Car dies after coming to a stop light?
01-08-2014, 02:01 AM
#1
4th Gear Member
Thread Starter
Join Date: Jun 2006
Location: Upland, California
Posts: 1,246
Car dies after coming to a stop light?
Hello Folks,
I haven't been here in a while and unfortunately haven't driven mustang in even longer. So I finally started getting my car started up after a few years of sitting (started it maybe once every 3 months). Its a 302 with a c4 automatic
Anyways. I drained the gas and got new gas. Sea foamed carb (edelbrock 1406). Reset the timing (10°), then proceeded to tune the carb (15° vaccum at idle) pretty good for this cam. Found out two different metering rods were installed fixed issue and adjusted everything else. So the car runs great. Choke closes fine/opens when hot. Fast idle works great on first fire. Idles where I want it (900 rpm in park). Fuel pressure is solid 5 psi limited by a regulator.
The problem I am having is that the car will start up fine. And will idle great when first starting and then putting car into reverse/drive. Am able to drive fine (No misfiring, runs great, sounds great, no stumble on acceleration, etc) but when it comes time to stop, while coming to a stop or when I make the stop the car will die or idle will drop extremely low to the point of dying. This will happen until the car is driven for a while then it seems to stay on and idle where I set it correctly. Even if car is up to operating temp and then stopped (car off) it will occur when I start driving 10 minutes later. When I am coming to a stop if I put it in neutral and rev it then let it come back down it seems like it catches the the idle again and even if I put it in drive it will stay on like it should while stopped. Yet the next light same issue occurs it will turn off (unless I neutral rev at least once at stop).
I am kind of stumped. Not sure where to go from here. When tuning carb I took out the adjustment screws and blew air in (as per edelbrocks video) but that did not help. I just took the fuel filter out and popped the 40 micron element out and see 3-4 specs large specs of dirt but it doesn't look terribly bad. I ordered a replacement element to be certain.
Does anybody have any ideas what could be wrong? Sorry for long post
I haven't been here in a while and unfortunately haven't driven mustang in even longer. So I finally started getting my car started up after a few years of sitting (started it maybe once every 3 months). Its a 302 with a c4 automatic
Anyways. I drained the gas and got new gas. Sea foamed carb (edelbrock 1406). Reset the timing (10°), then proceeded to tune the carb (15° vaccum at idle) pretty good for this cam. Found out two different metering rods were installed fixed issue and adjusted everything else. So the car runs great. Choke closes fine/opens when hot. Fast idle works great on first fire. Idles where I want it (900 rpm in park). Fuel pressure is solid 5 psi limited by a regulator.
The problem I am having is that the car will start up fine. And will idle great when first starting and then putting car into reverse/drive. Am able to drive fine (No misfiring, runs great, sounds great, no stumble on acceleration, etc) but when it comes time to stop, while coming to a stop or when I make the stop the car will die or idle will drop extremely low to the point of dying. This will happen until the car is driven for a while then it seems to stay on and idle where I set it correctly. Even if car is up to operating temp and then stopped (car off) it will occur when I start driving 10 minutes later. When I am coming to a stop if I put it in neutral and rev it then let it come back down it seems like it catches the the idle again and even if I put it in drive it will stay on like it should while stopped. Yet the next light same issue occurs it will turn off (unless I neutral rev at least once at stop).
I am kind of stumped. Not sure where to go from here. When tuning carb I took out the adjustment screws and blew air in (as per edelbrocks video) but that did not help. I just took the fuel filter out and popped the 40 micron element out and see 3-4 specs large specs of dirt but it doesn't look terribly bad. I ordered a replacement element to be certain.
Does anybody have any ideas what could be wrong? Sorry for long post
Last edited by nba1341; 01-08-2014 at 02:08 AM.
01-08-2014, 02:26 AM
#2
My first thought is vapor lock. Although it's just a guess. When you rev the motor you could be pushing out the hot gasoline from the fuel bowls and pushing in some new cooler gasoline fresh from the tank. You said that you have no problems restarting the car though...so vapor lock may not be your issue.
Check a couple things.
-Ensure that your gas cap has the spring system intact to allow a fluctuation in air pressure. Pop it off and look at the center of the cap.
-check your air cleaner, sometimes a huge one can trap hot air under it and heat the fuel bowls on your carb prematurely.
-ensure that your fuel line is not touching your head, water pump or laying on you radiator hose. If you can, put some heat wrap on it.
-install a small plastic carb riser plate. That will slow down the heat exchange from the manifold to the carb.
Google vapor lock and see if your symptoms match. Also there are some other fixes out there. Also wait for more replies here...I'm still not entirely sure that it's vapor lock.
It could be a return spring or something that is getting stuck in the carb which you have to jerk free by pressing the pedal at each stop. You could spray some WD 40 around the moving parts of the carb to ensure everything is moving freely and not sticking.
Let us know if you figure it out.
James
Check a couple things.
-Ensure that your gas cap has the spring system intact to allow a fluctuation in air pressure. Pop it off and look at the center of the cap.
