Revving/Deceleration causing rpm issue
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B*a*n*n*e*d
Joined: Nov 2008
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Revving/Deceleration causing rpm issue
Vehicle: 95 Accord Ex, Vtec, AT, Cruise Control
When I leave off the throttle after revving the engine to any rpm, it does not return to the idle it was at (750 rpm). It is not a wild surging idle, but more milder, and the rpm range is close together. For example, suppose I raise the idle to 1,500 rpm, sometimes it drops to 1,000 and then back to 750, while other times it takes longer to get back to 750 if at all. Also, shutting it off and restarting puts it back to normal.
But if I start the vehicle from cold and just let it idle on its own, it is fine, and it purrs with a nice steady rpm at around 750.
I have not had this problem for long, so that is all the info I have. There is no check engine light or fault codes (MIL). I was going to run a propane test for a vacuum leak, but then realized that would be a waste of time and effort because the idle is ok before I touch the gas pedal. I read where the FIA, IAR, and EGR solenoid valves all operate at higher rpms. All 3 tested ok.
It kind of seems to be either a Throttle Body problem of some sort, or a part that can trigger the MIL, that is ok electronically, but perhaps failing mechanically, as OBDI is known for. At least that is normal for European vehicles, not sure if Hondas do that. Is it possible for the cooling system to have an air lock and still idle ok, but then show up as surging when you touch the gas pedal to raise the rpms?
Btw, I previously checked, tested, repaired, replaced, cleaned, or adjusted: all kinds of electronic, vacuum, and mechanical stuff. All the basics and much more. Cleared the ecu memory.
When I leave off the throttle after revving the engine to any rpm, it does not return to the idle it was at (750 rpm). It is not a wild surging idle, but more milder, and the rpm range is close together. For example, suppose I raise the idle to 1,500 rpm, sometimes it drops to 1,000 and then back to 750, while other times it takes longer to get back to 750 if at all. Also, shutting it off and restarting puts it back to normal.
But if I start the vehicle from cold and just let it idle on its own, it is fine, and it purrs with a nice steady rpm at around 750.
I have not had this problem for long, so that is all the info I have. There is no check engine light or fault codes (MIL). I was going to run a propane test for a vacuum leak, but then realized that would be a waste of time and effort because the idle is ok before I touch the gas pedal. I read where the FIA, IAR, and EGR solenoid valves all operate at higher rpms. All 3 tested ok.
It kind of seems to be either a Throttle Body problem of some sort, or a part that can trigger the MIL, that is ok electronically, but perhaps failing mechanically, as OBDI is known for. At least that is normal for European vehicles, not sure if Hondas do that. Is it possible for the cooling system to have an air lock and still idle ok, but then show up as surging when you touch the gas pedal to raise the rpms?
Btw, I previously checked, tested, repaired, replaced, cleaned, or adjusted: all kinds of electronic, vacuum, and mechanical stuff. All the basics and much more. Cleared the ecu memory.
Last edited by AtoZ; Oct 23, 2009 at 07:24 AM. Reason: typos, grammar, shortening text
Junior Member
Joined: Nov 2008
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Re: Revving/Deceleration causing rpm issue
I've been having issues with my air boost valve causing idle issues. You may want to look into that.
Using propane for a vacuum leak test wont cuse any problems with your idle if there is a leak or not. It should raise your idle a bit if there is a leak, but will return to normal.
Using propane for a vacuum leak test wont cuse any problems with your idle if there is a leak or not. It should raise your idle a bit if there is a leak, but will return to normal.
Thread Starter
B*a*n*n*e*d
Joined: Nov 2008
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Re: Revving/Deceleration causing rpm issue
I've been having issues with my air boost valve causing idle issues. You may want to look into that.
Using propane for a vacuum leak test wont cuse any problems with your idle if there is a leak or not. It should raise your idle a bit if there is a leak, but will return to normal.
Using propane for a vacuum leak test wont cuse any problems with your idle if there is a leak or not. It should raise your idle a bit if there is a leak, but will return to normal.
Oh about the propane test. I will have to edit my post to clarify what I meant. I didnt mean to suggest that the propane would cause a problem. I meant that I did not see any reason to try a propane the test because the idle is ok, and the test would be a waste of time. The problem I have happens when I touch the gas pedal a little bit, and then release the pedal. RPM moves around up and down slowly in a narrow range.
Last edited by AtoZ; Feb 10, 2009 at 09:05 AM.
Honda-Tech Member
Joined: Jan 2004
Posts: 6,456
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From: New England, USA
Re: Revving/Deceleration causing rpm issue
Vehicle: 95 Accord Ex, Vtec, AT, Cruise Control
When I leave off the throttle after revving the engine to any rpm, it does not return to the idle it was at (750 rpm). It is not a wild surging idle, but more milder, and the rpm range is close together. For example, suppose I raise the idle to 1,500 rpm, sometimes it drops to 1,000 and then back to 750, while other times it takes longer to get back to 750 if at all. Also, shutting it off and restarting puts it back to normal, but I dont think of this as an idle problem.
