cdig

ok, solved my overheating problem (thanks cuisinartvette!). Can anyone tell me what kind of power I should be seeing in a stock 89 L98 car though? I can't get it to chirp the tires unless I hammer it going around a corner, let alone a brake stand. It just squats and bogs down.

Seems to have lots of pickup when on the hwy, but I'm looking for some grin factor at the stop sign... is this all I can expect of a stock vette or is there something wrong with mine?

BADDUCK

Stock auto was 240 CHP IIRC. Your problem may be gears. My 1989 6 speed will beat or stay with stock LT1's.

The Green Rocket

Of all the C4 generation, the TPI is most known for its get off the line grunt. Something IS wrong if it feels gutless in the stoplight grand prix.

Maybe all your car's details exist in other posts - but could you fill us in on the details beyond being an automatic (reference to brake stand): how many miles? which differential ratio? dragstrip performane if applicable? compression test results psi each cylinder? leakdown results?

What I am getting at is whether your engine is just tired, or if it is a solid foundation with fuel injection of ignition issues? The TPI is normally very durable and long lived. I think that forum member Beach Bum ran in the 11's/12's with a stock 150,000 mile bottom end, pistons and rings.

If you want to bypass all of the methodical approach; if I were to guess on just one thing it would be that the fuel injectors need to be updated. But "gutless" is a relative term - I could just as easily go along with Badduck's suggestion that geariung could be the issue. I think your two ratio choices are 2.59:1 or 3.07:1.

Thomas

RonsRed88

My stock 88 with automatic and 2.59 gear and 186k miles will gladly roast the tires from a stop. Something is wrong. We need a lot more details before starting the guess-athon.

cdig

ok, good to know! I was worried there for a bit!

she's an 89 convertible, stock engine as far as I know, 124000 miles, AT. Accel air filter (K&N style), newer accel plug wires, new accel high energy coil and cap/rotor, new bosch platinum +4 plugs. New fuel filter. Don't know about the injectors, how do I test them?

Haven't done a compression test on it yet, not sure on the diff ratio. I'll be checking that soon. No dragstrip experience.

It seems to idle a bit rough, and once it's warmed up and I've layed into the gas pedal a few times on the highway it seems boggy, especially when it shifts from 3 to 4.

Thanks for spending time on this guys... I tried to get someone from the local vette club to go for a ride with me to compare with their performance... no takers, they're all a bunch of polishers I guess.

kenmohr

check your timing. Should be 6* btdc.

kenmohr

make sure you disconnect the acs connector first.

856SPEED

my 85 was a dog when I first purchased it back in 2001 in stock form....ran the quarter in 14.99 to low 15's at 90mph.....originally an auto equipped car....everyone else on here claims their stock L98's run much better than that, so I guess mine was sick before I stripped the car apart.........

BTW: mine had only 59,xxx original miles back in 2001 when I purchased it too...

The Green Rocket

Generally the stock L98's that i have driven could easily spin their tires regardless of differential gear ratio - only dragstrip times revealed the difference in acceleration.

Without knowing the history of the car you will need to methodically go through all the engine mechanical, tuning, ignition and fuel systems until you find the culprit.

The fuel injectors need to be sent out to be professionally tested - then they either get flow matched if good, or replaced if not.

There are many possible causes of your complaint, you have covered the most basic. Now you need to dig deeper: have the injectors sent out and tested by the forum recommended vendor, really go over your ignition system to verify that your ignition advance curve is correct and functioning - this too may require professional help. An ignition system that is not advancing to the full amount will also display your symptoms of an engine that is lazy off the line.

Get a factory service manual and start using their excellent diagnostic charts to help you restore performance.

Thomas

MMOCguy

My '93 with automatic trans was sluggish coming off the line from the time I bought it. Once rolling with the revs up a bit, it had lots of grunt. Your description sounds exactly like my car before my mechanic found that the catalytic converters were melted internally. Mine had 135K miles when I bought it and I had nothing to compare its performance to so I thought it was normal. I had it about a year and my mechanic found it when doing something else. If you have not checked them recently, I'd check them before spending a lot of money chasing other causes.

Hope this helps.

Norm.

sfc rick

I have an 88 L98 Automatic and it's a real go getter from a standing start. That car really jumps and launches like a rocket! Your car may have bad cats that are plugged up and restricting the engine, and you stated that you replaced the air cleaner which is an often overlooked performance killer when it's plugged up as well.

Be sure and let us know what you find.



Oh and let me say once I had a customer complain about bad performance and I eventually found a rag that blocked the air ducting. Just an FYI!

cdig

great input guys.. much appreciated. This will definately give me some places to start. I'm going to check the timing tonight and if that doesn't solve it, move on to checking the cats.

Question: how do you tell if your cats are melted internally?

One more thing I should mention, I notice when sitting in the driveway with the hood up, if I hit the gas pedal I notice a sucking sound before the engine actually begins to rev up. Could this mean a vacuum leak or something?

WW7

Another thing to check is the TPS, if this isn't set right it can cause the engine to be sluggish ..I was told by my tuner that with my new engine I should set the TPS at 0.58 to 0.60 instead of the usual 0.54 . If you can, check yours to make sure its at least set to 0.54.. Im going to listen to my tuner and see if it works better at 0.60...WW

Pete K

Start with a good tune up.
Good tune ups start with a compression test fuel pressure and a vacuum gauge.
Start at the beginning. The poke and hope approach always costs more than a shop manual, and basic diagnostics.

Kool88vette

The 21 year old stock exhaust will slow ya down. My 88 would bog down until I got rid of the precats and the stock mufflers. I now have 2 1/2" pipes a high flow cat and cat backs. If you don't need to pass a smog I suggest true duals.

Pwnage1337

You don't need to do any mods to be able to roast the tires on L98's. All L98's should be able to cook them, even if they are bone stock. Something is definitely wrong with the car. I agree with the others on tune-up.

cdig

Stupid question: where am I going to find the acs connector? and what does ACS stand for? The service manual says to disconnect the ECM harness connector. This is the four pole flat one behind the distributor right? I disconnected that one, put the cap all back together, but it won't start. What am I missing here?

JrRifleCoach

Clogged cat? Have a good muffler shop pressure check your exhaust.

cdig

On the short list of future mods, hopefully sooner than later..

MMOCguy

cdig.

To answer your quesiton about how to check the cats, as was suggested, the best way to check the cats is to have a muffler shop do it for you. My mechanic found the problem with mine because he had to remove them to do some other work.

Hope this helps.

Norm.