poor running 84

[chevyagain]

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]

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]

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]

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]

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]

Replace the fuel pump with a later one. It'll wake it up. good articles on it here- www.crossfire.homeip.net

 

[chevyagain]

Replace the fuel pump with a later one. It'll wake it up. good articles on it here- www.crossfire.homeip.net

how hard is it to get to the fuel pump

 

[jim coulter]

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.

 

[scooter18155]

the throttle bodies on the crossfire engine could need to be ballanced. might wanna try going here for more info on that lots of usefull info and knowlegable peeps on the crossfire. http://www.crossfire.homeip.net/cftest/default.asp

 

[gmjunkie]

Before you go to nuts,PM wishuwerehere82 and quiz him!!! Pete is purdy sharp on crossfires!!!

 

[geekinavette]

"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]

"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]

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

 

[geekinavette]

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]

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]

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

 

[geekinavette]

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]

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

 

[geekinavette]

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]

bill,
specs call for a 45 spark plug gap, yet some say 35 whats the story
on that one---------------------john