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Hey guys, I don't know why I've waited so long to pull the trigger, but I picked up a 1995 Z28 6 speed this weekend. I've been wanting a Z28 camaro for a long time. It has 111k miles, a few bolt on mods, BBK sorties, KN intake, etc. I got it for 2400. I don't know what the usual going piece for older Z28s is, but I can't believe it was so low. I keep expecting to find something major wrong with, but aside from just needing some upkeep maintenance stuff, it runs and drives great! Goals for the car aren't too lofty. I want to be able to break into the 12s while keeping all creature comforts, a.c., stereo, etc. I live about 10-15 minutes from the Northeast dragstrip in Hertford, NC, I plan on her bringing her there 1-2 weekends a month. I'm glad to be here and I'll doing alot of reading/learning. Thanks guys!
Alright, I do have a quick question. It appears the camaro h
as some sort of aftermarket maf sensor. From the little reading I've been doing, it seems aftermarket mafs are a no no. Should I make it a priority to replace it with a stock maf?
I wouldn’t be too concerned with the MAF sensor at this time. Appears they run it with no inlet screen and an enlarged cross-section for “41% more flow”. A basically stock engine, and even we’ll modified setups are just fine with the stock MAF. The lack of a screen and altered cross-section can cause a mismatch between the sensor output and the sensor calibration table programmed in the PCM (computer). The PCM can adjust somewhat for the mismatch using the closed loop long term fuel trims (LTFT). As noted above, if it seems to run OK, leave it alone.
One way to check would be to download the free Scan9495 scanning/data logging program, available on this site. That would allow you (or one of us) to see if the LTFT’s are within acceptable limits. The scan can help you learn how the PCM controls the engine, and I can provide my 20+ page guide to interpreting the data. Useful for troubleshooting and pulling diagnostic codes.
Am I able to download that on a mobile phone? Or only an actual computer/laptop? I do need to do something like that to see what's going on. It runs and drives fine, but with the aftermarket maf sensor, also, it has O2 sensors after the headers before the cat, but no sensors after the cat. I want to make sure things are running as they should be.
The scan application Fred mentioned in Windows based, so a computer would be required.
If the rear O2s are not installed, and you don't have a service engine light, then they have been tuned out (or O2 simulators have been installed). As far as I know, the purpose of the rear O2 is to validate to the PCM how well the catalytic converter is functioning (team correct me if I am wrong), and the front O2s are what the PCM actually uses to control fuel enrichment. More information and curiosity is awesome, and I would encourage you to start looking more closely if you have that interest. However, if your goal is just to ensure that the car is okay, if it is running/idling well, and your gas mileage is normal (17-22 in town and 28+ highway), then it is safe to say the car is fine.
OBD-1 (93-95) does not have after-cat O2 sensors. They were added in 1996 to meet OBD-2 requirements.
Shoebox has a website that is the encyclopedia of the LT1 cars. His car was a 95, so many of the photos are his 95. One of the references he put together is the differences from year-to-year.
1995 confuses many people, because they see the 16-pin OBD-2 style DLC connector, and assume it's OBD-2 (or even GM's “OBD-1.5”). It is pure OBD-1, using a PCM that is identical to 1994. Then there is the existence of a limited number of 1995’s that came with dual cats. Those are California emissions cars, with auto trans (RPO “YF5”). All other 95's are single-cat.
Alright, awesome info guys, thanks. I'll have to pick up a laptop and download that. I don't know much at all about computer tuning and whatnot, but there seems to be more than enough knowledge here to help me out if I hit a rough spot. My biggest thing is I want to make sure the motor is as healthy as I can get it before throwing mods at it. Question though, tracking down an exhaust leak or 2, I pulled the headers and exhaust and are inspecting them for holes, I did notice that about half of my header bolts were loose. Is this something that can happen over time? Did someone just not tighten the bolts down all the way on the header install?
Hard to tell what went wrong with the bolts. Typically, after install, bolts may loosen after a few heat cycles. Need to be retorqued. Sometimes warped header flanges cause ongoing problems. Quality of bolts makes a difference. I uses ARP header bolts, and after the first retorque, never another problem. In any case, should be checked every few months. Stage 8 used to make header bolts with locking clips.... not sure if they still make them.
Exhaust leaks before the O2 sensors screw up the O2 sensor readings, and can cause the engine to run rich.
Just to clarify - Scan9495 is diagnostic software. You can’t tune the PCM with it. You would need tuning software like TunerCATS.
Ah, ok, I gotcha. I was already planning on replacing those bolts. I haven't found any leaks before the O2 sensors, quite a few after though. The guy that welded this exhaust wasn't a very good welder. The headers seem fine. No holes and the flange lays flat. I'm really hoping to go ahead and do valve springs and 1.6 rockers while everything is easily accessible with the headers off. I'm probably going to go with the LT4 hot cam, but I don't want to use the springs that seem to always come with the kit. I saw Alex's parts sells a set of of springs with a .570 in lift, would that be a better valve spring choice for that cam?
Some people claim the LT4 kit springs may be weak for LT1 heads, because the LT4 valves are hollow (sodium filled on exhaust) and lighter. But the LT4 valves are larger diameter, and the LT4 springs are supposed to have higher seat pressures, even though the valves are lighter. The specs for the LT4 cam springs are probably different than the LT4 HOT cam springs. I honestly don’t know.
This site has info on the LT4 vs. LT1 components, including valve and spring differences:
08-27-2018, 08:23 AM
