weird issue TB42e

Hey guys,

Having a weird issue with the Maverick after having converted it to EFI.

If I have the air flow meter connected, the car will not run, it'll crank over but will not run.

If I disconnect the AFM, the car runs, idles, revs. Bit rich but with nothing to tell the ecu how much air is coming in I assume it just richens it way the hell up.

Now, when I pull the AFM and test it(hook up to power source and blow air onto the exposed sensor, I get the readings I should. Same if I have it connected with the ignition on(not running) and the ECUtalk cable connected. I can blow on the sensor and see the voltage change as it should on the display.

TPS is fine and crank angle sensor in dizzy seems to be fine.

I was almost sure it was the afm and was preparing to fork out a lot of cash for a new one, until I hooked up the test leads and checked it, but now I'm not sure what to do.

With the AFM connected but the engine not starting I get no ecu codes, with it disconnected I just get the AFM disconnected code, so if it was a short or a connector in the wrong socket or something I'd expect to see other codes?

Any help/advice would be greatly appreciated.

Sorry I cant help you mate as I hated all this when I had the petrol.... Hopefully someone has more of an understanding and will help.

Would have loved for you to have the car ready for the trip this week.

If you are certain that the wiring is ok ,can you get hold of another ECU to swap it and check. Was the donor vehicle running when you bought the parts?

There's no air leaks in the intake system? leaking manifold gasket?

Have you checked the coolant temp sensor?. Try disconnecting the coolant temp sensor and see if it will run with the AFM connected.

Mudnut, the loom came from a donor car with a rooted engine, but I've found a horrorshow in the wiring loom thus far, been cleaning it up as I go.

The efi gear was from a supposedly fully running car.



Yendor,

New manifold gaskets, intake okay. Are you referring to the top coolant sensor(red/yellow wire)? It's a brand newie, but disconnected it to try, still the same.

Yeah the sensor with the two wires. Disconnect the ECU and measure the resistance of the sensor by back probing the ECU connector.

With the engine running you could spray something like carby cleaner (carefully so you don't start a fire) around the manifold and intake to confirm there's no leaks.

Going to be out and about this morning but will give that a go soon as I'm in front of it again, Yendor.

Okay, disconnected the ecu and checked resistance of that sensor at the ecu connector, looks like I'm getting infinite resistance, hmmmmmm.

Need to recheck it to make sure I'm not just a moron though, was pretty tired when I did it.

Also traced back the crank angle sensor wires and the afm wires. Pretty sure now the afm is okay, retested it too.

Rechecked the coolant temp sender wiring back to the ecu, it's all good. Checked resistance across the sender at the ecu connector, all good. 2.5k@ ~20deg.

So, afm working, tps working, temp sender working, crank angle sender working(will recheck to make 100%).

Refuses to run with afm plugged in, runs and revs with it out(flat spots at about 2500rpm but you can rev it past that).

Runs rough for a few seconds then dies with crank angle sensor unplugged.

Stumped.

Update, Sorted!!!

Got talking with Damian from 4X4 Offroad Clinic in Hallam, he let me pop by to try my ecu and afm on his comp truck. Turns out the AFM while testing okay, actually wasn't. He reckoned it's pretty common for them to seem fine(12v and signal voltage look okay on a meter) but the unit can still be operating outside of acceptable parameters.

So, one second hand AFM later and the mighty Maverick lives again!!!!!!!!

Thanks to everyone who has posted and messaged me advice(especially Yendor, mudnut and BA) to help and sort out this issue, it's been very much appreciated from one and all. Can't stress enough how cool Offroad Clinic were too, they know their GQ's, go see them, buy stuff!!!

Punch Damian in the neck for me Pete...

Glad you got it sorted mate.

That was an interesting one. I had my money sitting on it being a manifold leak.

Good to read you got it worked out.