EGR and pre-cat delete help

V
2001 Mazda MP3
Hello again everyone. If you've been keeping track of my issued, I've run the car about 500 miles without any real problems. It continued to throw codes, only at idle, and still oscillates at idle.

Since I chiseled out the cracked remnants of the pre-cat in my exhaust manifold, I'm guessing the diameter of the pipe has significantly reduced the pressure at the EGR connection. At idle, I think the EGR is actually flowing the opposite direction it is suppose to with the negative pressure being in the exhaust at low RPM. All my codes are idle/fuel/air related, but it doesn't always throw the same codes except for "absolut mani pressure".

To try something else I just disconnected the EGR up front, moved it out of line, and let it run. No codes over about 5 minutes. Obviously pretty loud, and idle seemed a touch high at 900rpm (where it had been about 5-600rpm with EGR hooked up); but it was smooth. Is there anything easy I can do to seal off the EGR temporarily and figure out if it will run well like that over a couple days? If it really solved all the problems; I will probably get a header to throw on there, assuming that will solve the pressure problem. I just don't want to drop a couple hundred and find out this had nothing to do with the problems.
 
V
2001 Mazda MP3
I did just wrap a milk jug cap in a bunch of aluminum foil and pinched it in between the connection. After a minute idle went down to normal, and started oscillating again. 2 codes also came on again, the usual one and "system too lean, bank 1".

Does that rule the EGR out as the problem?
 
V
2003 Mazda protege5
Have you checked for vacuum leaks? Sry I have not followed previous posts. Also is there an egr delete for the 2.0? If so I'd like to do it.
 
V
Protege5
The pre-cat's presence or lack thereof has no affect on EGR operation. Vacuum from the intake manifold pulls exhaust gas from the exhaust manifold, through the tube, and into the intake. You will have a vacuum leak if the EGR pipe is open to the atmosphere and the EGR valve opens or is sticking.

Your symptoms are indicative of a vacuum leak; shoot some carb cleaner around the injectors, EGR valve, the throttle body, PCV system, and intake manifold gasket. If you find an area that changes the idle behavior when sprayed, you have found the source of your leak.
 
V
2003 Mazda protege5
Can the egr be deleted? Maybe sealing the intake where it bolts on and just leaving the egr valve connected? Won't circulate exhaust but still connected to make computer see that it's still there.
 
V
Lancer Ralliart Sportback
EGR exhaust gas actually cools cylinder temperatures... It doesn't make sense - but it does. I would try to keep it holed up and find the vacuum leak (manifold top/bottom seal?)...
 
V
Protege5
Exhaust gas has already been burnt, therefore will not combust. When added to the intake charge, it inhibits combustion in the cylinder. Less violent combustion means less heat development, and consequently, a lower propensity to pre-ignite or detonate. The PCM can then add more timing and pull fuel, enabling a lean cruise that increases fuel economy. Because of this it's always best to leave it in place and functional.

You can "delete" it by capping both the manifold fitting and EGR tube, or capping the manifold and placing a breather on the EGR tube, but you'll have to live with a CEL and your fuel economy may suffer.
 
V
2001 Mazda MP3
I thought the point of the EGR was to burn off a portion of the fuel that wasn't burned off in its initial combustion cycle. Either way, I've hooked that back up since it didn't solve the problem.

I did spray around with carb cleaner. The only place that had any effect was the seal around the airbox itself, which I actually knew wasn't a good seal since one of the loops on the base of the airbox had been broken off. I've got 2 problems with that result though. The first is that it was like that the entire time I've owned the car and I didn't have this problem prior to the rebuild at all. Second, I would not think any leak prior to the MAF would have any effect. In my head that would only allow unfiltered air through, but not have any effect on the pressures, idle, or fuel mixture. I'm also just concerned that it changed the idle solely because the carb cleaner was introduced into the intake, and that is has nothing to do with the vacuum leak.

I did use an entire large can on every possible leak spot I can think of, but that was the only spot that had any effect at all. What do yall think? I would buy an intake if I thought it could honestly fix it, but I don't wanna waste a couple hundred dollars and get nowhere.
 
V
Lancer Ralliart Sportback
You are correct - a leak before he MAF only allows unfiltered air - but does not cause an idle issue.

Have you checked the PCV?
 
V
2001 Mazda MP3
I did replace the PCV when I put it all back together. I used the same hoses with it though. I did spray the carb cleaner all around that with no effect.
 

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