I have an '87 Iroc with a true 5.7 and I have a few problems.

I have the SES lighit on but I do not have a scanner till I get paid. But the car doesn't have good throttle response. It hesitates about a half second before it reacts. It wasn't so apparent till my father and I tore the top end down to do some mateinance. I changed the water pump, 180 degree thermostat, flushed and changed coolant and oil, and put a new screw in the TPS because it snapped somehow and became loose.

Before those changes (and after) the car won't start right up. It turns over for about 5 seconds and then kicks in with a rough idle but smooths out after it warms. I just purchased this car and now I'm trying to fix the minor things. I've had three cars before I got my permit and this is my first TPI and first with all these sensors. My father is a lot more knowlegable than me but we are both stumped. Any help would be great, thanks.

 

Start with the TPS. Mine was reading that the throttle was open when it was not. It was running too rich and would have that same hesitation as soon at you opened the throttle. Mine was not adjustable. I think yours might be. Test and adjust to spec and see what happens.

Was it one of the mounting screws or the TPS itself that snapped?

 

Yeah, when I looked for the TPS I noticed the screw in it snapped.

 

That is where I would start then. I'm not familiar with a screw in it, but these sensors are sensitive. I would replace it if it were me.

 

Well I ordered a new one this afternoon and it should be in tomorrow. Any thoughts on the starting issue?

 

Might be related. You said that you have a SES light on. I've had my scanner for so long now I don't remember which contacts to jump. You should be able to find it in either a Hayne's or Chilton's (Or on this forum). Anyway, you put a jumper wire between two contacts on your ALDL connector. Turn the key to the on position. Then count the blinks. This will give you your code. I can't remember specifically.... I think it will do each code 3 times before moving to the next one. Long for the first digit and then short for the second. The first code that you will always get is 12. This would be one long and then two short flashes. 43 would be four long and three short.

The code(s) should have more info for you. However once you replace your broken/damaged TPS it may fire right up. If the TPS is giving a signal to the CPU that the throttle is open when it is not it will richen the mixture. If it is far enough off I would assume that it may dump to much fuel for the engine to start right away. Kinda like when someone buys carb tuned for a 383 stroker and slaps it on a stock 350. It will run, but the over jetting makes it hard to start and run bad. You could pull the spark plugs and take a look at them to see if you are running rich.

Any vacuum leaks?? EGR not closing all the way?