Surging when cold on 97 wrx

[keeweechris]

Hi,

My stock (except for pod filter and bigbore) wrx is slowly getting annoying to drive. When its cold, just after starting, the engine automatically rev's slightly about 5 or six times then settles into a nice idle. Whats up with that? Then when driving while its cold, theres a subtle rythmic surging going on, most noticible when just cruising (not accelerating or deaccelerating). Its like driving through patches of water on the motorway... you feel the power being slightly taken away, then come back, at about 1 sec intervals.

Its not a huge issue, but its definately there, and quite annoying. Obviously something is wrong, but like I said its subtle. Its not noticible when driving hard, just when cruising.

When I first noticed it years ago, someone suggested it was the O2 sensor. I got a new one, but no change.

Oh yeah, its coming up to 200,000km :-/

Anyway, thanks for any info!

Chris

[Guest boostin]

Air flow meter? Pods kill them....

[Guest]

slight hijack here sorry.......

how do you check the 02 sensor, multimeter?

[madmike]

 keeweechris said:

Hi,

My stock (except for pod filter and bigbore) wrx is slowly getting annoying to drive. When its cold, just after starting, the engine automatically rev's slightly about 5 or six times then settles into a nice idle. Whats up with that? Then when driving while its cold, theres a subtle rythmic surging going on, most noticible when just cruising (not accelerating or deaccelerating). Its like driving through patches of water on the motorway... you feel the power being slightly taken away, then come back, at about 1 sec intervals.

Its not a huge issue, but its definately there, and quite annoying. Obviously something is wrong, but like I said its subtle. Its not noticible when driving hard, just when cruising.

When I first noticed it years ago, someone suggested it was the O2 sensor. I got a new one, but no change.

Oh yeah, its coming up to 200,000km :-/

Anyway, thanks for any info!

Chris

Garb a can of Upper engine cleaner dude.

Settled mrs 98 sti down nicely.

Used to get a slight up-down idle when it was cold.

After it starts and idles nice when cold, sounds crisper and def has more power.

[keeweechris]

True, havn't done the old upper engine cleaner for a while, forgot about that. Ta.

[keeweechris]

 boostin said:

Air flow meter? Pods kill them....

So my car came with some no-name pod filter jammed on right before the AFM. How does it kill the AFM? What are the alternative setups? Mount the pod further away?

[BC5RA]

 keeweechris']

[quote name='boostin said:

Air flow meter? Pods kill them....

/quote]

So my car came with some no-name pod filter jammed on right before the AFM. How does it kill the AFM? What are the alternative setups? Mount the pod further away?

Lack of filtration and mounting; ditch the pod.

[keeweechris]

So lack of a proper mounting shakes the AFM around slowly killing it?

And no enough filtration lets crap get through killing it too... as well as rest of engine? What about a good brand, eg K&N?

[BC5RA]

 keeweechris said:

So lack of a proper mounting shakes the AFM around slowly killing it?

And no enough filtration lets crap get through killing it too... as well as rest of engine? What about a good brand, eg K&N?

Many people on here won't recommend K&N due to them being oiled, this oil can over time coat the hot wire and slowly alter the signal.

In saying that I have run a K&N in all of my cars and never had a failure due to the filter.

My advice would be to go back to stock.

[keeweechris]

 BC5RA']

[quote name='keeweechris said:

So lack of a proper mounting shakes the AFM around slowly killing it?

And no enough filtration lets crap get through killing it too... as well as rest of engine? What about a good brand, eg K&N?

/quote]

Many people on here won't recommend K&N due to them being oiled, this oil can over time coat the hot wire and slowly alter the signal.

In saying that I have run a K&N in all of my cars and never had a failure due to the filter.

My advice would be to go back to stock.

I wish the previous owners gave me the stock piping!

[BC5RA]

Shouldn't be hard to find the parts to go back to OE.

[keeweechris]

So I tried the trick of disconnecting my O2 sensor before starting from cold. It started with no pulsing/reving, then drove smoother I think.

Does this confirm that the O2 sensor is the prob? It was brand new about a year ago.

Is it possible I got the wrong O2 sensor back then? I found it hard to work out if there was any particular type for the wrx, apart from the plug, so I just got one off a guy on TM, def new though.

Anyone in Auck care to meet up and swap O2 sensor for a bit to test? I'll shout ya lunch ;-)

[gazzy2000]

I had this prob on my v4 STI, removed and cleaned the Idle Air Control Valve (IACV) with brake cleaner, that helped. The IACV is the main componet keeping the revs up when cold and they can get all gummed up and need a good clean.

ALso clean your AFM with CRC AFM cleaner ($20 from ripco)

Also a cheap and easy thing to eleminate is to relocate the knock sensor, they can be be too sensitive with cold engine noises and driving etc, specially in their current factory location.

If the o2 isnt that old it wont /shudnt be that. By unplugging the o2 it makes the car run rich and will only mask the surging, not fix it.

Hope that helps

[keeweechris]

Thanks Gazzy.

Cleaning the afm... thats not on my list. Sounds like a good idea, ta.

Where is the knock sensor located? And wheres a good place to relocate to?

[log1call]

The O2 sensor is being ignored when the motor is cold anyway. Depending how long and how cold you are talking it probably isn't the problem.

If you really want to know what's going on in your ,otor and with all your sensors and acctuators get an adaptor and connect a laptop to your car.

[keeweechris]

Removing the O2 sensor def had some impact. Every other time I start up in the morning, I get the pulsing for a few sec. But with no O2, no pulses! But I hear you re the open-loop thing when cold. Confusing :-/

Yeah, I've thought about that. Trouble is its non-OBD2 (1997), so not sure if there is an easy way. Pretty cool if there was an adaptor though!

