shane haggerty

I have an '88 convertible that was running fine yesterday, I added antifreeze to the radiator today and did nothing else to it.... I started it up and didn't notice anything until I gave it some gas. The car revved (but it sounded much deeper than usual) and it accelerated slowly but not anywhere near like it should. Any ideas? Some threads I searched suggested O2 sensor. Am i on the right track with that?

C4firstvette

I have heard that if you have 2 cat converters then the first one disintegrates and the material blocks the second one causing this issue but have not heard of anybody having that issue.

jv9999

It could be any number of things. No way to tell from here.

playsdixie

not enough info to tell....why anti freeze???...did you overheat?.....i'd check my timing and TPS......after fuel pressure.....

ctmccloskey

If your main catalytic converter got plugged up it might have blown off the cold air injection hose which our 1988's (I have a 1988 C4 coupe) have on their main converter and that would cause your engine to sound deeper as the noise is escaping prior to your exhaust system. That alone would probably indicate that you have "too much" back pressure in your catalytic converter. You should be able to see if the air injection hose is still on your Catalytic converter by looking under the passengers side at the front end of the converter. If the hose is disconnected then you probably have a bad main catalytic converter. I replaced the main converter with one from Summit Racing and between it and the Chambered Exhaust system I picked up close to 14 hp. If you do have to replace the main converter be sure to use a "HI Flow" unit from a reputable manufacturer and it will make a difference. I have not changed out the front Y pipe that has the little "Pre-Cat's" on it. I drive my car on the roads still so I have an operating emissions system, I would not eliminate the main catalytic converter on my cars. Many people are doing that even though it is against Federal laws IF the vehicle is used on public highways.

I would start by removing the 02 sensor and verifying that the converters are okay. You should not have a lot of back pressure from the sensor hole. If the Catalytic converters get plugged up they tend to cause a lot of back pressure. Using a hand held non-contact thermometer try checking the temperatures of the two "Pre-Cats" and especially the main catalytic to see if they are all the same temperature range. The little pre-cats should be close in temperature. The main catalytic converter is another story. Check the front of the main cat and then measure the back end to see if they are close. A plugged converter will be hotter on the leading end as it is not allowing the exhaust to flow thru the converter.

Verify that your 02 sensor is putting out the proper voltages if you suspect the 02 sensor. If the 02 sensors are over 50 k miles old then you might want to replace them. I don't think it is an 02 issue myself.
Have you ever done anything with your EGR system? Verify that it is working and check the vacuum lines under your hood just to be safe.

Last but not least,
Welcome to the Corvette Forum! This is the place to be if you have issues with a Corvette C4!

Best Regards,
Chris

P.S. The profile is very important to fill out completely as we need as much information as possible about your Corvette to be able to help you. The more we know the better we can help you figure this issue out on your Corvette! Modifications are the most important to know about when diagnosing a Corvette's problems.
Good Luck with your 1988!

65Z01

Since it "sounds louder" I'd first check the exhaust system. As mentioned, possibly one of the two damn "pre-cats" has disintegrated into your main cat.
If that's the issue I suggest you get a front Y w/o any cats and upgrade your clogged main cat with a hi-flow unit, such as Random-Tech, of you can buy the front Y & cat as a unit.

If all looks ok under there, do the usual checks:
-fuel pressure, at idle and at say 2-3k RPM
-manifold vacuum
-spark plugs & wires

Good luck with it, let us know how it goes.