Throttle Issue
04-07-11, 02:25 AM
#1
Throttle Issue
I've mentioned this a couple of times before, but got nowhere.
1985 gs...emissions removed (only necessary vacuum lines are hooked up), all holes plugged.
New coils (diamond), cap, rotor, wires (mazdatrix 10mm), plugs, battery, battery cables.
O yeah....NEW FUEL FILTER!
Lots more but all irrelevant.
Anyway, when in neutral just idling, if I push the accelerator down quickly to 3/4 pedal or more (roughly) the car will want to stall. If I take my time...maybe half pedal or so it will climb up in rpms only to about 4500 or so....then begin to stumble and misfire like it is not getting enough fuel. The only thing I haven't replaced on the car is the fuel pump from 1985.
Could the fuel pump be too weak for when the car is under a certain amount of load?
(this problem also occurs while driving around, not only when in neutral. cant go above 70mph on mostly flat land....if I'm going up a hill I definitely don't have the 'pedal' due to this issue to maintain my speed)
I thought that maybe my secondaries weren't operating properly so I tied them to the primaries....but I still had the same issue.
1985 gs...emissions removed (only necessary vacuum lines are hooked up), all holes plugged.
New coils (diamond), cap, rotor, wires (mazdatrix 10mm), plugs, battery, battery cables.
O yeah....NEW FUEL FILTER!
Lots more but all irrelevant.
Anyway, when in neutral just idling, if I push the accelerator down quickly to 3/4 pedal or more (roughly) the car will want to stall. If I take my time...maybe half pedal or so it will climb up in rpms only to about 4500 or so....then begin to stumble and misfire like it is not getting enough fuel. The only thing I haven't replaced on the car is the fuel pump from 1985.
Could the fuel pump be too weak for when the car is under a certain amount of load?
(this problem also occurs while driving around, not only when in neutral. cant go above 70mph on mostly flat land....if I'm going up a hill I definitely don't have the 'pedal' due to this issue to maintain my speed)
I thought that maybe my secondaries weren't operating properly so I tied them to the primaries....but I still had the same issue.
04-07-11, 09:20 AM
#4
Waffles - hmmm good
iTrader: (1)
Do a simple flow and pressure test of the fuel as it come out right at the carb.
See how fast it fills a half gallon in a one gallon container and divide that into
an hour to get a gph hour number. It should do a half gallon in about 1 minute or
less for 30 gph I think. Look in the FSM for the specs on the stock fuel pump, it
may be less than 30 gph not sure. If its significantly longer then you have a tired pump
or some restriction somewhere upstream of the carb. Work your way back.
Since you have a new filter, its either a pump or a feed issue from the tank.
Don't rule out the new filter, it could have already gotten clogged by crap
from the tank, if theres crap in there.
The pressure you will need a gauge for but really the flow test will pretty
much verify it.
See how fast it fills a half gallon in a one gallon container and divide that into
an hour to get a gph hour number. It should do a half gallon in about 1 minute or
less for 30 gph I think. Look in the FSM for the specs on the stock fuel pump, it
may be less than 30 gph not sure. If its significantly longer then you have a tired pump
or some restriction somewhere upstream of the carb. Work your way back.
Since you have a new filter, its either a pump or a feed issue from the tank.
Don't rule out the new filter, it could have already gotten clogged by crap
from the tank, if theres crap in there.
The pressure you will need a gauge for but really the flow test will pretty
much verify it.
04-07-11, 09:22 AM
#5
Lives on the Forum
When you rebuilt the carb, did you specifically remove/clean/inspect the fuel jets found in the bottom of the float bowls? This step is not listed on some rebuild instructions, and I actually missed this on my first rebuild and had to go back to clean them out.
Also, when it begins to bog, does it feel like the more gas you give it, the slower you go?
Also, when it begins to bog, does it feel like the more gas you give it, the slower you go?
04-07-11, 10:15 AM
#6
Fuel pump should pump 1.5 quarts in 1 minute at 2.84-3.55 psi. Normally they either work or don't but I have had one that was intermittent for a few weeks before it died completely. Did you clean or remove the 2 inlet screens where the fuel lines attach to the top of the carb?
Since you replaced most of the ignition components, can we assume you have also tested the ignitors?
Since you replaced most of the ignition components, can we assume you have also tested the ignitors?
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04-07-11, 11:41 AM
#8
Do a simple flow and pressure test of the fuel as it come out right at the carb.
