Jaywalker

Hi guys,

Just bought a decat down pipe to replace my original, The problem i've got is the new decat pipe doesnt have a hole for the EGT sensor (which is about 12mm) it only has a 19mm hole at the top at the turbo end of the pipe which Im guessing is for the lambda sensor, I have seen a few threads on here that the EGT sensor AKA cat on fire sensor you just need to unplug it and leave it unplugged, and that you dont need to have it fitted to the decat pipe, I have the new decat pipe fitted and the sensor left unplugged, The EGT sensor is behind the cat towards the middle section i assume its the EGT sensor lol.

I have a 1995 WRX Wagon Jap import the engine is standard apart from a KN air filter (the one that goes inside the air box not the cone)

My question is does the EGT sensor have any affect on the fueling or mixture? Because my car now seems slower and a little hesitant than it was with the standard pipe on,

Is it ok to leave it unplugged or should i have a bose fitted to the new decat pipe?

Should i reset the ECU to allow the cars computer to adjust to the new pipe?

Thanks in advance for any help you guys can give

my94wrx

iTrader: (4)

you are correct in thinking that you can unplug and forget the EGT sensor , simple use of the search function on here would have answered that for you.

Jaywalker

Thanks for the help as i said i have already searched and found a few threads on here but just wanted to be sure, my other questions was,

"My question is does the EGT sensor have any affect on the fueling or mixture? Because my car now seems slower and a little hesitant than it was with the standard pipe on,

Is it ok to leave it unplugged or should i have a bose fitted to the new decat pipe?(answered thanks)

Should i reset the ECU to allow the cars computer to adjust to the new pipe?"

Again thanks in advance

my94wrx

iTrader: (4)

no the egt does not have any effect on mixture either leave it unplugged or tie it up out of the way.

scooby72

iTrader: (6)

As above but always worth an ECU reset bud - Should have no probs!
The Sensor in question just monitors the status of the Cat - you no longer have one so.....

Jaywalker

Help!! Thanks to you guys for the quick replies but now i have another problem don't know if its related my boost has dropped to 0.4bar and it was happily sitting at 0.7BAR before i swapped the pipes over, it has jumped back to 0.7BAR once but then went back to 0.4BAR,

Here's what I've done so far,

Swapped standard down pipe for a decat down pipe
Disconnected the EGT sensor
Reset the ECU
Drove the car 0.4BAR reading on the boost gauge (t'ed off dump valve)
Checked the fault codes no faults constant flashing every second
Reset the ECU again
Drove the car again 0.4BAR reading
Checked the fault codes again no faults constant flashing every second

And it's still at 0.4BAR

Do I wind the actuator in a turn or two and is this normal after putting these kind of pipes on to increase the boost to compensate or should i be looking at the boost solenoid or something else???

thanks for your help in advance this has stummped me

Jaywalker

Anyone have any idea of what I should do or check??

Jaywalker

Right,
I just turned the actuator in about 2 turns just to eliminate it and its still only boosting up to 0.4BAR but i did notice its peaks out at 0.5Bar then settles at 0.4 so could this be limp home mode??

Going to try cleaning the boost solenoid, but what i cant work out is it was ok before and the only thing thats changed is slightly bigger exit for the exhaust gasses from the turbo and the EGT sensor is not plugged in

Any help would be gratefully accepted thanks

scooby72

iTrader: (6)

Im really not sure on this bud - hence why no reply till now.
I never had any boost issues but with the amount your producing it does look like the car has gone into protected mode.
Hopefully someone will post up shortly.
Cleaning the solenoid and surrounding pipework cant do any harm as a place to start though eh!?!
Is the pipe all sealed up tight and no probs with the gaskets?

milliemoo

is the ecu standard or have you changed it since the de-cat fitting?

Jaywalker

No standard ECU its a 3b,

I cleaned the boost solenoid but it had no effect still 0.4Bar I'm lost don't know what to do now might have to put a standard pipe on more money as my old one has a hole in it so id have to buy another downpipe

Jaywalker

I hope that sensor is the EGT sensor and not the lambda sensor, only have one sensor in the downpipe and its after the cat by the middle section, i suppose if it was the lambda the ECU would flash up a fault code, engine still revs right up the rev range

thanks

scooby72

iTrader: (6)

I believe (after being corrected the other day) your lambda sensor will be found in the exhaust manifold under the engine on the nearside bud - so it should be your cat-on fire job. I assume it was located on the opposite side if the cat to the turbo??
Are you sure this hasnt thrown a crack in a boost pipe anywhere or that the exhaust isnt quite sealed and everything is tight?
My coils gave up after changing bits over but I tell you once working the de-cat is well worth it!
Have you check on any other local club forums bud. I'll ask around the Dorset crew for ya.

scooby72

iTrader: (6)

Just had thought and it reconfirmed by one of the guys - the de-cat is after your turbo so very unlikely to be causing your boost prob! - Is the turbo itself OK?? - As I said before I think you need to be looking at the turbo and the boost pipework - especially before you go buying another pipe that prob wont solve your problem.

