At idle my BLM is at 108. What could cause a problem like that. Is it running rich or lean? The car also idles rough but seems to run fine other than at idle. Thanks in advance.

 

The injector flow rate constant in your bin is wrong, too low for what the injectors are actually flowing. This usually happens when someone upgrades injectors, say from 19# to SVO 24#, without changing the injector constant to match.

Under these conditions, the computer pulses your injectors long enough to deliver a given qty of fuel thinking you're only running 19 lb/hr injectors. Since the actual injectors are much bigger than 19 lb/hr, they overdeliver big time. The ECM sees the error at the O2 sensor, and BLMs it's way down to correct. At 108, you're out of adjustment range and the ECM can't help.

Check the constant in your bin, post that here along with the injectors your running, and someone will probably jump in with a suggestion.

 

Read his signature on the above post. He's running Accel 21#/hour injectors. Since you're running a 350 and the stock 350 injector size is 21# then it's not likely anything to do with the programming of the chip. However, I'll bet your problem is with those headers and that O2 sensor you're using. This is common for people running headers and a non-heated O2 sensor. The O2 sensor has to reach over 600 degrees farenheit in order for the ECM to go into closed loop. At idle is when exhaust gas is at it's coolest point therefore it's also the point when the O2 sensor is at it's coolest. What's most likely happening on your car is that the temperature of the O2 sensor is dropping below 600 degrees at idle causing the ECM to go back into open loop operatioin. At this point the ECM is trying to compensate for the O2 readings by increasing fuel and causing the car to run rich. Also, if you have the cold start injector, this also comes into effect when the engine goes back in open loop. During open loop operation the ECM turns the cold start injector on and this extra injector distribures a small amount of extra fuel even amongst all cylinders. Once the ECM goes into closed loop it shuts off the cold start injector. In this case, when the temp of the O2 sensor drops below 600 degrees, the ECM goes back in open loop operation and kicks the cold start injector on again giving the engine more fuel than it needs and making it run rich.

Solution to your problem.... buy a heated O2 sensor and install it in place of the one you have now. The heated O2 sensors heats itself along with the exhaust gas heating it and ensures that the O2 sensors stays above the proper temperature at all times. You can order the 4 wire heated O2 sensor that came stock on the ZR-1 corvettes from your local parts store for a fair price. As far as hooking it up, don't ask me.... I haven't a clue.

 

When i put the headers in i was having a different idle problem so i installed a heated o2 sensor. I thought i might have had a vacuum leak so i took the plenum and runners off and bought another set of gaskets. I'm pretty sure there aren't any vacuum leaks. Another problem with it is when i let off the gas it tries to idle down too low and stumbles. I'm thinking i need to readjust my base idle. Would changing the injectors cause this to change? It acts like it's not getting enough air when i decel. Thanks for the help so far!!

Edit: Another thing i didn't think to check is the fuse for my O2 sensor and maybe the wiring. I don't know why changing the injectors has brought this about though.

 

I have found the stock GM eproms tend to be overly rich STOCK. Also, though you have installed 21# injectors, there is nothing saying the Accel flow the same as a stock GM 22# injector at the same fuel pressure. And lastly, if you bumped up your fuel pressure, your injectors are actually flowing more than their rated flow.

Also, a cold t-stat (like a 160*) without the appropriate changes to the eprom (and NOT just altering the fan enable temps) will cause your car to run excessively rich as the ECM will think it is in "warm up mode". This can be caused by a cooler t-stat, a weak t-stat that is sticking open or a weak CTS.

Plenty of reasons why you are running overly rich. As mentioned above, 108 is the end of the adjustments to the BLM. You only have the INT values to adjust at that point, and it can only go down to 80 before you throw an SES code 45.

 

The car has a 180 degree thermostat and it seems to run better when it's still cold and in open loop. It roughens when it goes into closed loop, could my o2 sensor be going bad? It's less than a year old and doesn't have all that many miles on it.

 

Fuel Pressure: 48 engine off, 38 Engine ideling.

Scanner Data:
PROM ID: 3418
Coolant Temp: 204
Start up Coolant Temp: 194
Throttle Sensor: .54 Volts
Engine RPM: Ragning from 610 to 708
Vehicle Speed: 0 MPH
O2 Volts: Ranging from 184 to 812
O2 Cross counts at end of test were at over 500
Block learn: 108
Block Learn Cell: 0
Intergrator: 120
Idle Air Meter Position: 33-48 steps
Desired Idle: 650 RPM
Engine Load: 57
Manifold Air Temperature: 118.4 'F
EGR: 0%
CCP: 0%
Battery Voltage: 13.7 Volts
Fuel Pump Sense: 13.4 Volts
Spark Advance: 15.7'
Knock Retard 0'
Injector Pulse: 1.6 ms
Engine Run Time 230 seconds
Mass Air Flow: 7-8 gr/sec
CCP purge: off
Air Diver Solenoid: On
Air Switch Solenoid: Off
Learn Control: Enabled
Rich Lean Flag: Switches between rich and lean about every second or two.
Loop Status: Closed

This Data was taken with an Auto Xray using the capture mode. The data was from 14 seconds of running at idle.

