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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #1 ·
I needed a new fuel pump so that's new, had leaky injectors so they are new 26lb accels, new MAF {stock unit} and plugs. the opti was replaced a few thousand miles ago with a gm unit. my long term blm's are split and i have read mixed info as far as what my MAP sensor should be reading, bank 1 is lean and the computer is trying to add fuel, bank 2 seems right. I did adjust for the new injectors in the constant table using tuner cats. i will try to get my data log uploaded because I am new at that and don't fully understand alot of what I see. I am using scan9495. any help would be greatly appreciated, thanks in advance.
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #2 ·
I forgot to mention that my O2's are oscillating the way they should as well.
 

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Have you put a fuel pressure gauge on the fuel rail and did a key on prime? Pressure @ key on prime should be around 43 psi. Start engine & let idle. Pressure should be at least mid 30's.

Tape the gauge to windshield & take a drive. Except for idle, pressure should be at least 40 psi.

Look for vacuum leaks.They can cause rough running & lean fuel trims. Also exhaust leaks before the cat can cause problems.

On my scanner, map is reported as a voltage. With key on & engine off around 5 volts should be reading. Crank engine & let idle. Voltage should be around 1.5 to 2 volts. Various other driving conditions, voltage will be between 2 & 4 volts.

If your scanner reads map as actual pressure reading, use your multimeter set to dc volts to get readings.

Your download log file doesn't give me the right info to make an educated guess as what your problem is. I need readings from MAF, MAP, TPS, fuel trims, O2 sensors, coolant temp that pcm sees, intake air temp, etc.

Here's a link to a pdf with good info on scanner readings. Also included is a pdf on split blm's
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #4 ·
thanks for the reply, I need to do a vacuum test and take a look at the 3 bolt exhaust flange or whatever they are called, I know I don't have any holes in the exhaust but its possible those could be lose and I may not notice. thanks for the information I will look that over. I use scan9495 and have all the data you mentioned and a lot more but I didn't upload it correctly so only the first few rows went up here. I will figure out what I'm doing wrong with the upload so someone who knows more than me about the data can have a full look because I am new to data logging and tuning. Once again thanks for responding and I will try to upload the data correctly today.
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #5 ·
my MAP is reading higher than it should at idle, scan9495 reads KPa and I'm getting 37.5 to 48 at idle with barometric pressure around 99.2 or 99.3 and at 1.49 to 2.2 volts. i will get my info up, i just noticed that when looking over the info you provided.
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #6 ·
all the data is here its just harder to look at in this format, every 74 0r 75 pages it shows the next info. so on page 75 it starts showing the data that should show up to the right, but since the data is wider than a page it shows all the data that fits and starts the next data on page 75 and every 75 pages after will show the next rows of data. i hope that makes sense, i will try to figure out a different way to put my data up but for now this is all i can figure out. sorry in advance i know it makes it harder to look at, but it at least helps to know where to look for the next set of data.
 

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Discussion Starter · #7 ·
so far from what I see my car thinks it is running lean, between what seems to be a higher number than it should be at 36 to 39 KPa of MAP at idle but it reads baro pressure key on engine off fine, my bank 1 lt blm is 140 and bank 2 usually about 130 at idle and the pulse width at idle for bank 1 is around 3.75 and bank 2 at 3.33. the car has a new stock type fuel pump and is in the normal range in all ways tested. i will be testing for vacuum leaks and checking the exhaust for leaks. The exhaust is in very good shape but I will check it. If I don't find a problem there I am at a loss since from what I have seen everything else is working as it should.
 

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You've been reading the sensor data, but have you scanned for codes? There are silent codes that don't turn on SES light.

Do a scan and see if car is going from open loop to closed loop. This is important because open loop is when engine is cold. It limits the # of sensors that PCM gets info from. When you go to closed loop, the PCM uses all the sensors to adjust fuel trims.

Read your blm's while in open loop. Are they closer to 128 than when car goes closed loop? Does engine run better when in open loop?

This may sound like a dumb question. But, did you put the spark plug wires on the correct cylinders? The lt1 distributor has a completely different plug wire order than sbc engines. Shoebox site & factory service manuals will have proper plug wire placement. # 9 in electrical section on shoebox site. www.shbox.com
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #9 ·
the only code that has ever shown up was 26 EVAP purge solenoid circuit, but that stopped being an active code once i replaced the fuel pump and the leaking injectors. the fuel pump was weak and i had 3 leaking injectors. the car runs stronger now with that done but still the same problem i had before, better but not fixed. the car goes into closed loop every time and runs the same closed and open. as far as the plug wires i did one at a time so there was no confusion. the BLM's act the same in open and closed loop bank 1 from 130s to 155 and bank 2 usually stays in the mid to low 130's sometimes going to 128. before i changed the pump and injectors bank 2 was higher than bank 1 with bank 1 around 128 and bank 2 in the mid 130s, only thing I could think was that the difference in fuel pressure made the difference, the pulse widths haven't changed just the BLM's.
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #10 ·
I just went through to look at the scans I did before the injector and fuel pump change and other than the long term fuel trim numbers going higher after the change the injector pulse width was 4.1-4.2 at idle now is a little better at 3.75-3.33 but definitely not good.
 

