1991 L98 Question: Bump-Steer/Pinging

[Rogue]

This is really Two questions in one post.

1) I noticed for quite some time now that my Corvette has a slight case of bump-steer. It usually happens at low speed (parking lot) when I go over a speed bump at the rear axle, the steering wheel jerks a bit.

The other day, I noticed it going around a very bumpy corner at about 35 mph.

Is this normal for a 1991 C4?

Mine has the FX3 shocks and 51k miles. No modifications to the suspension nor chassis.

2) Pinging. After doing a search on the subject, I failed to get a definitive answer. I ALWAYS use the highest octane available in my area: 91 Octane. I buy mine from the Unocal 76 & Chevron stations usually.

Ever since I got my '91 in 2003, I noticed the engine pings lightly at acceleration, especially on a hot day. It doesn't sound like loud marbles under the hood. I can only characterise best as light pinging. I'll bet most people won't even hear it but I can because I listen to such things.

It does not ping under hard acceleration or WOT.

Again, is this normal for a 1991 L98?

Thanks for all you help.

 

[c4c5specialist]

HI there,
We, bump steer could be the spring being broken or soft. The shocks might be worn or inoperative.
As for the knocking, your EGR valve may not be working correctly, or your knock sensor might not be working correctly or you might just have a bit of carbon buildup inside your cylinders.
Allthebest, c4c5

 

[Hot Rod Roy]

"Bump Steer"

What you've described isn't bump-steer. If the geometry of a front suspension system isn't correct, you may experience the car changing directions either to the left or to the right when the suspension moves up and down, such as when you hit a bump. So in effect, the car steers itself when you hit a bump. You can hold the steering wheel rock solid, and the car will still steer itself when you hit a bump, if you have bump-steer.

Independent Rear Suspensions can have bump-steer, too, if the design is wrong.

 

[speedmaster4]

bump steer is designed into suspension geometry, purposely, to reduce steering input in during hard cornering , to allow the operator to maintain control of the vehicle...relative positioning of suspension ''instant center'' and tie rod pivot points is intended, in most cases, to cause the tire to turn outward in jounce,which occurs with body roll...in a vehicle with limited suspension travel (necessary if low ride height is desired) a high rate of bump steer is required and may result in operator complaint of excessive steering feedback when negotiating irregular surfaces.

 

[grumpyvette]

as too your pinging.... (detonation, )
Id try each of four options,
ONE
backing off or retarding the ignition advance, timing,about 5-8 degrees and I think youll find the pinging goes away, but youll also more than likely have a reduced performance, but thats not a problem as its just a test, if the pinging did go away then youll need to slowly advance the timing about 1-2 degrees at a time untill the pinging returns, at that point back off or retard the igntion timeing about 2 degrees, and take notes as to your max timing
TWO
swap to a cooler spark plug,see if that helps

three
put in an octane booster and see if that helps
http://www.gnttype.org/techarea/misc/octanebooster.html

http://zhome.com/ZCMnL/PICS/detonation/detonation.html

http://www.elektro.com/~audi/audi/toluene.html

four
detonation is much more comon with a hot engine, try adding an oil cooler and keep the oil temp at between 215F-230f
clear out the radiator if theres trash blocking air flow,and add an extra pusher electric fan with a switch
youll want the coolant to stay under about 200F if you can


and before you ask...a gallon or two of toluene which is available from larger paint supply stores and a bit of marvel mystery oil (like 8oz ) in the tank of 91 octane gas,won,t hurt a darn thing, Ive used it for years as an octane booster with nitrous, just be careful and use a funnel, and don,t get it on you or the cars paint, because just like gas its not good for you or the paint