Please help me, my Vette is not being nice to me. I have a 1994 convertible with 92000 miles on it.

The problems started about three weeks ago when (I found out once I finally had time to look at it) the Heater inlet hose ruptured at the engine side.
I ordered and installed a new hose and used the FSM instructions for refilling the coolant system. The coolant seemed to be acting like it should, with the exception of the fact that the analog gauge is pegged low (the digital still seems to track)
Upon taking her out for a drive around the block, and she worked great. At least that is till I tried to accelerate.
At almost exactly 2000 RPM the power... goes away. Namely, at 2000 RPM the engine stutters hard, there are unhappy popping noises from the hood and exhaust, and the car completely stops accelerating.
Once I come back down under 2000 RPM the car acts like normal.
During all of this the coolant was holding right at 190.
I tried to accelerate up a small hill, and I couldn't maintain even 1500 RPM, which meant I was crawling up at less than 20 mph. When this happened the coolant temperature jumped up to 240-245.
When I pulled back into the garage and turned her off the coolant overflow tank was bubbling and overflowing.
I then pulled the codes and the only one was for the MAF sensor (which was a different problem that I already knew about).

I am sure that the answer is already out here somewhere, but I don't know the right terminology, and unfortunately don't have the time to look through the entire forum (even if I would like to).

Thank you for your help in advance.

 

Sounds like a bad fuel pump that's losing pressure at higher RPMs. Might be a dirty fuel filter.

Check your fuel pressure while driving.

 

Fuel filter is a cheap fix that you can do if you have jacks, if you don't it may be a bit more difficult. The popping noise is intake backfire from running lean.

 

Step 1 fix the known issue -- the MAF. Running lean also = more heat. Could account for some of increase in coolant temp. Did you bleed the cooling system properly after replacing the hose? LT1s use reverse flow cooling and air pockets are a recipe for big trouble. The different readings on the 2 water temp gauges (digital vs analog) could point at trapped air.

 

Did you check to see if the heater works? If not, that could indicate an air pocket as well. When bleeding the coolant system, I have had the best result by juacking the front of the car up, so that the bleeder screw on the coolant line is the highest point. Open it up, putting alot of rags under it of course, taking the pressure cap off, and running the car up to temp. Then I just wait for a steady flow from the bleeder, close the system up.

Yor analog guage sensor is located on the passenger side head. The fact it doesn't read anything tells me there may be a large air pocket, as air rises, the head is the logical place it would go. Bleed your system and then go from there.

The 2000 rpm issue could be fuel related, but I might venture to say that since the ECM is getting no reading from the head temp sensor, it is "limp home" mode to protect the engine?

 

The LT1 engine is self-bleeding (http://www.calgaryfieros.com/OSGdocs/mod.LT1.html).
Yes, I'm aware of the horror stories of huge bubbles, etc.

The analog coolant sensor/sender is near the area of your hose repair.
Any chance you removed the connector by accident?

Your heating symptoms could be linked to a tstat that has failed in the closed position. Replacement of the tstat is a cheap fix. Just make sure the new tstat is LT1 specific.

Another condition could exist that exhibits similar symptoms is a ruptured head gasket allowing exhaust gases to enter the cooling system.

 

Don't know what check valve the Fiero guy is looking at, but it's not on any LT1/4 Vette I've worked on. You have to open the bleeder manually and let the air escape until coolant comes out. Then you have to close the bleeder. Even doing that, air can still be trapped in the bowels of the engine such that it may take a couple attempts to fully bleed it.

OP...As mentioned above, make sure the wire is on the analog coolant temp sender that is located between the #6 & 8 cylinders (passenger side rear 2 cylinders). The sender is a single wire and it can pop off pretty easily. Ditto the above suggestion regarding the t-stat

The PCM uses only data from the coolant temp sensor (also feeds the digital display) for engine operation, cooling fan control, etc. The sender located in the cylinder head is Only to drive the analog gauge. It has no bearing on engine operation, fan operation, etc at all.

Regarding the stuttering...if the hose ruptured, WHERE did it rupture? Did it spray down the Opti? Was the rupture more towards the firewall and the plugs/plug wires were drenched?

What did you remove to replace the hose? Did you pull any plug wires? Crossed plug wires will give you low power and if it's only two wires a seemingly normal idle (depending on which two are crossed).

Pretty unusual for the heater hoses to rupture, even old ones. When it ruptured, was there evidence of coolant overflow from the fill tank? If not, then that would suggest the pressure at time of rupture was below that of the radiator cap used on the fill tank. If there was evidence of overflow then that could suggest, as mentioned above, that the head gasket went.

It's not a fuel issue.

 

Owned '93 & '92 LT1 Corvettes for about 16 years. If vette needed coolant repairs, or a complete flush, I have just filled the system, idled the engine with the surge tank cap off until the tstat opened, added coolant as required. No additional bleeding necessary.

 

I was expressly addressing the bleeder screw ("one way air valve") called out in the link you provided. It is not "self-bleeding" and did not come on Corvettes.

You are not using the bleeder screw at all. All engines, not just the LT1/4 will "self-bleed" by your definition. More correctly, the system is designed such that with the bleeder screw opened you can fill the cooling system and not have to worry about trapped air pockets. In reality, it's not quite that good but it's pretty close.

16 years with the LT1 huh? Rookie

 

Could it be a throttle position sensor?

 

OK ... In your original post - you said you had a heater hose failure "at the engine side". So - I'm guessing that hot coolant got all over the front engine. To me that sounds like an Optispark Failure should be suspected.

Once the heater hose was fixed, you add coolant till the system won't take any more. The start the car and let it idle - the water pump pushing the coolant through the system will help dislodge any air pockets. Just keep adding coolant coolant as needed, and when the system doesn't want to take any more - you're basically done. If you suspect that you still have an air pocket - you can open the coolant bleed valve, and let a little coolant trickle out, but I've worked on a few LT1/LT4 motors and I've never needed to do that.

How does the engine respond to revving with no load on it - will it do 3,000 RPM cleanly in neutral ??? If not - try hooking up a timing light and seeing if the spark seems consistent as the revs climb. If it's not - you're probably looking at changing the Optispark (you can find numerous posts about opti failures after it gets wet - typically due to a water pump failure here on the C4 Forum. You say that you have over 90K on the car - so assuming it's the Original OPti - you got your money's worth out of it.

 

This is the OP again. Sorry about the delay getting back, It's hard to find time to work on the second car when you spend 80-90 hours at work a week.

Back to the original problem. I wish that this was the original OPTI, but unfortunately about a year ago it was replaced (along with the water pump), and it is not acting like it did back then (as well as not pulling any OPTI codes.) The engine has no issues revving to 3000-3500 RPM while in park or neutral. It is just while driving that it causes problems.

I used all the same coolant filling procedure as a year ago(the procedure that has been recommended here). However, this time around I go for a drive after filling the system and, upon parking the recovery tank is overflowing with hot coolant.

I have yet to get a fuel pressure gage to test that out, but the weird reaction of the overflow tank worries me into thinking it is something else.

Still no new codes to help me out.

Thank you for all the help, I am hoping to get my car fixed soon, as she is no good just sitting in the garage.

One last question, if I ended up taking it to a shop, what are the chances that they would be able to figure this out without being retarded expensive?