[gazzy2000]

 keeweechris said:

Thanks Gazzy.

Cleaning the afm... thats not on my list. Sounds like a good idea, ta.

Where is the knock sensor located? And wheres a good place to relocate to?

Have read of this link

http://www.imprezasport.net/forums/index.php?showtopic=785&st=0

[log1call]

The pod filters can upset the mixture. The AFM needs a steady flow of air. They come with a wire gause to help difuse the air flow, if that's taken off that can be enough to cause irregular mixture. Even just having a free flowing filter can cause mixture problems because of the way the hot wire sensors work.

The knock sensor is very unlikely to be your trouble either given that the problem is when cold and at light throttle settings. It could be if you have a lot of mechanical noise but it's not meant to "hear" those sorts of noises normally.

You can make an adaptor to connect a laptop but then it may take a bit of work to find all the correct readings. The 95 model is documented and it's probably the same ecu so I'd say it would be an easy matter. Hve a read here... http://www.clubsub.org.nz/forum/index.php/topic,5652.0.html

It's simpler than it sounds. .

[gazzy2000]

Mate, just dont take anything anyone saye as gospel, i researched this subject hard when i had the prob on my STI.

Yes there is a list of things it could be, simply work through the easy DIY ones yourself.

and nope knock sensors are "not meant" to pick up "other noises" for sure, but ask Possum Bourne MS they dont hestitate to relocate the knock sensor if they are having issuses, its simply so easy to do and it eleminates that being the issue straight away and probably fixes half a dozen other probs you didnt know you had!

** PLUS **- each time you change, shift or clean ANY sensor you MUST reset the ECU so it can erase old false readings from sensors etc and relearn info from the fresh/fixed inputs etc (even after cleaning the AFM and IACV)

BTW - i had a K&N high flow flat pannel on my STI, when trouble shooting i even brought a factory flat pannel. cleaned the AFM (again) and reset the ECU, made no differance!

[Guest]

 gazzy2000 said:

Mate, just dont take anything anyone saye as gospel, i researched this subject hard when i had the prob on my STI.

Yes there is a list of things it could be, simply work through the easy DIY ones yourself.

and nope knock sensors are "not meant" to pick up "other noises" for sure, but ask Possum Bourne MS they dont hestitate to relocate the knock sensor if they are having issuses, its simply so easy to do and it eleminates that being the issue straight away and probably fixes half a dozen other probs you didnt know you had!

** PLUS **- each time you change, shift or clean ANY sensor you MUST reset the ECU so it can erase old false readings from sensors etc and relearn info from the fresh/fixed inputs etc (even after cleaning the AFM and IACV)

BTW - i had a K&N high flow flat pannel on my STI, when trouble shooting i even brought a factory flat pannel. cleaned the AFM (again) and reset the ECU, made no differance!

Hey sorry to hijack, did you ever get your boost prob fixed??

[gazzy2000]

 STi-TypeR']

[quote name='gazzy2000 said:

Mate, just dont take anything anyone saye as gospel, i researched this subject hard when i had the prob on my STI.

Yes there is a list of things it could be, simply work through the easy DIY ones yourself.

and nope knock sensors are "not meant" to pick up "other noises" for sure, but ask Possum Bourne MS they dont hestitate to relocate the knock sensor if they are having issuses, its simply so easy to do and it eleminates that being the issue straight away and probably fixes half a dozen other probs you didnt know you had!

** PLUS **- each time you change, shift or clean ANY sensor you MUST reset the ECU so it can erase old false readings from sensors etc and relearn info from the fresh/fixed inputs etc (even after cleaning the AFM and IACV)

BTW - i had a K&N high flow flat pannel on my STI, when trouble shooting i even brought a factory flat pannel. cleaned the AFM (again) and reset the ECU, made no differance!

/quote]

Hey sorry to hijack, did you ever get your boost prob fixed??

Yea i did aye, i tried heapsa of stuff bu the thing that nailed it for me was removing the coil over plug coils and fitting the standard 4 point coil pack off a V5 STI with leads.

The thing i found was if you know for sure all the plumbing for the boost control and teh turbo and solenoids are all operational (you have to be 100% sure here) then think about what puts the car in safe mode (i.e. low boost).

I can throw more suggestios you way but need a tad more info.

Please ask other questins on this subject here http://www.clubsub.org.nz/forum/index.php/topic,6951.60.html (cause this is not our thread )

[gazzy2000]

also, another DIY thing to do (if you havnt already) is fit an earth kit and/or clean up your battery terminals, regardless, this is a good thing to do as the factory earth system is rather substandard anyways.

[keeweechris]

 log1call said:

The pod filters can upset the mixture. The AFM needs a steady flow of air. They come with a wire gause to help difuse the air flow, if that's taken off that can be enough to cause irregular mixture. Even just having a free flowing filter can cause mixture problems because of the way the hot wire sensors work.

The knock sensor is very unlikely to be your trouble either given that the problem is when cold and at light throttle settings. It could be if you have a lot of mechanical noise but it's not meant to "hear" those sorts of noises normally.

You can make an adaptor to connect a laptop but then it may take a bit of work to find all the correct readings. The 95 model is documented and it's probably the same ecu so I'd say it would be an easy matter. Hve a read here... http://www.clubsub.org.nz/forum/index.php/topic,5652.0.html

It's simpler than it sounds. .

Thanks for that info re the laptop interface! Sounds like fun(ish).

May as well move the knock sensor... easy to do.

[log1call]

Yup, do the simple stuff first and if it doesn't cure the problem undo it again.

Otherwise you end up not knowing what you have and the experts can't help either.

Laptops... Yup they are the cool diagnostic aid. We need a few spread around the country, one in each town or so.