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poor running 84

chevyagain

Well-known member
Joined
May 13, 2007
Messages
77
Location
VIRGINIA
Corvette
1984
hi guys, pretty much new to this site. purcased a 84 crossfire, having problems. when first got car, could not seem to get any power gas pedal down went nowhere, backfire through one throttle body. changed gas, filter. still same thing. new plugs,wires,dist cap, rotor, ignition module and 02 sensor. seems to run a littla better but in neutral it seems to race then surges up and down
checked all vaccum hoses any help. also need to know what other wires
are included in wiring harness for coolant sensor have no books yet
thanks
 

3dale1

Well-known member
Joined
Mar 12, 2005
Messages
158
Location
PA
Corvette
65 convertible L-76
I think the timing on an 84 is the same as the other early C4's...6 deg. btdc.

Also has the car been off the road for a while? Might want to take a look at the sock at the bottom of your fuel pump if your pressure is low. I know the 84's don't run the pressure an L-98 does; it's much lower but don't know the number.

Maybe someone else can chime in about that.
 

chevyagain

Well-known member
Joined
May 13, 2007
Messages
77
Location
VIRGINIA
Corvette
1984
I think the timing on an 84 is the same as the other early C4's...6 deg. btdc.

Also has the car been off the road for a while? Might want to take a look at the sock at the bottom of your fuel pump if your pressure is low. I know the 84's don't run the pressure an L-98 does; it's much lower but don't know the number.

Maybe someone else can chime in about that.

thanks for the input, what do i have to do to get to this sock
i assume its a filter at end of pump
 

3dale1

Well-known member
Joined
Mar 12, 2005
Messages
158
Location
PA
Corvette
65 convertible L-76
Yes its at the end of the fuel pump. The pump will lift right up out of the top of the gas filler lid, no need to mess with the tank.

I offered this only a possibility...I would check and confirm FP before checking the sock. It would seem to me that there are more likely directions to go first. I am not that familiar with the crossfire setup.

Any codes thrown?
 

chevyagain

Well-known member
Joined
May 13, 2007
Messages
77
Location
VIRGINIA
Corvette
1984
Yes its at the end of the fuel pump. The pump will lift right up out of the top of the gas filler lid, no need to mess with the tank.

I offered this only a possibility...I would check and confirm FP before checking the sock. It would seem to me that there are more likely directions to go first. I am not that familiar with the crossfire setup.

Any codes thrown?

no codes at all ill keep posted
 

jim coulter

Well-known member
Joined
Dec 3, 2002
Messages
157
Location
covington,tn
Corvette
71 big block, 84 coupe
Not to bad, its in the gas tank. Theres 4 screws holding the outer door housing (I believe) and quite a few holding the top plate to the tank. When you pull the top plate on the tank, everything comes out with it. Just be sure to disconnect battery and get new sock with pump. I believe the link I listed before has some step by step instructions, just do a search on the site for fuel pump. All the cars on that site are crossfires, mostly 82 and 84.
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,547
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
Before you go to nuts,PM wishuwerehere82 and quiz him!!! Pete is purdy sharp on crossfires!!!:upthumbs
 
Joined
Aug 30, 2002
Messages
1,533
Location
Colorado Springs, CO USA
Corvette
84 Z51 auto R.I.P. 89 black roadster SOLD
"surging" in park/neutral is almost always due to a lean condition...which in turn is most always due to a vacuum leak. The most common candidate...the intake plenum lid.

There are other possibilities (bad IAC...etc), but I'd start there.

If the TBs have ever been removed...then they're most likely out of balance. Not terribly difficult to do...just have to know what you're doing (a homemade water manometer works very well). Also check for play in the throttle shafts...not really a cause of surging/backfiring unless they're REALLY bad, but can cause driveability issues.

Are you replacing the CTS? If so and it still has the original...the replacement will have two wires, and you only have one wire on the original. Connect the existing wire to one of the new CTS wires, and ground the other (there's a stud in the intake plenum lid for an AC bracket that makes a good ground point for the CTS).

For wiring diagrams: http://misterbill.homeip.net/Vette/wiring/

Bill
 

chevyagain

Well-known member
Joined
May 13, 2007
Messages
77
Location
VIRGINIA
Corvette
1984
"surging" in park/neutral is almost always due to a lean condition...which in turn is most always due to a vacuum leak. The most common candidate...the intake plenum lid.

There are other possibilities (bad IAC...etc), but I'd start there.

