jayblev95

My Z28 has been down for awhile. It was running great and all of a sudden developed a slight miss. It acts like its down maybe one cylinder, Its hard to tell with V8s sometimes. Its time for a tune up anyway so I tear it down and replace the cap, rotor, plugs. Wires are in good shape so I left them alone. I button it all back up and its still missing. Im not sure if the Opti has crapped out on me or what. I thought of replacing the whole unit but I thought if an Opti goes out, the car wont start at all. Mine will but like I said its down a cylinder or two. Im not sure where to go next. I did a scan just idling in the driveway and no codes showed up. I will post the link if anyone would take a look and hopefully point me in the right direction. Thanks in advance for all info/advice. http://www.mediafire.com/view/tvb0dv...P0S2209132.csv

Injuneer

I'll try and take a look at it in the next couple days... A couple others in front of you.

jayblev95

Thanks. I really appreciate it. I think its an issue with bank 2(passenger side) but just let me know what you find.

Injuneer

Seems to be running very cool.... CLT never goes over 162*F. T'stat working?

Nothing stands out at idle, other than the LTFT's - adding 4.6% (generally not a problem) fuel on Bank 1, with a typical O2 sensor range of 0.013 V - 0.941 V. Bank 2 is adding 13.3% fuel, with a slightly limited range of 0.120 V - 0.884 V. Response on Bank 2 O2 sensor seems slow and not wide swings. Scan rate is good at 9 to 10 frames per second, which make the slow sensor movement easy to see.

Check for an exhaust leak before the O2 sensor.

Check the plugs on the passenger side to see if all 4 look alike.

jayblev95

Thanks for taking a look. The tstat is brand new. When I did this scan I just got done putting it together after replacing the cap /rotor from my opti and was still bleeding the coolant. Not sure if thats why it was running cold. I will definately take a look at the passenger side plugs in the next few days and let you know what I find out. Thanks again.

Injuneer

Air in the system will usually cause it to run hot.

Did you get the correct, unique LT1 t'stat?

Courtesy of Shoebox:

http://shbox.com/1/tstat.jpg

GaryDoug

The intake air temp is stuck at 98F the whole time. Shouldn't that move up a bit as the engine warms up?

jayblev95

Yeah its the correct tstat. not sure why it was running cold. I will check the passenger side plugs. Of course it had to be that side. lol

Injuneer

It is normal for the temp to vary. The fact that it is recording at 9 - 10 frames per second may appear to produce a lot more duplicate numbers than we might be used to seeing. I looked at a log he sent me earlier, and it was moving down as air cooled down the intake track over time. Just depends whether the intake ducting was heat soaked or not when the engine started.

Probably worth checking to make sure the IAT is still working. But it should not be causing the idle problem.

jayblev95

YES!!!!! Its up and running great. Changed out all the plug wires and it runs like a top. Is it possible for a spark plug wire to short out internally? Reason i ask is that all the wires had no burn spots on them. Besides being dirty they looked just fine. Just curious.

timnfxr

One of the wires is probably open. You should be able to confirm it by measuring them with an ohmmeter.

jayblev95

I will do that. Like I said it was just out of curiosity. I have had that happen on another car years ago. It all of a sudden started to miss and turns out it was a spark plug wire. Same thing with them, no burn marks or anything out of the ordinary.