first off when i use a scan tool to get the code that my engine is throwing, the ses light wont come on. It wont even flash the code to say everything is ok. Nothing will flash, but the ses light comes on when checked with the scan tool in place. Anyone ever ahve this problem and know of an area that i should be looking for to fix it?

Now my second problem, the code itself. The car runs fine until it gets to operating temps. Once it gets to operating temps it runs about 100-200 rpms lower that it should. and it idles rough. Also the exhaust smells really rich. I was thinking it was an oxygen sensor problem. anyone ahve any input? thanks!

The car is a 1994 camaro 5.7l the car ran fine for the first 5 days then this just hit out of nowhere. No funny sounds or noises, everything sounds fine except for the roughness of the idle.

 

anyone? the car seems to run better once the light kicks on. anyone ahve any thoughts with this? thanks.

 

what type of scan too? Auto tap won't always pull codes. I had a couple of codes I couldn't get and had to take it in to work to pull them. Find someone that works at a GM dealership and get them to scan it with the Tech II

 

I"m not the best to answer this but I'll give it a bit of a go. This will get you back to the top as well.

Could be O2 sensors, or opti, or spark plugs, etc. the list goes on. You'll have to get the code to get pointed in the correct direction.

The reason your car runs fine at start up is that it's running off a predetermined set of values stored in the pcm. The car at this point is in "open loop" and does not read any info from the O2 sensors because they are not warmed up and active. There are also a few other variables that have to be met before it comes out of open loop such as coolant temp, etc.

The main thing that happens when the car goes into "closed loop" is that the pcm uses info supplied by the O2 sensors.

The problem you are describing points to possibe problems with the O2 sensors, one or both, but could also be a false code......maybe you have bad spark plugs and because of this the O2 sensors are indicating an over rich condition.....the problem is the plugs NOT the O2 sensors even though it looks like the sensors.

Bottom line.....check your plugs, wires, and wire connections and get the code that it is throwing....you may have to reset the pcm first to help narrow the search.

When your O2 sensors take a crap, they will give you the symptoms you are describing, I'm just saying check everything so you don't waste money and still have the problem.

Sorry this is long, hope this is of some help.

Coady

 

spark plugs are brand new, so i doubt that that's the problem. opti is fairly new, oxygen sensors are about 90k old, its running rich. The car really doens't run that great at start up, its just that when its cold the idle rpms don't come down too far until it gets closer to running temps. then it finally starts to be noticeable at idle, but it still drives like crap. The engine sounds great, no misfires or anything, just at idle in drive it gets a little 'wobbly'. So with all this combined i took a chance and bought 2 o2 sensors since it would be a nice way to finish the tune-up. I thought maybe it was an exhaust leak, but only time will tell right now, either way i'll avhe new sensors. I'm gunna install them tom. thanks for your help guys.

 

You have a 94. You can not flash the codes on the SES light by shorting the ALDL connector pins. 1993 was the last year that would work (contrary to what is written in some shop manuals and on scanner boxes ). You need a "real" OBD-I hardware scanner (AutoXray, ScanMaster), or a software setup for your laptop (FreeScan, TTS DataMaster). You can't use the $30 Acton "code scanner".... its no more than a paper clip to short the pins.
You've got to scan it. Check the IAC counts to see if the PCM is able to control idle speed. Look at the long term fuel corrections to see if there is any indication of a "false" lean due to misfires or an exhaust leak. The scanner will also allow you to look at critical sensors like the MAP, TPS, MAF, coolant and inlet air temps, etc.

But rather than "guess", get the codes read.

And in repsonse to one of the posts above, since you have an OBD-I setup, you can not use AutoTap.

 

last night i went out and got 2 new o2 sensors and replaced them today and now teh car runs fine, thanks for your help guys.

Injuneer thanks for clearing up the connector problem. Looks like i'll be buying some software and cable for my g/f's laptop.

 

I dont know if this is the same prob but my car seems to be surging a lil bit and idling a lil rougher than usual especially with the AC on, but the IAC is settled at 50 or so its not hopping around , Ive got codes for egr (400) low cat effeciency bank 2 (430) and the heater circuit error for the precat sensor on bank one . I keep scanning my car and it seems my rear o2's are locking at cirtain numbers and slowly changing values compared to the pre cats and the pre cats are all over the place. car has 104k miles on it and when I did the lt4 starter I noted the rear o2s seemed pretty old. Im gonna have them programmed out and I have 2 for the fronts just came in last friday (I worked all mem day weekend so I havent gotten them in yet). Is there anyway the precat o2s can cause egr and bank ineff errors too ???