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B4 sputtering on cold start


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#1 krazynayba

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Posted 07 May 2014 - 12:01 AM

Hi All,

 

For a while now (matter of months) my B4 has been starting very rough in the mornings, usually when it is below a certain temperature. I turn the key and it takes a little bit longer to turn over, and when it does it will:

  • Turn over then rev up a little, go right down again, and then conk out.
  • Sputter really badly (to the point where the whole car shakes) for about 10-15 seconds then the idle will even out. After this happens and I put my foot down on the accelerator slowly, the car feels "stuck" as if it's only accelerating at a fraction of the speed it should. After about 4-5 seconds the acceleration feels 'normal' again and the car behaves as it should.

Both of these may occur or just the second one depending on how cold it is outside.

 

Once the car gets going it seems to be fine; Idle seems normal, and it doesn't ever cut out while I'm driving. I suppose I'm just a little concerned for the engine's well-being. I've spun a big end bearing already and really don't want a repeat of that. I would take it in to S&J but they'd need the car for at least a whole day or two so that they can replicate the issue. If possible I'd like to find any potential DIY solutions to this, as relying on public transport to get to work is hopeless in SA.

 

Using general knowledge and what I've found online, I was thinking that the issue could be related to either:

  • The MAF sensor
  • The fuel filter

I didn't list the battery as I assumed that the engine turning over implies the battery is ok (not sure on that though). If anyone else has any suggestions of things I could have a look at before having to consult a mechanic then I would appreciate it immensely!

 

Cheers!  :D



#2 JhoffB4

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Posted 07 May 2014 - 01:19 PM

O2 sensor?

Start with checking the codes. They should lead you in the right direction

 

Never fun trying to work out this kinda stuff.

 

I've come across some helpful things and people in these forums that have saved me some headaches!

 

.



#3 krazynayba

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Posted 07 May 2014 - 03:44 PM

Thanks for the advice :)

 

Not long ago (while the issue was still occurring) I went to S&J and had the codes checked. They said that the only code was for the Differential Pressure Sensor but they weren't too sure what the underlying issue was. Apparently there are a few things it could be i.e. the actual sensor itself, or vac lines. Wonder if it's worth maybe replacing the sensor? Seems simple enough for a DIY job.

 

The CEL does actually come on sometimes but only for 2 seconds and at higher revs when the car is in second gear. Both this and the sputtering started happening after I got it back from an Ecutek tune, but I just haven't had the time to get S&J to properly diagnose it. Maybe I should just make the time...



#4 Guest_KONG_*

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Posted 07 May 2014 - 07:02 PM

Who did the tune?



#5 TSG

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Posted 07 May 2014 - 08:05 PM

Behaviour sounds similar to what mine did about this time last year, just as it got colder too. I went to the extreme of ripping out my immobilser and everything. But it was revealed that it was the fuel pump controller - it didn't throw this code until the last minute though. By that point I had also changed the fuel pump and all the fuses and relays, and it was starting to cut out under load. A fuel pump controller for mine was about $350 from Subaru. This issue was terrible to figure out on my car. Our theory was that my pump had damaged the control unit while it failed, as they are known to draw more power/amps when they start to go.

 

So I'd suggest changing the pump and filter first if you feel that's the cause. The filter is part of the pump assembly in the tank so you'll already be there anyway.

 

Edit: I should add that one of the symptoms I had was no fuel pump prime on occasion. But this went away with a new pump.



#6 WillC

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Posted 07 May 2014 - 08:25 PM

Go to your local mechanic and get the vac hoses put on a pressure smoke machine test. Usually the engine rough starts/misses and all kinds of unjoy and splutters when your vac lines are broken or leaking.



#7 krazynayba

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Posted 07 July 2014 - 09:41 PM

Thanks for the input all! 

 

Ended up going back as I was due for a major service. A couple of the guys there checked it out and said there was something wrong with where the vac lines were plugged. He said line 21 was going into one side of something but line 22 was coming out, so they switched them and reset the ECU. He reckons that it should have fixed the problem. I've yet to see the CEL yet but I haven't particularly been looking for it (after a while I sorta tuned it out). Although, I did try starting the car earlier today after leaving it in the cold, it still sputtered a little and it didn't start cleanly. Didn't seem like the same issue as before (sputtering for 10-15 seconds before evening out) and only sputtered for about 1 second before it started to rev up smoothly. I'm gonna keep an eye on it and see if it gets worse again then go back there if it screws up again.

 

The strange thing is, all of this stuff started happening after I had my bearing done, oddly enough before that I didn't have this issue. The vac lines being in the wrong spot would have happened when they put the engine back together, as the CEL only started once I got my car back after they replaced the bearing. I know replacing a bearing is a reasonably big job, so I guess I can't expect things to be all peaches 'n' cream when getting the car back.

 

Btw, plugs have been replaced about 6000kms ago



#8 WillC

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Posted 07 July 2014 - 09:47 PM

Can you record the spluttering for us to have a more accurate description of the problem.



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#9 Guest_KONG_*

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Posted 07 July 2014 - 10:06 PM

Do you still have the Brant hooked up?



#10 krazynayba

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Posted 03 August 2014 - 07:28 AM

I think all is well with this now. I've monitored the problem and it's pretty well gone entirely in that it doesn't sputter as much and shake the entire car! I was more just mentioning that on a cold start, it'll still occasionally give a single sputter(revs dip really low) for maybe 0.5s - 1s. Not sure if it's really too much to worry about so I guess I'll leave it for now. Though, if anyone has any suggestions on the getting rid of the occasional single sputter on start then I'm all ears! :)

 

The brandt alarm isn't hooked up and I'll try to record when I start my car in the mornings then post it once I get a decent recording.



