My 1990 3.1V6 Firebird is hard to start initially but will start when warmed up.
It surges and loses power. I have noticed when it is not running right the speedometer doesn't work. I replaced the ECM about a year ago with a new one from Ebay. I recently replaced the fuel filter but the car was doing that before I replaced it. The injectors were replaced when the car had 35K on it, now it has about 75K.

I replaced the EGR valve about 3 years ago, have not replaced the O2 sensors, or the coolant sensors. I need some help with diagnosing instead of just replacing parts. The power loss and surging is intermittent but the hard starting when cold in the morning persists.

 

How's your fuel pressure?

 

It sounds like the distributor needs to be replaced with some new spark plugs*

 

I'd start with a FULL tune-up first before you go throwing a $200 distributor at it.

And check your fuel pressure. Should be between 37-47 PSI and hold pressure for 20 minutes after the pump shuts off.

 

ohh no, I meant to say the distributor cap might need to be replaced, start there first I was having a similar problem, it turned out to be the cap itself, it was not lining up correctly and causing all sorts of problems, once I replaced it with a decent one , the problems stopped altogether!...what was happening was the cap was not centered and causing hard start ups and the car sounded like a 62' Buick that was beat to Hell and back!

 

Where is the schrader valve located to check the pressure? I can rent a fuel pressure gauge at autozone.

 

on the rear of the fuel injector rail towards the back of the intake - in front of the distributor.

 

I neglected to mention there is a lot of rattling coming from the rear and it sounds like I have an exhaust leak. Do you think the Catalytic Converter has collapsed and that is causing my problems?

 

I neglected to mention that there is a lot of rattling coming from beneath. Is the catalytic converter bad? What is best to replace it with?

 

I had that same issue (rattling exhaust) when I first bought my IROC. It had rough acceleration and idle after deceleration. With the cats replaced with magnaflow stock replacement cats, I still had the same issue and it didn't seem to fix anything, except the noise. So, that being said, I don't think that's your issue, but it might have affect the V6's a bit differently. What was that fuel pressure reading?

 

I had this issue. Changed ALL the damn sensors, ran seafoam, complete tune up and fluids change including ICM and pickup coil.
Still there. Finally changed fuel pressure regulator. Still there. Then driving home the fuel pump went. So now I'm thinking it was a weak *** fuel pump all along.

 

My issue is hard to start when cold (takes 3 or 4 tries) and loss of power and surging. Problem lessens as the motor warms up. I have GOT to take car of this rattling catalytic converter first. When I replace that then if no improvement then I will start with the fuel system.

 

Possible moisture in the distributor cap? Cause when it warms up the moisture evaporates. But cold would cause condensation. Kinda like if its cold outside and you breathe on a window.
Distributors aren't too fond of moisture.
But I'm with mav on this. START with a full tune up ( including fuel filter).
As for the cat...my car hasn't had one in years. But we only have safety inspections to reg a car here. If visual was needed I'd straight pipe with a CaT shell welded around the straight pipe.

 

A full tune up generally includes about 60% of the ignition system and most of the secondary ignition, which is what fires the plugs...

Cap and rotor, plugs and wires.

After that, the only old parts in the system will be the dizzy (ignition module and pickup coil included), the ignition coil, and the wiring.

And when you replace the cap and rotor, make sure that the vent screens in the base of the dizzy are clear. For some reason, they tend to get clogged...

 

Where are the screens? damnit I didn't check my screens. Drivers side or passengers side? Maybe that's why my icms keep burning out.

Unless I just got a bad one and it dumped the same time my fuel pump went.

 

The screens are in the dizzy base. You can't miss them as they're the round things in the base plate. There is one on either side of the shaft.

It's doubtful that a pair of clogged screens are causes of ICM failure as they don't let in enough air to make much of a difference. They're mostly there to help keep condensation from building inside the cap.

Check for an AC voltage coming out of the alternator at the BATT terminal (with the big wire on it). There shouldn't be one, or very minimal. If there is, the rectifier assembly in the alt is suspect.

 

OK cool. Thanks.
Quick question... when I stop at a light or to park the rpms drop 100-200 and almost bogs. Would that be a tps going bad? New fuel pump, fuel filter, ICM, cap, rotor, & coil.

 

I know the guy above has already replaced his, but I would check to see if one or more of the solenoids in the EGR valve is sticking open when it's hot. EGR into the engine at idle can cause stalling and other issues...

 

My egr has been tuned out of the ecm and long gone and sealed the holes with block off plates.