pelensky

I am fairly new to the forum because I recently bought a 1995 Pontiac Firebird Formula. It is a 6-speed and has 19,000 original miles on it. I just replaced the OEM plugs with NGK iridium gapped to exactly .050 in. In addition, I have no codes or no driveability problems. I also replaced the O2 sensors. Everything else is OEM.

I just recently got a scanner and reset the computer to let it learn with the the new hardware. After about 20 minutes of easy driving around town, the Block learn values started to have a pattern. Although block 16 (idle) looks good (very close to 128), other low map, low rpm blocks look low numerically. Most were in the low teens. Block 6 even got down to 109/111. Both the R/L values are always within 3 or 4 of each other. The fuel pressure with key on/engine off is 42/43 psi while the pump is running (I think it is okay because spec is 41 to 47). It stays at that pressure for a while so it does not seem like an injector is leaking. At idle the pressure drops to 37/38 which is an acceptable drop according to the spec of 3-10psi drop with the regulator working.

Anyone have any ideas if these Block values are okay? I know they bottom out at 108 and then set a code. What could be going on? Running Rich?

Injuneer

MAF sensor could be dirty. EVAP canister purge could be stuck open, canister may be saturated with fuel. O2 sensors could be faulty. Leak in the fuel pressure regulator, feeding fuel to the manifold via the vacuum line (although your pressure looks "normal"). Intermittent readings from the TPS sensor can cause excessive fuel use, if the PCM is responding to what it sees as an anticipated fuel demand. Since both sides are showing negative long term fuel corrections, its not likely to be a single injector, which would only affect one side. Whatever is wrong is affecting both sides. Pulling out 15% fuel (109 BLM) is not OK.

95Blackhawk

Check what mods were done. There are plenty of things that could affect the BLM's such as removing the MAF screen. You should thoroughly go through the car to see if it is in good shape and all connections are made.

pelensky

MAF screen is still in and I sprayed the MAF resistors with MAF spray cleaner after driving with the K&N for a while (in case it got oil on them). No leak in the fuel pressure regulator (dry as a bone and no smell). The car is all stock including program. I installed a 160 F thermostat and the car runs at 178-180 F when the ambient is about 90 F. I checked again today on the way to work and all the blocks have moved to high teens. Some of the higher MAP ones are in the low 120's. Maybe it just took some more time to learn?? I will check the EVAP canister. I also checked to verify there is no EGR at idle and it appears to be well seated. I also verified proper operation (lifting EGR under load and no vacuum leaks in EGR.) Car idles great and runs great. I double check all connectors and they look good. Idle is pretty smooth, but not 100% perfect. I can't really feel a miss during driving. At idle the steering wheel is smooth, but I can feel the shifter vibrating a little.

Is it possible that the opti, coil or plugs aren't firing all the time? Would that cause a rich situation? Is it really possible for both 02 sensors to be bad at the same time? They seem to go above and below 0.5V like you would expect. Any other thoughts?

WS6T3RROR

If you pull the pcm batt fuse in the side of the dash it will zero the blms and then it will learn very quickly the next time you get it warmed up and drive it. Your report today sounds more normal than what you first posted 120's wouldnt bother me a whole lot 11x is getting pretty far out of whack.

A cylinder missfire would cause the injectors to fire more fuel and the blm's to go the other way and add fuel.

Out of curiosity, whos o2 sensors did you end up with. You might try putting the old delcos back in there and seeing if the problem fixes itself. I have seen more trouble out of aftermarket o2's than I care to talk about.

It could also be that its time to remove the injectors and have them serviced/cleaned and flow matched. Perhaps they are slow to close and are adding a little extra fuel.

pelensky

I like the idea of cleaning the injectors. I have used "cruzin" in the past for this. Do anyone have a favorite?

I replaced the sensors with new Bosch units. Are these acceptable or is it that important to stick with AC Delco?

WS6T3RROR

I don't know about a favorite for cleaning injectors. But the first thing i would do is clear the computer and try again. After that I would try putting your old o2's in and see if the trims are any better.