1989 C4 top speed lacking
Thread Starter
Heel & Toe
Joined: Jul 2003
Posts: 17
Likes: 0
From: victorville CALIFORNIA
1989 C4 top speed lacking
i have a 1989 C4, when romping on the throttle it winds out for quite a while before switching gears, also i think it does not go as fast as it should at top speed. any and all suggestions are welcome, thanks, chris :banghead:
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Re: 1989 C4 top speed lacking (JCAIRE2)
L98s are not high RPM monsters without some help. As was said they'll top out around 155mph, but it takes a loooong time to get there. I'm talking a couple of straight highway miles easy. Typically in stock form depending on your transmission you'll want to shift it in the 4200-4400 RPM range.
Pro
Joined: Aug 2002
Posts: 715
Likes: 0
From: Warner Robins GA
Re: 1989 C4 top speed lacking (gambleonus)
The first things I'd check are the precats and the main cat. I had a similar problem (top speed of about 115, hung at like 4000 rpm before shifting at WOT), and it turned out my precats had emptied themselves into my main cat, which was now clogged up.
Basically try clearing the exhaust up and see if it helps.
Basically try clearing the exhaust up and see if it helps.
Thread Starter
Heel & Toe
Joined: Jul 2003
Posts: 17
Likes: 0
From: victorville CALIFORNIA
Re: 1989 C4 top speed lacking (JCAIRE2)
shift points are high, it reaches peak rpm and hangs there, if i let the throttle off a little then it will shift. also, it took me a little while to get up to 120 and cant get much above that. thanks for your reply i really appreciate it! :)
Thread Starter
Heel & Toe
Joined: Jul 2003
Posts: 17
Likes: 0
From: victorville CALIFORNIA
Re: 1989 C4 top speed lacking (scorp508)
your right, it does take a long time to get there, but will only top at around 120, and when at high rpm it hangs there before shifting, sometimes i have to ease off the throttle before it shifts. thanks for your reply i really appreciate the help! :)
Thread Starter
Heel & Toe
Joined: Jul 2003
Posts: 17
Likes: 0
From: victorville CALIFORNIA
Re: 1989 C4 top speed lacking (Tourney3p0)
of course the first things i did was basic stuff, cap, rotor, wires, coil, plugs, k&n, checked fuel pressure and that was good. the next step will be replacing the cats, should i just remove them or go ahead and get new ones? thanks for your reply i really appreciate it! :)
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Thread Starter
Heel & Toe
Joined: Jul 2003
Posts: 17
Likes: 0
From: victorville CALIFORNIA
Re: 1989 C4 top speed lacking (65Z01)
it definatley gets up there and just hangs, it will eventually shift, it will shift sooner if i let go of the throttle a little bit, but it does it winds out in all gears. thanks for your reply i really appreciate it! :)
Burning Brakes
Joined: Jan 2001
Posts: 1,169
Likes: 0
From: Manhattan
Re: 1989 C4 top speed lacking (gambleonus)
an exhaust shop can do a backpressure test to see if your cats are clogged.
check your timing, it should be 6* BTDC.
I don't have an auto, but maybe check that the TV cable is adjusted properly, that will affect how the trans shifts.
check your timing, it should be 6* BTDC.
I don't have an auto, but maybe check that the TV cable is adjusted properly, that will affect how the trans shifts.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Hmmm.... now that I think of it I've heard of some CA C4s having speed limiters from the factory. I have no way to prove the truth to this besides word of mouth. Is yours an original CA emissions car?
Thread Starter
Heel & Toe
Joined: Jul 2003
Posts: 17
Likes: 0
From: victorville CALIFORNIA
Re: (scorp508)
yes it is a california emissions equipped vehicle, i will have the cats replaced and i think this may solve the problem. as far as a speed limiter goes the place where i work recently purchased a whole slew of new vehicles, i had the chance to drive my bosses vehicle, cruising down the freeway at around 96 it all the sudden cut out, it wouldnt let me get past 96, so i think a speed limiter is not the cause. thanks for your reply i really appreciate it! :)
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Re: (gambleonus)
another corvette fan replied that he was able to hit 154! :steering: so maybe there will be something in changing out the chip, thanks, chris :)
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
Re: 1989 C4 top speed lacking (gambleonus)
What you are saying is that it winds out 3rd gear at around 120, and doesn't upshift to OD unless you let off the gas a bit?
That usually means a worn transmission. Mine does that too now. I have to let off the gas around 115mph to switch to OD and once in gear, floor it again and I'm accelerating again..
That usually means a worn transmission. Mine does that too now. I have to let off the gas around 115mph to switch to OD and once in gear, floor it again and I'm accelerating again..
Melting Slicks
Joined: Jul 2002
Posts: 2,072
Likes: 3
From: Walled Lake MI
Re: 1989 C4 top speed lacking (MrNuke)
What you are saying is that it winds out 3rd gear at around 120, and doesn't upshift to OD unless you let off the gas a bit?
That usually means a worn transmission. Mine does that too now. I have to let off the gas around 115mph to switch to OD and once in gear, floor it again and I'm accelerating again..
That usually means a worn transmission. Mine does that too now. I have to let off the gas around 115mph to switch to OD and once in gear, floor it again and I'm accelerating again..