At work yesterday a gentleman came in to have a stereo installed in his 85 Vette. I talked with him for a few minutes and told him about the forum, perhaps he'll come by soon. In any case he said that the car was too loud and he wanted to quiet it down.

I looked at the exhaust and it looked like it could be the stock exhaust, it certainly wasn't flowmasters but I couldn't tell for sure what it might be. I saw a clamp on the exhaust that really didn't look like it would be stock. After a while I just fired it up to see how loud it was. I was suprised in that it didn't sound stock, it was actually pretty loud. I blipped the throttle a few times and immediately figure out that he has an exhaust leak because it cackled loudly when I did so.
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Now on to my question. When I went to blip the throttle it suprised me, this L98 torque monster didn't respond well at all, in fact it stumbled badly. It seemed to rev alright when you get over the initial tip in but I don't think I could handle it like it was. The exhaust also had a particularly bad smell to it. I know the rotten egg smell you get when you're running lean with cats, this was NOT that smell. I can't really describe it other than just plain bad. My car smells way better and it doesn't even have any emissions equipment!

I'm sure the stumbling and the bad smell is related, what could cause such a problem? My first thought was a thorough tune up. New plugs, wires, cap, rotor & O2 sensor for starters. Then where do you go? New filters everywhere wouldn't hurt. The car didn't seem to set any codes, what is there to check? Double check the timing and test the calibration on the TPS possibly?

Assuming all of that wouldn't fix the problem what could it be?

Thanks guys :cheers:

 

Scan it first. What's the TB look like? The tip in on an L98 should be very crisp.

 

Well I was just looking around, what can you use to talk to an 85? Datamaster seems to only go down to 86. :smash:

 

Could have got some bad gas. Look into the the plenum through the throttle body, may just need a good old fashioned cleaning. Mine used to have that "hesitation" but after I cleaned the TB, plenum and injectors it was back to normal. You can view the computer with a Snap-On Scanner if you have access to one.

 

Sounds like he has an exhaust leak and a rich/lean condition.

 

To check error codes, jump terminals A+B and it will flash 1,2,,1,2,,1,2 then any stored error codes followed by 1,2,,1,2,,1,2.

To see sensor data use Winaldl, it by JoBy here on the forum:

http://winaldl.webhop.net/

You will need a 10k ohm resistor between A+B to get all the data. The 85 uses the 870 ecm.



[Modified by Bluevette85, 11:14 AM 2/7/2003]

 

Ugh.... scan tools + 1985 do not go along very well. The ECM on '85 was very slow and you didn't get many datapoints over a series of time.

 

Could be any number of things:

TPS
IAC sensor
TB needs cleaning
TB bushings (common over time)
Tune up
Exhaust leak before the O2
Vacuum leak

Just to name a few. If you want to check the codes you should be able to jumper the A B terminals and read the check engine soon light.

 

It sounds to me like it has no catyliotic converter. The reduction in backpressure might cause some ehaust backfire when revving in park. I would need to know how it drove to guess at a problem. Its likely a lack of maintenance type problem.