Big ABF problems (Update 15/5... FIXED... or so I thought!!!)

Some may have seen my other thread re tracking down a microswitch for the throttle body (thanks to Ess Three, I have one on the way, though!).

In the meantime, I'm still not certain this'll cure my problems.

I'm currently away for work, so have a left my car with a trusted friend to keep working on the issue in the meantime, but when I get back it'd be nice to tackle it with some more ideas.

Basically, idles high, fouls plugs at idle and intermittently misses at idle because the mixture is so rich. Initial throttle response is also very "numb" and general performance is flat, as though there's not enough ignition timing.

I've planned to replace the microswitch because whenever it was plugged in, it was richening up the mixture even further (and raising the idle even more). According to vagcom, the TPS is working fine. I've replaced cap, leads, rotor and ECU CTS.

Initially, there were codes for "MAP sensor out of range" and Coolant Temp Sensor - after I replaced the CTS and cleared the codes, none have come back.

The engine has the dBilas Dynamic ITB kit, which comes with a mapped chip and uses all the original sensors, so this shouldn't really affect anything - plus, I trust a company like dBilas can map an ECU properly. In saying this, I'm going to try putting the standard chip in to see what happens, but I doubt it'll change anything.

In the meantime, does anyone have any ideas? ECU relay? Has anyone had issues with ABF MAP sensors before?

Any help much appreciated. Sick of throwing money at the bloody thing

 

Things that have caused the same problem with my ABF are:

- Crap in the vacuum line to the map sensor blocking the vacuum to the ecu. Ran very rich on idle and cut out.
- Air temp sensor not working properly making the ecu think it was too cold outside and causing rich idle and running.
- Coolant sensor but you have checked this. Probe the wiring for this to make sure the ecu is seeing a good signal and that you haven't got a break in the loom.

I am running an aftermarket ecu but these problems can still affect you.

Gurds

 

Cheers Gurds. All the vac lines are new, so that's all good. I had considered the air temp sensor, but I've never seen one affect the mixture so drastically when it failed (plus, the last one I replaced on an ABF had thrown a code). I might order a new one just to be safe, though.

We need to get the car out again with the air/fuel meter to see what it's doing under load, but judging by the way it drives, the problem is only affecting the idle.

Thanks for the suggestions

 

So this is a motorsport ECU or a Digifant speed density ECU? You did mention VAGcom and some fault codes.

I missed that you run itbs previous post.
itbs and speed density ECU???

 

These are two different cars. The one question is a stock Mk3 (formerly a 1.8) now with an ABF with Digi 3.2 intended to be a daily driver (hence why I need to get it running properly). The only thing I've noticed which is different with this engine is it has a KR head and cams (no idea why).

We only got 3dr Mk3s here in 1.8 CL spec, so I'm trying to get a GTI-spec 3dr together for something different.

P.S. The other (perhaps valid) point is that I've not had this engine running previously - it just came from eBay DE and I've used part of the injection system/complete harness that was in my Mk1 of a few years ago (which I know is good). The consistency of all the wiring is fine too.

I'm pretty over the whole thing at the moment - blown headgasket on my Mk1 and problems with a basically standard Mk3 runabout Certainly testing my patience...

 

Right I am the same wave length.
If it is a standard controlled engine, then there is a possiblity that the vaccum line inside the ECU is compromising the signal to the internal MAP sensor. You may want to check this.
At throttle openings higher than much idle you will be close to 100kpa (WOT) anyway and the car will appear to drive ok.
Check this and let us know the result.

 

If you are going to change the air inlet temp sensor then check the wiring to these also, they sometimes break around the conectors, along with the wiring to the TPS - very commen to break/loose the protective platic insulation due to the heat of the manifold. There is a second temp sensor that mounts onto the inlet manifold (i am not sure of its purpose) but again the wiring could have failed on this too - it mounts to the front centre of the upper inlet where it neets the lower inlet. It sits behind the plastic HT lead guide and in between 2 and 3 runners.

 

That's the fan run-on remperature sensor for cars with air con.
Mine has it, my mates 16v didn't. All it does it run the electric fan after the engine stops to cool the engine bay down - from what I can deduce anyway.

If you don't connect it, it just never triggers the second fan into life.

 

Are you still running the lambda sensor?
Mine went very rich at idle when I'd managed to break a wire on the lambda sensor.

 

Always wondered what it was for, the wiring on mine was damaged so i replaced it when i did the engine conversions. Thanks for explaining that.

 

Air temp sensor from the airbox will not cause his issue though.

 

Thanks. I know the little hose section you're talking about - I'll check it asap and report back. In saying that, I do recall running my eye over the ECU board when I put the chip in and all appeared ok.

I've had ABFs with a more minor version of this problem before, but it's always been the CTS.

P.S. Yep, the lambda is installed and it's brand new

 

Vac line inside is all ok... the mystery deepens

 

An update... I'm about to burn this damn car

Ok, so we put the engine on the carbon clean machine, which made a big difference to the running - it now idles ok (only once warmed up, though) - so the injectors must have been a bit grubby.

Next thing was to attach the Autronic AFR meter and take it for a drive... turns out it's actually running lean as feck throughout the range!! Fuel pressure is ok, but it's like the injectors are too small (which obviously isn't the case)

I put a slide crimp on the return line to raise the fuel pressure and then it ran a million times better... but the pressure was up to like 75psi to get this result. And, If I crimp the vac line to the MAP sensor, it also starts to run much better!

What the hell is going on... I assume the FPR is fine, as it's happy at 45psi.

Do I try a different ECU or MAP sensor? Could there be a voltage issue at the injectors? Should I replace the FPR regardless?

I'm truly out of ideas with this car and sick of throwing parts at it [:^(]

P.S. I've also put the standard chip in just in case the dbilas one was a dud - no difference!!

P.P.S. Despite the lean AFRs, it's still fowling plugs too...

 

I had a duff fpr. But it wouldn't run at all. Have you replaced ecu relay? All vac lines?

 

All vac lines are new - I even double checked them again to make sure.

ECU relay is unchanged. TBH, I've never had to replace one, so have no idea of the symptoms - sounds like it might be worth a try though?

I'm really wondering if there's something pulling back the injector voltage or something like this. The injector plug was cut off the harness a while ago and rejoined, so there may be a gremlin here (unlikely, though)... I can't think what else would be stopping the injectors from dumping enough fuel in right across the range, though... Ground problem pulling back voltage?! Who knows!?

 

As you mentioned that raising fuel pressure made things better leads me to think that the fuel pressure regulator isn't working correctly. Are you using the Vw regulator in the aftermarket manifold?

Gurds

 

The dBilas ITB kit actually uses the ABF fuel rail and FPR so all is stock The fuel pressure is ok; it's just that the injectors aren't spraying enough fuel in as far as I can gather

 

If you say some of the injector wiring has been cut and rejoined have you proved the mechanical and electrical soundness of the join with a meter and a good tug on the wires? Jus a complete random 1, but a high resistance joint will result in poor current flow, do they need high amps or is it just a 12vsignal they need to function?? Prob not your issue but maybe one to check/prove/dismiss?

 

ECU relay regulates voltage to ECU too its not a standard relay.. I Changed one on mine when i had problems and it did make an improvement IIRC. Was a long time ago.