Engine suddenly went very rich and died - Microsquirt

[ajg193]

Hi All,

I installed a microsquirt system (fuel only, triggered off of coil, R20 replaced on board with 1k+/-1% ohm 0.5 watt resistor) into my car and managed to get it running yesterday. After driving about 200 km and building up a reasonably smooth running tune we were going up a hill and the engine suddenly went full rich - as if the injectors were stuck open, this happened over the space of about a minute and the system did not recover. The o2 sensor ended up being pinned at AFR 7 and the car had no power at all/running on three cylinders. We managed to get the car turned around to get it down the hill and then towed it home.

The problem was that it was night time so we needed electrical power for the lights and needed braking so I disconnected the fuel pump and had the engine in 5th gear most of the time for towing. I think this may have damaged the engine as the vehicle was blowing a lot of blue smoke this morning when I managed to get it running again (it has never blown blue smoke in it's life). When I checked the oil this morning it was very diluted with fuel and no.1 and no.2 spark plugs were wet with oil. I changed the oil and started the engine again, only running for about 15 seconds and it was still smoking and running on three or so cylinders. I'm thinking that the no.1 and no.2 cylinders were bore washed and then scored during the towing operation as the old oil had lost a lot of its lubricity and viscosity. I'm currently waiting on a friend to come around with a compression tester to see what sort of damage has been done.

Before getting it running this morning I pulled off the fuel pressure regulator and lowered the seating pressure and put it back on. The fuel pressure regulator appeared to be working correctly. I *think* that the cause for the rich situation was too much fuel pressure - I do not know why this suddenly became a problem though as we had driven up that hill earlier in the day under similar loading conditions without any issue -, but I have no fuel pressure gauge to confirm this at the moment.


We had datalogging running at the time, but shortly after the onset of this situation, the battery on the laptop died so we don't have much data after the point. I'm not sure how often it saves a log file, but I do recall the AFR reading being pinned right at the bottom of the guage before the laptop stopped.


I am running 4x low impedance (2.6 ohm) 145 cc/min injectors, with a 10 ohm/25 watt resistor in line with each injector. The injectors are all run through one 5 amp fuse and this fuse has not blown, so I can't imagine a short on the injector ground lines before the resistors - which are mounted right next to the ECU.


The engine is a Toyota 4K.

I've attached the most recent tune that was on the controller at the time and a few graph images from the log file (the log is 23 MB so I don't think I can upload that much on here?).

The first graph shows the point at which it started to go a bit odd, right when I shifted up a gear. The second graph shows the remaining data.

As you can see the AFR dropped down to 10 and the pulse width dropped down to about 6 ms before the laptop died, this would indicate to me that the ECU was trying to reduce the amount of fuel going in.

Where the TPS starts going wavy after it started going rich is when I was moving my foot on the pedal thinking "the response is getting very mushy, this isn't good" and trying to find a sweet spot to get more power somewhat as I would do on a carburetor equipped engine.

Cycling the power to the ECU and flashing on an earlier tune had no effect, the car was still running insanely rich/poorly with no power and the exhaust smelled like unburnt fuel.


In summary: I think either my fuel pressure regulator somehow got stuck in a somewhat closed position and forced the fuel pressure to spike or an injector driver was locked on full - I'm not sure if it was on both banks or just one bank.


Does anyone have any other ideas as to what may have caused this and how can I avoid it again if I ever get the engine running correctly again?

4K rich failure.png

4K rich failure 2 and 3.png

Thanks

[Matt Cramer]

A wavy TPS can be causing excessive acceleration enrichment.

[ajg193]

A wavy TPS can be causing excessive acceleration enrichment.

The waviness was caused by my foot when it started going bad.

I did a compression test the other day, pretty much no compression. I'm going to pull the engine out this weekend and inspect it, hopefully it will be salvageable.

I'm just going to put the carburetor back on the car after rebuilding the engine and pretend the whole EFI saga never happened.

[Matt Cramer]

Can you post up the complete data logs? There may be something going on in there that doesn't show up in the screen shot.

[ajg193]

Maximum allowed size is 1 MB. Should I upload the file to an external location?

[Matt Cramer]

Maximum allowed size is 1 MB. Should I upload the file to an external location?

You can put the log in a ZIP file and upload it, or truncate it if you have the registered MegaLogViewer.

[ajg193]

Here's a 7zip (renamed to .zip to allow for uploading, should still open with most archive viewers) of the logs from for the last ~21000 entries or so, I tried with a .zip but the file was still slightly too big to upload here. I can remove more entries if you need a zip file.

[Dennis_Zx7r]

FWIW, log looks alright to me.

[ajg193]

Well I found the cause. d*** I'm an idiot.

In the excitement of getting the engine running I forgot to put the last few cable ties in place holding the loom to the chassis. The loom came in contact with the hot exhaust manifold and melted through the injector ground for cylinder 2, causing the injector to be stuck open (this probably would have also provided a ground path for injector 1 through the resistor pack) - this would have caused a current draw not too far off of the limit for the 5 amp fuse.

