Weird Engine / ECU issue

[Ashy]

Weird one this but thought it was worth posting as I'm scratching my head

This issue is on my F4R conversion running a DTA S40 pro ECU. I haven't changed the ECU or loom on the new build and it was all running fine on the old engine.

So, Built the car and engine and its been on the road since May, in that time I've done about 400 miles without any issues. Until the weekend before last driving home from the old folks (100mile run) when I pulled up at the roundabout off the A1 and the car just cut out, as I came down through the gears it was hesitating but if kept in gear above 2000 rpm it still ran ok until I stopped and it just died.

I had a look around it, couldn't see anything wrong, fired it back up and it started, drove all the way home, a further 5 miles, then it cut out again as I came over the speed bump into my street.

So I thought it was a dodgy crank sensor, so I bought a new one. I also fitted a new fuel pump.

So took it out tonight for a test run. It was absolutely fine for about 10 miles. Took it through the revs, stopped and started at junctions without issue. Then, about 1 mile from home it did it again. once it started up it was asif it had gone into limp mode...

Heres a video of the issue, you can see its at 7% throttle and it just jumps up and down.

http://www.youtube.com/watch?v=Ggiih...ature=youtu.be

I managed to get home at 1000rpm, but it took ages.

It seems to be some sort of electrical problem, the AFR's go really lean as if its cutting the fuel. I can't see any errors in the diagnostic and I've uploaded a known good map to eliminate it being a corrupt file...

Any ideas?

Thanks!

[Big Steve - Raider]

Probably a country mile off what the problem is, but i'm sure I read in a magazine once about an issue like this & it turned out to be the temperature sensor playing up and making the ECU think the engine was cold one minute & then hot the next?? Or something like that???

[Ashy]

Thanks Steve, I've heard of that aswell but think its just std 172 ECU's. Mine doesn't run an air temp sensor so just has a default value entered and the water temp is soild.

[Os8472]

Check your fuel pump relay, if the get wet they can sometimes just fine for hours on end then play up for a few mins then be fine again

[Ashy]

My fuel pump relay is mounted inside the car, behind the dash mate so it hasn't got wet... Thanks though... Any other ideas?

[Robbo]

bet the wiring is like a rats nest, that will be the problem

[SCHWARTZ]

Icv working properly?

[Mart]

Dodgy maf?

Slight air leak post throttle body?

[THE MASTER]

my guess is throttle position sensor

[Brigsy]

Wiring to the fuel pump ok?? Fuel pressure ok??

[SCHWARTZ]

Dodgy maf?

Slight air leak post throttle body?

Are using a maf ashy? Would have thought it was a map sensor but could well be maf at fault if you are using one.

[Scoff]

sensor values looks OK in the video mate.

S40's have a horrible habit of killing injector output FETs. Run the injector diagnostics in DTAswin with the engine off, check that all 4 injectors are sweeping through the ranges OK. You may need to disconnect all bar one at a time to hear if that channel is responding properly. Make sure the fuel pump is off during the test.

other likelyhood is the crank angle input. DTA's need a CLEAN CAS signal. Make sure you've used screened wire and 100% make sure it's connected exactly as DTA suggest in their diagrams. I think the screen must be connected at the ECU and not at the CAS end. Check the polarity of the CAS if you havn't already, but guess you will have done.

final though, it could be a failing coilpack. Its hard to determine from the video but it almost sounds like its dropping on to 2 cyls intermittently.

[Ashy]

Scoff, when you run the injector diagnostic are you just listening for them clicking? I guess it just cycles them for a few seconds?

As you can see in the video all the sensors are reading OK although there are a lot of rejected crank pulses and crank sensor errors so I will be checking that again tonight, maybe adjust the position and gap then re-time.

[Scoff]

Scoff, when you run the injector diagnostic are you just listening for them clicking? I guess it just cycles them for a few seconds?

As you can see in the video all the sensors are reading OK although there are a lot of rejected crank pulses and crank sensor errors so I will be checking that again tonight, maybe adjust the position and gap then re-time.

It think you answered your own question, so run a new piece of 2 core screened for the CAS. Check the DTA diagram but I think the screen needs connecting at the ECU connector to one of the ground pins.

Yes, injector test just clicks the injectors and cycles through different speeds which causes the injectors to sound different notes, which should sound clean.

[Scoff]

I just realised you might have read my reply before I'd edited and added some extra, sorry.

[Ashy]

I just realised you might have read my reply before I'd edited and added some extra, sorry.

Yeah I did, thanks mate, the CAS is screened as described in the DTA guide also the loom was used on the previous engine with no issues... It sounds like the crank sensor needs to be looked at as this is the major thing that I've changed on this engine.

I'll check it and report back!

[Scoff]

I find that running the crank pattern detection feature is a good test of the CAS system as a whole. If it runs time and time again without error and reporting the same valid data then it's probably OK.

If you find it runs OK at high RPM but is struggling at low RPM it might be that the air gap is too large.

[Ashy]

I find that running the crank pattern detection feature is a good test of the CAS system as a whole. .

Is that a DTA feature? I haven't really played with the S40 / new version of SWIN much.

If you find it runs OK at high RPM but is struggling at low RPM it might be that the air gap is too large.

Thats what I'm finding.

Why does it go lean when cutting out? I thought it would go rich. Unless its so rich the sensor thinks its lean

[Scoff]

Is that a DTA feature? I haven't really played with the S40 / new version of SWIN much.



Thats what I'm finding.

Why does it go lean when cutting out? I thought it would go rich. Unless its so rich the sensor thinks its lean

Yes mate, called "crankshaft oscilloscope" or something like that, in the test menu.

Forget the AFR, it means bugger all in misfire situations. If theres no spark, your not burning fuel, and you need to burn fuel before there is left over oxygen for the sensor to read ie, no burn = lean AFR gauge

[Ashy]

Hooooray, looks like its fixed

A lad on the DTA forum informed me that the Marelli crank sensor is wired pin 1 ground, pin 2 signal which is opposite to the standard ford sensor and can give a false or limited rev range as if the rev limiter is being reached early.

Can't believe that a simple wire swap has done the trick. Went for a blast tonight, no sync errors or CPS errors!!

Will go for a longer blast tomorrow but looks like its sorted!

Thanks for everones input!

[Matt Cole]

Hooooray, looks like its fixed

A lad on the DTA forum informed me that the Marelli crank sensor is wired pin 1 ground, pin 2 signal which is opposite to the standard ford sensor and can give a false or limited rev range as if the rev limiter is being reached early.

Can't believe that a simple wire swap has done the trick. Went for a blast tonight, no sync errors or CPS errors!!

Will go for a longer blast tomorrow but looks like its sorted!

Thanks for everones input!

great matey! Remember my 'wire swap' issue with the standard renault TDC sensor with the Adaptronic?