zdav28

I have a 1994 z28 that Ingineer (Fred), helped me get started a while back.
I have finally been able to get back to working on it again and have the same issue as when I put her away last year.
She Smokes...within a minute of the startup, big billowing clouds of black smoke. I have not been able to get her smogged because I know she won't pass, so I can't drive her on the streets to get a larger data log.
The rebuilt LT1 sat on my garage floor for some time before I got it installed.
Once I got her started she had a horrendous miss and black exhaust. I checked the plug wires to make sure I had the firing order correct. Pulled the spark plugs and 4, 6, and 8 plugs were wet, with fuel pouring out of cylinder 6. Checked the oil level and it was way over full.
Problem: Leaking Injectors. Solution: Accel 24lbs Injector.
Not knowing how bad the bottom end might have been scored from the fuel-thinned oil, I pulled the motor and rebuilt it again.
I finally got her running again, but I still have a miss, and cyl 6 is still wet with fuel.
I did a "freescan" Diagnostic it is attached. (Yes, it's from Jan.)
Any help suggestions are always appreciated.
Dave

Injuneer

I'll take a look. Might take a bit of time because of issues recovering from eye surgery.

Why Accel? Seem to have more problems than other brands, like the Bosch III injectors. Did you buy them from a reliable source? A lot of counterfeit parts out there.

zdav28

Hey Fred,
What the sales rep from Summit suggested. Just wanted something close to stock.

Injuneer

Your attachment is not a data log……

What format is the FreeScan log? I can only work w/ .csv or any Excel format.

zdav28

sorry attached the wrong file.

Injuneer

Couple odd things in the log:

1 - the right O2 sensor keeps swtiching in and out of "ready". The PCM is trying to reduce the amount of fuel being injected, and has the long term fuel trims (LTFT) down to 108 (-15.6% fuel). That is a low as it can go with stock programming. So the PCM starts using the hort term fuel trims (STFT) to pull out more fuel. The STFT's drop as low as 101 (-21% fuel). They have no lower limit, but they reset to 128 because every so often the Bank 2 O2 sensor shows "not ready". Could be a loose wire, or maybe there is so much raw fuel pouring out it is cooling the sensor to the point below which it doesn't work (600-degF).

2 - PCM is operating on LTFT Cell #4. At idle (TPS = 0% / MPH = 0%) should be operating in Cell #16. I cannot find an explanation for that.

3 - You are getting a tiny amount of knock retard (0.06-deg) which roughly corresponds to the O2 sensor going "not ready"

4 - the O2 sensors are not showing a massively rich condition that would be required to cause dense black smoke. They may have been destroyed by the excess fuel, or something else.

I have never seen items 2 and 3 before.

Have you checked the fuel pressure? If not, you need to measure the pressure at idle, both with and without the vacuum compensation line on the fuel pressure regulator.

Do you have a part # for the Accel injectors?

zdav28

Fuel pressure is at 42lbs, without the vacuum disconnected. I'll check tomorrow and report back.

injector part number: 150824 8 pack 24lbs/hr

Do you think new O2 sensors would help? I'll check the wiring also.

Injuneer

Is the tune stock? Are you sure the PCM you transferred from the wrecked car is the correct part #, and has the correct tune? Did you use the harness from the wrecked car? Was the damage to the wrecked car such that the PCM or harness was likely to be damaged? How are you going to handle the VIN in the wrecked PCM will not match your chassis VIN. Will CA accept that mismatch on an emissions check?

Does that part # appear on every injector?

Could you run a data log from a cold start? This one started after more than 7 minutes of run time. You indicate the problem first appears after 1 minute. You need to follow my guide. I understand you can’t drive it on the street, and if it’s rich enough to pour out heavy black smoke, you're running chances of doing more damage. Does the oil smell of fuel? Is it

https://www.camaroz28.com/forums/com...-guide-886891/

With fuel pouring out of #6, you concluded the injectors were stuck. Did you check the possibility that they (or at least #6) was staying open because there was a short to ground? I would expect DTC 18 for an injector fault, but it’s not in the log. Might want to pull the rails up, injectors intact, turn the key to run and see if an injector is leaking when the pressure builds up. Cold engine, container under each injector, outside if possible, fire extinguisher handy.

zdav28

I'm sorry it took so long to get back to you.
It finally cooled down enough to back to diagnosing my car. (It's only been 103 outside).

Fuel Pressure Test.
Key On / No Start: 42 psi - when the pump stops the pressure drops to 30 psi then slowly to zero.
Key On / Start - Vacuum hose connected. (Has trouble starting) 15 to 22 PSI engine running
Key On / Start - Vacuum hose disconnected. (Has trouble starting) 12 to 15 PSI engine running
Looks like I need a new fuel pump.

