hoses for leaks, exchanged many clamps, added them where they have not been from factory. I had exchanged the tuned ECU for the stock one, there had been no changes to the issues, the car just felt stock on power.

I might be thinking an injector perhaps - stuck being open too long under certain conditions and dumping that fuel. But can this even happen? I can imagine they being clogged and not delivering fuel but the open close cycle would be managed by the ECU, right?! So both stock and tuned ECU would need to send incorrect data in that certain condition.

Or maybe the plugs -  came incorrectly gaped and still working just fine under most conditions, but maybe not igniting 100%, where I would smell fuel even driving slow, and being much worse in the high rpm. But would a bad ignition cause the ECU to dump even more fuel? I would think the opposite and it would be less fuel.

Coils - but would think the same as plugs, less fuel not more fuel...

Do you have any ideas/recommendations what to look at and/or how to test something DIY way?

Many thanks guys!

 

Edit: BTW, no CEL what so ever at any time, or limp mode. Is just the one occasional power loss that I take as negative. I love the exhaust pop but scared to damage anything if I drive much.

Edited by Jamesjesse

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Found the plugs I have run before and went to compare them with the ones I run now on carbon build up etc.

Noticed the number stamped on them is different in the last  smaller 3 digits but a google search did not bring anything. Google found the plugs only when using 30637308 (without the last 3 digits) which brings the pn 8692071 - kit of 5 plugs, which I had in both cases. I assume is some kind of production number only?! There does not look to be any other difference in them, although I do not have a tool to measure the gap.

30637308 758 vs 30637308 112

IMG_1840.thumb.JPG.4f3c83bef10774835f89c377ca4ada8b.JPG

Changed them and will go for a test drive just to rule out this being the issue.

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Have you checked the ECT sensor and its connector?

The values from your logs look OK, but it's possible that there is a small delta that is messing with your fuel trim? Even a bit of corrosion on the connector can cause issues.

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No I did not previously. Looking now at the connections, they seem to be OK, no rust or oxidation. But the sensor it self - the brass part is full of green/brown oxidation on the outside part, will not be better inside the thermostat housing. I assume it will look like this:

dscn2834.jpg

Reading about the issues a bad ECT can cause, is mostly it gets stuck in HOT position causing radiator running longer or constantly, bad idle, bad cold starts, temp gauge not correctly working, etc. I do not have any of these symptoms.  But it might cause ignition timing or injection speed differences which might be my issue at certain rpms.

What causes the sensor to fail? Would it be just the oxidation that changes the resistance and should be worth to hit it with some 2000 sand paper to get back the clean brass and test if it helps? Or are there any electronics inside that just fail over time and only a new sensor will tell me?

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Car is cold in the garage and the resistance is showing 2220 ohms by 22°C (71.6 Fahrenheit).

Found this table: https://www.___.com/forums/viewtopic.php?f=1&t=52203 and it would look to be OK:

* -20C: 16,000 Ohms (16 kOhms)
* 0C: 7,300 Ohms
* 20C: 2,600 Ohms
* 80C: 300 Ohms
* 90C (Operating Temp): 200 Ohms
* 100C: 150 Ohms

Will have to measure once I drive again.

Edited by Jamesjesse

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Today I went for a drive and noticed immediately after start up the fan started to run. It ran thru the whole drive and even after the motor shut down - like for the next 7 minutes.

I have not been able to go above 87°C (188.6 Fahrenheit) because of the fan running. I have measured at this temperature it had 260 ohms which looks OK. At 51°C (123.8 Fahrenheit) it had 815 ohms.

So according the measurements the sensor would seem to work properly but whats up with the fan suddenly running after I have yesterday disconnect and connected the connector?  Could it somehow damage the relay?

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It's possible the relay is bad, or failing. If it's still running after the engine has stopped, try pulling the small, trigger connector from the relay to see if it stops. If not, it's most likely a relay issue. If it does, it could be an issue with your ECT sensor/connector that didn't become an issue until you messed with it. (I know, "It's not broke until I fix it", right? )

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Thanks Chuck for your replies!

I have disconnected the battery for the night and the fan did not start by it self anymore after start up. I have now placed my order for the ECT anyway since it seems to be a wear part that needs replacing occasionally.

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