My '89 with the 5.7 tpi has had a problem a few years now where when I start the car cold, it'll sometimes stumble and lose almost all power when I put it in drive and go to drive off. Weirdly, it doesn't do it until I touch the throttle in drive, it'll always rev happily in park and idle just fine in drive. Once I get going, it stops doing it. Though it will also sometimes feel like it's missing at full throttle at higher speeds. Everything I can test seems fine, resistances look good on the TPS, fuel pump is new, new plugs, wires, cap, and rotor, new ignition coil. Injectors were replaced.

I've heard the MAF can be an issue, but reported symptoms don't match mine. The TPS is suspect if it didn't have good readings. I have heard the coolant temperature sensor can be an issue, but my gauge reads just fine. No vacuum leaks can be found either, and I've checked everywhere. Any other ideas? The car runs great outside of these specific circumstances.

 

Test or check the pickup coil and regular coil? MAF can cause issues to. Do you happen to have a service manual?

You're looking for voltages on the tps, nice clean sweep/ increase

 

The gauge and ECM have different sending units.

Personally I let an engine run for 30 seconds or so when it is cold before putting it into gear and driving away. When I am driving away I use fairly light throttle until it warms up. Don't beat on a cold engine if you want it to live a decent life.

I have not looked at a MAF setup but the Speed Density setups do not command timing advance until the coolant is over about 110F. The retarded ignition timing, combined with the over rich air/fuel and the air being blown into the manifolds heats the exhaust and thus cat like a blow torch would to get it working as quickly as possible. The engine runs super lethargically while this is occuring.

 

I haven't checked the pickup coil, I'll add it to the list. I still have the Haynes manual but the original books were thrown out or stolen by a mechanic when my brother had the car for a while. As I said, I checked the TPS and it's fine. MAF is basically always suspect, as I understand.

 

Good to know the sending units are separate, I wondered about that. The stumble on takeoff can happen whether it idles before driving or not. There's no reason to warm up a car with fuel injection at all before driving off, though it's nice to at least let the RPM's settle to a normal idle before putting it in gear. The car is at full operating temperature before I do any spirited driving, the issue is present then. It feels like a miss. I'm not sure if it's related to the occasional stumble right after startup or not. It occurs to me that when the chassis brace was installed, the shop removed the catalytic converter. I wonder if that's causing issue. I've been debating whether or not to reinstall it just for the smell the car makes without it, they never asked me before they chucked it in the dumpster.