Hi All,
I am having a strange problem with the Computer Control system on my 350 TPI powered 82 Firebird. First I will give you all some history.

I purchased the car new in Jan, 1982. In 1998 I replace the original LG4 V8 with 350TPI engine. Now I’m not racing but wanted to improve the derivability, durability, and fuel economy of my Firebird. I basically succeed in the conversion. I order the complete TPI system from Fuel Injection Specialties in San Antonio, TX. The TPI came with a custom programmed ECM that was set up for my 3-speed auto and 2.73 rear end. I am using the GM Goodwrench 5.7 Liter motor P/N 10067353. At that time I installed a 2 ˝” in/out high flow converter, and 170 degree thermostat. In 1999 I moved to Wake County, and added the Air-injection back onto the engine. The TPI 350 passed state emissions tests with absolutely no problems from 1999 though 2002. In 2000 I installed an SLP cat-back system and a MSD 6A ignition system. The Firebird ran perfect, got great fuel-economy 25MPG on highway, 18 in town and was a blast to drive.

In November 2002 a woman driving a mini-van, ran a stop sign and hit the front right corner of my bird. The Bird stayed in the body shop till October of last year. The bodywork is great and the suspension is great, have absolutely no problems with handling.

Now the hard part, she is failing emission testing. I have replaced MAF, O2, verified Canister operation, EGR, tuned it up with new plugs, cap rotor, wires etc. Please note the MAF was toast when the car was return to me. I have been able to connect my laptop to the ALDL connector and scan the ECM. The temperature sensor read out agrees with my dash gauge. The problem is that the ECM is staying in OPEN-LOOP mode at idle. I can rev the car up and after a few minutes the ECM will go into the CLOSED LOOP mode. But as soon as it drops back to idle, the ECM returns to OPEN LOOP mode. When driving the ECM will go into Closed-Loop and switch back to Open Loop at stop-lights.

The only changes to the engine setup that been made is now I have a SLP Y-pipe and 3” in/out High Flow converter.

Please note that when the body shop had the car that they was doing welding while the ECM was still mounted in the car and the battery connected.

I have disconnected the O2 sensor at idle and connected a voltmeter to it and the voltage is varying. The scan of ECM indicates the the O2 voltage is varing from about 30? to about 45? MV.
The car does not smoke, seems like it running OK, plenty of power, “like not it was”! Exhaust smell is a little OFF, seems like its running rich.

The high voltage on the TPS is about 4.13 VDC, should it be able to reach 4.85VDC.

So is it possible that the ECM is now defective?

Due to SLP Y-pipe, do I need to switch over to a heated O2 sensor? Yes I am still using stock exhaust manifolds.

Has anyone of you purchased an ECM from Advance Auto?

Thanks for your help.

 

I would tend to suspect the ECM. I bought a rebuilt unit from Autozone and it is working great going on 4 years now. It wasn't real expensive either. Also I never got any kind of code to clue me in to the ECM. I just became convinced it was the problem and I replaced it. I was right, it was the ECM.

 

I would suspect the ECM also. battery should be dissconnected while welding due to the fact that you could mess up the computer.

 

Thanks 89Warbird and grafx,
I picked up a ECM at autozone. Since VATS was bypass, I have to call Fuel Injection Specialties to make sure that the memcal is the only thing that has to be transfer over. I have a copy of the schmatics for the ECM and it looks like there is another chip inside of the ECM that may have to be moved over to the new ECM.

If anyone has any more comments, please make them!
Thnaks

 

Not true!

 

Hi all,
Here is 82 Bird.

 

another pic

 

If the new ECM doesn't help, try a heated O2 sensor, and/or change to a 180 T-stat. It sounds like the O2 sensor or engine is cooling off and putting you back into open loop.

 

My thinking is that if its not the ECM, then the SLP Y-Pipe in combination with the 3 inch convertor has less back pressure thus allowing the exhust manifolds to cool at idle. But I find it hard to believe that the exhust manifolds can cool that fast. Or is the exhust cooler is temperature because of the decreased back-pressure.

This problem is real strange since the car passed emission testing three years in a row without any problems. So I don't think the 170 T-stat is causing the problem.

 

First off what type of test do you have to go through, is it a Dyno sniffer test or a no load idle and 2500rpmish test? Is the factory O2 located in the exhaust manifold or further down the exhaust? Personally I would install a heated sensor to make sure its warm enough for closed loop at all times.

 

Back pressure has nothing to do with it, it is temprature related, if you are running headers the O2 sensor is placed further down stream than factory and the exhaust is cooler.

As far as the T-stat, the engine is getting older and may be more suseptable to temps, 160* coolant temp (or there abouts) is where closed loop happens, if you are running on the hairy edge it may not enter closed loop at idle.

 

Test is idle, so car must stay in Closed Loop mode in order to pass. When it goes out of closed loop, it gets rich causing it to fail emissoins. I'm am running the factory exhaut headers used on the L98, complete emissions etc. Never had a problem before passing emissions.

