Hey, all, been lurking here for years and may have been registered many moons past but can't remember that login! Anyway I have a 1992 3.1l Firebird. My problem is with the startup. I usually can't get it to kick over unless I give it a little gas. Overnight it tends to kick over in the morning but not smoothly. Sometimes it'll start then want to stall, catch before dieing and surge to about 1500rpms before it settles down (this usually after several cranks where it never kicks over). The weird thing is that after I get it going I can shut it off and for about 10-minutes or so and start it again with no problems at all, if it sits any longer, I have to use the pedal to get it going again.

This started in late October so I figured it was a cold start issue as my area finally began to cool off. I've replaced the coolant temp, thermostat, air temp, AIC, TPS (threw a code for that before this all started), PROM and MAP (made it throw a code by messing with some other sensors, seemed nothing was wrong with the initial unit). Had the fuel filter replaced about 3-years ago and plugs, wires, rotor, cap, coil and ignition module replaced (more on that later!) within the last 2-years. Haven't checked fuel pressure at the valve yet, looked for leaks at the pressure regulator and found nothing when I had it apart for the T-stat. I have tried the old prime the fuel pump trick a half dozen times before kicking over to no avail. Fuel pump relay and inline fuse check out, and the pump hums fine from the fuel tank with engine on (although sometimes the hum can seem louder and higher pitched and sometimes I get a gurgling sound but it's done that for decades now).

So in the last month I began getting rough, sputtering acceleration, I'll say rough idle (it's never really idled smoothly) and on occasion a cylinder burp. Monday it seemed to loose about half it's power so I took it in for work. Plug wires fell apart in the mechanics hands and the plugs contacts were pretty rounded. It was assumed whoever did the work about 2-years ago never replaced anything but charged me for the work. They did the full tune-up, replaced cap, rotor, wires and plugs. Runs great now, kicked over normal most of the time, sometimes I'd get the surging but last night it was back to not starting unless I did some pedal work. Still runs good, no missing like before, however.

I'm pretty confounded by the fact it can start like nothing is wrong within a few minutes once I help it kick over and the fact that the tune-up did something to make it want to start normal for the last few days. I was thinking the start-up and issues fixed by the tune-up may not be related. I initially thought it was something computer related due to all the sensors being replaced and cold weather coming in (maybe a choke failure in the ECM?). I started with the PROM because I found one really cheap and figured an extra chip is always a good thing to have considering their rarity these days. I was about to move onto the ECM when the driving problems started.

So any help is appreciated. I'm retired army and have had this thing for 20-years but made it my daily driver a few years ago. I usually don't travel that far these days but last year it's been a lot of old-age related repairs and this year isn't starting off great! I got my small Government pension to live on and mechanics in CA get top dollar by law even though they know next to nothing about cars, especially ones this old. I can't afford to have them poke around the engine at $100 an hour for a few days and hope they know what to look for!

 

Welcome back to the forum. First off, I'd get that fuel pressure checked. Fuel pump may be getting ready to die and if you haven't changed it out yet it's about due. Also, I'd ohm the injectors. If they're the originals it's probably time for them to be replaced. When you checked the FPR did you pull the vacuum hose from it while the car was running and see if it bled fuel? Check all your vacuum hose routing and make sure it's intact. The reason for the above actions is that I've had to replace all these items on my 3.1 as well before I got it running good and strong, as well as, a lot of the items you already changed out. Good luck.