What I have is a 91 firebird, v6 3.1 liter

The problem: Intermitent stalling, slight hesitation during accelerating from being completely stopped, intermitent drop in rpms while decelerating.

There are no codes stored in the ECM

Heres the deal, for a long while now I have had a slight hesitation while initially accelerating from a stop, such as a traffic light. Never really paid it much attention as the car has ran relatively good otherwise.

Recently on my way to work in the mornings the car will start fine, run good, but by the time I get into town (10 miles) The car will stall at every light and every stop sign or every time I slow down and the rpms drop below 1000. The car then starts up fine but dies immediately unless I quickly give it some gas to get the rpms back up over 1000.

Now it seems to be getting worse. A few days later it will do the same thing but if i do not try and restart it almost immediately after it stalls, it wont start at all, just cranks over and over.

And just today when I finally made it to work, I waited about a minute and tried to start it just to see if it would and it wouldn't. But by the time my shift was over (10 hours) and was ready to go home, it started up fine and idled fine. After about 6 miles down the highway traffic forced me to slow down and the idle became very erratic going from 0 rpms back to 1500 down to zero, lot of sputtering and jerking. So I pulled over tried to restart it, which it did, but it immediately started idling very very erratic again and would run for about 73 seconds and die. If I jumped on the gas real quick and got the rpms up above about 2000 it would run good but as soon as I took my foot off the gas it would sputter again, as long as i kept the foot on the pedal it would stay running fine. By the time I finally got it home (by powerbraking to keep the rpms up) and pulled into my driveway it was idling at a nice 650rpms again.

I dont know what it is. A year or two ago when I was having problems I spent way to much money replacing part after part (learned a lot, obviously not enough) and I dont really want to do that again.

I did have my scanner with me so I hooked it up and got some data of it sputtering and trying to run but not winning the battle. I really cant make head or tails of the information. I captured roughly 14 frames of data. If anyone has any suspicions and would like to know what some of the sensors were reading, just ask.

 

Without your sensor data, there can only be guesses.

I can relate some of the common problems with that year and engine. The Multec injectors are prone to solenoid coil failure and sticking. Your problems could also be caused by inadequate fuel pressure. A fuel pressure tester can help diagnose both issues. No codes will be displayed for either a failed injector or low fuel pressure unless something catastrphic happens with them.

 

Thanks Vader, unfortunately my dad decided to scan his truck and it wiped out my saved data...

Car goes to the shop on Monday.

I put a new o2 sensor, fuel filter, and new plugs in tonight, started up fine runs okay but thats no surprise really. The problem doesn't appear until I've driven it for a little while.

Hooked up the scanner again to see what was going on after the minor changes. In park it kept switching from open to closed loop occasionally. While it was doing this the o2 was reading around 800mvs then would slowly drop to 450 ~ 500ish and it would idle kind of rough but not to bad then it would surge back up to 800mv and hold for a time and rinse repeat. It didn't do this before so I think maybe I gapped one of my plugs slightly wrong? I dont really know. In drive it idles real good but it still runs rich (800mv). Every time in the past that I had my scanner hooked up and I've experienced hesitation or sputtering it has leaned way out to below 100mv.

One thing I wasn't sure about was the map sensor. When I would rev the engine up a bit the voltage would increase slightly then decrease down to about .88volts, this was around 2500 to 3000 rpms.

If I've learned anything about stalling its that there are a million different things that can cause almost identical symptoms. Its very frustrating and without the knowledge of how a sensor is supposed to act, its hard to pinpoint. Are there any good posts here that maybe give a little insight to sensors and how to read scanner data to help diagnose a problem? Something like that would be very helpful.

Thanks

 

I'd recommend putting a gauge on the EGR and checking vacuum. IIRC, there should be none past the solenoid when @ idle and at ~2000 RPM it should jump up to 15+ inches vacuum. I get 22"-25".

 

My make and model comes with the digital EGR valve, no vaccum to check. I did check it out as best I know how, resistance between the terminals are all in spec, and the solenoids open successfully with no sticking and it doesn't seem to leak.

Those digital EGR valves are expensive, and they dont have any servicable parts.

 

Ahhh...forgot about that. I think all the other thirdgen engines (with the exception of *maybe* the 2.8L) have mechanical vacuum EGR valves.

On a side note: Do you like Static-X or are you from MI?

 

Ya it seems the 3.1 is sort of the oddball. A lot of parts for it are actually hard to get. For example the fuel pressure regulator is not servicable according to all the part stores. And the dealship will only sell you the entire fuel rail which runs for a pretty penny. Although somebody on these forums, I dont remember who or where, pointed out that the 2.8L (I think, dont remember) FPR is the same thing and you can buy that at part stores separate from the fuel rail. Sounds like a money scam for a 20 dollar part to me. So I'm calling

And it would be a static X fan, one of the better bands of recent history in my oppinion.