S&S header install and weird transmission shifting

[chris_gt_74]

Okay to start out the weird shifting was not present prior to installing the headers. So here's the deal, I installed my headers the other day and understandably I did get the P0420 code but nothing else. I have checked all of my vacuum lines and connections I may have came in contact with while installing the headers and have nothing out of place. The headers I got also came with the downpipe w/cat. The car has a noticeble increase in power but I seems to be having issues with the transmission line pressure I guess. The car acts like it does not want to shift or kind of like drags out before it does shift especially if I get on it. I might also ad that I still have the stock catback. Which means there is no gradual transition to the smaller diameter pipe. I believe the downpipe is 2.5" but could be mistaken and iirc stock it 2.25". But I'm not sure if that would even cause my symptoms or not. Can someone out there help me out here. Oh and it does not have a tune and the only other breathing mod is a cold air intake at the moment.

[Starglow]

I think extended shift point intervals are normal if you're really "getting on it" at least in my experience as I've observed on most cars during heavy acceleration periods. Perhaps the increased power is also a contributing factor.

Even though you don't have a tune, the computer is still monitoring conditions and making adjustments based on new parameters it may be seeing because of the headers. Personally I wouldn't worry about it if the transmission isn't jerking or hard shifting.

I assume you also transferred the old oxygen sensors over to the new exhaust system...right?

[chris_gt_74]

No it's not jerking or hard shifting. It really just feels like it's trying to shift but it drags it out kind of like a little hesitation before it finally shifts. It's not actually slipping though like if it was in neutral and just revving. Yes I transferred the 2 old 02 sensor's over and to date I haven't got any codes other than P0420.

[bob442]

access to a good scanner?

[chris_gt_74]

No, nothing more than a normal code reader and eraser.

[chris_gt_74]

For whatever reasons it had something to do with the chromeintakes cold air intake or a loose MAF connection maybe. Using the same filter from the intake I switched back to my short ram warm intake I had prior to the other and my shifting issues have stopped as best as I can tell. Once I get hold of an adapter and get my lx5 intake on I'll try the cold air intake again but for now it's working so I'm leaving it alone.

[deathamatend]

It's none of those. Very simple. It is running in open loop due to the cat trouble code. You need to get one of those O2 sensor simulators for the 2nd post cat one. Otherwise the transmission will shift like that. Works like a charm.

[chris_gt_74]

Well the trouble seemed to fix itself. I'm guessing the computer was doing it's thing making adjustments to everything. After several days the shifting issue disappeared and hasn't come back. I also quit throwing the p0420 code. It's not to say it couldn't come back but I cleared it maybe 2-3 times and it hasn't showed up again in about a week or two.

On another note beside the headers, I also installed ported heads with new valves and a valve job, ported LIM, ported UIM and I picked up an LX5 throttle body and got an adapter from Ben. Everything other than the throttle body was put on a few days after I did the headers 2 weeks ago. Yesterday I put the LX5 throttle body on and it's running great. I plan on getting a 2.5" catback soon and I will probably be done with mods for awhile well other than a tune.

[gectek]

It's none of those. Very simple. It is running in open loop due to the cat trouble code. You need to get one of those O2 sensor simulators for the 2nd post cat one. Otherwise the transmission will shift like that. Works like a charm.

That was wrong anyway so it would have led you in the wrong direction.

[deathamatend]

That was wrong anyway so it would have led you in the wrong direction.

Upstream sensor waveform should fluctuate downstream sensor waveform should be steady indicating catalytic converter efficiency. P0420 code was set due to increased air/fuel flow through the engine. Look at all the improvments in cfm efficiency. ECM was just trying to it's job. This was definitely the direction given the code/symptoms. Some vehicle manufacturers have a cat O2 sensor light dedicated to monitor cat function or blink the CEL when there is a problem. A more advanced diagnostic scanner with real time data would have shown that than a code reader.

[boomofdoom88]

How many pcms actually use the post cat o2 sensor for anything other than catalytic convertor effiency? On my 2k Grand Am its only a warning light. Disabled and turned off with HPtuners tho. Had no effect on transmission parameters either way. I have heard of Toyota using the post cat o2 for other things

[chris_gt_74]

I'm not sure the post cat o2 was causing my shifting problems. I think it was due to the increased air flow change that was affecting shifting pressure. It would still shift just had hesitation in it before it would shift. As I said it was pcm related and corrected itself after a few days of driving it.

[deathamatend]

How many pcms actually use the post cat o2 sensor for anything other than catalytic convertor effiency? On my 2k Grand Am its only a warning light. Disabled and turned off with HPtuners tho. Had no effect on transmission parameters either way. I have heard of Toyota using the post cat o2 for other things

Exactly, when disabled ECM ignores post cat input like it was never there. ECM's have a cat saving default to prevent expensive cat damage due to upstream enrichment problems. Which is why post cat O2 sensor was added in the first place. When you study engine management theory you will realize the post cat O2 was added to be more than an effiency monitor. I have diagnosed vehicle problems that cause TCM to have crazy behaviors and odd shift points, which have originated way up the data stream. Tech 2 allows you to have a heart to heart talk with powertrain control modules to really get to the root of the problem.

[chris_gt_74]

Well I spoke to soon lol. I just threw the p0420 code again. Not sure if it's from the original addition of the headers or because I just added the 65mm throttle body Sunday. I'm guessing the latter since it added more air to the mix yet again.

[3400-95-Modified]

Having the P0420 code thrown has NEVER put me into open loop... not even on my 07 Subaru. Its simply an efficiency code and warning, it will not change the operation of the engine or trans shifting.

You will continue to throw a P0420 code if you removed your catalytic converter, thats why its going off. It has nothing to do with "increased air" it's simply stating that the cat you have or don't have is not cleaning the exhaust enough.

So I will ask, did you remove the cat? or what cat do you have on the car?