I've got an 88 corvette thats an automatic. It sat for a few months while i was fixing it up a bit. Got new plugs, wires, fuel pump, tps, air intake, distributor cap. Pulled a lot of sound damping out of the exhaust because it was completely plugged up. But now that it idles and drives, I've noticed that 1st gear is slacking hard. Theres little power to it. But 2nd and up are running excellent. When i got it, i could hit the gas and tires would spin. Now i hit the gas and it picks the rpms up slower. Theres no noise coming from transmission and it still shifts fine.

Would this be my transmission going out? I'll check my fluid tomorrow to see if thats it too. But what other problem could it be? Could it be my IAC? I pulled the old one out and installed a new one probably 8 months ago.

 

First of all I want to say that you have a beautiful Corvette there! I have the exact same spoiler but painted silver like my C4 is. Do you know who made them by chance?

BTW Welcome to the Corvette Forum! We are glad you are here and hope you learn lots while here!

The slacking of First Gear doesn't make too much sense to me. Can you describe the symptoms in a little more detail for us?

I too have a 1988 C4 and it has never really been able to spin it's tires even with the 3.07 rear axle ratio and a healthy L98. I have Pirelli Tires on it that are very sticky and that might be the reason. The car has never seemed like a power house in first gear to me anyway. I bought my C4 with almost 90k miles and my transmission was starting to slip a bit. I made a quick trip to the local AAMCO and $1400 later I had a rebuilt 700R4. The difference in performance from having the transmission rebuilt was pretty impressive. I would take your Corvette to a reputable transmission shop and have them evaluate your transmission for you.

The knock sensors in the C4's would sometimes get out of whack and trigger falsely. I had one that had failed and was keeping the timing retarded all the time because of knock sensor erroneously sending out false signals. To test the Knock Sensor just take a metal wrench and tap the cylinder head while the engine is running. The idle speed should drop a bit and then recover after the "tap".

 

The spoiler was on it when i bought it so im not sure! Thank you tho! I've never had any codes pop up yet so im happy about that

I just took it around the block and it seems to be back to when i bought it or even better. The fuel pump must have been to new or something but the symptoms were simply 1st gear didnt have much power to it. I would stomp on the gas and it would kick out the *** end and squeal the tires for a solid 50 yards without hitting the brakes. But the other day it just wouldn't. Fuel pump must have been to new or something. Today i went around the block a few times, it would spin the tires good. So now im just confused 🤣 but it seems to be good. Transmission fluid is good. Doesnt shift hard or anything. So i might be in the clear.

Im thinking your tires are probably to sticky. But youre take off should be better than mine. I have firestone tires and they're great.

Im still going to check out a Transmission shop and see what they have to say.

My only problem right now is my brakes. one day while driving, i tried to stop and it went to the floor and didnt stop. Thankfully i was only going less than 5mph. So i replaced brake booster and master cylinder but they still dont work correctly. Especially after its been driven for a while. Brake lines dont leak. Im hoping its just brake pads and rotors, possibly need calipers but I'll know once i install the new pads.

 

Hello again KingWyatt!

You want to be REALLY Careful about the braking system in your 1988. As I mentioned before I have an 1988 C4 Coup as well.

The bad thing is that this 1988 Corvette is a One Year ONLY Corvette when it comes to brakes. The master cylinder is a one year item and only has two ports on it. One is for Fluid IN and one is for Fluid OUT, it is not like any other Brake master Cylinder you have likely worked on. The ABS Controller is what sends the fluid to the brakes, on the 1988 there are three loops, Front Right, Front Left and Rear. Be careful with your ABS controller as they are not easy to get fixed. I bought a spare working unit to be safe down the road.

On my C4 I went out one day to drive it and I stomped the brake pedal and when I did that one of the brake Lines Ruptured and the master cylinder was DRY afterwards. The spot where it rusted is right where they go into the box behind the drivers seat. I had to order a complete set of new Brake Lines and Install them. Classic Tube makes the brake lines all pre-bent exactly for the C4 Corvette and they fold them in half to ship them. The Box was 5 feet long but it had the whole set. Classic tube also makes a kit to remove the ABS system from the C4's if you chose to go that route.

If you have had a brake line rupture then it is likely that your Fuel Lines might have been affected as well. The gasoline with Ethanol will absorb water and it will sit at the lowest point in the system. On the 1988 it is behind the rear of the passengers seat under the car. I had to replace the fuel supply and return lines as well on my C4.

Where did your system rupture the line? How hard did you have to push the pedal to break the line? Have you inspected your brake lines from front to rear yet? I found a spot near my ABS pump where the line was re-shaped by ice inside. Flush the brakes every five years on the C4's and you will have brake lines last longer.

Merry Christmas to you and your Family!

 

I had the brake lines inspected afterwards and theres no rupture they said. I'll look at the ABS. My fuel lines are all good too. So im thinking i have bum calipers. Hoping friday or Saturday I'll get them on. After that no brake experience, i still managed to drive from FL to AL and back. But i had to keep messing with my brake booster. All of that seems to be working good. As i did replace brake booster and mastercylinder. Now my next options is rotors, pads and calipers. We'll see where that takes me. If i still have problems I'll definitely have to take it to a shop.

