Hunting GSL SE Surge
04-07-11, 10:19 PM
#1
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Hunting GSL SE Surge
Evening everyone! Thanks in advance for stopping by, any advice is greatly appreciated.
1984 RX7 GSL-SE . I took a read on the surge FAQ, and I couldnt find a situation that describes what problem I'm having quite right.
For all intents and purposes, the GSL SE is as stock as I can make it. Also, I've checked for Vacuum leaks, and replaced as many vac lines as possible, so we're dealing with almost all new lines. Gaskets are also all new, tightened down per factory specifications. I know I have a small leak at the exhaust, but back a ways and not associated to any manifold etc. Just in front of the Oxygen sensor though.
On start up, cold, the engine idles steady at about 1500 rpm or so until warm, until it drops down to about 1000 rpm at idle. It idles well, with the occasional blip, but so far - pretty smooth.
The issue I'm having is when I'm out driving, and come to a light and move the stick into neutral, the vehicle drops to 1000rpm at its 'Idle' . Now, when i depress the clutch - nothing happens, UNTIL I move the car into car. If I move it into gear, with the clutch still in, it begins to surge. It drops to about 600 rpm, jumps to about 1200, and back down again. over and over again, it doesn't seem to idle out. I bring it back to neutral, and it's back to being fantastic.
Any idea's guys? Lastly -
Engine is a fresh rebuild. I did NOT replace the variable resistor. I also know that thing has been tampered with. I did test it with the meter today, to make sure it was not broken or malfunctioning, and in the FSM It states the voltage. It does pass the voltage test. I have no idea though if its way out of adjustment. FSM says to replace the resistor with a new engine. Not sure how important this is. The previous owner gutted the goo in the resistor and was playing with it for sure.
Thanks again!
1984 RX7 GSL-SE . I took a read on the surge FAQ, and I couldnt find a situation that describes what problem I'm having quite right.
For all intents and purposes, the GSL SE is as stock as I can make it. Also, I've checked for Vacuum leaks, and replaced as many vac lines as possible, so we're dealing with almost all new lines. Gaskets are also all new, tightened down per factory specifications. I know I have a small leak at the exhaust, but back a ways and not associated to any manifold etc. Just in front of the Oxygen sensor though.
On start up, cold, the engine idles steady at about 1500 rpm or so until warm, until it drops down to about 1000 rpm at idle. It idles well, with the occasional blip, but so far - pretty smooth.
The issue I'm having is when I'm out driving, and come to a light and move the stick into neutral, the vehicle drops to 1000rpm at its 'Idle' . Now, when i depress the clutch - nothing happens, UNTIL I move the car into car. If I move it into gear, with the clutch still in, it begins to surge. It drops to about 600 rpm, jumps to about 1200, and back down again. over and over again, it doesn't seem to idle out. I bring it back to neutral, and it's back to being fantastic.
Any idea's guys? Lastly -
Engine is a fresh rebuild. I did NOT replace the variable resistor. I also know that thing has been tampered with. I did test it with the meter today, to make sure it was not broken or malfunctioning, and in the FSM It states the voltage. It does pass the voltage test. I have no idea though if its way out of adjustment. FSM says to replace the resistor with a new engine. Not sure how important this is. The previous owner gutted the goo in the resistor and was playing with it for sure.
Thanks again!
04-08-11, 10:39 AM
#2
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I'm having a similar problem so I'd like to see what others say.
I just pulled my intake to replace the injectors. The vacuum lines that go to the oil injectors were completelly shot. I replaced them and it helped the idle quite a bit. I still have a little surge but not as much.
I just pulled my intake to replace the injectors. The vacuum lines that go to the oil injectors were completelly shot. I replaced them and it helped the idle quite a bit. I still have a little surge but not as much.
04-08-11, 03:52 PM
#3
84SE-EGI helpy-helperton
Alright, here goes; 'Surging' is almost always caused by a feedback loop which occurs when the engine is cold and when the Secondary Throttle Plates (effectively a vacuum-powered choke mechanism) are trying to solve airflow fluctuations in spite of sticky Throttle Body shafts.
In brief, the aluminum TB has stainless steel shafts which run through it without any bushings or bearings, and this creates spalling and divergent metals corrosion resulting in increased friction between the shafts and the TB. This results in slow throttle response at idle, and is fixed by removing the TB and oiling the shafts on the outside and inside wherever you see a steel shaft going into the aluminum TB. Usually, that fixes it for a number of years; eventually, the problem will resurface - and re-oiling seems to fix it again for awhile.
