Wait... so, the ECU actually compares data from the MAP and/or O2 to see exhaust gas recirculating? Are you sure it doesn't just look for EGR solenoid continuity and call it a day? 

 

Not having a problem, just curious. That's pretty impressive, if so.

Yes it is likely using the MAP sensor for this. The older models pre-EGR didn't have a MAP sensor so it's introduction (on an otherwise MAF based system) was likely to comply with OBD2 requirements to monitor the EGR, etc. Opening the EGR at light throttle cruise is going to result in a change to manifold pressure.

 

GD

Edited June 8, 20178 yr by GeneralDisorder

I'm confused.

 

Wouldn't a 99 Legacy have had a Phase II 2.2 liter?

 

A Legacy Outback would have had a DOHC 2.5, but a regular Legacy would have been a Phase II and would not be compatible with any other earlier 2.2

Yes you need the harness - really it would be best to get the complete manifold with all sensors and throttle body, harness, etc since sometimes the sensor wiring can change year to year. If you get a 97/98 you will also need the plug wires. 

 

I wouldn't drill and tap the head unless you have the engine out. We don't - it's too risky. Plus you will need to buy some fairly expensive 16mm plug and bottoming taps, and a matching drill bit, etc. Just plumb it to the idle control hose coming off the intake tube. 

 

GD

 

Be careful too.  Not all heads have the proper casting to be able to be tapped.

 

If the boss where the EGR tube would be tapped is a single shallow hole, about 12mm in diameter, it CANNOT be tapped.  you will just hit the water passage.

 

If the boss has a deeper hole, with a step halfway down and a smaller diameter at he bottom, then it can be carefully tapped.

 

I am assuming  his engine is a 95 manual trans 2.2 liter, because of the dual port exhaust but lack of EGR.  95 heads likely can be tapped, but double check first.

OK, hold the phone... The metal tube where it plumbs into the head is the SOURCE for the exhaust, to recirculate to the intake manifold. If you cut that off and plumb it to the IAC hose, it is only recirculating air...

 

I'm betting as long as you have the EGR intake manifold wiring harness with the solenoid, the ECM will be happy.

OK, hold the phone... The metal tube where it plumbs into the head is the SOURCE for the exhaust, to recirculate to the intake manifold. If you cut that off and plumb it to the IAC hose, it is only recirculating air...

 

I'm betting as long as you have the EGR intake manifold wiring harness with the solenoid, the ECM will be happy.

 

 

NOT correct. It is pulling air from above the throttle blade and it drops the manifold pressure. 

 

I understand why you think that, because the EA's are like this. But if you try to fool the ECU by giving it only the solenoid you will fail. I've seen many cars come in with engine swaps where this was not properly addressed and they couldn't figure it out. It needs to see the MAP signal change or it throws an EGR flow code. EGR solenoid circuit is a different code. 

 

GD

Be careful too.  Not all heads have the proper casting to be able to be tapped.

 

AFAIK this is only true of OBD-I heads. But yes there are heads from the early 90's that cannot be drilled or you hit the water jacket. Done it myself. In this case the only viable choice is to T off the IAC hose. 

 

GD

I'm confused.

 

Wouldn't a 99 Legacy have had a Phase II 2.2 liter?

 

A Legacy Outback would have had a DOHC 2.5, but a regular Legacy would have been a Phase II and would not be compatible with any other earlier 2.2

 

It is probably an Outback or GT. Either would have the 25D and can be swapped to phase-I EJ22's. 

 

GD

Oh.

 

So just the drop in manifold pressure is what it's looking for...

 

You'll pardon my confusion...

So that's actually the best way around that, since you won't actually be recirculating exhaust... ewww.

AFAIK this is only true of OBD-I heads. But yes there are heads from the early 90's that cannot be drilled or you hit the water jacket. Done it myself. In this case the only viable choice is to T off the IAC hose. 

 

GD

 

 

I did the "T" method off of the IAC hose and I still get EGR code.  Can't speak for everyone, but my 2.2 swap in my 98 Forrester still throws EGR code with that setup installed.

We have done it a couple times with positive results. Have you checked to insure clear passages and that the transducer is good? 

 

Watch the MAP sensor while activating the EGR solenoid? That's where I would go with the next test. 

 

GD

We have done it a couple times with positive results. Have you checked to insure clear passages and that the transducer is good? 

 

Watch the MAP sensor while activating the EGR solenoid? That's where I would go with the next test. 

 

GD

 

98 Forrester has no MAP.

It does have a MAP. It is not used for fuel mixture control. It is on the passenger strut tower along with it's switching solenoid. This sensor is used both for atmospheric pressure as well as manifold pressure sensing. Thus the switching solenoid. It is used to detect when the EGR flow occurs which is probably it's primary function and why OBD-I models did not include it.

 

GD