The engine is in excellent shape, always used Mobile One. This is not your typical TPI conversion. The whole conversion was engineered by 30 year experianced service service shop superviser at a Chevy dealer that builds race engines, experiance parts manager and myself.

When engine was instaled, we used all new parts.

 

Hi All,
Just came back from having the Bird retested, she is now passing emissions tests . YA YA! I had to wire in an heated O2 sensor.

Thanks for your help!

 

hey guys. i have a an 87 gta with 350 tpi i switched over to speed density 730 ecm and have flowtech headers they are not long tube but not block hugger shorties either. they are specifically designed to for f-body's 82-92 anyway i cant pass emissions either since the switch. i have replaced my egr, intake air temp sensor, new map sensor, new 160 degreee thermostat all from dealer. i put in another ecm from autozone. i have a throttle body k and n air filter with an air foil behind it. and i fial emissions at idle. exhust smells real rich. now a new thing has been ocuring where it back fires after i i give it a lot of gas then let off while driving. also at idle it fluctuates badly between 500 to 750 rpm. i have put in a new dealer O2 sensor. also some times when i go to take off the car like hesitates and wants to die then goes. i was thinking tps or iac but maybe something else?

 

Hi polygaryd,
The 160 thermo is too cold, for sytem to enter Closed Loop. I had the same backfire, running rich, etc problems at idle. After switching over to the heated O2 sensor, all of these problems were solved.

I drove the Bird for a few hours today, all power is back. It now pulls harder in the 2000 to 5000 power band of the motor then it every has before.

 

do you think that i could have any problems with my TPS or IAC??? some people were having trouble with them on their cars and it fixed their problems. even when i step on the throttle and hold it at 1500 rpm or so it flucuates around. also how much was that heated O2 sensor and where did you get it???

 

Hi,
First, don't play any guessing games. Before you start to blame the TPS or IAC, you need to verified that they are not working correctly.

The O2 Sensor
is Bosch part # 13077 or GM 25176708.
You will need a 3 wire Weather-Pack connector, part # 12126012.

The O2 Sensor is about $46 from Autozone.
The Weather-pack connector is about $30 from a GM dealer or a little less on line.

I went to Advance Auto and purchased a APC flog lamp wiring kit for about $11. I connected the relay control circuit to the Fual pump circuit. I connected the power for the heater though the relay to the main Computer power circuit. The Heated O2 will draw about 4 1/2 amps when it starts up and drops to about 1 1/2 amps.

I would recommend that you either build or get ALDL cable assembly and download Moates free scanning software. I have recently discovered that most of the Auto Repair shops have gotten rid of the OBD1 scanners. So if you plan on keeping you car, the cable and scanning software would be a worth-while investment.

 

ok the wiring kit you bought from advanced auto parts was that the 3 wire weather pak wiring? or something else? also why did you pull power from the ecm relay? and for the O2 relay use the fuel pump relay wiring also i am assuming oyu drew power for the o2 relay from the low side of the fuel pump relay (low amps) correct? and why didn't you juts hook it up to power all the time? to both leads??? i have no idea how this part works so that is why i have so many questions.

 

also which wires are the power, data, and ground or whatever they are. can you tell me the colors according to what they are and where i should wire them??? your help is greatly apreciated. i have been through hell and a load of money trying to get this car to pass.

 

Hi,
Please look at a wiring diagram for the engine computer harness. I connected the relay for the heated O2 sensor to the same circuits that provides power to the MAF power relay.

I purchased the 3-wire weather pack connector from a Chevy dealer.
The Flog lamp wiring harness was purchased from Advance Auto

The 3 wire weather pack connector / O2 sensor
Black -- ECM O2 Sensor data
White --- 12 volt switched power from relay
White ---- Ground.

The two white leads on the O2/weather pack are interchangeable.

I will take some pictures and diagram in a few days.

 

hi i thought you connected the switched power supply to the fuel pump relay not the maf relay. also i dont have maf any longer i went to speed density so what should i hook mine switched power up to?? also once the car is on doesn't the maf get power all the time??? so it would be the same if i had the O2 sensor switched power to the accesories power outlets in the fuse pannel so it will turn on when i start the car and shut off when i turn the car off??? that is what it sounds like to me

 

Please see attached PDF file. It contains some pictures and drawing.

 

Some Pictures: Engine compartment, Control relays, and O2 connection.

