That's a neggative. The MAF is utilized at all times by the ecm as it's primary input for fuel calculations regardless of loop status. And while you are correct that the MAF values will be reported by the scanning software, you would be hard pressed to identify a slightly out of callibration sensor based on those values. Say for example the MAF is reporting 10-20% less air flow than actual. Would you REALLY be able to identify it? I've seen this very senario on cars that have heavily oiled K&N filters for example. This contaminates the sensing elements and the sensor reports low. It isn't readily apparent on the scan data unless you are very familiar with what that particular engine normally reports. Admittedly I'm refering to the later sensors like on the LT1s and many Fords that use those small resistors for the sensing elements and not the hot wire type like the '88s use, but the principal is the same. After cleaning the elements carefully, the fuel trims return to neutral. I'm not saying that his is out of calibration due to contamination, but possibly is just in its early stages of failure. If I rememmber correctly, these sensors were problematic at best on a good day. I still say he swap in a known good sensor and recheck. One other thing, I've seen remanufactured MAF sensors of this vintage also report skewed readings. Sometimes reporting more air flow. I never trust the remans. And anyway, "close to right" values are no good. Even a slight deviation can cause havoc with the fueling.

 

No, once you exceed the 255 grms/sec the MAF is useless and you go into alpha/N fueling, I have watched this process happen on my car.
Not to the extent he is seeing. I've been scanning/tuning MAF TPI's for a bit, you can tell if something is wrong with the MAF readings. And to be causing the problem he is seeing there would be a gross reporting error from the MAF.

 

Wow there has been a lot of information presented in the last day or so. I will try and address everybody's suggestions. I also thought the MAF since it seemed that it was the primary metering device, I bought a new one off Ebay and there was no change. I have verified with the scan program and volt meter that the MAT and ECT sensors are accurate and close to each other in values, I think there was a 2 degree difference between them. The O2 values drop to 0 even when the car is still in closed loop mode not just in open loop. I haven't had the chance but need to drive the car more with the laptop hooked up so that I can get a better idea of the BLM and INT numbers. The injectors have been changed but not with new ones, I bought some off somebody on the forum here that were out of an 89. There was no change between the old bosch ones or the multec that are in the now. I have noticed on occasion that when I hook the fuel pressure gauge up there seems to be a lot of fluctuation in the needle and other times not. I'm really wondering if I'm having a fuel supply problem as maxlean has suggested in the past. I rigged my fuel pressure gauge up from some old air-conditioning gauges, maybe I need to find one with better resolution say in 1 or 2 psi increments. Does anyone have a favorite, I bought one from harbor freight the other day (I know bad idea) anyway the lens shattered the first time a little gas hit it so I took it back. I really need to get this fixed spring test and tune is almost here and I can't lose to a guy at work who has a neon.

 

Ohm out the injectors, multecs aren't known for reliability.
Hook your laptop up and start the car and allow it to idle until it reaches closed loop. At idle in closed loop you should be reading 9-12 grms/sec flow. If you are seeing a lot more than that, try rapping on the MAf housing with a screwdriver handle while watching the readings. If they fluctuate wildly your MAF is bad.
Next, remove the vacuum line fron the regulator and plug it. Look for any fuel coming from the regulator (even a drop or 2), if there is fuel, the regulator is bad. If there is no fuel, take the car for a short drive and data log with the hose still disconnected and plugged. See if this improves on your lean condition.

 

Okay I will give that a try tomorrow.

 

Any luck tracking down a problem with the injectors or the AFPR?

 

Sorry for the long delay but the weather here in Idaho has been damn cold the last couple of weeks. Today was a little nicer and the wife was at work all day so I decided to take another crack at it. I checked the resistance on each injector. All of them on the right side of the motor measured 16.6, on the left side 2 measured 16.5, one measured 16.2 and the last one measured 16.0. I did take the fuel pressure regulator apart and did not find anything much wrong with it, the diaphragm was hard and deformed I'm sure from being in there for 18 years so I did change it but there was no difference in the performance of the car. The maf was reading 10 grams/sec at idle and there was no change when tapping on it. I checked the fuel pressure again after working on the regulator and found that it is 35 with the vacuum line hooked up and 45 unhooked. When the engine is turned off the pressure seems to fall quickly to 25 psi, I would say in about 1 minute then stays at 25. I tried pinching off the fuel pressure line and the return line but neither seemed to affect the pressure drop. With the return line pinched the fuel pressure jumped to 70 so the pump seems to be capable of delivering good pressure. I wonder if a leaky injector is causing my headache.

 

Just did a fuel pressure test on my 87 today-mine fell from 41 to about 38 but it took 15 minutes, and held-so, I would say it sounds like yours leaks down a little to far and to quick.Shoulda posted my problems here.And BTW-that's just my opinion.

 

Damn Ethan - you're definitely beyond my limited knowledge base at this point

I don't know if a leaky injector(s) would cause the lean condition, so long as it is spraying properly when "on".

You could have them flow tested, but that could wind up being money thrown where the problem does not lie. At this point, I don't know what else to do

 

Well I had changed the injectors in the past but did not notice any difference. I did put in used injectors so maybe I but back in bad ones but I would think that would be a stretch. When I had the exhaust off I could see each exhaust pipe from the head and none of the cylinders showed running rich instead they were all very lean. I'm wondering if a bad cold start injector could be my problem, since if it is leaking it would basically leak to all 8 cylinders equally so at say cruise the computer would think the car is running rich and lean out the main injectors. I don't know, maybe I'm just reaching now. I still have the original injectors maybe I will send them to that Cruzinperformance and have them cleaned. Maybe I just need to talk the wife in to a new C6.

 

Now THAT'S a solution!! Way better than anything I've offered up thus far

 

cold start is only supposed to be activated during cranking. and it's only supposed to stay on for 8 seconds, of course it's tied to coolant temps.Do you have the FSM? cause you can disconnect the cold start
switch.But I doubt this is whats your problem-just my opinion.You probably already checked the 02 right and coolant temp sensor?

 

IS CHANGE YOUR FUEL FILTER AND CLEAN YOUR INJECTORS
AND CHECK OHMS