If the TBs have ever been removed...then they're most likely out of balance. Not terribly difficult to do...just have to know what you're doing (a homemade water manometer works very well). Also check for play in the throttle shafts...not really a cause of surging/backfiring unless they're REALLY bad, but can cause driveability issues.

Are you replacing the CTS? If so and it still has the original...the replacement will have two wires, and you only have one wire on the original. Connect the existing wire to one of the new CTS wires, and ground the other (there's a stud in the intake plenum lid for an AC bracket that makes a good ground point for the CTS).

For wiring diagrams: http://misterbill.homeip.net/Vette/wiring/

Bill
thanks for the input, actually that was my next move
to change the plenum gasket, although i just replaced the knock sensor
the old one was destroyed and not hooked up. so thats new, oxy sensor new
cap, rotor, wires, etc. etc. car is still up on blocks in garage. gotta check timing also. after all this is done will see what happens!!!! then do gasket
thanks again--------john
 

chevyagain

Well-known member
Joined
May 13, 2007
Messages
77
Location
VIRGINIA
Corvette
1984
thanks for the input, actually that was my next move
to change the plenum gasket, although i just replaced the knock sensor
the old one was destroyed and not hooked up. so thats new, oxy sensor new
cap, rotor, wires, etc. etc. car is still up on blocks in garage. gotta check timing also. after all this is done will see what happens!!!! then do gasket
thanks again--------john

oh i forgot, i am looking for a small trim piece on pass side of my 84
in front of reat wheel well about 3 3/4" long black this is the molding that
goes arond the whole car for tht year
 
Joined
Aug 30, 2002
Messages
1,533
Location
Colorado Springs, CO USA
Corvette
84 Z51 auto R.I.P. 89 black roadster SOLD
thanks for the input, actually that was my next move
to change the plenum gasket, although i just replaced the knock sensor
the old one was destroyed and not hooked up. so thats new, oxy sensor new
cap, rotor, wires, etc. etc. car is still up on blocks in garage. gotta check timing also. after all this is done will see what happens!!!! then do gasket
thanks again--------john

When you check/set timing don't forget to disconnect the EST bypass (single brown wire near the brake booster).

Also check out the EGR valve and IAC valves...both potential sources for massive vacuum leaks.

Bill
 

chevyagain

Well-known member
Joined
May 13, 2007
Messages
77
Location
VIRGINIA
Corvette
1984
When you check/set timing don't forget to disconnect the EST bypass (single brown wire near the brake booster).

Also check out the EGR valve and IAC valves...both potential sources for massive vacuum leaks.

Bill

thanks bill will keep you posted
 

chevyagain

Well-known member
Joined
May 13, 2007
Messages
77
Location
VIRGINIA
Corvette
1984
When you check/set timing don't forget to disconnect the EST bypass (single brown wire near the brake booster).

Also check out the EGR valve and IAC valves...both potential sources for massive vacuum leaks.

Bill

when i disconnect the est bypass, engine will not stay running long enough
to time it, any input
 
Joined
Aug 30, 2002
Messages
1,533
Location
Colorado Springs, CO USA
Corvette
84 Z51 auto R.I.P. 89 black roadster SOLD
Sounds like possibly someone before you set the timing with the EST bypass connected. Hook it back up and see if the advance is sitting somewhere around 6 degrees BTDC (or anywhere on the tab for that matter). If so, then the timing is just WAY retarded...advance it until the mark is off the timing tab (in the "A" direction), that should be enough to allow you to disconnect the EST bypass and set it properly.

Bill
 

chevyagain

Well-known member
Joined
May 13, 2007
Messages
77
Location
VIRGINIA
Corvette
1984
thanks bill, will try this evening, should the mark be totally off the tab
in the A direction or ok to be on a little
 
Joined
Aug 30, 2002
Messages
1,533
Location
Colorado Springs, CO USA
Corvette
84 Z51 auto R.I.P. 89 black roadster SOLD
thanks bill, will try this evening, should the mark be totally off the tab
in the A direction or ok to be on a little

It should be totally off the tab in the A direction (CCW as viewed from the front of the car). I don't recall how much advance the stock '84 chip gives at idle...it might even be so much that you can't see it.

Bill
 

chevyagain

Well-known member
Joined
May 13, 2007
Messages
77
Location
VIRGINIA
Corvette
1984
bill,
specs call for a 45 spark plug gap, yet some say 35 whats the story
on that one---------------------john
 

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