Jaywalker

Thanks for replying just seems like you and me left on here lol,

Yes its at the other end of the pipe to the turbo and I just replaced all 4 coil packs this year so my wallet is a lot lighter lol,

I wonder if the resest has anything to do with it after spending a silly amount of time on here searching and reading over the past week or so alot of people with simular problems, IE: reset ECU then low boost, the problems seem to sort them selfs out with no explination of actually doing anything just before it fixes it self, maybe the ECU takes a while to do its learning bit,

I will also be double checking all boost pipes and the exhaust gaskets over the weekend and I have also reset the ECU again last night and will be driving slow for a couple of days to see if my theory is correct,

With regards to the pipe being after the turbo so shouldnt affect boost problems thats exactly what I thought which i why ive been scratching my head for so long because it was working fine before I changed the down pipe, checked the plug off the EGT last night also and confirmed it as the cat on fire sensor that i diconnected, when i bridged the connectors i got the exhaust shape symbol with the 4 wavy lines coming of the top light come on the dash,

Other than that if after checking the boost pipes it doesnt work i will be at a loss and will proceed to bang my head against a wall lol

scooby72

iTrader: (6)

Righty ho!
I rekon that you could have point with the ecu taking a little time to fathom what the hell sort of car this is now?? lol!
Have you tried asking Joz abouth this - hes been on here a while and is pretty well read on probs - he may be able to help.
Sorry dude Ive not been a great help.

joz8968

iTrader: (13)

On a MY93-96 the sensor in the std downpipe is indeed an EGT sensor. As has already been mentioned, when you slap on a decat its redundent as there's now no restriction where the exhaust could build up dangerous heat. It's okay just to leave the socket in the engine bay (makes sure it's tie-wrapped securley somewhere though and not fouling anything important). Might be a good idea to seal it with some heatshrink (to protect it from the elements - you may want to return car back to std for resale... ).

As regards the boost, I'm stumped. The only 'logical' thing is you just may have disturbed element/s of the BCS system when fitting the decat, etc.(?) I'd go through the BCS system with a fine tooth comb first.

0.4bar is pretty much raw w/g spring pressure, so it looks like you have either a mechanical issue with the BCS and/or the electrical communication between it and the ECU, etc.

What you could do is temporarily plumb a cheap brass bleed valve in, totally bypassing the BCS. Start with the valve wound fully in, making sure it boosts at 0.4bar still. Then wind it out quarter a turn and see if boost inceases for every 1/4 turn you do. Be careful - watch a boost gauge to make sure it don't go too high (no more than the OEM 0.7bar/10psi). If it stll stays at 0.4bar then the only thing it can be is the w/g opening at 0.4bar regardless of the valve's state. This must mean something mechanically awry with the w/g actuator e.g. fatigued spring or something(?)

If, however, you do see increases in boost corresponding to the valve's increases in its openings, then the problem probably lies with the BCS, plumbing and/or ECU electrical communication between it and the BCS....

Jaywalker

First off I'd like to thank you guys for all the help you've given cheers,

Right thanks again for the reply Joz, I took your advice but before i fitted my old dawes device i thought I'd try it out this morning after driving around on no boost for a day or 2, RE: My theory of the ECU taking its time to do its bit and learn, so drove around let the car warm up, At the lights pulled away and hay presto straight to 0.7BAR I thought blimey it workerd so next set of light went green and again straight to the correct boost, So turned around to head home put my foot down again and it went back to 0.4BAR and stayed there until I got home bugger, Don't know what this means maybe like you said the ECU and the BCS are argueing lol, On to the next test,

I installed my old dawes device which i know works because i got it brand new and used to have it on this car, Its set at 0.7BAR or just a little bit over lol and put my plugs/bungs onto the BCS and checked the 2 pipes I removed, While I was there I had a check of the boost pipes all looks good, Took the car out warmed her up and boosted straight to 0.7Bar, by the time i got to 5th gear its was boosting just over 0.8Bar, I know the higher the gear the boost doest go up a little,

Just a quick question do I set the boost to 0.7Bar at low gears 1st 2nd or set the boost to 0.7Bar by higher gears 4th 5th??

