Since my header install I had "morning sickness" during the intial closed loop operation. Rough idle and stumbling would disappear when the car warmed up/closed loop. I could hear the AIR pump doing weird things and was throwing EGR code. OK, got LT1 edit and deleted both AIR and EGR in the software. The car runs TONS faster, the AIR pump is not running that I can tell, but I still have a very brief "morning sickness." It is much shorter, and less noticeable than before, but....what is next to check? The mechanic thinks it is the O2 sims fooling the O2s until they get hot. Is that possible? Thanks.

 

As far as I know that's what O2 sims are for...to fool the o2s. I have never heard of them causing a "morning sickness" condition. As for the computer issue, did you reset the computer after the install? Whenever you make a modification it could take the computer a bit to adjust.

 

O2 sims are only for OBD2 cars and they only make them for after the cat.
You use these when you have deleted the cat but O2 sims tell the PCM that there is a cat there and its functioning normally.
The PCM ignores the O2s on a cold start till they warm up so your cold start problem could not be caused by O2s.
Sounds like a sensor problem but not O2 related.
Do you have access to a scan tool?
I would hook one up on cold start and check what the MAP and IAT and other sensors are doing while in open loop.
You said you had an EGR code?
Did you remove the EGR valve or leave it on there?

 

Thanks for the replies. I am leaning towards IAT myself and will scan the beast next week. I think since the upload to the PCM and a reset the car is just going into closed loop earlier making the symptoms less noticeable.

The EGR and AIR are still physically on the vehicle for visual inspection, but I did think about disconnecting the power to them. But, I don't hear them functioning anymore. If I start replacing suspect sensors, where should I start and what should be the sequence in terms of cost and probable cause of problem? Again thanks, I know others have this condition and when I solve it I will post a big solution and thanks thread.

Bart

 

IMO, anyone that does programming should also have a scan tool or data logging software. There is just no way that you can inelligently make changes to things without knowing what the pcm is seeing.

 

I agree shoebox and my buddy is getting one very soon so that we will always be able to hook up. It is just one of those one thing at a time deal ya know? If I can just find this one nagging problem I will have the foundation complete for cam/head/ who knows.

Back to the question though. Any ideas what sensor would effect idle and performance in open loop like that?

 

The Coolant Temp Sensor at the Water Pump. A while back I was testing an Automatic Fan Mod of my own design. I tapped into this sensor and mistankenly disrupted its reading. The car would just turn for a long time before it would start. Once started it would idle almost normaly for the next 5 seconds and then it would be just fine. Only when it was cold though.

That sensor Seldom goes bad but when it does it will make the PCM disrupt the fuel tables or the spark advance. I am not sure wich one. But yes My car had developed morning sickness... Check yours against shoebox Table of resistance versus temperature... there is also a table in the Chiltons book.


Marvin

 

You see what I am saying though, instead of guessing what might be causing a problem, you use the scan data to point you in the right direction. You can easily tell if a sensor is not giving the correct reading and is faulty. Seeing the data is the key.
You can use a long serial cable connected to your home computer and with an adapter cable, you can use TTS Datamaster (OBD-I)downloaded for free off the internet (free for so many log runs).

 

Interesting... Do the smog check technicians JUST do the visual for the EGR and AIR? I'm in California.

 

Shoebox, I have a laptop and a connector cable. Are there any freebies for OBD2?

Here in Ga, the techs on 96 and newer vehicles just plug up to see if you throw codes, and visually check for cats and smog equipment.

 

as far as i know autotap is the only scanning device/software available for OBD2.

 

I can answer this question partially. My Z is a California twin cat model. The last two times I had her smoged checked in the Greater Los Angeles Area I sat right by the mechanic (I wanna call him grease monkey but he was the coolest).


Anyway. he did not physically conected "ANYTHING" to the car except for the battery and the fumes sniffer on one of the tailpipes. He took this large Plastic device that was conected to his computer and while looking at the readings off his screen he located the device on top of the Windshield by the drivers side.
He placed the device carefully on this one spot while he checked the readings off his computer and then he just left it there.
He did a preliminary test on the Dyno and I could see the computer displaying RPMs Speed Emissions with graphics and all.
He then went through other screen and I saw Timing and what I believe was Oxygen sensor readings,,,, I could not read the letters but the numbers were moving up and down in about one second or so... After that the entered all the car info in the computer and proceeded to do the actual testing. He went down to check for Cats and with his check-out list... he visually inspected the other parts with the aid of a flash light.

I was sitting by the drivers side just outside the testing area and I can honestly tell you he did not hook anything to the ALDL conector. I knew then there was more to the PCM than meets the eye. somehow it does emit codes or something but they know how to read them and its on one spot on the windshield just above the area that has the VIN number.

Marvin

 

You are OBD1. They do the same here if older than 96. The thing on your dash was reading the motor rpms not the PCM by induction. To test your car they have to drive at certain MPH and RPM in two tests with the sniffer going.