Rough idle up and down / smoke on start up
03-20-16, 10:48 AM
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Rough idle up and down / smoke on start up
My first introduction to this car was for the original owner, he stated he had he car for 4 years , drove it maybe 4 times and started once a month. He said his fuel gauge didn't work so he never knew how much gas he had so he put about 5 gallons since he has had it.
Then on the once a month start he started it , it ran fine, then the idle started going up and down then died. He attempted to start it and it wouldn't start. He left it alone at that point and called me. First Thing I did was before starting it checked all the fluids and basics, added 4 gallons of fuel and charged battery, attempted to start with no luck on 3-7 cranks 4 times. So I got the starting fluid out gave it a squirt and she fired up with the assistance of opening the throttle by hand, when she started she started to smoke ( a LOT ) so I shut it down after 10 seconds. She sounded healthy but the smoke concerned me. Thick white smoke that smelled sweet I thought ( coolant )
So I told him we should do a compression test and radiator pressure test.
Well...... 3 months go by and he hasn't found the time. Then he pushed the car onto the street to work on driveway, 4 hours later it got towed.
Long story but he couldn't afford to get it out so I paid for it, now it's in my driveway.
Ok here we go. So I did a compression test and it was pulsing 65-85 on both sides
Radiator pressure test was good . Yay.
I checked plugs and the are clean. So I said well let's see how long she smokes and for how long. She started without starting fluid and had the heavy smoke and idled up and down 1200- 1800 rpm for about 5 minutes then the smoke became less and less. Idle still up and down tho. After 15 minutes idle time the smoke was all cleared up and she was running the same idle. After it warms up ( half way on gauge ) it will idle at 2000 rpm but shakes like hell. Shut it down let it cool and started it again and let it warm up, after 15-20 minutes the idle slowly goes to a rough 1200 rpm and will occasionally go up and down. So I'm thinking ok possible bad gas. I put 10 gallons with some fuel system cleaner in her and run a few more cold to warmed up cycles. It's still doing a idle up and down until it warms up then has a rough idle sometimes 1200 sometimes 2000 and sometime 1000. It's not consistent. Now here is something to add, after a warm up it will have a rough idle and steady after doing the up and down dance while warming, butttttttttt when warmed up if I **** it off and start it back up she idles around 2000 and it's smooth as silk for about 10 seconds then idles down to about 800 sounds like it's gonna die then goes up to about 1200 and is really rough. This will happen every time it's warmed up and I shut it off then on again.
Any help or advice or hey dumb dumb did you do this will be mucho appreciato
Then on the once a month start he started it , it ran fine, then the idle started going up and down then died. He attempted to start it and it wouldn't start. He left it alone at that point and called me. First Thing I did was before starting it checked all the fluids and basics, added 4 gallons of fuel and charged battery, attempted to start with no luck on 3-7 cranks 4 times. So I got the starting fluid out gave it a squirt and she fired up with the assistance of opening the throttle by hand, when she started she started to smoke ( a LOT ) so I shut it down after 10 seconds. She sounded healthy but the smoke concerned me. Thick white smoke that smelled sweet I thought ( coolant )
So I told him we should do a compression test and radiator pressure test.
Well...... 3 months go by and he hasn't found the time. Then he pushed the car onto the street to work on driveway, 4 hours later it got towed.
Long story but he couldn't afford to get it out so I paid for it, now it's in my driveway.
Ok here we go. So I did a compression test and it was pulsing 65-85 on both sides
Radiator pressure test was good . Yay.
I checked plugs and the are clean. So I said well let's see how long she smokes and for how long. She started without starting fluid and had the heavy smoke and idled up and down 1200- 1800 rpm for about 5 minutes then the smoke became less and less. Idle still up and down tho. After 15 minutes idle time the smoke was all cleared up and she was running the same idle. After it warms up ( half way on gauge ) it will idle at 2000 rpm but shakes like hell. Shut it down let it cool and started it again and let it warm up, after 15-20 minutes the idle slowly goes to a rough 1200 rpm and will occasionally go up and down. So I'm thinking ok possible bad gas. I put 10 gallons with some fuel system cleaner in her and run a few more cold to warmed up cycles. It's still doing a idle up and down until it warms up then has a rough idle sometimes 1200 sometimes 2000 and sometime 1000. It's not consistent. Now here is something to add, after a warm up it will have a rough idle and steady after doing the up and down dance while warming, butttttttttt when warmed up if I **** it off and start it back up she idles around 2000 and it's smooth as silk for about 10 seconds then idles down to about 800 sounds like it's gonna die then goes up to about 1200 and is really rough. This will happen every time it's warmed up and I shut it off then on again.
