85 vette chatter when under hard acceleration
Thread Starter
Cruising
Joined: May 2011
Posts: 11
Likes: 0
85 vette chatter when under hard acceleration
hello to all,
this is my frist day, first post, frist VETTE!
i am very happy about this car. i have had it for a week now and something has happend. 4 days ago i replaced the entire tune up parts right down to the fuel pump. it ran great but i wanted more sound so i installed flowmasters wow what a diffrence. today i charged the ac and it blows ice! but there is something going on now, in gear and moderate accleration i am hearing a chatter from under the hood, if i back off it goes away, if i give it gas i hear it again. this hasent happend in the week prior so i pulled over to see what happend and i noticed the check engine light was on. i shut the car down and proceded to check the engine! i saw nothing out of the ordnary. got back in it fired right up. pressed the throttle to the floor and it sounded perfect. put it in gear, got back on the highway mashed the gas and there it was again......anyone else had this kinda thing..? im sure it will be an easy fix once i know what it is.
this is my frist day, first post, frist VETTE!
i am very happy about this car. i have had it for a week now and something has happend. 4 days ago i replaced the entire tune up parts right down to the fuel pump. it ran great but i wanted more sound so i installed flowmasters wow what a diffrence. today i charged the ac and it blows ice! but there is something going on now, in gear and moderate accleration i am hearing a chatter from under the hood, if i back off it goes away, if i give it gas i hear it again. this hasent happend in the week prior so i pulled over to see what happend and i noticed the check engine light was on. i shut the car down and proceded to check the engine! i saw nothing out of the ordnary. got back in it fired right up. pressed the throttle to the floor and it sounded perfect. put it in gear, got back on the highway mashed the gas and there it was again......anyone else had this kinda thing..? im sure it will be an easy fix once i know what it is.
Le Mans Master
Joined: Mar 2002
Posts: 5,889
Likes: 2
From: Castro Valley Calif.
St. Jude Donor '03 thru '26
Welcome to all your firsts, it's fun stuff! I'm wondering about the base timing if you hadn't heard anything before this? If it's spark knock, be careful to get it corrected 
Safety Car
Joined: Jan 2008
Posts: 3,939
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From: Vero Beach Florida
Thread Starter
Cruising
Joined: May 2011
Posts: 11
Likes: 0
ok, the manuel says i need to unplug the etc to get a proper reading...i am assuming this is the plug on the behind the tach/batt terminal..because as of now the reading is off the charts i would say about 1inch to 1 1/2inch away from the plate. if i am wrong about the etc please inform me because my manuel has a few pages that are missing.
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Race Director
Joined: Jun 1999
Posts: 14,924
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From: Merritt Ils Fl
Just to the right of the windshield wiper you should find a tan wire with a black connector. That is the EST wire that must be disconnected. In simple terms it eliminates the computer from controlling timing. With it unplugged timing is set in the traditional manner to 6 degrees BTDC. That is base timing and is what your computer expects it to be. I strongly suggest you pull fault codes before you take on timing. Something caused the SES light to come on, you need to find the reason.Why before, when you unplug the tan EST wire a code will be set, it is cleared by disconnecting the negative battery terminal. Obviously that will clear any and all stored fault codes.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
As noted above, you need to check for fault codes stored in the computer. Refer to this post.....
http://forums.corvetteforum.com/c4-t...tus-codes.html
The codes that apply to the 85 are listed in this post.
To check for codes, you will find a terminal (plug) next to your right knee as you sit in the drivers seat. There should be a black plastic cover that slides over this terminal. Take a paper clip and straighten it out to form a "U". Insert this clip into the top far right terminals (1st and 2nd from the right). Now turn on the key but do not start the car. The check engine light will flash once then twice. It will do this three (3) times. This is a code 12 which indicates the diagnostic mode is working. Any additional codes will flash three times. When you get the code 12 flashing again three times you have observed all the stored codes. It is a good idea to take paper and pen with you as you observe the codes so you can write them down. If you didn't catch the codes the first time, just turn the key off and then back on. The codes will remain in the computer until you reset the computer. To reset the computer, disconnect the NEGATIVE battery terminal for about 30 seconds and then reconnect. All the stored codes will be cleared.
Good Luck,
http://forums.corvetteforum.com/c4-t...tus-codes.html
The codes that apply to the 85 are listed in this post.
To check for codes, you will find a terminal (plug) next to your right knee as you sit in the drivers seat. There should be a black plastic cover that slides over this terminal. Take a paper clip and straighten it out to form a "U". Insert this clip into the top far right terminals (1st and 2nd from the right). Now turn on the key but do not start the car. The check engine light will flash once then twice. It will do this three (3) times. This is a code 12 which indicates the diagnostic mode is working. Any additional codes will flash three times. When you get the code 12 flashing again three times you have observed all the stored codes. It is a good idea to take paper and pen with you as you observe the codes so you can write them down. If you didn't catch the codes the first time, just turn the key off and then back on. The codes will remain in the computer until you reset the computer. To reset the computer, disconnect the NEGATIVE battery terminal for about 30 seconds and then reconnect. All the stored codes will be cleared.
Good Luck,
Thread Starter
Cruising
Joined: May 2011
Posts: 11
Likes: 0
well, after alot of sweat, cussing, turning the dist, and getting my 6' 200lbs butt in and out of the vette the only thing i have forun is that it still has the clatter! so i set it to 6, turned on the a/c put it in gear held the brake mashed it to 2000 rpms and got the clatter. i set it at 12 turned on the a/c mashed it to 2000 and still the clatter! i have set it every where inbetween same procsess same clatter. any ideas? maybe gas it crappy? i run the cheap stuff..
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
Did you figure out the code it threw the first time it happened? is it a "chatter", like vibration that you can feel, or more like "clatter", more noise like?
Last edited by powerpigz-51; Jun 3, 2011 at 08:02 PM.
Advanced
Joined: Jan 2011
Posts: 77
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From: Winona Mo.
If your valves are pinging and you're setting the time faster (going from 6 to 12 degrees) you're going the wrong way. The detonation you hear is from the timng being too far advanced for the compression and yes, the cheap gas. try adding some octane boost to see if it gets better.
Thread Starter
Cruising
Joined: May 2011
Posts: 11
Likes: 0
Got to looking and it is not there!!! WTH! Hmmm... I will put it on jacks tomorrow and take a closer look. Thank you guys so much. It's so much more easier to trouble shoot if you listen to the guys who know the car. Thank you guys again
Le Mans Master
Joined: Dec 2006
Posts: 5,154
Likes: 2
From: Ft Myers Florida
Thread Starter
Cruising
Joined: May 2011
Posts: 11
Likes: 0
Couldn't stand I and had to look. Knock was hooked up wire is in bad shape but inact. I will play hard tonight with hot gas And wait for the light. Worse come to worse I will back out it it when I hear the rocks in a can. Lol. It is set at +10 and I hear it just barely after 2200rpm. You will have to remember that it ran fine the first week. When hooked up the a/c this happend. I know it's freak but,......? I guess if hot gas helps I will back off on the advance a tad.