-check your air cleaner, sometimes a huge one can trap hot air under it and heat the fuel bowls on your carb prematurely.
-ensure that your fuel line is not touching your head, water pump or laying on you radiator hose. If you can, put some heat wrap on it.
-install a small plastic carb riser plate. That will slow down the heat exchange from the manifold to the carb.
Google vapor lock and see if your symptoms match. Also there are some other fixes out there. Also wait for more replies here...I'm still not entirely sure that it's vapor lock.
It could be a return spring or something that is getting stuck in the carb which you have to jerk free by pressing the pedal at each stop. You could spray some WD 40 around the moving parts of the carb to ensure everything is moving freely and not sticking.
Let us know if you figure it out.
James
01-08-2014, 06:49 AM
#3
2nd Gear Member
Join Date: Nov 2006
Location:
Posts: 356
Hello Folks,
I haven't been here in a while and unfortunately haven't driven mustang in even longer. So I finally started getting my car started up after a few years of sitting (started it maybe once every 3 months). Its a 302 with a c4 automatic
Anyways. I drained the gas and got new gas. Sea foamed carb (edelbrock 1406). Reset the timing (10°), then proceeded to tune the carb (15° vaccum at idle) pretty good for this cam. Found out two different metering rods were installed fixed issue and adjusted everything else. So the car runs great. Choke closes fine/opens when hot. Fast idle works great on first fire. Idles where I want it (900 rpm in park). Fuel pressure is solid 5 psi limited by a regulator.
The problem I am having is that the car will start up fine. And will idle great when first starting and then putting car into reverse/drive. Am able to drive fine (No misfiring, runs great, sounds great, no stumble on acceleration, etc) but when it comes time to stop, while coming to a stop or when I make the stop the car will die or idle will drop extremely low to the point of dying. This will happen until the car is driven for a while then it seems to stay on and idle where I set it correctly. Even if car is up to operating temp and then stopped (car off) it will occur when I start driving 10 minutes later. When I am coming to a stop if I put it in neutral and rev it then let it come back down it seems like it catches the the idle again and even if I put it in drive it will stay on like it should while stopped. Yet the next light same issue occurs it will turn off (unless I neutral rev at least once at stop).
I am kind of stumped. Not sure where to go from here. When tuning carb I took out the adjustment screws and blew air in (as per edelbrocks video) but that did not help. I just took the fuel filter out and popped the 40 micron element out and see 3-4 specs large specs of dirt but it doesn't look terribly bad. I ordered a replacement element to be certain.
Does anybody have any ideas what could be wrong? Sorry for long post
I haven't been here in a while and unfortunately haven't driven mustang in even longer. So I finally started getting my car started up after a few years of sitting (started it maybe once every 3 months). Its a 302 with a c4 automatic
Anyways. I drained the gas and got new gas. Sea foamed carb (edelbrock 1406). Reset the timing (10°), then proceeded to tune the carb (15° vaccum at idle) pretty good for this cam. Found out two different metering rods were installed fixed issue and adjusted everything else. So the car runs great. Choke closes fine/opens when hot. Fast idle works great on first fire. Idles where I want it (900 rpm in park). Fuel pressure is solid 5 psi limited by a regulator.
The problem I am having is that the car will start up fine. And will idle great when first starting and then putting car into reverse/drive. Am able to drive fine (No misfiring, runs great, sounds great, no stumble on acceleration, etc) but when it comes time to stop, while coming to a stop or when I make the stop the car will die or idle will drop extremely low to the point of dying. This will happen until the car is driven for a while then it seems to stay on and idle where I set it correctly. Even if car is up to operating temp and then stopped (car off) it will occur when I start driving 10 minutes later. When I am coming to a stop if I put it in neutral and rev it then let it come back down it seems like it catches the the idle again and even if I put it in drive it will stay on like it should while stopped. Yet the next light same issue occurs it will turn off (unless I neutral rev at least once at stop).
I am kind of stumped. Not sure where to go from here. When tuning carb I took out the adjustment screws and blew air in (as per edelbrocks video) but that did not help. I just took the fuel filter out and popped the 40 micron element out and see 3-4 specs large specs of dirt but it doesn't look terribly bad. I ordered a replacement element to be certain.
Does anybody have any ideas what could be wrong? Sorry for long post
You mention your idle in park is 900 Rs. What is your RPMs in drive, when fully warmed?
01-09-2014, 07:56 AM
#4
2nd Gear Member
Join Date: Sep 2007
Location:
Posts: 248
I had the same issue for a long time and for me after getting rid of the Edelbrock I had no more issues. That being said, try hooking the distributor advance to the port that is vacuum at idle not the timed port as indicated in manuals. If you have a big cam this will help. Could also be a float issue so that too much fuel is in the bowls.