Any help or advice or hey dumb dumb did you do this will be mucho appreciato
03-20-16, 11:11 AM
#2
S5 RX7? If so, then the fast idle cam is likely not set up properly. It's located on the ear of the throttle body and its job is to allow the cold engine to idle at a higher than normal speed (usually close to 1500 rpm) until the engine gradually warms up and as it does the idle speed drops eventually to close to 800 rpm. There is a lever on this mechanism which has an upside down screw. The screw rests upon a metal rod which extends from the thermovalve as the engine heats up. The FSM shows how it is supposed to be set. You could override the system by placing a large rubber vacuum cap on the screw so the lever is pressed down as far as it can go. This positioning of the lever represents an engine which is fully warmed up. Also, after the engine has been thoroughly heated up the Green/Red wire of the TPS should read close to 1 volt w/key to on. When the sensor is not set correctly a bumpy idle can occur when the engine has been sufficiently warmed. And make sure the timing is set properly, too. Last but least, check for error codes. (and your compression numbers are low especially the 65. Normal is closer to 100 for an aged engine)
03-20-16, 11:18 AM
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Yes S5 RX7
I will check the fast idle cam this morning and operation of the linkages.
Also will meter out the TPS and post results.
Timing will be checked , do you know what the spec is?
And I don't have a CEL on but will check for logged codes, I have a snap on scan tool I'll use but the connectors to use is a bit confusing, not sure where to hook up excactly.
And I will double check the compression.
Also what is the FSM? Still learning here
I will check the fast idle cam this morning and operation of the linkages.
Also will meter out the TPS and post results.
Timing will be checked , do you know what the spec is?
And I don't have a CEL on but will check for logged codes, I have a snap on scan tool I'll use but the connectors to use is a bit confusing, not sure where to hook up excactly.
And I will double check the compression.
Also what is the FSM? Still learning here
03-20-16, 11:37 AM
#6
Timing light and RPM
Yes S5 RX7
I will check the fast idle cam this morning and operation of the linkages.
Also will meter out the TPS and post results.
Timing will be checked , do you know what the spec is?
And I don't have a CEL on but will check for logged codes, I have a snap on scan tool I'll use but the connectors to use is a bit confusing, not sure where to hook up excactly.
And I will double check the compression.
Also what is the FSM? Still learning here
I will check the fast idle cam this morning and operation of the linkages.
Also will meter out the TPS and post results.
Timing will be checked , do you know what the spec is?
And I don't have a CEL on but will check for logged codes, I have a snap on scan tool I'll use but the connectors to use is a bit confusing, not sure where to hook up excactly.
And I will double check the compression.
Also what is the FSM? Still learning here
But I read somewhere that the idle has to be under 1000RPM in order to check timing. My rx7 won't idle below 1200, so I ended up following the CAS-crank angle sensor- re-stab to make sure it was in the proper place/angle.
03-20-16, 12:15 PM
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It is all factory and all the vacuum hoses have been previously replaced with blue silicone hoses. I've checked all the vacuum hoses visually , have not used an areosol spray to find vacuum leaks tho.
Did the re-stabbing of the CAS correct your high idle?
Also want to note that I noticed the engine bay and engine very very clean, and it has a atkinsrotart engine oil filter on it, so I'm thinking previous owner has been inside motor, to what extent I don't know tho but it's in super clean shape
Did the re-stabbing of the CAS correct your high idle?
Also want to note that I noticed the engine bay and engine very very clean, and it has a atkinsrotart engine oil filter on it, so I'm thinking previous owner has been inside motor, to what extent I don't know tho but it's in super clean shape
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03-20-16, 12:20 PM
#9
The FSM is available online (free).
Also, w/the car idling you can press upwards on the front throttle linkage and it might reduce your idle speed. If it does so after the car is running as low as it can w/respect to the idle speed (fully warmed) then it is indicative of the fast idle cam not set correctly or the throttle plates/linkage is not set properly or both items are out of spec.
Also, w/the car idling you can press upwards on the front throttle linkage and it might reduce your idle speed. If it does so after the car is running as low as it can w/respect to the idle speed (fully warmed) then it is indicative of the fast idle cam not set correctly or the throttle plates/linkage is not set properly or both items are out of spec.
Last edited by satch; 03-20-16 at 12:24 PM.
03-20-16, 12:59 PM
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S5 RX7? If so, then the fast idle cam is likely not set up properly. It's located on the ear of the throttle body and its job is to allow the cold engine to idle at a higher than normal speed (usually close to 1500 rpm) until the engine gradually warms up and as it does the idle speed drops eventually to close to 800 rpm. There is a lever on this mechanism which has an upside down screw. The screw rests upon a metal rod which extends from the thermovalve as the engine heats up. The FSM shows how it is supposed to be set. You could override the system by placing a large rubber vacuum cap on the screw so the lever is pressed down as far as it can go. This positioning of the lever represents an engine which is fully warmed up. Also, after the engine has been thoroughly heated up the Green/Red wire of the TPS should read close to 1 volt w/key to on. When the sensor is not set correctly a bumpy idle can occur when the engine has been sufficiently warmed. And make sure the timing is set properly, too. Last but least, check for error codes. (and your compression numbers are low especially the 65. Normal is closer to 100 for an aged engine)
TPS voltage is 1.5 v and 4.8 wide open
Compression is at 95 psi , replaced bad oring on tester
03-20-16, 01:03 PM
#14
Remember, the fast idle cam is at the rear of the throttle body as opposed to the front. Secondly, as stated, it has an upside down screw which rests upon a metal rod. And when you find it you will quickly realize you have very little space to work with. The valve also has a coolant hose coming off of the BAC which provides coolant to the valve. The valve might be clogged with gunk from the coolant and this could interfere w/the idle.
