Saxo

I have a 1989 GTA with a 350 TPI. Everything is stock. It has a surging issue that will come and go randomly, I haven’t been able to find a pattern. Sometimes will run ok, then it will have a meltdown. It will surge, then almost stall then catch itself. Happens idling in park, sometimes sitting at a light, sometimes coasting as well it will surge and make the car buck with no power. I’ll attach a video. Any suggestions on what to try would be awesome.

What I’ve looked at so far:
- Throttle position sensor voltages are good
- Coolant temp and manifold air temp sensors have correct resistances (tested in hot/cold water)
- Fuel pressure primes to 44PSI and takes a while to drop so I don’t think I have leaks. Drops to about 40 running
- I’ve cleaned all the carbon out of the throttle body and IAC passages. Also replaced and calibrated IAC valve
- Manifold vacuum is at 10 inHg idling which seems low
- When surging happens car blows black smoke, smells a lot
- I have no SES light, but pulled codes and got code 33 (MAF issue)
- I used the ALDL connector to look at closed and open loop while running. Should be fast flash when open and slow when closed as far as I’m aware. When it surges, the SES light stays solid. When it’s not surging it flashes as it should

ULTM8Z

[size=16px]that's a huge clue.

stock you should be up around 18 inHg I believe.

Sounda like you might have some sort of intermittent MAF problem. [/size]

Saxo

Yeah 18 is what I thought it should be too. I’ll spray a bit of carb cleaner around see if I can find any leaks, otherwise it’s looking like a new MAF

Eightyninef

Check the timing, and distributor. My distributor was so worn, it was idling all over. Then it didn't run correctly until I set the timing exactly at 6 BTC.