 

Relays

 

O2 Connection

 

ok i checked over these schematics and you still didn't answer me as to why is has to be hooked up to the fuel pump relay instead of and easier acc power connection like the radio is on or the power windows? it seems to be the same i mean the fuel pump turns on when the car is on then shuts off when it is offsame with the amf power signal. seems simple and these connections you made are over complicated unless i am missing something. i can harldy read the relay info on the drawn in one. it seems like you just tapped into pins c and e of the maf power relay for another relay (the one i cant read anything on). i see how pin c of the maf power relay is switched from the oil pressure switch and the fuel pump signal. and how pin e is fed 12v all the time from the battery. also i am assuming the data wire you just connected one of the 3 pin wetaher pak connector to the old data wire for the o2 data signal out of the new o2 signal. am i correct on all this stuff??? also i am assuming the drawn in signal is representation of the internals of the heated o2 sensor relay right in the sensor itself. that we cant see?? correct or no?

 

i forgot to ask why in the hell you would ground on of the white terminals . you said in an ealier post black is data white is ground and the other white is 12volts. by the schematics you gave me i dont see how that is the case. i see how one is 12v all the time. and the other is 12v switched but not ground at all. i would think the seonsor being screwed into the exhaust and all would gorund itself to the headers which would be grounded to the block which is grounded to the battery. and i thought of something technically i could switch both of the white wires to 12v becuase the o2 sensor needs no memory and therefor doesn't need a 12v all the time source.. like a radio or clock would. ya know. i could be off hey getting these thoughts out here and trying to learn something new.

 

Hey,
I'm a engineer, and I set it up the best way that I know to prevent any surges from feeding back into the ECM.

Be careful, the wires coming out of the weather pack connector are all white. So you have to match the weather pack connector up to the O2 sensor. Thus making sure that the black wire is connected correctly to the ECM.

The white wires of the O2 sensore are interchangable. As long as one is supplied with 12v and the other white wire is connected to ground, then the O2 sensor heater will work.

Oh, you need to look at the schematics again!

 

i looked again and saw how it goes to ground and all so i think i am good. pin c of the maf goes to ground and the fuel pump signal pulls to ground i am assuming and pin e of the maf goes to power. i am not confused on how to hook this up any more but i am confused about what happens whent he oil pressure switch is not opent has power on one side of it and ground on the other what is that all about, when it is not opent the 12v go to ground and create a short

 

Iˇ¦m not going to have any discussion with you. Apparently you really donˇ¦t know what you are locking at. I would recommend that you take you car to someone who can determine real problem with. As I said early in this thread -„ł

I would recommend that you either build or get ALDL cable assembly and download Moates free scanning software.

Before you start changing components or adding other components, you should debug the problem, determine the cause and apply the correct fix.

As for the schematic, you are still reading it incorrectly. It clearly shows that the positive to the fual pump is being switch on and off. Please note when there is oil pressure in the engine, the contacts at the Oil Pressure Switch is closed, thus supplying +12V power to the fuel pump. This connection is also tied to Pin C of the MAF Power relay.

 

ok no need to be snotty i came on here to find out things and i do know what i am looking at. your schematics where you drew in your relay isn't clear at all then cuz it looks to me like you have 2 power sources and none going to ground so i am trying to figure out what you did and i dont think your drawing is correct. because pin e has 12v all the time from bat and pin c is 12v switched from the oil pressure switch when the car is on i took electronics and i can read schematics very well infact that is why i am so confused as to what you did here. i am 100 percent sure your drawing is wrong now if one of those white wires goes to ground. your not showing it anywhere in the schematics you are showing me. please review your own sheet here. you have made soemthing so simple very confusing and now your quite frankly ticking me off telling me i dont know what i am looking at. when i have been reading schematics for years. within all this trouble i have gotten an answer i wanted though i am hooking it up to a switched power source and to ground and being done with this mess of wiring you have created. way over complicated!!! engineers HUH!

 

For your infor, I did not do that drawing. I just added the infor about the Heater for the O2. The marked up drawing is part of my engine build documentation.

Yes the entire 350TPI installation was documented. And since its been working for six years and the engine pases emission testing with no tricks, then I must have done some thing correctly. The drawing is from Hayns's "Pontiac Firebird, 1982 thru 1992, Automotive Repair Manual". The manual contains all wiring diagrams for the Third-Gen Firebird. So I guess GM has created a mess of wiring!

The funny thing is if you been reading schamatics for many years then you should know what a ground symbol looks like.
___
__
_

 

thanx i know what a ground symbol looks like and i know where the rest of the drawing came from i am talking about the littrle sribled in o2 sensor wiring. and since i know what a ground symbol looks like i know you dont have (in your drawing the one you scribbled in..) one of those white wires going to ground. now i am sure you hooked it correctly i dont doubt that. i am saying the drawing isn't correct... thats it!! i see the ground symbols comming out of the damn o2 heater part but you also have 2 connections to a power source one constant power, one switched power, and then 2 grounds comming out also. no i know there isn't 5 wires comming out of this thing 4 for gournd and power and one for data. so check it out and see what i am saying so you dont give this markup to anyone else and they hook it up wrong... check out what i marked up here then maybe you wont think i am stupid or something

 

Hey, The O2 data connection(black wire) to the ECM is not shown on this drawing. That connection is shown on another page!