Engine Mechanical problem
1995 Acura Legend 6 cyl Two Wheel Drive Automatic 100000 miles
My car is driving me crazy. Upon startup, idle is at normal range (~650rpm). However after accelerating in any drive gear the RPMs will not return to their normal idle position. They tend to come to rest at 1100-1500rpm. This creates the following scenario; you’re driving down a road, you decide to take your foot OFF of the accelerator the engine speed drops, but stays high, causing the car to continue accelerating (1100-1500rpm). This does NOT occur in the Park or Neutral gears.
Things I have inspected so far;
1) Idle adjustment screw set too high- This is not the problem, I calibrated this when the car was previously in working condition- and it normally (when not malfunctioning) rests at ~650rpm.
2) Throttle Body sticking, doesn't seem to be the problem, removed it to clean and test the TPS (Throttle Angle/position) sensor as well.
3) EAVC (Electronic Air Control Valve) sticking or malfunctioning. Initially I thought this was the problem; there is NO check engine light however. Swapped EAVC with known working EAVC problem continues.
4) Fast Idle Valve. According to the test in the helm (Acura shop manual) it is functioning this part was replaced with a dealer part less than 5months ago to fix the SAME problem in the past... But now the problem is back, passes test that failed last time; the test basically consists of checking for suction (when cold) on one of the hoses leading to the Fast Idle Valve, when it failed 5months ago suction was occurring, replaced problem went away. Now it’s back, but this time it is not failing this test. For peace of mind, I replaced it with another Fast Idle valve and the problem continues…
5) Replaced the ECU, I swapped the ECU with another for testing purposes, no change.
6) Purged the cooling system again with heater set to full and car at normal operating temp, no change.
7) Inspected throttle/cruise cables, seem fine- even disconnected them and re-set them.
8 ) PCV acts fine per helm instructions
don’t see any damaged hoses...although I find this hard to test there are many hoses…
I took an actual video of the problem which can be viewed here:
Direct link to video:
In the video you can see in Neutral/Park I can rev/accelerate and the rpms return to their normal range. In Drive/Reverse they do not after an acceleration (occurs 80% of the time). I'm only holding the brake in the video because I didn't want to smash into my garage door :) The problem occurs regardless if any pressure is applied to the brake.
Your problem is related to vacumn leakages and I would suggest you check the Air Boost Valve for internal leakages.
September, 10, 2008 AT 3:30 PM
I happen to have another of the same car, so I will swap those two to see if there is any change.
Also, I noticed something odd today- The idle only gets stuck in the Drive Gears (not in Park or Neutral). But today I disconnected the EAVC valve electric plug.
I noticed when I do this, the idle will also get stuck around the same range in PARK and Neutral - which normally does not happen if the EAVC is plugged in.
Could this just be a side effect of not having the EAVC plugged in; or maybe another indicator in the right direction?
Please note; I already swapped the EAVC with another known working one.
September, 10, 2008 AT 8:25 PM
I just swapped the entire air boost valve and no change occured. Problem persists.
September, 11, 2008 AT 7:39 AM
I don't believe it is from the EACV. A vacumn somewhere is leaking or not returning after operating.
Apart from all those you have checked there is one more vacumn valve you should check but I do not know if your vehicle is equipped.
Air Suction Valve at end of intake manifold. Try to vacumn test all vacumns for diaphragm leakage.