But if I start the vehicle from cold and just let it idle on its own, it is fine, and it purrs with a nice steady rpm at around 750. .
I have not had this problem for long as I prefer to fix things immediately, so that is all the info I have. There is no check engine light or fault codes (MIL). I was going to run a propane test for a vacuum leak, but then realized that my idle would also be messed up and the idle is fine, at least before I touch the gas pedal. Also, I read where the FIA, IAR, and EGR solenoid valves all operate at higher rpms, so, I did not bother to test them all, but I did test the IAR out of curiosity at idle speed, and there is no vacuum, so I am not about to check those other two.
The only thing that makes any sense to me is that a part that can trigger the MIL is a part that is ok electrically, but perhaps failing mechanically, as OBDI is known for. At least that is normal for European vehicles, not sure if Hondas do that.
Btw, here is what I previously fixed, replaced, cleaned, or adjusted:
Been fixin an 95 Ex up for awhile now part time as I could get to it. Replaced all the basics with new parts: NGK plugs, Air filter, cap and rotor, wires, exhaust system, various new gaskets, cleaned and adj the FITV cleaned the IACV, cleaned TB, new OE stat, cleaned the Trans and Vtec solenoid screens out, checked the Alt brushes, new rad, all hoses and wiring in good condition, fans work [albeit, not for long, 15 seconds max @ idle], cleaned all electrical connections, cleaned sensors, and EGR valve, all new fluids. Clearedr ECU memory and let fans come on twice without touching the gas pedal or anything else.
When I leave off the throttle after revving the engine to any rpm, it does not return to the idle it was at (750 rpm). It is not a wild surging idle, but more milder, and the rpm range is close together. For example, suppose I raise the idle to 1,500 rpm, sometimes it drops to 1,000 and then back to 750, while other times it takes longer to get back to 750 if at all. Also, shutting it off and restarting puts it back to normal, but I dont think of this as an idle problem.
But if I start the vehicle from cold and just let it idle on its own, it is fine, and it purrs with a nice steady rpm at around 750. .
I have not had this problem for long as I prefer to fix things immediately, so that is all the info I have. There is no check engine light or fault codes (MIL). I was going to run a propane test for a vacuum leak, but then realized that my idle would also be messed up and the idle is fine, at least before I touch the gas pedal. Also, I read where the FIA, IAR, and EGR solenoid valves all operate at higher rpms, so, I did not bother to test them all, but I did test the IAR out of curiosity at idle speed, and there is no vacuum, so I am not about to check those other two.
The only thing that makes any sense to me is that a part that can trigger the MIL is a part that is ok electrically, but perhaps failing mechanically, as OBDI is known for. At least that is normal for European vehicles, not sure if Hondas do that.
Btw, here is what I previously fixed, replaced, cleaned, or adjusted:
Been fixin an 95 Ex up for awhile now part time as I could get to it. Replaced all the basics with new parts: NGK plugs, Air filter, cap and rotor, wires, exhaust system, various new gaskets, cleaned and adj the FITV cleaned the IACV, cleaned TB, new OE stat, cleaned the Trans and Vtec solenoid screens out, checked the Alt brushes, new rad, all hoses and wiring in good condition, fans work [albeit, not for long, 15 seconds max @ idle], cleaned all electrical connections, cleaned sensors, and EGR valve, all new fluids. Clearedr ECU memory and let fans come on twice without touching the gas pedal or anything else.
If the throttle plate should stick partially open, the IACV will 'hunt'; trying to maintain the proper idle speed. This could be made worst by a worm pindle valve (the plunger tip that regulates air flow through the Throttle Body idle circuits)
Thread Starter
B*a*n*n*e*d
Joined: Nov 2008
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Re: Revving/Deceleration causing rpm issue
Look for anything which will keep the throttle plate from consistantly closing ... If the throttle plate should stick partially open, the IACV will 'hunt'; trying to maintain the proper idle speed. This could be made worst by a worm pindle valve (the plunger tip that regulates air flow through the Throttle Body idle circuits)
Honda-Tech Member
Joined: Jan 2004
Posts: 6,456
Likes: 10
From: New England, USA
Re: Revving/Deceleration causing rpm issue
Is it ok to totally remove that fat black rubber air intake tubing before I start the engine, for the purpose of observing what that throttle plate is doing, while I have an assistant touch the gas pedal? Not sure if taking that tubing off would cause any additional problems.
Just mark off a 'safety zone: around the inlet. You don't want low flying birds, neckties and important papers being ingested. GOD knows you don't want to end up in the Hudson.....
Thread Starter
B*a*n*n*e*d
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Re: Revving/Deceleration causing rpm issue
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