Okay..hopefully this will make sense..and someone can give me some pointers on where to start looking.
I have a 1994 corvette. Going on 73,000 original miles. Never had a problem with it running rough or hot till a few weeks ago. I live in Florida, the car has always cooled down on its own..and never had any problems.

Ive notice as of lately that when having to run at slower speeds in traffic will say..the car is starting to heat up 240. At this point the car starts running sluggish..at a stop light..it will start to idle rough and hiccup..and lurch a little at a stop. As the car moves on..it loses power...no pickup..till engine cools as it drives. If you step on the gas..it robs the a/c of the cold also..till you let off the gas.
At first it was running a little rough every once in awhile before it got hot..and i thought it was a fuel problem..dying fuel pump or clogged fuel filter. Then it started to run hot. Yesterday..at my buddies house..we checked radiotor fluid..looked good. The fan kicked on at 220 or so..the fan came on with the a/c when turned on. I noticed today as the car starting heating up out of nowhere again..that when i turned OFF the a/c..the engine starting cooling off and went to about 224. Which is normal in the florida heat. as i got near home..i turned the a/c on at about 35 mph..and it started to go into the 230's and run a little rough. As i pulled in my garage..i could hear the fans running like they should. The car has no engine check light on..and runs great when cold. Full power and cold a/c.
Somebody said maybe the spark wires were why it was hiccuoping cause they might need to be replaced and after they heat up..they swell..and could be an arc. I honestly dont have a clue..because i ruled out the fuel problem..since it runs fine..most of the time when cold.

WHERE DO I START?? Thanks for any help!!

 

LT1's are programmed and are known to run hot, but it shouldn't be running that hot. First thing, which gauge are you checking the temp off of, and do they roughly correlate? I know it's hard to get an accurate feel for the analog gauge, but take your best guess.

You see the analog and digital gauges are fed by different sending units and can be a sign of a problem. If the analog gauge is hot but the digital is cool, you have a circulation problem, possibly a blocked hose or a failing / water pump. If they both read hot then the coolant is circulating and you likely have an airflow through the radiator problem.

These cars work like hoover vacuum cleaners for sucking up crap into the radiator shroud. I'll bet that you've got so many leaves and junk in there that it just can't breath. That would be the first place I would start looking.

 

Change the thermostat and flush the coolant. There could be bubbles in the cooling system causing it to heat up quickly. LT1's are sensitive to this because of the reverse flow of the coolant.

Is the check engine light coming on?

 

gauges both read the same..no check engine lights. Check the front..no leaves.

 

cmon guys..nobody else have any thoughts?

 

My 94 did the same thing as yours. I did not get that high of a temperature. I had about the same mileage.
My problem was the opti.
I had surge at stop lights, rough running after 20 minutes, engine under low load was missing, full throttle bad hiccup.

 

Fix the cooling system. What have you done to it?

 

They are no more sensitive to air in the coolant than other engines.

I would start by cleaning out the space between the radiator and the AC condensor.

 

Due to the reverse flow to the heads first, they are.

Also, if you read his earlier post (which is NOT in the FSM) he said he cleaned the radiator area.

 

Same for my 94. Opti AND Water Pump. Same symptoms, same result. My mileage was 100K, but I don't know the age of these components.

 

I will forgive you because I know reading and comprehension is not your strong suit. He said he "checked the front for leaves." That would lead most folks to think that he checked the front of the condensor. We all know that the junk collects between the rad and cond.

How could you possibly know what is in the FSM?

 

MK82..your right..i only cleaned the debri in the front of the ac condensor..going to check between the other now

 

Any luck?

 

my mechanic buddy wants me to replace the radiator. he says for the 125 bucks it wont hurt, cause he thinks it could be partially clogged. while im at it..im going to put n a new front spoiler kit..so it will look better than the bent up , scratched peices there. I guess after that..i will see where im at.

 

mine has been doing the same thing, i am going to replace the opti and water pump, mine is a 94 as well it has 90k on it. May do a cam swap while i have it apart, its a good excuse to change it out

 

Whereas it could be the radiator, it could also be a bad thermostat.

And most likely the high temps are what is causing the engine roughness, but it could also be a dirty MAF.

When was the anti-freeze AND thermostat last changed and which type of anti-freeze was used?

I had an experience with the thermostat where the lower part (the extra plate which is unique to the LT1), had actually come off the main plunger - result was 1/4" to 1/2" less of an openning and 15-20 degrees hotter.

Once thermostat and anti-freeze was replaced, typical temps are now under 200 without AC.

Also remember our 94's came original with good ol' green anti-freeze -- difficult to find, but some local shops still carry the Texaco brand -- which is what we need for our year car.

BTW, once you get the cooling problem solved, consider having the oil changed too -- as it's been cooking it..

 

Good starting approach.


Lot of suggestions so far but first and simple things first. As said, fix the over heating problem. Approach it a systematic way and in logical steps, not a weird or tough problem.

Airflow blockage has been at least somewhat checked. This has classic symptoms of a tired thermostat not opening up all the way. Change the stat and the coolant first before you change the radiator. Radiator can also be changed later if need be.

If you don’t want to pop for the cost of coolant for you may have to change the radiator, just use water and change the stat to see if it fixes it. If your good to go, you can replace the coolant later.

If the radiator is changed, then no loss of money, stat has to be changed anyway with the radiator.

I have had defective stats and ran hot also in time in FL with not runability problems. So my guess is that you might have two separate problems.

 

Huh?

 

I found the symptom of robbing cold from a/c interesting. May be your serp. belt is slipping or bad or pulley issues, which would also cause the engine heating and loss of power from hot engine.

 

OK, I’ll admit it does look weird, would get my attention to. Definitely a wrong word. Well, in a rush grabbed the wrong work in the spell checker. But now fixed it up and time for a brew.