In effect, what's happening is that the engine senses the throttle dropping, the Secondary Throttle vacuum valve opens to allow more air to pass the choke plates, and with that additional air coming in, the idle speed goes up. As the idle speed goes up, the vacuum valve closes, the throttle rods rotate to slightly close the Secondary Throttle butterfly valves, and the idle speed goes down, to which the vacuum valve opens up to allow more air in, and the idle speed goes up; (repeat, over and over). The surging of the idle usually has limits, and can ramp up and down quickly from anywhere from 600rpm to 3k rpm or anywhere in between, and as rapidly as peaking every second or two (* like, rrrrRRRRRRRrrrrrrrRRRRRRRRrrrrrrrRRRRRR...)
In the OP's case, it's my belief that when you remove the additional rotating mass of the transmission by pushing the clutch in vs. with the gear lever in neutral and clutch out, it effectively reduces the flywheel effect which is helping to keep the engine idling consistently through driving a heavy weight (the engine rotating parts plus your transmission gears), all of which retains more of the rotational inertia with the clutch out vs. in. It seems to be right at the threshold of what mass your engine likes to have for a nice smooth idle speed.
Also, what exactly do you mean by 'variable resistor'? Is that the Throttle Position Sensor?
In brief, the aluminum TB has stainless steel shafts which run through it without any bushings or bearings, and this creates spalling and divergent metals corrosion resulting in increased friction between the shafts and the TB. This results in slow throttle response at idle, and is fixed by removing the TB and oiling the shafts on the outside and inside wherever you see a steel shaft going into the aluminum TB. Usually, that fixes it for a number of years; eventually, the problem will resurface - and re-oiling seems to fix it again for awhile.
In effect, what's happening is that the engine senses the throttle dropping, the Secondary Throttle vacuum valve opens to allow more air to pass the choke plates, and with that additional air coming in, the idle speed goes up. As the idle speed goes up, the vacuum valve closes, the throttle rods rotate to slightly close the Secondary Throttle butterfly valves, and the idle speed goes down, to which the vacuum valve opens up to allow more air in, and the idle speed goes up; (repeat, over and over). The surging of the idle usually has limits, and can ramp up and down quickly from anywhere from 600rpm to 3k rpm or anywhere in between, and as rapidly as peaking every second or two (* like, rrrrRRRRRRRrrrrrrrRRRRRRRRrrrrrrrRRRRRR...)
In the OP's case, it's my belief that when you remove the additional rotating mass of the transmission by pushing the clutch in vs. with the gear lever in neutral and clutch out, it effectively reduces the flywheel effect which is helping to keep the engine idling consistently through driving a heavy weight (the engine rotating parts plus your transmission gears), all of which retains more of the rotational inertia with the clutch out vs. in. It seems to be right at the threshold of what mass your engine likes to have for a nice smooth idle speed.
Also, what exactly do you mean by 'variable resistor'? Is that the Throttle Position Sensor?
04-08-11, 04:24 PM
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i think this is in the factory manual, but the variable resistor gets adjusted just like the idle mixture screw on a carburetor.
so you basically turn it so that the engine idles the best, if you have to pass smog, go a tad richer. if its maxed out in either direction, its telling you the car still has a problem. all the way rich = vacuum leak all the way lean = bad ACV....
for the surge, i would start with a basic TPS and idle speed adjustment. (mixture too, but covered above) i believe idle speed should be 850rpms so 1000 is high.
once you have the electrics sorted, then the throttle body would be next. like long duck says, the TB gets dirty first, and it does like to stick/be inconsistent, second is that the bores wear. i have actually heard of the TB being rebushed, its very common practise on carburetors.
in the inspection though, push down on the levers, and see what it does. the TB should return to the same place if you open it by hand, and it shouldn't need any additional help to close
the second thing to look at is the switches in the transmission, there are two, and i've have to look to see which switch is which, but the ecu does know if its in neutral or not
so you basically turn it so that the engine idles the best, if you have to pass smog, go a tad richer. if its maxed out in either direction, its telling you the car still has a problem. all the way rich = vacuum leak all the way lean = bad ACV....
for the surge, i would start with a basic TPS and idle speed adjustment. (mixture too, but covered above) i believe idle speed should be 850rpms so 1000 is high.
once you have the electrics sorted, then the throttle body would be next. like long duck says, the TB gets dirty first, and it does like to stick/be inconsistent, second is that the bores wear. i have actually heard of the TB being rebushed, its very common practise on carburetors.
in the inspection though, push down on the levers, and see what it does. the TB should return to the same place if you open it by hand, and it shouldn't need any additional help to close
the second thing to look at is the switches in the transmission, there are two, and i've have to look to see which switch is which, but the ecu does know if its in neutral or not
04-11-11, 03:14 PM
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Thanks for your input everyone. I'll take the throttle body off tomorrow and give it a good cleaning and lubrication. Any recommendation for oil? What about a white lithium grease?
