Hello everyone I've got an oddball issue at the moment with my '88 Firebird 305 TPI automatic, I did a search but nothing really came close to this issue.

I bought this car about a month ago and it was running fine, passed emissions and all that jazz. Had a random issue where the idle would go wacky after you hit a bump, checked my cap and found it was "secured" with a self tapping screw through the side. Had to replace cap, rotor and distributor. Also put in a MSD Blaster coil while I was at it. (Cap & Rotor are ACCEL brand, and the new distributor is a Proform.)

I followed the steps and disconnected my ECM so it reset and the car ran like a dream. Now about a week later it has developed a erratic idle where it bounces from 600-400; sometimes lower, when in drive and at a stop light with my foot on the brakes but only after it has been running for about 10 to 15 minutes. Shift into park and it idles fine. I do have an issue with my TV cable coming out of adjustment now and then, but I check it regularly (until I have a chance to replace it) and readjust it.
This car is bone stock almost everywhere; doesn't look like much has been improved or replaced. It's well looked after aside from the cap and rotor being mangled. So my question to all of you is what else can I check?

Vacuum lines all look fine, no cracks or missing lines, the wiring harness is (surprisingly) uncut and original, and the MAF sensor is definitely a aftermarket BOSCH; I do need to change the plugs but as we all know a 305 equipped with that AIR pump system is a royal PIA to do plugs on, and I do have to change my valve seals (puff o' blue smoke at cold start). I haven't checked fuel pressure yet, but I haven't had any starting issues yet so I'm not too worried about my pump or rail pressure.

Apologies for the long post, just want you all to be informed on what I've already checked (at least the stuff I can remember lol). I am rather new to fuel injected cars, gimme a carb on my big ol' 400 and I'll play all day but this TPI setup is a whole new beast to me.

Thanks in advance!

 

I would do the rest of the tune up meanring plugs and wires. The plugs are not that bad to do from underneath. you just have to get past the greese and dirt falling in your eyes

 

That's my plan for the weekend, thanks for the tip, I'll try 'em from underneath hopefully I'll have better luck lol. Gotta get some new plug wires too while I'm at it, the ones on it looked good but I've found some nicks in the insulation lately.

 

hey man did you ever get the idle issue fixed? mine has recently started doing this too.

 

Hi sorry I haven't been keeping focused on things here with my work being very busy.

I never fully solved the issue, plugs and wires helped but my IAC valve is caked with carbon so I've had to clean it almost weekly (bought a new one have to change it this weekend) so I'm hoping that is the last piece of the puzzle. Everything else checks out fine so that's gotta be it.

I am also wary of my rear three injectors ticking like time bombs so I'm gonna have to change those soon too.

 

I have heard of the ignition control module causing this problem also

 

I've been looking into that one too, the IAC Valve will determine whether or not I need to seriously investigate it next lol.

 

Yeah but he changed the distributor and most of the time when you change the distributor it comes with a new Control Module mounted on it already

 

Update for anyone still following this. IAC Valve change helped but again after a week it started acting up again. There's a massive build up of pressure in the fuel tank making the pump whine, so I have been investigating that too. I am changing my regulator diaphragm this weekend to see if that helps but I believe it is the solenoid on the fuel vapor canister not opening or a little known valve at the tank not opening to release pressure. I will update later this weekend again.

 

Alright so finally solved the issue for anyone still following this or who needs a kick start.
Last month my ESC started acting up causing a massive hiccup in the idle and bucking while driving so I disconnected it and the issues went away. Car ran fine for a while so I decided to wait til warmer (ie. higher than -23) weather rolled around to investigate it.
Suddenly last week the car started bucking and stalling, throwing a code 22 and finally left me stuck at work one night. Towed it home and ordered a new TPS out of the states ($142 CAD up here, vs $22 down there. You guys have it nice)
Got the part Monday night, installed it and car started up and ran fine. Yay. Good to go. Set out for a friend's heated garage to change the trans filter which was causing a lot of problems, and halfway there it starts bucking, surging, stalling and generally making a nuisance of itself.
Finally make it to the garage, pull it in, fight to install the new filter, change the oil, clean connections, fix a ground and fire it up only to have it stumble and stall every time.

So long story short: Got stranded out in the boonies on a farm for 20 hrs only to discover that the ignition module that came in my brand new $200 distributor was dead and I replaced it with one I picked up off the floor of the garage and my car runs perfectly fine now. Not even a stumble or vibration.
Morale of the story? I carry a spare module in my trunk now.