Right, replaced spark plugs, coolant temperature sensor, this morning I go to start it, it ticks over , then dies, if I had given it a few revs I think it would have started. Start it a second time and starts no problems.

Has anyone got a list of things to check that may affect cold start up?

Does MAF, fuel pump, battery?

Once it starts it runs fine, and starts first time the rest of the day.

Any help would be appreciated, thanks

 

Have you inspected & cleaned the ICV? Also what ecu do you have?

 

Apexi ecu, not looked at the ICV, because in my lack of knowledge thought that it would affect idle?

Where is it and how can you check/clean it? Also can you test/ clean a MAF?

 

I've heard this a few times that if you start the car and un-plug the connector on the MAF, if the car is still running this means its faulty & if it stalls its working fine. However i dont know if this is proven? You can clean the ICV with brake cleaner, it is located towards the right hand side of the inlet manifold.

I dont think it would be fuel pump related as it does prime. I had a similar problem on my V4 Type R, it was doing the same thing. Once i got it mapped it just disappeared.

 

With regards to unplugging the MAF, does the car need to be running first? I will have a look at the ICV, thanks

 

Ye iys has to be running. When you un-plug the connecter it will stall or either stay on if its knackered.

 

Sabas
Aladdin's advice on testing your MAF is no doubt well-intentioned, but wrong nonetheless.

If you wanted to do any kind of test on your MAF, it should go as follows:
- unplug the MAF (with engine off)
- start engine
- rev a tiny bit
- drive about tiny bit, at parking speeds. If your idling issues are much less obvious or completely gone, there's a good chance your MAF is faulty.

(All credit for the above goes to Splitpin - Mods, maybe it's about time we had a sticky on this somewhere?)

In any case, if the only problem you have is when you very first start up - in other words, you don't have unsteady idle at other times, or hesitation when pulling away from junctions once the engine is fully warmed up, or stuttering when revving at certain speeds and/or in certain gears while on the move, and so on - then I don't think a dodgy MAF is all that likely.

Other things worth thinking about:
- what model car is it, and how heavily modded
- is your battery earth lead clamped down good and tight on the terminal
- what kind of plugs did you fit, and what did you gap them to
- what kind of fuel do you normally run in the car

 

the car is on an Apexi ecu it will jsut not start with the maf disconnected full stop.

disconnecting it whilst it is running will get no indication or help as it will just stall becasue the apexi only uses the maf to run.

If you prime the ignition and then start it (ie. turn ignition on and wait 5 seconds) does it start and run fine?

Simon

 

Hi Simon,

I will have to check tomorrow morning or tonight when it is properly cooled down, I usually just turn it straight on, could priming it help, or would that lead to the problem?

The plugs were NGK 7b's I'm guessing gapped to what they should be, however, it was doing it before they were changed, when it starts it runs fine and starts throughout the day as it should, no idle problems or missfire

 

the fuel pressure disappears over night.. you try and start it and the pump has to try and build the pressure up as you are starting it..

try priming the pump and then spinning the starter .. could just be that the fuel pressure reg is allowing fuel pressure to drop.. and is nothing to worry about

Simon

 

oops, will try that, better stop replacing needless bits!!

 

Also, don't touch the throttel AT all before spinning it on the starter, they have a bad habit of flooding if you do.

 

If it is that, needing to be primed, why has it never done it in the two year I've owned it, and just now, is it a sign of anything on the way out? Never needed to prime it before, had fuel pump replaced last year, surely it doesn't need priming? It always started first time, does ICV do anything on start up, or would I have an erratic idle if it was that?

Alcazar, will not be doing that!


Could it be the fuel pressure regulator on the way out or do these not replacing?

 

could something have failed to cause a drop in the fuel pressure?

 

If so, then the most likely culprit would be the fuel press. reg.

 

have you actually tried it before you panic down that line David

 

well, my thinking is, if it has never had a problem before, and it isn't right at the moment, then something must be causing it, but, I don't want to be replacing bits needlessly, and I appreciate it is hard to diagnose a problem over the internet and appreciate everyone's help

 

if it is that it could be the reg, if could be the pump, it could be a fuel leak, it could be an injector oring.

Simon

 

Yeah, anything of the fuel system could be to blame.

