Engine lopes on cold start.
01-27-11, 01:34 PM
#1
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Engine lopes on cold start.
My FC I just picked up seems to lope in the morning when I start it. Once the vehicle reaches operating temperature it smooths out. Sometimes when driving I can depress the clutch and give it just alittle gas and the engine will start to lope again. It fluctuates between 500 and 1000rpm. It's only died once while it was loping. I'm at a loss but I would assume it's fuel related. Any ideas? Anyone else experienced this problem? Thanks for any help.
01-27-11, 01:45 PM
#2
TPS problem or vacuum leak. You may also have some of the cold start components missing, which will cause the idle to be rough when cold. In stock form, it should go to about 3k RPM for 17 seconds (unless in-gear), then drop to 1.5k RPM. Once warm, it should sit at 7-800 RPM.
FAQ: https://www.rx7club.com/showthread.p...06#post5131106
FAQ: https://www.rx7club.com/showthread.p...06#post5131106
01-27-11, 01:54 PM
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TPS problem or vacuum leak. You may also have some of the cold start components missing, which will cause the idle to be rough when cold. In stock form, it should go to about 3k RPM for 17 seconds (unless in-gear), then drop to 1.5k RPM. Once warm, it should sit at 7-800 RPM.
FAQ: https://www.rx7club.com/showthread.p...06#post5131106
FAQ: https://www.rx7club.com/showthread.p...06#post5131106
The car has never gone to 3k rpm on startup. Once started it revs to maybe 1500 then lopes between 500 and 1000. So that would seem to point to a TPS issue huh? Is there a way to check that without replacing the part?
EDIT: Nevermind, I think I just found the info in that link. Thanks.
Last edited by Stout7; 01-27-11 at 01:57 PM. Reason: Found it
01-27-11, 02:03 PM
#4
Follow the link I provided to the FAQ. There's a thread covering TPS adjustment. Adjusting an S4 is also simpler than an S5, since there are only 3 wires. The one by itself on the plug should measure 1.0 vdc with the engine fully warm. You can warm up the car, shut it off, then put the key to ON to do this measurement. You should also test the resistance sweep of the TPS to be sure there are no dead spots. These things are tempermental, and after 20+ years, there are not many that will behave perfectly anymore.
If the idle never goes to 3k on startup, someone has probably removed or disabled the BAC (bypass air control) valve and the AWS (accelerated warmup system) valve. A second function of the BAC is to stabilize idle when there are electrical and mechanical load changes (such as power steering or the head lights). If the idle does not hold around 1.5k RPM, someone has removed the thermowax, or it is not working. There should be a couple coolant lines going to the back of the throttle body. These go to the thermowax, which has a small plunger that moves the throttle plates. As the engine warms, the piston disengages the cam, and the throttle plates will rest on the throttle stop.
If the idle never goes to 3k on startup, someone has probably removed or disabled the BAC (bypass air control) valve and the AWS (accelerated warmup system) valve. A second function of the BAC is to stabilize idle when there are electrical and mechanical load changes (such as power steering or the head lights). If the idle does not hold around 1.5k RPM, someone has removed the thermowax, or it is not working. There should be a couple coolant lines going to the back of the throttle body. These go to the thermowax, which has a small plunger that moves the throttle plates. As the engine warms, the piston disengages the cam, and the throttle plates will rest on the throttle stop.
01-27-11, 02:34 PM
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Follow the link I provided to the FAQ. There's a thread covering TPS adjustment. Adjusting an S4 is also simpler than an S5, since there are only 3 wires. The one by itself on the plug should measure 1.0 vdc with the engine fully warm. You can warm up the car, shut it off, then put the key to ON to do this measurement. You should also test the resistance sweep of the TPS to be sure there are no dead spots. These things are tempermental, and after 20+ years, there are not many that will behave perfectly anymore.
If the idle never goes to 3k on startup, someone has probably removed or disabled the BAC (bypass air control) valve and the AWS (accelerated warmup system) valve. A second function of the BAC is to stabilize idle when there are electrical and mechanical load changes (such as power steering or the head lights). If the idle does not hold around 1.5k RPM, someone has removed the thermowax, or it is not working. There should be a couple coolant lines going to the back of the throttle body. These go to the thermowax, which has a small plunger that moves the throttle plates. As the engine warms, the piston disengages the cam, and the throttle plates will rest on the throttle stop.
If the idle never goes to 3k on startup, someone has probably removed or disabled the BAC (bypass air control) valve and the AWS (accelerated warmup system) valve. A second function of the BAC is to stabilize idle when there are electrical and mechanical load changes (such as power steering or the head lights). If the idle does not hold around 1.5k RPM, someone has removed the thermowax, or it is not working. There should be a couple coolant lines going to the back of the throttle body. These go to the thermowax, which has a small plunger that moves the throttle plates. As the engine warms, the piston disengages the cam, and the throttle plates will rest on the throttle stop.
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01-27-11, 05:46 PM
#8
If the coolant is below a certain temperature the 3000 rpm start up will not occur. Have you had this car long enough where the weather was warm when you cold started the car? If you have only owned the car briefly and you live in a cold environment that would help explain why it has yet to engage. There is a temperature sensor located towards the lower part of the radiator on the side of the radiator that faces the engine and on the end of the radiator which is on the driver side. This sensor has two wires running to it. If these two wires are jumpered together then it will force the engine to go through the 3000 rpm rev upon start up if it is intact and working properly.
01-27-11, 06:01 PM
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If the coolant is below a certain temperature the 3000 rpm start up will not occur. Have you had this car long enough where the weather was warm when you cold started the car? If you have only owned the car briefly and you live in a cold environment that would help explain why it has yet to engage. There is a temperature sensor located towards the lower part of the radiator on the side of the radiator that faces the engine and on the end of the radiator which is on the driver side. This sensor has two wires running to it. If these two wires are jumpered together then it will force the engine to go through the 3000 rpm rev upon start up if it is intact and working properly.
That maybe the case. I've only had the car for two days, Although the guy that sold it to me told me about the situation prior to purchase and I have experienced it every time since but he also told me that when they first purchased the car that it didn't do it. The car sat in a garage and was driven rarely. I didnt know if that would have something to do with it or not.
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