The variable resistor I was mentioning is the little thing attached to the passenger side strut tower. Has a little **** you have to get wax out to access, and then it turns towards richer or leaner. I know that thing has been tampered with, but not by me. Is it worth replacing? In the FSM it says to replace it when the engine is replaced.
The variable resistor I was mentioning is the little thing attached to the passenger side strut tower. Has a little **** you have to get wax out to access, and then it turns towards richer or leaner. I know that thing has been tampered with, but not by me. Is it worth replacing? In the FSM it says to replace it when the engine is replaced.
04-11-11, 03:39 PM
#6
84SE-EGI helpy-helperton
On your first question - any light machine oil will work on the TB rods.
On your second question - Oh, THAT Variable Resistor!
My experience with it has been that it's more akin to a 'fine idle' or 'idle-quality' adjustment, and should be the last thing you mess with when adjusting idle speed. What most -SE owners do is try turning that big, flat-head screw on the top of the Throttle Body thinking that it will adjust the idle speed - and it does - but that's because you're adjusting the air bypass screw which is like a controlled vacuum leak. Same with the variable resistor on the passenger side front wheelwell, and that is an emissions control resistor used to tune the computer for slightly rich or slightly lean running conditions by the manufacturer - hence, why they sealed it with wax so that owners wouldn't mess with it.
The true Idle Speed Adjustment is a tiny silver, flat-head screw without a head just to the right of the Throttle Body that also has a brass lock-nut on it. Most people would overlook this, as it's usually gummed up with road grime and oil, but it's there. When turned, it adjusts how far open the throttle plates are held at idle, which is what really sets idle speed.
To be clear; adjust idle on an SE in this manner;
1) Work with the idle adjustment screw to the right of the Throttle Body and which changes the primary throttle plates - small adjustments press against a stop plate on the primary throttle rod, so this has the largest effect on idle speed.
2) Use the Air Bypass Screw on the top of the TB to make fine adjustments to idle speed and idle quality - hunting revs (up and down) is a sign of a lean mixture; I set mine just so that it stops hunting revs at idle for a smooth idle speed.
3) Use the 'Variable Resistor' to adjust idle quality for rich/lean, as above. It only has about 270 degrees of rotation between Lean and Rich, so I'd put it to the center of the range and then start with #1 and #2, above.
Keep in mind that every time you change one of these variables, it will require tuning of the other 2, and it usually takes me about 30-45min of playing with all 3 of them to get idle where I like it, as smooth as I like it, and without stumbling or rev hunting. Most people give up well before this point, but if you keep at it you can get what you're after.
On your second question - Oh, THAT Variable Resistor!
My experience with it has been that it's more akin to a 'fine idle' or 'idle-quality' adjustment, and should be the last thing you mess with when adjusting idle speed. What most -SE owners do is try turning that big, flat-head screw on the top of the Throttle Body thinking that it will adjust the idle speed - and it does - but that's because you're adjusting the air bypass screw which is like a controlled vacuum leak. Same with the variable resistor on the passenger side front wheelwell, and that is an emissions control resistor used to tune the computer for slightly rich or slightly lean running conditions by the manufacturer - hence, why they sealed it with wax so that owners wouldn't mess with it.
The true Idle Speed Adjustment is a tiny silver, flat-head screw without a head just to the right of the Throttle Body that also has a brass lock-nut on it. Most people would overlook this, as it's usually gummed up with road grime and oil, but it's there. When turned, it adjusts how far open the throttle plates are held at idle, which is what really sets idle speed.
To be clear; adjust idle on an SE in this manner;
1) Work with the idle adjustment screw to the right of the Throttle Body and which changes the primary throttle plates - small adjustments press against a stop plate on the primary throttle rod, so this has the largest effect on idle speed.
2) Use the Air Bypass Screw on the top of the TB to make fine adjustments to idle speed and idle quality - hunting revs (up and down) is a sign of a lean mixture; I set mine just so that it stops hunting revs at idle for a smooth idle speed.
3) Use the 'Variable Resistor' to adjust idle quality for rich/lean, as above. It only has about 270 degrees of rotation between Lean and Rich, so I'd put it to the center of the range and then start with #1 and #2, above.
Keep in mind that every time you change one of these variables, it will require tuning of the other 2, and it usually takes me about 30-45min of playing with all 3 of them to get idle where I like it, as smooth as I like it, and without stumbling or rev hunting. Most people give up well before this point, but if you keep at it you can get what you're after.
Last edited by LongDuck; 04-11-11 at 03:40 PM. Reason: Came back to answer your question (!)
04-11-11, 05:38 PM
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On your first question - any light machine oil will work on the TB rods.
On your second question - Oh, THAT Variable Resistor!
