Runs Rough at Cold Start

JTGrant · Jul 4, 2006

I have had my exhuast setup for about 2000 miles. I don't have a cats. Lately I have had a cold start problem. The car runs rough and after it warms up it runs great. I just figure out how \to data log with the my laptop and the xcal2 so I need to data log when cold. The only thing that I can think of is the now since the pre cat 02 are father away from the engine it is taking longer for them to get to temp. I realize that they are heated. From what I understand is that others have had this problem after installing LT headers. The wierd thing is that I would think that this should have happened right after installing the exhaust system. The only DTC that was thrown was p2196 which means that bank 1 sensor 1 is stuck rich, which means that the pcm is trying the compensate for an overly lean mixture. I switched the sensor to the other bank to see if the code would follow the sensor, so far I have not gotten a code. I did install the LM-1 permanently on the car, and the a/f ratio is between 14.5-15.0 at criuse which is right where is should be. At wot it is at 12.6 (Good). I noticed that on cold start up that the ratio is between 14.8 to 16.0 which seems too lean for a cold startup. I have tryed reprogramming it. Any ideas?

JTGrant · Jul 6, 2006

anything?

bleedingvayneAD · Jul 6, 2006

I also am interested in this same thing. I have an O/R h-pipe and the SLPs and get a very rough cold startup as well. I'm trying to not let it worry me too much, but still...

JTGrant · Jul 6, 2006

Something needs to be changed in the tune.

JTGrant · Jul 6, 2006

Do you have an A/F gauge and wideband?

bleedingvayneAD · Jul 6, 2006

no sir...

JTGrant · Jul 6, 2006

so it only runs rough at cold startup.

AznStanger3v · Jul 6, 2006

thats a tuning issue. open loop doesnt really care how far away the O2s are.

JTGrant · Jul 6, 2006

yes thank you I know that .since the O2s are farther form the engine now they take longer to heat even though they are heated o2s. I have heard of the being an issue on other cars after install LT headers. I realize that in open loop the PCM sees the o2s but ignores, it realies on preprogrammed information. I realize that this is a tuning issue. The car runs great after it is in closed loop. I am taking it to my dealer(the one that provided the tune) tomorrow.

JTGrant · Sep 6, 2006

Car needed o2 sensors. Problem solved.

official_style · Sep 6, 2006

mine had the same problem, but i am running a catted x with LTs. changed an 02 sensor, problem solved! sometimes this obd computer actually knows what its talking about!

bigcat · Sep 6, 2006

the question now is why are O2 sensors going bad?

official_style · Sep 6, 2006

Well I just went out to take a drive, and it was still running rough when it was cold. No check engine though, I guess it did need an 02 sensor. So is there something I can have my tuner adjust for when the car starts up? Or I will just have to let it warm up for a whole? I daily drive the car so it could be annoying in the winter.

JTGrant · Sep 7, 2006

bigcat said:
the question now is why are O2 sensors going bad?

Yeah really, well turns out that the new o2 only fixed the problem for about a month. The car is okay once it is up to temp, it only does this sometimes on cold start. On the wideband the car runs really lean and runs rough, once the car is driven it goes away. No codes at all.

official_style · Sep 20, 2006

same problem. its not even worth changing the o2 sensor, it will just start happening again. sometimes i get the code, i guess ill just drive with it on or keep clearing it for now. is there really no solution to this problem?

official_style · Sep 21, 2006

check it out, i did some datalogging, since i changed the bank1 o2 sensor already, so thats not it. i am thinking it could be a problem with the o2 extension wire, it seems like the heating element in bank1 sensor isnt working! in one of the graphs you can see that it warms up and starts working better after i rev it up. im gonna try and get one tomorrow. what do u all think?

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Mike97gt · Sep 22, 2006

after looking at those graphs the bank one 02 is acting very odd. now if I am reading your graphs right they start at a engine temp of 190 and end at 198 so these were taken with the engine warm. Was it running rough when you took these?

the first and the forth graph are very interesting.. in the first one you see that the pcm is adding fuel like crazy to try and bring the mixture back to stoch at this point both 02's are not switching. at the end of the second graph the bank 2 o2 sensor starts to switch.

the forth graph is kind of interesting. If you look a 1/4 of the way into the 02 sensor graph you will see the blue line start to go nuts. this is what happens when the pcm is confused and as a last ditch effort before jumping into open loop it tries to correct the bad readings by projecting 02 sensor readings. The reason I find this very odd is that it's doing that on bank 2 the one that is switching fairly normal. most of the time you see this the pcm will do this on the bank that is not responding well.

I think what you need to do is try to help the sensors warm up quicker by using header wrap or some other way to increase the sensor temp. the problem with headers is they move the sensors much farther downstream than they were in the stock manifolds.

official_style · Sep 22, 2006

in graph 4, i revved the engine up a bunch of times, that is why the bank 2 o2 sensor reads like that, i was trying to get the bank 1 warmed up enough. the car was running rough for a little bit of this datalogging. what i dont get is, the bank 2 sensor heats up fine, but the bank 1 sensor doesnt, and they are both the same distance from the motor and in the same shape/size header. this car has heated o2 sensors. this is why i am kind of thinking the heater is not coming on in the bank 1 sensor, and it is only getting warm from the exhaust. im gonna try a different o2 extension on that side.

Mike97gt · Sep 23, 2006

official_style said:
in graph 4, i revved the engine up a bunch of times, that is why the bank 2 o2 sensor reads like that, i was trying to get the bank 1 warmed up enough. the car was running rough for a little bit of this datalogging. what i dont get is, the bank 2 sensor heats up fine, but the bank 1 sensor doesnt, and they are both the same distance from the motor and in the same shape/size header. this car has heated o2 sensors. this is why i am kind of thinking the heater is not coming on in the bank 1 sensor, and it is only getting warm from the exhaust. im gonna try a different o2 extension on that side.

the bank 2 o2 sensor reading like that is not caused by revving it up. That is built into the programming of the pcm and is used as part of the PCM strategy to try and correct itself when the 02 sensors are not switching properly. This was taught to us in one of the driveability classes

Even with heated sensors ( all modern EEC systems use heated 02's) when you have long tubes the sensor is moved further away from the head so the exhaust gas temps are a lot cooler there then in the stock 02 sensor location. Since the sensor heaters were designed to heat up the sensors in the stock location they are not capable to bring the sensor to the temps needed for proper operation when they are moved to the location they are in your headers.

One thing that could cause one sensor heater circuit to not heat as much is if you had damage to the heater circuit of that 02 sensor. Now the damage would have to be in a way that you would have continuity on the heater circuits but not be able to carry enough amperage to light off the heater correctly, if you had a wire with only one or two strands left could cause that.

Well good luck, keep us posted

Runs Rough at Cold Start

JTGrant

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start with the upper hole, and if more traction is

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it doe snot

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