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Have you tried the old trick of misting your plug wires with water, and running engine at night. See if you have spark leakage. Have front of car up on jack stands. That way you can look for leakage on the bottom of engine.

Spark leakage can cause miss along with affecting the air/fuel mixture.
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #12 ·
Thanks, I will try that, dtc 26 came up again so I am going to replace the EVAP purge solenoid circuit, since I already have the part. I found a vacuum leak at the throttle body and fixed it, it helped a little but not the main problem. the car starts easy just like it always has and I can feel that it wants to go so I'm hoping I'm down to the last issue, at least for now. If the spark plug wire thing or the purge solenoid circuit doesn't do the trick I will see if I can get my data logs uploaded in a way that is easier to see everything. Its been along time since I have had a windows computer so I'm still re learning how to upload things in different ways.
 

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I took a look at the data. It's a slow process of reading 1 line at a time. The only thing that jumps out at me is the ignition voltage column is reading around 12.6 all the way down.

What does your volt meter gauge in car read? Normal voltage while running should be 13.5 to 14 volts.

I,m running out of suggestions. Maybe it's time to hire a witch doctor to excise the evil spirits dwelling in your car.
 

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Discussion Starter · #15 ·
very nice, I will check the voltage on my other scans, and use the volt meter. I'm hoping I can figure this out without paying for help but I'm saving that as a last resort because of the cost. I found another vacuum leak where the EVAP system would plug into the throttle body except the person who I bought the car from 9 years ago deleted the EVAP but the plug he used was not working anymore so I'm hoping that does something. I only noticed it gone when I went to replace the purge solenoid circuit and it wasn't there. I really appreciate you looking at my numbers, its alot easier to do in the scan app where I can graph things or just hit play and watch the numbers change, I just only understand so much of what I see but I am still learning. Before this I only had older cars with carbs and was nervous to mess with the electronics but had to start to learn when I started having problems. the car has been down for over a year, I thought it was just my fuel pump because I definitely had weak pressure but that is fixed now along with the injectors that were leaking. I am about to go out and plug that properly and go from there. thanks again.
 

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Seeing that car was down for over a year, did you drain old gas out and put new gas in? Old gas will make a huge difference in how the engine runs.
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #17 ·
yeah I did that and put seafoam in as well, I am now pretty sure I have a weak battery at least and maybe a weak alternator or a slipping belt with weak battery. I am used to storing the car for winter since I live in Minnesota now and I bought the car when I lived in Missouri so I am keeping it rust free and storing it for the winters, I also put stabil in the gas before it gets stored.
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #18 ·
I need to drive the car now to be sure, I'm just waiting for the rain to stop. The belt is fine and the battery is at 13.8 when charged and when I started the car with someone holding the volt meter to the battery it held high 13s after starting and when I would rev the engine. it doesn't mean there isn't a problem there but I need to check the next time I drive with the computer hooked up. The volt gauge in the car also read well within the good zone and was steady. I need a new data log since fixing the probable vacuum leaks as well to see if it helped and I will look at the volts again from there.
 

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1994 camaro z28 convertible lt1 90k original miles
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Discussion Starter · #19 ·
I drove the car without the computer since I could hear and smell that it is still dumping fuel in. The car will have light backfire with a rev in park of close to 2k rpm's and I can smell the fuel smell when I shut the vehicle off so that tells me the high blm's are an indication of a false lean condition not a real one where it actually needs the added fuel. I ordered a vacuum tester and I'm hoping I can find a vacuum leak that I have missed or something. I'm getting good spark, I don't see any sparks from the plug wires when I looked in the dark, and it cold or warm starts quicker than some new vehicle's do and it always has. If I don't find anything with the vacuum tester when it gets here I really wont know what to try next.
 

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Buy a PC based oscilloscope & learn how to use it. You can buy one for around $70 on ebay, amazon,etc. You need to check the low & high resolution pulses that opti puts out

I know you bought a GM opti, but since they are all rebuilt, you may have gotten a clinker.

Low & high res signals should be a nice square wave. With no drop outs and no wave distortion. And while at it, get a new opti pigtail. They can go bad with age also.
 
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