86Z28w350

After replacing the bad IAC valve, the spark plugs, and the TPS, clearing up the stalling, and fixing the throttle hesitation. At first I thought it just didn't like starting in cold weather, because I tried running it on a 50 degree day and it would not want to run, I tried again the next day when it was 75, and it ran fine, now I'm having another problem... it'll start right up and idle fine, but when I give it anything more than minimal throttle, it'll die, and forget about running it in gear, the instant I give it any gas it chokes out and dies. sometimes it runs fine, but most of the time it does this stalling thing, we think it's fuel delivery. The engine is a TPI 350 from a 1990 Corvette, with an older intake (because it has a 9th injector) in case any of this information is important.

Vader

What is the standing fuel pressure, KOEO? What about the idling fuel pressure?

86Z28w350

I haven't checked, I keep the car stored at a relative's house, so I'll have to stop by after work and check, but I wouldn't be surprised if it dropped.

ULTM8Z

Could be a problem with the MAP sensor. If it's mistakenly reporting a lot higher manifold pressure to the ECM that what's really there, the ECM will dump in more fuel and it'll run very rich. Once the fuel trim BLM is maxed out, the ECM can't correct any more and the car will literally start running super rich.

Then when you give it some throttle, the accelerator enrichment kicks in and dumps in some more fuel. So yeah, you could be flooding it.

If you have the ability to scan the car (or if a friend does), I'd recommend doing that. Otherwise you're "flying blind"...

86Z28w350

we checked the spark plugs, they looked fine, plus we can hear the fuel pump shutting off when we give it too much throttle at once, but we know it's not the fuel pump, because it runs fine when it wants to.

vinny R

You really need to check that fuel pressure with a gauge and while it is running. I would not assume it is working all the time. I had that issue before and it was the fuel pump relay was cutting in and out. I had this same issue, dieing out when put in gear, when i first got my car and as UTML8 said it was a problem of running rich, The thing I have found out with TPI is that it could be a lot of things that cause this. MAP sensor, TPS sensor, O2 the list goes on. In my case it was the CTS coolant temp, the one located under the thermostat housing. It was bad and not telling the ECM that the car was heating up and kept it in start mode.

86Z28w350

I still haven't checked the fuel pressure yet, but I have observed something of a pattern, I disconnect the battery every time I'm not running the car, and it seems to act up like this every other time I reconnect the battery, could this just be the ECM resetting itself? Because it seems to run fine the other half of the time. I'll be back with the fuel pressure #'s either tomorrow or Tuesday.

Vader

Try it sometime after NOT disconnecting the battery.

86Z28w350

I finally got my hands on a fuel pressure test kit, and I have some #'s. The first time I turn the key to on position... 40 PSI. 2nd turn of the key, 45 PSI, then I started the engine, then it jumped to 47 PSI, then stayed there while idling, turned it off and it started to drop immediately to about 42, then very slowly continued to drop. Bad Fuel pressure regulator maybe?

86Z28w350

I also forgot to mention, you said it could be a MAP, but the engine is a TPI 350 from a 1990 corvette, didn't they have both MAP and MAF?

Vader

The fuel pressure should actually drop about 6-8 PSI when the engine is running at idle.

I'd be checking the vacuum source to the FPR and the action of the FPR itself.

86Z28w350

I inspected the Vacuum line to the FPR, there's no fuel leakage into it, what else should I look for?

Vader

Verify that the vacuum line has full manifold vacuum - 17 to 21" Hg at idle. It might also be revealing to use a hand pump connected to the FRP to draw it down to 18" Hg. That should drop the regulated fuel pressure about 7 PSI. If not, the FPR diaphragm is suspect.