Hi folks, I am a new owner of my 84 and I am chasing a problem that it has had since i bought it. The car starts up and runs but after it is warm and you give it a little throttle, the car just wants to stall out and cut off on you. So far I have replaced the following parts. spark plugs, wires, distributor cap, rotor, fuel pump, fuel filter, throttle body gaskets. Other things too but not engine related. The spray pattern from the 2 injectors looks good at idle. I have a new coolant temp sensor, but have not installed it yet, as i am waiting on the new connector to come in. It still has the original coolant temp sensor. Could it be the fuel regulator? I have also heard a bad battery can do this.. so i am just completely puzzled at this point.
Thanks for your suggestions.

 

Have you tested the throttle position sensor?

 

No I have not. Don't have the test jig needed. I've seen video of how to do it so once i get the jig think i can figure that out.

 

I just found a post on how to do it without the test harness that i would have to purchase, so i will give it a try tomorrow. Thanks for pointing me in this direction.

 

Welcome. That'll usually cause all sorts of issues and is easy to test. Also, yes. A regular meter will easily back probe the harness without the jig. Make sure to check the voltage sweep for smoothness.

 

Will do

 

check fuel pressure. just to know where its at. fuel pressure is very important

 

One thing I need to add is that the coolant temp gets up to 235. Problem seems worse, the hotter the engine temp. Also, I dont know if it is related but the cooling fan only runs for a few moments and turns off quite quickly.

 

I changed to a 180 degree thermostat and a fan switch that turns on at 200 and off at 185.
here's a link. fan only runs when not moving
1984-1996 Corvette Cooling Fan Control Mods | CC Tech (corvettecentral.com)

 

So by going to a 180* stat will NOT and is NOT a cure for a high temp, poor cooling system issue. No matter what the stat rating is for temp, once it gets to that temp it will be wide open period and you are getting max flow. If your cooling system keeps going up in temp, you have other cooling issues or an indication issue. I would verify that your temps are indeed getting that hot first and 235* is too hot for a Gen1 sbc block IMO and would be concerned if that temp is correct...The stock stat is 195*. jus sayin'. GL

 

The stock 84 fan switch kicks on somewhere around 230 plus or minus 3 degrees or so. I'd have to double check the fsm but my dash always said 232 when it came on. The ecm saw 225 however. It always reads lower than the dash on mine. While hot it is kind of normal I believe.

 

84 43, This is exactly how my system is operating, with the fan not turning on until 235 and this really bothers me. When I did a radiator flush the coolant was really dirty. Worst I have ever seen, though it wasnt oil, just really old and possibly 37 year old antifreeze and water.

I know the vacuum system has been screwed with as well. For example, the small vac line that wraps around the air filter that is supposed to be connected to the throttle body on the drivers side was disconnected and the throttle body capped off. Both vac inputs on the throttle body are capped off. Have a feeling one of the 2 previous owners did that for a work around to the actuators not working that open the flaps for those mounted inside the air filter housing, though not 100 percent sure on that. Yesterday when i put the air filter housing back on, I put the small vac line back onto that throttle body though all that did was force the flaps closed. Also the vac line was off of the driver side head light motor assembly.

This morning I am going to replace the ignition coil & the HVAC check valve. No air blowing out of the vents. Might also replace the thermostat and the cooling fan switch with a lower temp one.

 

I also put in a radiator twice the size of stock radiator. put on a transmission cooler and temp gauge. my car runs from 185 to 205. this is just what I did.
I didn't like the fan coming on at 240 degrees.

 

Thanks for the info and would always go with a temp sensor coming on a bit earlier, but if my motor was running at 235* or more, I'd be panicking. A stock motor with iron heads running hot is not a great idea and if for some reason it goes hotter you stand a good chance of warping the heads since you would be very close to overheat and it won't take long to get there on a cooling failure of some kind. Some don't get too concerned about running hot, but on a Gen1 block I don't like it and have had an overheat once a long time ago and warped the heads. That was painful back then 25 years ago. I tend to watch mine living in Arizona more than I guess I need to, but I do keep an eye on it, plus running a Dewitts rad as well, stock fan and aux fan. Usually stays around 180-185*.

 

Hey guys, wanted to give you an update.
So I have been working on her all day so far. I replaced the ignition coil first. The old one had a date stamp from 1986. Also, I found that one of my new plug wires that I installed wasnt making a connection to the spark plug. Think that is why it had blown blew smoke on startup and ran rough. After replacing the coil and re-seating the plug wire I tested it out. She started right up with enthusiasm and was hoping that was going to do the trick. Took it for a test run and unfortunately it still had the same stall out problem and it cut off on me while on the street. It started back up and i got back home.

Next.. on to the TPS adjustment.
So, my redneck method was I took 2 push pins.. they are like a sewing needle but with a handle, and poked these into the bottom 2 wires and alligator clipped my volt meter probes to the push pins. The instructions I found here said to test the top two wires, though it was just reading 4.58 volts.. more volts than i was looking for and think that was a ground to the main voltage..Watched a guy on youtube test his and he used the bottom two wires. So, I checked the bottom two wires and there i found the -1 volts. I had to move the TPS probably about 1/8 -1/4 inch up from its old position to get close to the .54 volts.

After changing the TPS positioning, I took it out for another test and no more stalling out!! I ran her for about 10 minutes and it no longer had the stall out, cut off problem. Also, it wasnt getting that hot, though I need to test on it a bit longer i think.

My existing TPS and its connector is really falling apart. The connector lock down tab, broke on me at the slightest pressure. Also, one of the torx screws was just locked in so tight, I stripped the star screw and had to use a vice grips to unscrew it. Going to order a new TPS sensor today and a new connector for it. We might have this particular issue resolved.

Thank you everyone for your input and your knowledge!! Yall are the best.

 

Set the TPS as close as you can get it to .525v, it will work the best at that setting. As you tighten it down, it will move, keep readjusting until you get it tight and to that setting. GL

 

don't go too crazy with it though. It'll work just fine from. 515 to .535. Mine was a pain to get dead on and it didn't make much a difference. I actually set mine on the data stream now so it's "more" accurate to what the ECM wants to see.

Any rate, glad it was something easy.

 

Thanks Buc & 84+3.
Do you all know where I can find a test harness that I can hook my volt meter to? I checked a few places, Eckards & Amazon and cant seem to locate one.

The one there now is shot and so is the connector. If I cant find a harness, i will use the same method i did today and try my best to get it close. Probably anything in the neighborhood of .5 is going to be like a new engine compared to the way it is now.

Something else i didnt even bring up I think will get resolved as well by replacing the TPS is the transmission shift points. Now it is shifting to the next gear at odd rpm's.

 

PM sent.

 

You have a 700r4 correct? (Automatic) if so start a second post on that and alert arbee. He knows those better than pretty much anyone I'd say.