What is your opinion on the injectors? I always thought Accel manufactured a reputable product, have I been deceived? I have been away from the race track for quite a few years now, things change.
Yes, they are all the same part number, they came in a single box with eight individual injectors inside of their own box and protectors on each end of the injector.

The car is registered already, CA DMV is always a nightmare anyway. Once it passes smog it can be street driven but I have to get a permit to drive to the smog shop.
They don't check the PCM to the VIN, just the VIN to the License Plate and how much smog it is putting out.

I used the PCM from the donor car and the wire harness, although I still have the PCM from the original car and the damaged harness.
The donor car was the exact copy, except for the rims, Polo Green 94 z28, M6, T-top, tan leather interior. The donor had salad shooters, I have chrome vette rims.
I picked it up for $300 no engine/trans/interior, 175k miles. The person I got it from didn't need the PCM, he was going to carb/dist it and drop it in a rat rod.
(I don't know why maybe the same reason I'm trying to fix this)
The accident took the passenger's side of the front end and moved it to the left side of the car.
Damaging the radiator, fans, electrical connectors to the water pump, intake, and water hoses. But didn't damage the pass side wheel.
I haven't run it long enough for the oil to be fuel-contaminated, so not yet.
But it did before....
This is the second time I have sought your help, you and ShoeBox are a wealth of knowledge and a rare commodity.
https://www.camaroz28.com/forums/lt1...p-help-888536/
I have had the issue with it running rich since I first got it started, (probably because the engine sat in the corner of the garage floor for a couple of years). It had a terrible miss, the oil pressure would drop to zero when it warmed up, then I noticed the oil pan filled with oil. I pulled the injectors and tested them on the fuel rail and they all leaked. I sent them out to be cleaned, changed the oil/filter reinstalled the cleaned injectors, and the same thing happened. I tested the injectors on the rail again and 4 of the 8 were leaking. Once again the oil was fuel contaminated. So I ordered a rebuild kit from Summit Racing,(I ordered the injectors also). I had the block hot tanked, line bored, the cylinders weren't worn so it was just honed, new cam, main and rod bearings, timing chain, and hi volume oil pump. I got put back together and now I'm stuck. I can figure out a cam/distributor/carb, but this fuel injection stuff kills me.
I purchased a set of noid lights, and checked the pulse was not staying on, shorted, they aren't.
I will do another data log from a cold start and post the results after I replace the fuel pump.
Thanks for your time and for sharing your knowledge.

Injuneer

Those results look strange. At idle, the fuel pressure should be higher with the vacuum line disconnected, and drop 8 to 10 PSI when you attach the vacuum line. Yours is just the opposite????

Low flow from the fuel pump wouldn't explain the PCM subtracting large amounts of fuel from the standard calculation. It would be just the opposite - LTFT's would be rising above 128, not dropping to the lowest possible subtraction at 108.

The O2 sensors just don't seem to be working correctly. In closed loop they should be cycling rapidly back and forth over a range of 0.0xx to 0.9xx volts, Your driver side range is 0.557 to 0.635. That indicates a rich mixture, and that is what is driving down the left bank LTFT's. The passenger dies range s 0.444 to 0.586 volts. That is slightly rich. But the PCM supplies a 0.450 volt reference to the sensors, and the sensors add or subtract voltage based on rich or lean. The sensors are either "stuck", the wiring may be suspect, or the injectors are simply not responding correctly to the PCM's directed pulse width.

I have never used an Accel fuel injector. I am basing my thoughts regarding problems on comments and performance issues posted on LT1 sites like this (and the 2 others I participate in regularly). People have traced problems to using these injectors. I doubt Accel actually makes them, they are probably obtained from a name brand manufacturer and repackaged.

Unfortunately there are numerous examples of high quality manufacturers producing a few duds. MSD make excellent ignition systems.... you see them on the top NHRA race cars. But their Opti has been nothing but a problem over the 20+ years they've been attempting to get it right. Aeromotive makes excellent fuel systems, but their LT1 fuel pressure regulator has been a failure for 20+ years, and they don't seem to be able to fix it. My first question on cases with LT1 fuel pressure problems is "are you using an Aeromotive FPR?". Bosch makes excellent fuel pumps and injectors, but their multi-electrode spark plugs are not good. So many people have traced problems with misfires and rough running to them. I've never used an MSD Opti, an Aeromotive FPR, or a Bosch spark plug, but based on the problems I have helped people with for 20+ years, I can't recommend them.

I'll extend this to O2 sensors. If you decide to replace them, use ONLY AC Delco sensors. As good as Bosch O2 sensors seem to be, LT1 owners report problems with them.