See how fast it fills a half gallon in a one gallon container and divide that into
an hour to get a gph hour number. It should do a half gallon in about 1 minute or
less for 30 gph I think. Look in the FSM for the specs on the stock fuel pump, it
may be less than 30 gph not sure. If its significantly longer then you have a tired pump
or some restriction somewhere upstream of the carb. Work your way back.
Since you have a new filter, its either a pump or a feed issue from the tank.
Don't rule out the new filter, it could have already gotten clogged by crap
from the tank, if theres crap in there.
The pressure you will need a gauge for but really the flow test will pretty
much verify it.
See how fast it fills a half gallon in a one gallon container and divide that into
an hour to get a gph hour number. It should do a half gallon in about 1 minute or
less for 30 gph I think. Look in the FSM for the specs on the stock fuel pump, it
may be less than 30 gph not sure. If its significantly longer then you have a tired pump
or some restriction somewhere upstream of the carb. Work your way back.
Since you have a new filter, its either a pump or a feed issue from the tank.
Don't rule out the new filter, it could have already gotten clogged by crap
from the tank, if theres crap in there.
The pressure you will need a gauge for but really the flow test will pretty
much verify it.
04-07-11, 03:25 PM
#9
04-10-11, 06:56 PM
#11
And I looked in the fsm I printed out...same one obviously. My only issue is that yes, the fsm is great, but it lacks in certain departments just as the Haynes does. It says...."as shown" for the relay and its location yet I have no idea where it is. The only thing I found was the main relay/fuse box on the left under the interior light adjust/choke/etc. I had my head on the gas pedal and all I could see were wires and plugs, no relays laid out like the picture. Not very descriptive. Are the relays in that exact location in the picture, or are they elevated to look like they're behind the instrument panel? Poor picture.
If anyone could enlighten me a little more it would be a big help. thanks!
If anyone could enlighten me a little more it would be a big help. thanks!
04-10-11, 08:32 PM
#12
Ok update time. I found the fuse/fuel pump connector and jumped it. No issues...fuel pump flows very well. I love when I test things on this car...everything always checks out so while it's good news that my 26 year old pump is in great shape, I have only eliminated something that the problem IS NOT caused by.
what the hell is it?
what the hell is it?
04-10-11, 09:18 PM
#13
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accelerator pump work?
04-10-11, 10:44 PM
#14
I believe so. New gasket and all cleaned up. Shoots out gas when i move it by hand, but i will have to check it with a helper to see when the car is on.
Since this problem occurs later in the gas pedal use...or at a higher rpm, could it just be the secondary jets? And if so...would i be able to get to them by just removing the air horn and leaving the carb on the car? Much easier if i could
Since this problem occurs later in the gas pedal use...or at a higher rpm, could it just be the secondary jets? And if so...would i be able to get to them by just removing the air horn and leaving the carb on the car? Much easier if i could
04-10-11, 11:10 PM
#15
When you rebuilt the carb, did you specifically remove/clean/inspect the fuel jets found in the bottom of the float bowls? This step is not listed on some rebuild instructions, and I actually missed this on my first rebuild and had to go back to clean them out.
Also, when it begins to bog, does it feel like the more gas you give it, the slower you go?
Also, when it begins to bog, does it feel like the more gas you give it, the slower you go?
What does this mean?
did not take out the jets...but i guess there may be reason to now.
04-10-11, 11:29 PM
#17
I will check...again....the secondaries but im pretty sure theyre opening. I can feel the difference when they open....but they seem to open about the same time im having my issue so thats why i thought secondary jets. I have the secondary arm mechanically attached to the primary arm.
04-11-11, 08:15 AM
#20
Lives on the Forum
Pull the jets and inspect them. You can do this through the little inspection plugs, just reach in with a screwdriver to loosen the jet, then jam a toothpick into the jet and use that to unscrew and remove it. That way you don't have to disassemble the carb again.
I will be absolutely amazed if you find that your jets are not clogged.
I will be absolutely amazed if you find that your jets are not clogged.
04-11-11, 08:37 AM
#22
Lives on the Forum
Read this very long thread, and you may have a sense of deja vu. One of the first threads I ever started, and it all led back to clogged jets.
https://www.rx7club.com/1st-generation-specific-1979-1985-18/12a-power-loss-%40-full-throttle-316922/
https://www.rx7club.com/1st-generation-specific-1979-1985-18/12a-power-loss-%40-full-throttle-316922/