Any way back to the point, So it was boosting ok drove round for 30mins and then drove to work about 1hour and it stayed constant all the time, No drop and no over boosting the car was now spot on, Its alot better pulls lower and earlier in each gear and I also have a little back fire when i change gear when I'm poodeling which I've always had,

So does that mean that all the boost pipes (except the two i removed from the BCS which i will test), turbo and actuator are fine and there are no leaks? And that like you said Joz that the problem lies with the BCS or the ECU communicating with the BCS, So this leads me to my next test,

I connected the green plugs under the steering wheel, Turned the ignition on and the BCS clicked away like it was going out of fasion, Sprayed a bit of brake cleaner in there anyway which came out clear, Does this mean that the BCS is working propely or just that the valve inside is working?

any more advice of what to check next?,

Thanks in advance for your help,

Although Joz I didnt start off with the MBC at minimum should i still do that?

joz8968

iTrader: (13)

The tests you've performed seem to prove that the w/g is working fine and that the BCS itself sounds like it's working fine too. This would lead one to conclude that there's something awry between the ECU's and BCS's electrical communication.

Unless, your restrictor pill in the bottom vac pipe of the BCS has far too small a bore in it i.e. the incorrect one for your car?! This would prevent target boost being achieved... But to be fair, you still wouldn't expect only 0.4bar, as the pill would still be bleeding some air out, thus raising the boost target at least a little more than raw w/g pressure. But still worth checking.......

joz8968

iTrader: (13)

I've just realised something... perhaps the MAP-sensor has failed?!?!...

Jaywalker

arhh and I bet theres no way for an average joe like me to test that lol,

Would it be ok to leave the MBC plumbed in ?

joz8968

iTrader: (13)

2nd hand MY93-96 MAP sensors can't be much?! I have one on my WRX which I believe is redundent (as my PFC is running its bespoke one). But I'm not sure if it works other stuff - I could find out at APi tomorrow! If I don't need it, I could get Nathan to remove it and make good my plumbing again.

I'll let you know later tomorrow. In the meantime put out a post for one in the classifieds. Also check for 3-port boost solenoids in the classifieds and ebay, to see if anyone is selling one with the MAP sensor as well!

You could try contacting JGM - he might have some lying around....

joz8968

iTrader: (13)

Yeah, to enjoy the std 0.7bar you can just run on the MBC instead. Thing is, it will always boost to 0.7bar i.e. you don't get the ECU's protection by it intervening and possibly lowering boost (when it see's something's not right). But you should be okay....

joz8968

iTrader: (13)

Thing is, this is all just guessing really. I believe your best course of action is to take it to an Impreza specialist who has access to a rolling road... I'm certain they'll be able to pinpint the root cause of your 0.4bar boost issue...

scooby72

iTrader: (6)

Ok you guys! Im glad your getting somewhere! Thanks e so much Joz for getting involved! I just got stumped n it seems a right pain to decipher! passed my bedtime really but will look again tomorrow! loadsa thanks joz!! just wish I could have solved it all!

Jaywalker

Hi Guys,

Once again thanks for all the help you given at least we narrowed it down a bit lol,

I will check the restrictor pill is in the bottom pipe cant see why it wouldn't be as it all worked fine before I put the down pipe on, but just to rule it out it makes sense to check it,

My next job will be to have a look on Ebay for a second hand boost solenoid and a map sensor, going take of the dawes device off and reconnect the BCS and give it a couple of days to see how she behaves,

My next mod was going to be a better ECU, been looking about for which one fits in and gives the best upgrade for just a simple swap but this all happened, don't suppose you would know off hand which ones would just plug in and play I found a list of what ECU's are in what car but it all looks a bit french to me lol,

Thanks again guys its not so bad when you have a little help lol

joz8968

iTrader: (13)

Thing is, it's all too conicidental for something to do with the BCS to fail at the same time as you doing the decat. It all point to you accidentally disturbing something when changing it...

Jaywalker

yes thats true, how do you check for the restrictor pill just pull the pipe off and squeeze it or stick a coat hanger throught the pipe ?

joz8968

iTrader: (13)

You should be able to feel it when you squeeze hard that vac pipe.

Squeeze all along it's length. It should be in the section nearest the BCS (not after the kink). But check all the length of pipe.

Or just remove vac pipe from bottom of BCS and look in both ends with a torch or mobile phone light....