Anywho, I pulled the cylinder head off expecting to find cylinders 1 and 2 to be completely scored and damaged but they look fine. Hopefully the rings are still good. All of the blue smoke was not fun, but I didn't really see any evidence of blow by anywhere, I think that the compression tester I used must have been bogus. In hindsight I probably could have just kept running the engine for about 5 minutes to see if that would clear the smoke, but I think ripping the head off was good insurance. A new head gasket is less than $45 from Toyota.

I took the opportunity to tidy up the wiring loom and install a better MAP sensor, so now I just have to wait until Tuesday so I can pick up the new head gasket/oil/filter for the engine and see if it is better now that everything has been ripped apart and cleaned. I'm also going to install a fuel pressure gauge in the system.

Is there any chance that the ECU's injector driver could have been damaged by this? I can't really imagine it as all the ECU does is grounds the injector?

With any luck I will be up and running again with the EFI and I won't have to pretend it never happened.


Another question, with the MAP sensor, I have no datasheet for it (just a random one off of a Daihatsu Charade or something). Is it alright to just calibrate it such that it is reading atmospheric pressure at 5 V and leaving the lower value as 10 (what unit?) at 0V? I guess I would just tune the vehicle to suit what the MAP sensor is outputting by bodging the VE values if the calibration isn't quite bang on?

[LAV1000]

ECU does ground injectors.
You probably can use the output test function to test injector outputs.

[hybrid]

Well I found the cause. d*** I'm an idiot.

In the excitement of getting the engine running I forgot to put the last few cable ties in place holding the loom to the chassis. The loom came in contact with the hot exhaust manifold and melted through the injector ground for cylinder 2, causing the injector to be stuck open (this probably would have also provided a ground path for injector 1 through the resistor pack) - this would have caused a current draw not too far off of the limit for the 5 amp fuse.

Anywho, I pulled the cylinder head off expecting to find cylinders 1 and 2 to be completely scored and damaged but they look fine. Hopefully the rings are still good. All of the blue smoke was not fun, but I didn't really see any evidence of blow by anywhere, I think that the compression tester I used must have been bogus. In hindsight I probably could have just kept running the engine for about 5 minutes to see if that would clear the smoke, but I think ripping the head off was good insurance. A new head gasket is less than $45 from Toyota.

I took the opportunity to tidy up the wiring loom and install a better MAP sensor, so now I just have to wait until Tuesday so I can pick up the new head gasket/oil/filter for the engine and see if it is better now that everything has been ripped apart and cleaned. I'm also going to install a fuel pressure gauge in the system.

Is there any chance that the ECU's injector driver could have been damaged by this? I can't really imagine it as all the ECU does is grounds the injector?

With any luck I will be up and running again with the EFI and I won't have to pretend it never happened.


Another question, with the MAP sensor, I have no datasheet for it (just a random one off of a Daihatsu Charade or something). Is it alright to just calibrate it such that it is reading atmospheric pressure at 5 V and leaving the lower value as 10 (what unit?) at 0V? I guess I would just tune the vehicle to suit what the MAP sensor is outputting by bodging the VE values if the calibration isn't quite bang on?

Personally I would try and get a part number and look for a datasheet to get the correct specs.
Theoretically you could use a vacuum pump with a gauge to test it, but you'd have to be sure the gauge was accurate.

[LAV1000]

Well I found the cause. d*** I'm an idiot.

In the excitement of getting the engine running I forgot to put the last few cable ties in place holding the loom to the chassis. The loom came in contact with the hot exhaust manifold and melted through the injector ground for cylinder 2, causing the injector to be stuck open (this probably would have also provided a ground path for injector 1 through the resistor pack) - this would have caused a current draw not too far off of the limit for the 5 amp fuse.

Anywho, I pulled the cylinder head off expecting to find cylinders 1 and 2 to be completely scored and damaged but they look fine. Hopefully the rings are still good. All of the blue smoke was not fun, but I didn't really see any evidence of blow by anywhere, I think that the compression tester I used must have been bogus. In hindsight I probably could have just kept running the engine for about 5 minutes to see if that would clear the smoke, but I think ripping the head off was good insurance. A new head gasket is less than $45 from Toyota.

I took the opportunity to tidy up the wiring loom and install a better MAP sensor, so now I just have to wait until Tuesday so I can pick up the new head gasket/oil/filter for the engine and see if it is better now that everything has been ripped apart and cleaned. I'm also going to install a fuel pressure gauge in the system.

Is there any chance that the ECU's injector driver could have been damaged by this? I can't really imagine it as all the ECU does is grounds the injector?

With any luck I will be up and running again with the EFI and I won't have to pretend it never happened.


Another question, with the MAP sensor, I have no datasheet for it (just a random one off of a Daihatsu Charade or something). Is it alright to just calibrate it such that it is reading atmospheric pressure at 5 V and leaving the lower value as 10 (what unit?) at 0V? I guess I would just tune the vehicle to suit what the MAP sensor is outputting by bodging the VE values if the calibration isn't quite bang on?

Personally I would try and get a part number and look for a datasheet to get the correct specs.
Theoretically you could use a vacuum pump with a gauge to test it, but you'd have to be sure the gauge was accurate.

Use some transparent hose and work with inch/H2O or cm/H20 whatever suits you, H2O = water.
Convert those values to mBar.