I have a '91 RS 305 TBI thats having a few problems, but stalling out is the worst of it. So, thinking there is a chance that the problems are connected I will try to explain them all the best I can.

First of all, sometimes the car will not crank. Everything will come on but the starter will not engage. I can put the window down shut the door and leave it sitting for anywhere between 3-10 minutes and I can go back to it reach through the window to start it and it will fire right up. I'm thinking this is a security problem. The person I bought the car from had a Bulldog alarm installed, but after it started acting up I disconnected the power wire. I don't know if the factory securtiy system could be it either.

Second, I had a problem with the cooling fan, but after replacing the relay it starting working again til recently. I can turn the air on and the fan will come on. Also, is it common for these cars to wait until redlining before fan kicks on?

Third( the worst one), the car will run for a certain length of time and stall out. It happens at random whether I am in the throttle or sitting at a red light. I can however slip it into neutrel and while coasting feather the throttle til I hear the RPMs start rising then floor it and after a couple of what I would call coughs I can put it back in drive and continue on for a short distance. After the first stall on the drive if I come to a stop it will stall for sure. I can put it back in neutrel while slowing downing and ease into the throttle however and it wont stall while stopped. When I get to where I am going I can get out, and if the car is still running, I can take the gas cap off and alot of pressure is released then the cars dies. I recently put a new fuel pump in and the fuel filter was just changed a few years back. I thought it might be the ventilater valve, but when I take it off the car will not start, and apparently GM decided to stop making them. I was thinking since the stalls happen at random that maybe hitting a pothole or the pressure getting so high in the tank that it all releases at once and messes up the pressure on the line.

Well, help with and of these problems will be a plus, but I would love to get the stalling problem fixed asap. Thank everyone in advance for any help.

 

Seeing as how no one has responded, maybe this problem is a little too difficult. But I was thinking about the passkey decoder and wondering if that could cause the non-start and stall-out. Could it be possible that the key is bad, decoder is bad, or a bad connection?


Was thinking that if any of those are bad then the brain box might think im trying to steal he car so it doesnt let the starter engage(cause as long as the car is not disturbed i can start it), and when the car is jolted something messes up or loses connection shutting something off thinking the car is being stolen.

 

VATS security is set up so it is not capable of shutting down an engine while is running. If it is keeping the starter from engaging it will light the security lamp. One of the problem may be the aftermarket security piggy backed on top of VATS. By pulling the power lead on the aftermarket unit, most likely does not disable it. You need to completely remove it and fix any wiring changes that were made when it was installed.
Pressure build up in the tank is common, but should not affect how the engine runs. The EVAP system may be in trouble, and Craby has a stickky on how to test it.

 

Diagnosing an intermittent problem can be hard to do in person, and even harder online. The no start, then start after a time out, sounds like it might be a security issue.
The stalling could be fuel, or ignition related. However, this: "I can take the gas cap off and alot of pressure is released then the cars dies" is pointing to a fuel flow/pressure problem.

 

I just remembered about this and thought this could narrow down the problems are thinking of. The service engine light does not come on before during or after the stalling problem, but I do remember a while back I did get a dummy code off it say something about system overvoltage yet that code has gone away now and I have done nothing to my knowledge that could have fixed it. Wouldnt the light not coming on mean that this is something not connected to the brain box like the ventilator valve?

 

Do you remember what code # that was you got? What caused the code could have been a momentary "hiccup", and if it didn't happen again, the system will clear it after a number of restarts. If you did anything involving disconnecting the battery, that will clear any error codes too. Also, you can have a code present without the light being on, so if you haven't flashed for codes recently, you might want to just for fun. Fyi, getting a code 12 is an automatic given, since the engine is not running when you flash the codes, but you may have already known that.

 

Its been a while ago, but as far as I can remember it was Code 53 which by the tech book could be System over-voltage(ECM over 17.7 volts), Alternator voltage out of range, or(and I don't remember this one) Vehicle anti-theft (PASS-Key) circuit (5.0L TBI). But I have checked codes recently and no codes are pulling up now except 12, and yes I let 12 flash more than 3 times to see if there is another code.

The car use to have a stereo system set up in it consisting of a Kenwood flip-face, 2x 12 inch MTX sub, and a JBL amp(cant remember exact wattage). The guy that sold it to me had already put in an alternator for the system, but I took out the kenwood for lack of code and moved the amp and subs to another car while this one was shut down and "lost" them. With the aftermarket alternator and nothing pulling extra power now, will it cause problems?

 

Trying to make some videos to upload. I will try to have them up to watch tomorrow, and start trying out ideas you have starting with the EVAP.

 

Non-start:

After a few trys I finally got it started:

While running and releasing pressure, but no stall. It hadnt been running that long though.:

After running for around 1-1 1/2 hrs. I release the pressure off the tank and the first time was extemely high pressure, but even after wait seconds I release it again, lower pressure release, but it still stalls. The car will not start with cap off, and it takes a couple trys for what seems like fuel pressure building back on the line.:

 

Finally found a fuel tank vent valve on www.gmpartsdirect.co. Should be here in a few days, and hopefully fix the stalling problem. I did a visual check on the evap system and nothing seems to be cracked, kinked, or clogged, so hopefully thats not it.

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