 

Anyway to check these things for sure?

 

Wouldn't a poor functioning fuel pump cause general poor running? I am not convinced this is a problem with the fueling system itself (but certainly open to argument, here to learn, that's my motto!) as said it runs fine during normal driving etc etc...

Has anyone driven a car with manual choke? Sounds like it's not getting a rich enough mixture when the engine is cold or at least during the first start attempt, which suggests some sensor is out of whack somewhere but the question is which one?

Coolant Temp?
Air Temp? Is this sensor in the MAF itself?

What does the ECU use to determine fuel mixture requirements for a cold start? I have never come across a modern car that requires the fuel to be primed before starting. I've had some fairly aincent vehicles in my time and I could leave them for weeks and this wouldn't happen... Not being deliberately contradictory.. but I just trying to understand the logic here that's all..

Thoughts?

 

That's why there must be something up somewhere, but how can I get these things tested for sure?

As said above, it runs fine every other time, coolant temperature sensor has been replaced

 

I will put some start up videos when I get chance

 

Could it be a fuel relay ?

 

well to be fair i have started to have this at the mo when it does not fire up as qucik as when its been left all day or all night but i run a simtec so its not my maf but i will say this is only started to happen with this real hot wetaher, maybe nothing to do with it at all but the plaugs are brand new and gapped, the fuel reg is not evena year old and the feul pump is coming up for two years old the injectors seem ok but then they might need some new orings in which case where the can i get some of them from for some power enterprise jobys but sabas if you find out what the problem is give us a heads up cheers dude

 

will do, I'm leaving it at a garage over night so they can start it first thing, bet it will start okay, trouble is, there is deiantely something wrong as it's never had problems before

 

It's not proven at all, it's total and unmitigated f'ing b*ll*cks, but nevertheless seems to have become established Scooby myth (until enough threads like this put it to sleep).

It's a moot point on this particular thread given the Apexi ECU. However, if you unplug the MAF sensor on a Subaru ECU with the engine running, it's a matter of total chance whether or not it stalls, irrespective of whether the sensor's brand new or partially gone.

Indeed if the sensor is totally gone, to the point where it isn't outputting at all, or is occasionally dropping below the undervolt threshold, you wouldn't need to run any sort of "test" to determine as such, as your check engine light would be on, and you'd get a code 23 (or the newage equivalent) when you check. As such, even if this "test" worked as claimed, it'd prove nothing you wouldn't already know anyway. Complete and utter b*llsh*t.

None of which is any criticism of you, btw, I'm aware you're quoting, but there's only one way to address myths like this, and that's by debunking them head-on.

Sabas: Have you given the entire idle speed control system a thorough spraying out with brake cleaner, and do you have an FC Commander, or any other method of displaying what the ECU thinks the coolant temperature is?

If Sabas' car is a UK model it doesn't have an inlet air temperature sensor at all. If it's a classic STi, it's in the early part of the induction tract, before the filter. Newage cars integrate the IAT sensor into the MAF unit.

Main fuel map plus coolant temperature indexed cold run enrichment plus extra start mode enrichment most probably. Not sure whether the earlier ECUs add both enrichments together or just use one or t'other.

It will be happening, whether you're aware of it or not. Whether it's quiet enough for you not to notice, or whether the ECU does it during the startup process (rather than at ignition switch-on), pretty much all fuel injection cars will pre-pressurise the fuel rail before commencing injection. Otherwise there's no way for the controller to quantify the amount of juice going in.

 

Hi Splitpin, I have a controller and the water temperature goes up like normal, to about 86,87,88 degrees driving around , it sometimes drops down to 83 after being fully warmed. Is there a certain type of brake cleaner to buy, what does the ICV look like and where is the rest of the idle speed system?

Seperatley, I think you have answered this before, so apologies if you have, I have a vf 23 turbo and a baileys dump valve, the car has been mapped with these bits, if I wanted to go back to standard re- circ, would it need a tweak, do VF's run okay with oe re-circ?

Thanks

 

no it would be fine as long as both dump valves were sealing properly etc

Simon

 

It may be nothing, but just before I had the starting problem, I got the standard inner wing bit taken out and replaced with a CAF, could this be related? Seriously tempted to go back to standard airbox