Help! IAC causing no start in ‘93 940

[swedishsledmafia]

Hey everyone! I’m new here but have been stalking threads for months; it’s my go to when issues come up. Unfortunately, this time I have one that I am unable to find a solution for. I own a ‘93 940 non turbo B230F wagon with the Regina/REX system (Canadian over here eh).

After parked in town for a few hours, I tried to start the car and it turned over but didn’t start. First time it’s ever done this, tried a few times, same same. Tested the battery (all good) took a look at wires and all but everything seemed ok. Was gonna call a tow truck when I tried again to start it and it ran fine. Once started, it ran just like normal, and I was able to get home.

At home, I turned it off and on multiple times with longer and longer intervals, and it was fine each time. I hoped it was just a freak accident, but decided to check for codes. I got 2-2-3: “Signal Missing to/from IAC valve”. Took a look at the IAC valve, and disconnected then reconnected the electrical connector on the back of the IAC to see if that would clear the code. Unfortunately, after this I was unable to get the car to start again, same no start as earlier. Belts spin, gas pedal won’t apply at all..

I took out the IAC and gave it a really good clean, and brushed the contacts until shiny with scotchbrite. Put everything back together and still, no luck.

Kind of getting desperate here, this mofo is my daily driver. No clue what to do next, the only thing that comes to mind is to get a multimeter and use it to measure each connection related to the IAC system (including the one up by the air box, that the small hose leads to).

My thoughts also went to fuel pump, but I almost want to say it’s IAC related (especially electric and not necessarily IAC valve itself??) because it had the no start issue again after unplugging/replugging the IAC connector, but what do I know..

Any suggestions or similar stories would be much appreciated. Thanks!

[Steve940estate]

Will it start if you hold the throttle open a bit with the pedal ? Possibly a stupid suggestion but other than logging a possible fault does the ECU actually need the idle control valve to make everything else work.
Normal suggestions on later cars at least would be crank sensor and fuel pump relay although not sure you car has the relay.
Are you getting a spark and does the fuel pump run as normal ?

[Laird Scooby]

Firstly the EICV/AICV won't cause a non-start - there is still an air bleed past the throttle butterfly to enable a base idle speed of ~600rpm when hot. It might make life tricky when the engine is cold but as Steve points out above, opening the throttle slightly should enable a cold start if the AICV isn't moving.

As such, the AICV fault code is almost certainly a red herring. It does provide a clue though - can you hear the fuel pumps running when you release the key after trying to start? They should run for 1-2s after releasing from the start position.

If not, remove and inspect fuses #1, #11 and #13 ensuring no hairline cracks exist in any of them and the blades are clean and bright - clean with emery paper or renew if in any doubt.

When it's trying to start, does the rev counter needle flicker slightly? If not, inspect the wiring to the CPS on top of the bellhousing.

[Rversteeg]

I do not have any particular knowledge about the Rex Regina system, but when comparing the electrical diagram with a LH diagram you see largely the same setup. So the same rather crucial fuel pump relay feeding fuel injection and ignition. As a common point of failure I would start by checking/replacing this relay.
I am inclined not to give too much attention to the IAC fault code at this moment. It could very well be that this code has been there even before the starting problems and I can't see it being directly related to starting problems. If the throttle housing is clean, you should at least get some life out of the engine when starting as 2/3 of the air needed for idling does not flow through the IAC valve anyway. Compared to modern systems the diagnostic system is rather primitive and often more misleading than helpful.
Does the tacho needle move when starting? If it does, there is ignition and the crankshaft position sensor is working.

Edit: Apperently Dave and I were typing at the same time with similar advices. Two minds, one thought....

[TonyS9]

Cleaning the IACV will do nothing for this code. The ECU is detecting it is connected by passing a small current through it. You have a bad connector or broken wire somewhere.

[Laird Scooby]

Originally Posted by TonyS9

Cleaning the IACV will do nothing for this code. The ECU is detecting it is connected by passing a small current through it. You have a bad connector or broken wire somewhere.

That's only for the self-test on start up Tony. When it throws the code as a result of a "dynamic" fault, it means the engine hasn't responded to the AICV action that the ECU expects.

In this case it is expecting to see the engine speed increase which hasn't happened for another reason (lack of fuel pump action perhaps which may be due to the CPS not giving a signal) but still throws the AICV code as that's the only one it has "evidence" for.

[swedishsledmafia]

Thanks everyone for the replies wasn’t expecting to get this many. Tried to start it up again this morning and after everything you guys have said I am leaning towards fuel pump/relay related issue. Yes the tach needle moves when starting, so there is ignition and the CPS can be ruled out. When turning it over and listening for the fuel pump, I didn’t hear anything..

Besides the dead pedal feels like the engine is not getting fuel. Fuses 1,11,13 seem to be in fine shape as well - even swapped all 3 out and didn’t change a thing. How can tell which one of the two fuel pumps it would be that’s broken? As far as I know, this car has two, an in tank one and the main one (where would this be located?)

Also, I found the fuel pump relay, how could I test this first, before I rule that out?

Cheers

[Laird Scooby]

You should be able to see the pin numbers on the relay, work out which two slots in the relay socket relate to pins #1 & #3 and link them with a short piece of wire - you should hear the fuel pump run. Pin #1 is connected via a fuse to battery +ve so i'd suggest connecting your jumper wire to pin #3 first to avoid any accidents!

From what i can ascertain the Regina system used one in-tank pump only but i may be wrong on this, the main pump (if you have one) is under the left hand front seat area on the underside of the car in a cradle with the fuel filter, the in-tank pump is a bit of a pig to get to.

[swedishsledmafia]

Made a jumper wire and took out the relay and got confused, not sure which ones are pins 1 and 3, and I want to be sure before I start sticking wires in slots. See attached photo for what the numbers for the relay pins look like.

Also, sounds like you might be right! I researched it some and looks like Reginas only have the one fuel pump in tank - which makes my job easier if it is the pump. Still want to rule out/in the relay tho.

[Laird Scooby]

Originally Posted by swedishsledmafia

Made a jumper wire and took out the relay and got confused, not sure which ones are pins 1 and 3, and I want to be sure before I start sticking wires in slots. See attached photo for what the numbers for the relay pins look like.

Also, sounds like you might be right! I researched it some and looks like Reginas only have the one fuel pump in tank - which makes my job easier if it is the pump. Still want to rule out/in the relay tho.

The terminals you're after on the relay are 30 and 87/1 :



In your pic, top and bottom right pins, 30 is the bottom one and the +ve feed from the battery via a fuse. Work out which way round the relay sits in the socket (was it half loose to remove by the way?) and then where those pins are in relation to each other and link those two pins in the socket.

Good chance it is the relay, they have a habit of failing sadly.