st8ples

Sorry if this seems to be a broken record, but I've looked through all sorts of previous threads and yet to find my solution to it.

Story of the car, it is an 87 firebird AT that was through some rough times and sat for 10 years with a mix of parts got the thing for $200. It has the TPI on top of a 305 with the swirl heads.

I am having a massive issue with it running way to rich. When it runs rich it spews out the black carbon in the exhaust, and will foul the plugs. It only does it when its cold, the colder it is the worse it is. It will through the codes right when it should switch loops at the EMC. At the same time even when its cold and I"m sitting at a Red Light for a long time the light will go back off. I have a Snap On scanner that I tossed and gives the rich exhaust and an Issue with the MAF circuit codes I cant remember the numbers off the top of my head.

It idles rough when it is first started, and it will surge at low RPM, but goes away after warming up for a few mins. When it is running/driving I constantly smell very rich exhaust and have had a friend saw when I accelerate hard that I will push out black smoke.

When it is hot I can still smell the rich exhaust when its first started but will not throw a code when its running down the highway, but still believe it is still running too rich.

Irregardless of weather it doesn't backfire, or when you are going down the highway you wouldn't think anything is wrong except for the light. It doesn't run rough after its warmed up either.

So like I said I had a scanner on it and to my knowledge everything was within their parameters I will soon check everything yet again.

I have new (mostly to replace wrong/missing parts):

O2 sensor
MAF sesor (replaced this a couple times due to a faulty one)
ECM (Original was dead)
Had a flashed chip (mine was for a 350)
Fuel Injectors (again mine were for a 350)
Holley Adjustable Fuel Regulator (I can adjust it to get rid of the code but then runs to lean when its warmed up so I don't call that a fix)
Fuel pump (original was toast)
Plugs/wires
CTS

Fuel lines were clear of blockages.

As well as voltage checks.

Also the Distributor is set 0BTDP. I heard it should be like that due to the swirl heads that I read from this forum.

Which from what I saw so far are all the major causes of my issue. I am at a 100% lost and the more this goes on the less hope I have to get this car right. The car is so close to running right, but this has been a thing I been fighting with for a year now messing with.
Hopefully you guys can help me cause I love what the car when its running and driving, even taken it to one of the shows organized by this forum and got voted on for best project car, but even this is taking it out of me.

ZZ42Fast

iTrader: (2)

A few things concern me here.

1) Flashed chip. Could be the sole problem as we know nothing about it
2) Injectors- what injectors? Was it compensated for in the chip?
3) What is your fuel pressure?
4) Have you replaced distributor cap/ arm and coil, pick up coil?

Finally try and take a data log.

vinny R

Try an new TPS also. Make sure you get an A/C delco. This was the issue on my buddies 92, his ran rich for so long it killed his cats. We chased his problem for awhile also

southbay08

we recommend running 19lb injectors for a 305
if you're still smelling fuel just for ***** and giggles check the diaphragm in your regulator

st8ples

Ok checked a few things.

Injectors are 19lbs Bosch Injectors

Fuel pressure is currently at 33lbs while idle.

I have not done anything to replace the distributor but came off a running 305.

I did forget to mention I did swap the coils once thinking that was an issue for a different problem, as well as tried a new TPS.

I don't have charts or anything for it at the moment.


For the Chip it was a newer flashed chip for an 89 that had the 9th injector disabled and makes the fan turn on at a lower temperature.

Here is the distributor internals if that helps with any distributor questions. Beyond that it was the one that came with this engine so I can't give you any numbers.

Tuned Performance

iTrader: (92)

Did you ever address the maf code 33 or 36 ?

st8ples

Yes, we ran some checks against the original MAF and saw it wasn't working properly on voltage readouts. We replaced and thought for sure that was the issue because both codes came at the same time and been there ever since.

Unfortunately it did not go away after that. Even though the voltages appear to be proper and the running diagnostics I have ran seem to have everything in check it still does not go away. The scanner I have is quite old, wont even work on cars newer the 99, so it really hard to get proper charts and full system readouts because I don't have any PC that allows it to connect.

To me I still think its along those lines of the MAF because the car is saying it is, but I checked it numerous times as well as the connectors and can not see even physical damage to the circuit.

Tuned Performance

iTrader: (92)

It could be a bad ecm just a thought if the maf burn off and voltage feedback to the ecm is ok.

305sbc

iTrader: (3)

don't the maf burnoff relays go bad more often than the maf itself?

Since i'ts MAf you might want to check that your PCV is hooked up and operating correctly . If it's plugged, then more air will be going through the MAF. The ECM should be able to easily compensate, but you have to datalog and acutally look to see what it's doing.

st8ples

Well I just took it out and got my scanner on it. Had to fix my scanner, always something.

Well like I said with it getting warm outside, 75F here; it is no longer throwing codes. I took it out on a road test and ran some graphs and the MAF seems to responding properly. I still see normal voltages coming from sensors. The exhaust flaps from Rich to Lean and back. I'm at a loss again.

The only pieces of information I can give now at this point is I remember the block learn trying to adjust the pulses on the injectors but it would go as lean as it could and still give a rich exhaust when I was last diagnosing this with it still cold outside.

When its cold outside <40F it will start up Rich and continue to stay like that. With it now around 75F outside it will start up and be lean but richen up and give normal results.

Sorry I can't give more info I'm learning all of this stuff as I go and are going off the responses given to me.

st8ples

So I was doing some research and found some conflicting information. The MAF or the IAT

This is from chevythunder.com

yet I read some posts here and people say it does not control Air/Fuel Mixture.

To me the

falls directly into the symptoms I have explained.

As well as in a different section of the site goes on to say here.

Could someone please elaborate on this for me? This is one sensor I have not replaced and am not sure if it is the proper one or not. What is the normal IAT for these cars?

305sbc

iTrader: (3)

I would ignore the MAT/IAT and concentrate on the above info ^.

Generally what causes your BLMs to bottom out is a fuel leak, as in leaky injectors, a fuel pressure regulator leaking into the plenum via the vacuum line, or malfunctioning cold start injector - or the temp sensor that controls it.

That's where I'd concentrate.

st8ples

Well I checked for Leaky Injectors and I didn't see any pressure drop in the fuel rail. The Regulator was just replaced but checked the line anyways and no signs of leaking. The Cold start injector is gone and disabled in the chip, and as for the sensors that are involved all have been replaced and appear to function within their normal ranges.

burnout88

Do you have a new Bosch maf? Or that circuit board Wells unit. I have seen a lot of problems with those Wells type units. Also, I have run into this a few times is a bad wire running from the O2 sensor to the ECM. Use two multi meters and check the reading coming off the wire at the 02 sensor and right before it goes into the ECM. Reading should match on both ends of the wire. If they don't you have trouble on the wire and need to run a new wire. Have seen this issue on several thirdgens

305sbc

iTrader: (3)

hmmm this is tricky

st8ples

indeed it is, been dealing with this for a while to the point i was so tempted to get rid of that Fuel system.

I am currently trying to source an OEM chip/ECU to plug in and see what it does.

Tuned Performance

iTrader: (92)

I have several memcal sim doubting its that. When they fail but flip you usually get a 41 or 51 error.