My experience with it has been that it's more akin to a 'fine idle' or 'idle-quality' adjustment, and should be the last thing you mess with when adjusting idle speed. What most -SE owners do is try turning that big, flat-head screw on the top of the Throttle Body thinking that it will adjust the idle speed - and it does - but that's because you're adjusting the air bypass screw which is like a controlled vacuum leak. Same with the variable resistor on the passenger side front wheelwell, and that is an emissions control resistor used to tune the computer for slightly rich or slightly lean running conditions by the manufacturer - hence, why they sealed it with wax so that owners wouldn't mess with it.
The true Idle Speed Adjustment is a tiny silver, flat-head screw without a head just to the right of the Throttle Body that also has a brass lock-nut on it. Most people would overlook this, as it's usually gummed up with road grime and oil, but it's there. When turned, it adjusts how far open the throttle plates are held at idle, which is what really sets idle speed.
To be clear; adjust idle on an SE in this manner;
1) Work with the idle adjustment screw to the right of the Throttle Body and which changes the primary throttle plates - small adjustments press against a stop plate on the primary throttle rod, so this has the largest effect on idle speed.
2) Use the Air Bypass Screw on the top of the TB to make fine adjustments to idle speed and idle quality - hunting revs (up and down) is a sign of a lean mixture; I set mine just so that it stops hunting revs at idle for a smooth idle speed.
3) Use the 'Variable Resistor' to adjust idle quality for rich/lean, as above. It only has about 270 degrees of rotation between Lean and Rich, so I'd put it to the center of the range and then start with #1 and #2, above.
Keep in mind that every time you change one of these variables, it will require tuning of the other 2, and it usually takes me about 30-45min of playing with all 3 of them to get idle where I like it, as smooth as I like it, and without stumbling or rev hunting. Most people give up well before this point, but if you keep at it you can get what you're after.
On your second question - Oh, THAT Variable Resistor!
My experience with it has been that it's more akin to a 'fine idle' or 'idle-quality' adjustment, and should be the last thing you mess with when adjusting idle speed. What most -SE owners do is try turning that big, flat-head screw on the top of the Throttle Body thinking that it will adjust the idle speed - and it does - but that's because you're adjusting the air bypass screw which is like a controlled vacuum leak. Same with the variable resistor on the passenger side front wheelwell, and that is an emissions control resistor used to tune the computer for slightly rich or slightly lean running conditions by the manufacturer - hence, why they sealed it with wax so that owners wouldn't mess with it.
The true Idle Speed Adjustment is a tiny silver, flat-head screw without a head just to the right of the Throttle Body that also has a brass lock-nut on it. Most people would overlook this, as it's usually gummed up with road grime and oil, but it's there. When turned, it adjusts how far open the throttle plates are held at idle, which is what really sets idle speed.
To be clear; adjust idle on an SE in this manner;
1) Work with the idle adjustment screw to the right of the Throttle Body and which changes the primary throttle plates - small adjustments press against a stop plate on the primary throttle rod, so this has the largest effect on idle speed.
2) Use the Air Bypass Screw on the top of the TB to make fine adjustments to idle speed and idle quality - hunting revs (up and down) is a sign of a lean mixture; I set mine just so that it stops hunting revs at idle for a smooth idle speed.
3) Use the 'Variable Resistor' to adjust idle quality for rich/lean, as above. It only has about 270 degrees of rotation between Lean and Rich, so I'd put it to the center of the range and then start with #1 and #2, above.
Keep in mind that every time you change one of these variables, it will require tuning of the other 2, and it usually takes me about 30-45min of playing with all 3 of them to get idle where I like it, as smooth as I like it, and without stumbling or rev hunting. Most people give up well before this point, but if you keep at it you can get what you're after.
also messing with the throttle plate stop screw messes with the TPS.
the variable resistor is just like the idle mixture screw on a carburator.
the shop manual spends a couple pages, and is very clear on this. its here foxed.ca
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12-31-18, 10:22 AM
#8
Junior Member
This is an old thread but I am interested if Tobias ever resolved his problem. I have the exact same issue on my SE. Idle great until coming to a stop, pushing in clutch and as soon as in gear it "hunts".. Exact as Tobias describes at beginning of thread...
12-31-18, 07:07 PM
#10
Junior Member
Thanks for response Kansas... As an update for anyone who is interested, I went out today and while up on lift try to duplicate the issue. Was able to at both cold start and warm up.. I also put the car in 1st while up in air and it also had the hunt there also.. Didnt know that until today due to actually driving the car over summer. Checked my TPS with light and it was off. Turned counterclockwise per manual (both lights lit up) and adjusted. Issue greatly improved. I still got it to hunt maybe 2 times out of say 30 attempts so I think I am on to something here..
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