#11 HowFarToAsgaard

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Posted 24 August 2014 - 09:32 PM

Dose it start on the second attempt though?

mine dose a similar thing where it takes for ever to start first go in the moring and splutters, but if i stop and try agen it starts no problem

might be same problem 



#12 krazynayba

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Posted 29 September 2014 - 01:47 AM

Dose it start on the second attempt though?
mine dose a similar thing where it takes for ever to start first go in the moring and splutters, but if i stop and try agen it starts no problem
might be same problem 

Yes, if it ever sputters then stalls completely it will always start the second time round. It seems to depend on the temperature a lot in that it is worse and more likely to occur when it is cold. Even when the car has been off for a while though and the weather is warm it'll have the same problem. My thoughts are that it's something to do with fuel, maybe the pressure is too low on startup? Is there something in an EFI system that controls fuel injection on startup specifically? Even once the sputtering calms down and I start driving, I get this strange feeling that the accelerator is "sticky" then "unsticks" itself after five or so seconds. Its hard to explain, but it seems like the car stops accelerating once it reaches a certain speed, no matter how hard I press down on the accelerator. This happens for the five or so seconds then there's a surge of power, as if something has "unblocked" or maybe pressure has built up in the fuel system enough for it to run properly. My thoughts so far are that the fuel pump is having problems (not sure if they're a working/not working part or can be somewhere in between?) or maybe the fuel pump relay is a bit finicky.. I'll take it into my mechanic soon to get it checked out. A bit annoying that I'd have to leave it with them overnight in order to replicate the problem. Though, hopefully with a good rundown of the symptoms they have enough to go by :) If anyone has any other thoughts, feel free to let me know!

#13 krazynayba

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Posted 17 November 2014 - 01:03 PM

Just to add more information, recently I took this to my local mechanic to have a look. The first morning they started it they were able to notice the problem I was talking about. They had a look at it, checked the spark plugs (which were fine). Started it the next morning without any issues, and the following morning without any issues. They then ran some intake cleaner through it which they said seemed to clean quite a bit of crap out. I had them test the battery which failed, so I put a new one in (glad Repco recently had 30% off!). Unfortunately I've still been experiencing the issue.

 

The longer I leave the car sitting without driving it, the worse the problem gets. One night will cause sputtering most of the time, and the car will shake from side to side until it evens itself out. Occasionally the car will sputter and die. Two nights without driving will cause sputtering and shaking most of the time and is more likely to cut out. Recently I left it for three nights without driving and had to try 4 times to start it as it kept dying. Each time it would sputter and shake, but then rev up to 1500 rpm for 4-5 seconds (as if it was warming up normally) then the revs would drop completely and the engine would cut out.

 

So, TL;DR:

-Cleaned intake system and replaced battery but issue still occurring

-Gets worse the longer I leave the car without driving

-Engine sometimes stops running when trying to start in the morning

-No issues occur once the car is running



#14 duncanm

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Posted 17 November 2014 - 01:44 PM

I'd be checking out the fuel system - certainly sounds like the culprit.

  • shitty fuel - water in the tank?  This may explain why its shit after sitting. Chuck in a couple of cups of metho to absorb the water so it gets emulsified.
  • fuel filter clogged?  Pull and replace the in-tank filter.
  • like you say - check the pump. Maybe get the mechanic to run a fuel pressure test, or just pop in a new Deatschwerks DW65c pump ($150)

 

The B4 runs a fuel pump controller, which will settle down to lower voltage at idle and low throttle settings. Maybe the pump is struggling at that setting or the upstream control circuit (relays, controller) are suss - check the voltage at the pump (under the DS back seat) sees when you first key on (should be the full 12V for about 5s of priming), then at idle it should settle to about 8V.



#15 krazynayba

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Posted 19 January 2015 - 10:48 AM

Thanks for the suggestions mate. Not sure if it'd be water in the tank as it has been happening for a while now. Took it back to the mechanic who found a fault code for the O2 sensor and replaced it. Didn't fix the problem though. Next I think I'll just replace the fuel filter, I've looked up some guides and it seems straightforward. Failing that I reckon I'll try replacing the pump, my only question is would this interfere with an ECU tune at all, or is it just plug 'n' play? 



#16 allpaw4

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Posted 20 January 2015 - 10:25 PM

No, a pump change won't upset the ecu at all. Probably means the return line might get a bit more work as the new pump will be flowing more than is needed at full throttle, which is not a problem at all, its what the system is designed to do. Definitely look at checking the pump controller though. While I haven't heard of many pumps failing, I have heard of the controllers going bad.

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#17 HowFarToAsgaard

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Posted 22 March 2015 - 10:45 PM

Might sound crazy but try a new battery
I had a very similar problem with mine
Turns out the batter was stuffed.
After putting a new one in every problem went away
Starts first go and never fails

#18 Tim.

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Posted 23 March 2015 - 11:04 AM

This is typical behavior of a dead or dying MAF sensor.

#19 Robbks

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Posted 24 March 2015 - 08:53 AM

A few things to try
1) don;t wait for the fuel pump to prime before going from ACC to START position. - see if problem is better or worse
2) hold throttle flat to the floor when cranking (let off when the engine catches). - see if problem is better or worse

3) Prime fuel pump twice, then start. -  see if problem is better or worse

this can help to show if it's an issue with too much or too little fuel






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