You must be in a colder region than me because theres definitely no ice forming in Florida where im at. Im definitely going to need a new radiator soon. If you have any recommendations for them, I'd be happy to look at them. Im thinking i need something 40% cooler if that's even possible. I replaced thermostat and cleaned all the debris out of my radiator previously. Since i havent been driving it, i have to see if im overheating again.

With the master cylinder, im assuming you're talking about the front and rear reservoir? I thought they were just separate for front and rear brakes?? If i do end up having to replace brake lines, how difficult is that? Or is that something i should bring to a shop?

Thank you for your replies! Helps a lot! Happy holidays

 

Hello again KingWyatt!

That is good news that your brake lines are in decent shape on the outside at least. I am not sure where the Brake system could have opened up if you lost your fluid. On my C4 the brake reservoirs were "Bone Dry" after I broke the hose going into the ABS system. The puddle was under the rear of the drivers seat after the rupture. It was my understanding that all U.S. made Cars were required to have dual reservoirs to prevent both front and rear failures at the same time. This clearly did not apply to the original 1988 C4 Corvette. Be absolutely sure to get the right master cylinder for your Corvette IF you decide to replace it. I would also start saving the original parts in case they can be rebuilt later. Any mechanical or electrical part I take off I save, bag it and tag it.

Do you have a scanner or a Code Reader available? The Scanner is the first choice for trouble shooting as you can see the various outputs and identify the faulty sensor more easily. Code readers just read codes and that can be done on a Corvette using a paper clip.
Do you have the Factory Service Manuals for your 1988 Corvette? It comes as a hard copy for about $85 and on DVD for about $30-35 from RockAuto. I personally have two sets as I keep one in the garage and one inside the house. You will NEED the FSM's at some point so get them early. Also get a Gasoline Pressure Test tool so you can verify the correct fuel pressures at the fuel rail. I bought an OLD Snap On MT2500 from a Forum Member and it does what you need it to do, I can see the data in real time. I can also use this device on my newer Cars as well. A handy gadget to have when you own a C4 Corvette!

Rock Auto is NOT my favorite place but I did buy a set of four re-built calipers and new slotted rotors from them. The 1988 has the best Parking /Emergency Brake as they got rid of the Honda Drum brakes inside the rotor and went to a Cable pull system that works very well. The brake lines are a real PIA to install correctly, it helps to have the Car off the ground and up high enough to get around comfortably. It is a lot of on the back work. I wish I had paid someone to do mine for me....

How familiar are you with Corvettes in general? How mechanical are you? The 1988 has good brakes when they are working properly. You might want to switch over to the S.S. Braided Brake Hoses that connect the chassis to the caliper. They are not too expensive but they do help as they don't expand like the old factory Hoses could after years of service. Just be sure to get a set that is D.O.T. approved, the Chinese ones on EBAY are NOT D.O.T. Approved. Once you get this Corvette working properly be sure to flush the brakes every Five years.

You mentioned the pedal going to the floor, was there any brake fluid left in the reservoirs? Where did the fluid go? I would guess at the Master cylinder being the culprit if you lost no fluid. I personally would not rest until I "KNEW" where the problem was on your brakes. The ABS system is complex and not designed for user serviceability. There is one post where a gentleman from Europe took his ABS box apart and cleaned the components, great and useful video if you have issues with the ABS systems used in these C4's.

Your digital dashboard was designed with 15 year life expectancy on the components, it is easily twice that age so when problems happen go to BATEE.Com and all your Digital dash and C68 (Electronic Air Conditioner Control) problems. I had to rebuild both my dashboard and the C68 in my C4 Corvette. They offer the service to do it for you or if you are electronically inclined you can try it on your own with the new parts. Batee is a true blessing for we with the old C4's.

As far as radiators are concerned the DeWitt Brand comes to mind but they are a bit pricey. Eastwood offers new radiators (cheap) for HOT running vehicles. One point to be made here, the 1988 C4's cooling fans don't come on until the engine is much hotter than most people are aware of. Does your Corvette have the single fan behind the radiator or dual fans? I am curious whether you have the auxiliary cooling fan or not. C4 Corvettes are notorious at getting stuff between the radiator and the Condenser. Open that cover up and be absolutely sure the space is clean. Under the front end of your C4 there is supposed to be a rubber air dam that forces more air through the radiator. If it is broken or missing then you need to fix that.

I went to college in Fort Myers, Florida. I lived on a 36' Boat the whole time and I remember seeing Ice and frost on the windshield but very rarely. While in School I installed a Perkins 4-236 diesel engine in the boat and after school I brought it all the way to Virginia via the Inter-coastal Waterway. I went over 1500 miles at 12 knots and saw the best parts of the United States while making the trip. I love the SW area of Florida and miss it every time I go outside...

Merry Christmas to you and your Family

 

So my mastercylinder i replaced as well as brake booster after the occasion happened. I didnt loose fluid, nor am i leaking any fluid from anything while on the topic. At the time of the event, my mastercylinder was jammed in and i was able to pull it back with a screw driver i had in the car.