Foxed.ca is where the online FSM is.
And pressing in the plastic rod of the TPS to simulate an idle position is wrong as the rod is not supposed to be pressed fully inwards as that could damage the sensor. In a normal idle speed the rod is not fully compressed.
Foxed.ca is where the online FSM is.
And pressing in the plastic rod of the TPS to simulate an idle position is wrong as the rod is not supposed to be pressed fully inwards as that could damage the sensor. In a normal idle speed the rod is not fully compressed.
03-20-16, 01:20 PM
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Remember, the fast idle cam is at the rear of the throttle body as opposed to the front. Secondly, as stated, it has an upside down screw which rests upon a metal rod. And when you find it you will quickly realize you have very little space to work with. The valve also has a coolant hose coming off of the BAC which provides coolant to the valve. The valve might be clogged with gunk from the coolant and this could interfere w/the idle.
Foxed.ca is where the online FSM is.
And pressing in the plastic rod of the TPS to simulate an idle position is wrong as the rod is not supposed to be pressed fully inwards as that could damage the sensor. In a normal idle speed the rod is not fully compressed.
Foxed.ca is where the online FSM is.
And pressing in the plastic rod of the TPS to simulate an idle position is wrong as the rod is not supposed to be pressed fully inwards as that could damage the sensor. In a normal idle speed the rod is not fully compressed.
Last edited by ronald crissup; 03-20-16 at 01:24 PM. Reason: Typo
03-20-16, 01:41 PM
#16
The TPS range at idle for an S5 ranges between 1 to 1.5 volts, so while yours is basically in range, you can use the adjustment screw and lower it to see if it makes difference concerning a bouncy idle. Also, reading the TPS voltage requires the idle to be rather close to 800 rpm as opposed to well over a 1000.
03-20-16, 08:33 PM
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Now I've been adjusting and I got the idle at 1000 , the lowest I can get it.
It runs rough at this rpm can't seem to get it to run smooth at lower rpms.
While warming up it still goes between 1200 and 1800 until it warms up, I've checked the linkage on the backside and it's good, the thermovalve isn't causing the fluctuation , it seems it's either the BAC or I dunno
03-21-16, 11:27 AM
#21
I've never heard of looking at the fast idle cam to see if it was within spec. Also, you make mention you were able to get the rpm down to 1000 but you left out how you achieved that (not good). The BAC helps to maintain idle when the engine drops below 750 rpm, which I do not believe is occurring with your car. If you really believe the BAC was at fault you could just unplug it to prove so. When the idle speed is rather high it can cause the timing to advance and then it doesn't advance so that could cause a loping high idle.
03-21-16, 01:52 PM
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I've never heard of looking at the fast idle cam to see if it was within spec. Also, you make mention you were able to get the rpm down to 1000 but you left out how you achieved that (not good). The BAC helps to maintain idle when the engine drops below 750 rpm, which I do not believe is occurring with your car. If you really believe the BAC was at fault you could just unplug it to prove so. When the idle speed is rather high it can cause the timing to advance and then it doesn't advance so that could cause a loping high idle.
I got it to idle at 1000 by adjusting the idle speed screw while my DMM was hooked up to the TPS and adjusting until I got 1.v .
And you are correct about the BAC. I've unplugged it and it continues to idle up and down during warm up.
The more cold to warm cycles I do it seems to be getting better, still idles up and down while cold then gets to a constant 1000 rpm but runs rough, sounds like it's bogging down while idling. keep in mind the car sat for 4 years with a start once a month and rarely driven.
I still don't know why it smoked so bad the first couple times I ran it and now it doesn't smoke at all.
I'm considering removing the complete intake system and cleaning the butterfly valves, inspecting the (thermowax) and thermovalve .
I have little knowledge of the thermos ax and thermovalve but intend on removing, cleaning and inspecting.
Good idea!? Bad idea? Not needed?
Last edited by ronald crissup; 03-21-16 at 01:54 PM. Reason: Left something out
03-21-16, 02:17 PM
#23
If the engine was flooded that could cause smoke or coolant in the housings would do the same thing. A rough idle could be caused by many things and clogged injectors (especially the primaries) could be one of them. If you take off the intake tube running to the throttle body it will show you whether the primary plates are within spec or not. If you pressed upwards on the front throttle linkage you should be able to close the plates as much as possible and in doing so the open gap is like the width of a fingernail (the FSM indicates the proper gauge opening).
03-22-16, 11:30 AM
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If the engine was flooded that could cause smoke or coolant in the housings would do the same thing. A rough idle could be caused by many things and clogged injectors (especially the primaries) could be one of them. If you take off the intake tube running to the throttle body it will show you whether the primary plates are within spec or not. If you pressed upwards on the front throttle linkage you should be able to close the plates as much as possible and in doing so the open gap is like the width of a fingernail (the FSM indicates the proper gauge opening).
So i warmed up the engine this morning and it did its usual idle up and down until I disconnect the TPS, it idles smooth when I disconnected it. Plugged it back in and idle up and down again.