01-09-2014, 10:37 PM
#6
5th Gear Member
Join Date: Feb 2007
Location: Ramona, CA
Posts: 2,682
http://www.summitracing.com/parts/hly-11-4/overview/
Get a dashpot. It keeps the throttle from bottoming out when you let off the gas too fast. I had a 78 302 that used to do the same thing when I would get off the interstate or come to a stop after hauling butt for a little bit.
Get a dashpot. It keeps the throttle from bottoming out when you let off the gas too fast. I had a 78 302 that used to do the same thing when I would get off the interstate or come to a stop after hauling butt for a little bit.
01-09-2014, 11:13 PM
#7
Moderator
Join Date: Dec 2005
Location: Hills of California
Posts: 5,208
I found that if my Holley died when I backed off the throttle it was because it was running lean. Going up a size or two on the main jets and maybe a bit more rich on the idle circuit totally solved the problem.
It should run fine without a dashpot
It should run fine without a dashpot
01-11-2014, 08:51 AM
#8
2nd Gear Member
Join Date: Sep 2012
Location: Tx
Posts: 204
You might look at the float level. Sometimes, if the bowls are too full, you can get spill-over into the carb throat when stopping, especially if stopping quickly. That causes the carb to stumble and possibly die. I've had this problem with Carter/Edelbrock carbs in the past when coming to a quick stop or hard cornering without accelerating. The A/T magnifies the problem as opposed to a standard tranny.
Best,
Al
Best,
Al
01-16-2014, 01:35 AM
#9
4th Gear Member
Thread Starter
Join Date: Jun 2006
Location: Upland, California
Posts: 1,246
Thanks for the suggestions guys. Its not a heat soak issue as I have a 1" plenum spacer because I used to get that problem really bad in the summer. The car will also die in neutral coming to a light and the transmission seems fine. I took off the top of carb and verified float levels are at 7/16".
I changed the carb to #7 on the 1406 chart which is Base power mode and 1.5 stages lean in cruise mode which ran fine in the past. While trying to re-set the idle mixture I noticed something. Idle was at 900 rpm and vacuum was at 13 so I continued leaning both screws little by little. Vacuum rose to 15 but the idle jumped to 1000rpm so I went to back off the idle speed screw. This screw did absolutely nothing. Turning counter clockwise did not lower idle. Important note was that car was fully warmed up and choke was fully open.
Any ideas? I last rebuilt the carb with the kit 1477 in 4/2009.
Thanks
I changed the carb to #7 on the 1406 chart which is Base power mode and 1.5 stages lean in cruise mode which ran fine in the past. While trying to re-set the idle mixture I noticed something. Idle was at 900 rpm and vacuum was at 13 so I continued leaning both screws little by little. Vacuum rose to 15 but the idle jumped to 1000rpm so I went to back off the idle speed screw. This screw did absolutely nothing. Turning counter clockwise did not lower idle. Important note was that car was fully warmed up and choke was fully open.
Any ideas? I last rebuilt the carb with the kit 1477 in 4/2009.
Thanks
Last edited by nba1341; 01-16-2014 at 01:59 AM.
01-16-2014, 05:12 AM
#10
2nd Gear Member
Join Date: Nov 2006
Location:
Posts: 356
Thanks for the suggestions guys. Its not a heat soak issue as I have a 1" plenum spacer because I used to get that problem really bad in the summer. The car will also die in neutral coming to a light and the transmission seems fine. I took off the top of carb and verified float levels are at 7/16".
I changed the carb to #7 on the 1406 chart which is Base power mode and 1.5 stages lean in cruise mode which ran fine in the past. While trying to re-set the idle mixture I noticed something. Idle was at 900 rpm and vacuum was at 13 so I continued leaning both screws little by little. Vacuum rose to 15 but the idle jumped to 1000rpm so I went to back off the idle speed screw. This screw did absolutely nothing. Turning counter clockwise did not lower idle. Important note was that car was fully warmed up and choke was fully open.
Any ideas? I last rebuilt the carb with the kit 1477 in 4/2009.
Thanks
I changed the carb to #7 on the 1406 chart which is Base power mode and 1.5 stages lean in cruise mode which ran fine in the past. While trying to re-set the idle mixture I noticed something. Idle was at 900 rpm and vacuum was at 13 so I continued leaning both screws little by little. Vacuum rose to 15 but the idle jumped to 1000rpm so I went to back off the idle speed screw. This screw did absolutely nothing. Turning counter clockwise did not lower idle. Important note was that car was fully warmed up and choke was fully open.
Any ideas? I last rebuilt the carb with the kit 1477 in 4/2009.
Thanks
When you stated " so I went to back off the idle speed screw. This screw did absolutely nothing" You are referring to the linkage idle scr and not the idle mix scr? If so, I would check to insure the throttle plates are closing and there the idle scr linkage is not binding. Is the low vac due to a cam change? I'm thinking, you have a vac leak. I've ran a 1405 (non electric choke) Eddy carb and was trouble free for years. Even with a "hotter" cam and vac in the 16s, the engine idled fine at 900-1000 Rs with a C4 tranny.
Something is fishy in Denmark!