Im relatively mechanically inclined. Ive worked on many vehicles. Im only 22 but I've pretty much done all my own work. I have many more years to go to call myself anything more than novice. Its also why i work on my vehicles to learn more about them. I easily have $2000+ into this project.

Radiator fan (single) does come on at 220 like its supposed to. (And running while AC is on) i ended up taking off my shroud when i switched to a cold air intake. Only to find out to put it back on after i road around for a day. While It was off, i have to vacuum it out, it was half full of debris. I gotten hate and love from the air intake but it definitely helps keep it cooler. I just feel like an engine shouldnt even get that hot to begin with, thats why im asking about radiators. I know they're not supposed to be too cool and that Corvettes run hot.


(I have the cover that goes over distributor cap)


When i replace my calipers, rotors and pads, I'll check for any damages to lines while i have it jacked up. No codes have been thrown except once but that was after i replaced something. Once i restarted the car, it went away. I will definitely be buying that fuel gage. If im not mistaken, doesnt that only read the fuel pump? Not the fuel rail/injectors itself? Or does that go hand in hand? My ABS seems to be working correctly, although i guess i dont know the symptoms of a failing one.

My car makes a tsk noise, sorta like a sprinkler while in drive but not very noticeable or any noise while in park or neutral. Im thinking of just replacing fuel rail and injectors. I do have to adjust my TPS. Will be buying a multimeter to make sure its correct. Ive found random plugs that werent connected and an occasional hose that wasnt connected to anything. Once i found those, it ran a hell of a lot better.

I keep everything i take off. Except plugs and wires, my old master cylinder and brake booster went back to the shop for the discount.

My end goal once i get it all running and stopping correctly. Is a low boost, rear mounted turbo set up. And to get actual side pipes. Mine currently are fake and it drives me insane.

 

My car also hasnt been getting hot until now. After i did cleaned radiator and air intake, its stayed relatively around 196-207 but now it stays above 205 and upwards of 226 (which then i shut the car off)

theres still lag in the pedal once it gets to running temperature. Also idles in drive 6-7 and in park neutral its 11. At 6 and 7 rpms it doesnt want to stay on. So im really thinking that the fuel rail or injectors arent doing its job. Fuel rail is also stained yellow around these ports

 

I must add that its 5-7 rpms while AC is on. When i turn it off, it goes well.

 

Have you checked the basic setting on the throttle body and EFI system setup? The Throttle Position Sensor needs to be set precisely to get the idle to be smooth. Then clean and verify the Idle Air Control Valve is still working properly. There bis a lot more to setting the system up than most new owners are not aware of. I bought a set of harness' that allow me to see the parts in action in the EFI system. They were about $80 for the set but they make the set up a simple process.

These engine are designed to operate between 195 and 205* (F) so the temperatures you saw were normal. Clean under the radiator Cover between the Condenser and the Radiator. Be sure that you don't have more than 50% anti-freeze in the Corvettes Coolant. Too much anti-freeze is a bad thing as it doesn't transfer heat like water does. It sounds like your temperatures while running are okay.

Take pictures of the loose ends and we should be able to help you identify the parts. The FSM has a diagram showing each connector and identifying it. Having a set of the FSM's will make your life easier as it has troubleshooting charts and schematics of the various systems used in the C4.

I have never been much of a Side-pipes Guy but the system on your Corvette looks really great! I still have a scar from 40 years ago on a side pipe. They really look nice on your C4!

We are here to help you out so keep on with your questions and we will do our best to answer them quickly and correctly for you!

Be careful buying new Injectors unless you need them. The original ones were not able to handle Ethanol and by now they should have failed. When buying Fuel Injectors you buy them as a set of 8 and they can be had a reputable shops so please don't buy them on Ebay or Amazon. People on this Forum use FIC ( Fuel Injector Connection (??)) and I have used South Bay Injectors who are located in NYC. My last set was less than $200 for Bosch Brand Injectors which I trust.

One item that does wear out is the O2 sensor on the C4's. It was designed for a 24 month/50k life expectancy and then replaced. They are inexpensive and can have a huge effect on the Corvette if your is old and malfunctioning. You get better performance and Economy with a new Oxygen sensor.

I would have kept the Master Cylinder off your Corvette and had it rebuilt when convenient. Being a One year item they will get harder and harder to find. Finding a rebuilt 1988 Brake Master Cylinder might get tough in a few years... The booster is a common item but the master cylinder you should have kept.

The auto parts stores will sometimes lend things like the fuel pressure tester, get one and let us know what you find. Having the gauge on a long hose allows you to tape it to the windshield if you are having things happen while driving. Have you found anyone with a scanner that works on OBD1?

Good Luck and have a great day!

 

If you mean slipping and the engine revs and the car is not accelerating then you may have an internal transmission problem.

If the car is just sluggish and the trans is not slipping, possibly wants to creep forward idling in drive, possibly a torque converter problem.
My 89, when cold is very sluggish until the engine warms a little.