Thanks for the help so far!!!

 

Three more questions:

1.) What is the fuel pressure, idling with the regulator vacuum line disconnected and fitting capped? I saw you mentioned 48 engine off and 38 idling...having trouble putting them together in my head.

2.) What is the injector flow rate constant set to in your .BIN? If unknown and no access to WinBin, etc., what chip are you running? Should be a little sticker on the PROM itself with four letters, eg. APYU, ARAP, etc.

3.) What is your static ignition timing set to? EST disconnected, idling at operating temp, what does the timing light show?

I still think there's a mismatch between injector flowrate in the .BIN and the actual injectors. Almost sounds like you're running a 305 chip, which would drive the 21# injectors way long and cause what you're seeing.

Lacking this, severely retarded timing will cause exhaust richness as the charge gets ejected from the exhaust port before combustion is complete. Header primaries usually turn cherry red also.

 

The fuel pump primes the injectors with the engine off to 48 pounds. With the vacuum line disconnected and the engine at idle it also shows 48 pounds. WIth the vacuum line hooked up and the motor idleing it shows 38 pounds. The chip is a stock gm so i assume it's set at 22lb's It could however be a 305 chip but because the guy who owned it before me wasn't exactly the greatest when i came to electronics. The base timing is at the factory 6 degrees.

 

Ok, I just went out and dropped the computer down and got the id numbers off it. The ECM service # is 16198259 and the ecm has a sticker on it that says:
-DELCO
-APYN
-3496

 

The chip checks out, according to http://holman.cs.uml.edu/~sdurphey/bccfind/ it's:

--------------------------------------------------
BCC used in 1989. (Scroll down for more info)
BCC= APYN3496 Scan id= 3481 Part number= 16133470
Release date= 08/31/88 Engine size= 5.7 Trans Type= Auto trans
ECM/PCM: ECM #01227165

Used in cars:Chevy
Possibly used in:CAMARO SPORT CP/CONV

Options:
With GH3 AXLE, REAR, 2.77 RATIO

With L98 5.7L GAS 8 CYL MFI

With MD8 AUTO 4 SPD THM 700 R4

With NA5 FEDERAL REQUIREMENTS
----------------------------------------------------

I'd bring the fuel pressure down to the stock setting of ~44psi (my '88 GTA setup was 44psi so I'm using that as a reference) and re-test.

Next, I'd leave the fuel pressure gauge connected and verify pressure stays up for ~20 minutes or so after shutdown. This will rule out a leaking injector. Mine drops to ~35psi within a few minutes of shutdown and stays there.

Stick with it, this is fixable.

-Kevin

 

Thanks for the help guys. I'm guessing i have a clogged return line since my pressure is so high and this is with a factory pressure regulator. What would be the procedure for fixing a possible clogged return line?

 

That is unusually high for a stock FPR, but it is not unheard of either. As I said in your other post on the DIY Prom Board, I have found the most basically stock GM cars tend to run overly rich. I had to increase my Injector Constant from 22# to 26# (to lean it almost 20%) to get my BLM/INTs more reasonable and this is when I adjusted my fuel pressure as low as I could go (38 psi) and still have the engine running "normal". I still had to tweak my VE tables on top of that. I had to further lean out the engine when I adjusted my fuel pressure to what I wanted (46 psi).

Anyway, it doesn't sound like a big deal to fix if you get the eprom burning equipment. In fact, then you can get your fuel tables closer so you can invoke Highway Mode to save gas (pays for your eprom burning equipment) and then work on your spark tables, which are the real key to get the most power out of your engine.

The best thing of all, it's BEST to start with a basically stock engine since you really can't goof it up too much. But "fine tuning" will definitely pay for itself in gas savings and power. Then, if you decide to build that Miniram 383 AFR head engine; you'll know how to burn an eprom to make it perform optimally.

 

Thanks so much everyone you've been a big help! I'm thinking very seriously about getting the stuff to burn my own proms now. Just to clear one thing up though, the overly rich condition would be causing the rough idle and stumble, right? Kinda off subject but do you guys know if there is an update for the prom i have? If i start burning chips i want to start with one for a 3.23 geared car as well as the most recent. Thanks again!

 

Another thing, Is it common for a car with as few mods as mine has to run this rich? I'm guessing it can mainly be attributed to my unusually high fuel pressure? If i get an afpr will i be able to get this thing a little closer to running right or does it sound like it's running to rich so i need to just get the chip burning stuff?

 

I suspect that you are not the original owner of the car. It is highly possible a previous owner put a quarter in the "hat" of the fuel pressure regulator act as a shim and increase the fuel pressure. With my AFPR, I could easily increase fuel pressure but I could only go so low. You may find a similar problem if you don't find a "shim" in the hat already.

Lowering the fuel pressure will help but based on the low BLM values, I doubt it will be enough on it's own. In reality, I think you'd be better off running higher fuel pressure (I prefer 46 as a happy medium) for the better atomization it provides and tune the eprom accordingly.

As I said, I have notice the stock GM eproms tend to be overly rich. I believe GM does this on purpose most likely for warranty reasons and for "long term" operation as engines become older and worn.