Okay, I have a 1990 Camaro Iroc with a 305 tuned port injection. I bought the car not running. I have been working on it and people have worked on it before. It's a headache.. and I dont know everything about the car but I have found a lot of information in the last week about it.

Problem:

Vehicle wont start. If I put fuel into the intake it will start and run. After I get it to start that way, I can stop putting fuel into the intake and it will quit again, but will try really hard to start back... but wont actually start. It has a new fuel pump, and fuel pressure regulator, and the fuel line has 47 lbs at the shrater valve on the fuel rail. The pickup coil and ignition module are both brand new, just replaced. The tach does something weird. When I try to start the car it max's out on the dial... Way beyond the red line. I can turn the key off and on and bump the starter and the tach resets itself. While it is running (From an outside fuel source) there is no check engine light on, but the tack is still maxxed out the whole time. The check engine light flashes only a code 12 over and over again.

We put a scanner on the car and it showed no alda data I think... I dont know if that acronym is correct, but it definantly said no data. He said he possibly had a bad line so I dont necessarily have 100 percent faith in that reading. The wire to the diagnostic plug is good from the computer and not grounded to anything. The injectors are all showing good according to the ohm readings in the service manual. The TPS is also checking good according to the mulitmeter. The fuses seem to be all good. I have checked wires and checked wires to see if I could figure out something. I have another computer and prom on its way to me from ebay from a like car.

I dont know if I have put in here all the stuff that I have done but this is the bulk of what I have checked on. I have the service manual so I have went through it but I dont have continuous access to a scanner so there are some tests I can not do at home. ANY Info anyone can give me on possible problems would be EXTREMELY helpful.

Thanks

 

If it runs on external fuel source you can rule out the ignition. If other people have worked on it, it sounds like a problem with the passkey (anti-theft feature). Check to see if the crank relay has been bypassed. They may have figured that it was all the passkey keeps from working and it is not. The ECM will not fire the injectors without the signal from the passkey decoder. This prevents the car from starting if someone "hotwires" the starter solinoid. "Extra" wiring and cut wires are what to look for here.
Another thing to look at is the Black/Red wire that provides the ignition pulses to the ECM and tells it the engine is turning and is ok to fire the injectors. Continuity check from "B3" at the ECM to the distributor.
Curious about the TH400 behind a 305???

 

K , se we know it ain't spark , and the fuel system up to the injector is fine ( pump regulator and ohmed out fine)

Can be either the passkey stuff . Or the oil preasure switch . How is it ?

I had a bad injector ...all ohmed out fine . But the pintal would jam on it and it really messed things up . I got what is called a pulse tesotr . It fires the injector to see if there is an oerror there. Ohming out the injectors missed this .

good luck

 

(Check to see if the crank relay has been bypassed. They may have figured that it was all the passkey keeps from working and it is not. The ECM will not fire the injectors without the signal from the passkey decoder.)

Where can I find this decoder? Is that the small box under the drivers side dash left of the brake pedal?

I know that the security light goes off after a few seconds when the key is put in. I know that if I unplug the wires to the keyswitch, nothing happens. I havent tried any other tests on the vats as of yet.

I will checked all the wires on the computer as the book told me to (The service manual) and all the wires had the correct amount of voltage on them while it was not running, because I could not start it, accept one side of the green plug. The end wire I think was a brown color and had 12 volts battery voltage from another source, but some of the rest were sopposed to have a smaller amount of voltage and I didnt really get anything from them. I was trying to hold off til the computer got here before I spun my wheels to much.

I am not sure if the tranny is for sure a 400, but I know that it is missing a gear to be a 700r4. It has only6 selector positions, and the pan on it is like a square with the corner cut out. SO it looks like someone just cut the corner off of the square, I havnet checked the amount of bolts on the pan or anything, but I know it dont seem like a 700...

On a side note, I have the chance to get either a 400 small block for it, or a 350 4 bolt main... anyone think one is better than the other? I want 350 horse, the cheaper and easier, the better...

 

I can't remember if the '90 is the same as '88 or not. My car doesn't have one but I think I remember someone saying that it is way up under the top of the dash ie:hard as hell to get to. If the box you see has 2 plugs, one bigger than the other, smaller one has more wires than the bigger one, and the bigger one has only 3: orange, brown, and black/white, then that's it. Try the ECM swap first and see what you get.
The trans is a TH350 or 350C lockup. The TH400 has a pan shaped like Illinois, the 700R4 is square.
For 350 HP I prefer the 350ci motor. If a 400 & 350 are both built for 350 HP, the 400 will get consistantly worse gas mileage. But that is just my opinion, so no need for a urination contest.

 

Mine did the same thing one time. Try unpluging the coolant temp sensor. If it starts its bad.

 

Okay, I tried the coolant sensor and that did nothing as far as helping... I checked the red and black wire from the computer to the distributer, and it is good. Checked out. However, I found something interesting in my endevors....

I used fuel to start the car from an outside source, fuel pressure guage bleed off valve... it ran like absolute crap... I disconnected the 4 wire plug on the distributer, and then I checked the wire, and I found it to be good... Well, after that I forgot to plug it back in, and I turned the key a few minutes later and it started from the leftover gas in the intake for a few seconds... then I used external fuel to start it again, and it ran smooth and good, as long as the 4 wire distributer plug was disconnected, and the external fuel was being added... Anyone know any possible cause of this?

 

I think that's the way base timing is set, so it should run with it disconnected.

You stated that the engine runs differently with the 4-wire plug disconnected, that means that the engine is controlling the timing when the plug is connected, the ECM wouldn't be able to control if it wasn't getting a dizzy reference pulse, so I think at this point I'd look into the injector inable pulse from the VATS module to the ECM, and Yes the module is behind the HVAC and the firewall.
Do that before changing the ECM because that won't fix a bad signal from the VATS module unless the ECM is the source of the problem.