Engine idling high/low/high/low aka rpm hunting. Please advise.
01-27-15, 08:18 AM
#31
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Hi, I'm bumping this thread and still seeking a solution. The original post is updated showing all I've done to date to find a solution.
Thank you.
Thank you.
01-27-15, 08:48 AM
#32
I haven't re-read the thread, and I don't recall what my previous comment was that I'm subscribed for, but a quick glance at the first post makes me think some combination of your throttle and A/T cables are at least partially to blame.
The "seeking" clunk around 45 mph sounds like what I had when I thought the throttle plate was being sucked close from a bad throttle stop screw adjustment, but I believe it was actually the A/T cable being over-tightened and creating an awkward up/down shift right around 55 mph while cruising. I've tweaked so many things, it's tough to remember exactly what did what.
The weird idle stuff could be throttle cable related, although I would think that would be steady not erratic...unless the IACV is trying to correct for it.
The "seeking" clunk around 45 mph sounds like what I had when I thought the throttle plate was being sucked close from a bad throttle stop screw adjustment, but I believe it was actually the A/T cable being over-tightened and creating an awkward up/down shift right around 55 mph while cruising. I've tweaked so many things, it's tough to remember exactly what did what.
The weird idle stuff could be throttle cable related, although I would think that would be steady not erratic...unless the IACV is trying to correct for it.
11-03-15, 07:37 AM
#33
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I also added this update to the original post.
BTW, t2d2's comment echoes what I eventually figured out about the throttle cable. A very small adjustment did help with the idle rpm. That does NOT solve the revving, but may be very helpful when resetting the ECU as outlined below.
Another update:
I see there have been over 2500 views of this post. So, obviously, this garnered interest and is likely an issues for other forum members.
I can only conclude the following to help others:
1) The ECU is/was the likely culprit causing the revving issue.
2) Although the ECU was rebuilt, I may not have "re-set" it properly. Someone told me that you must not only disconnect the
battery, but you must wait 20 minutes. THEN, with the positive connected, you must "tap" the negative post connector to the negative
battery post lightly a couple of times. He said that's the only real way to properly re-set the ECU. All I know is that I did this and it DID
make a difference. The revving stopped. The car ran like crap for several miles as the ECU was likely re-interpreting the new data while
I was driving. But, it worked!
3) I also made a very minor adjustment to the throttle cable because I found the idle to be a bit too low. I may have moved it the width
of a nickel, but that's all it took.
I hope this is helpful to someone else down the road.
BTW, t2d2's comment echoes what I eventually figured out about the throttle cable. A very small adjustment did help with the idle rpm. That does NOT solve the revving, but may be very helpful when resetting the ECU as outlined below.
Another update:
I see there have been over 2500 views of this post. So, obviously, this garnered interest and is likely an issues for other forum members.
I can only conclude the following to help others:
1) The ECU is/was the likely culprit causing the revving issue.
2) Although the ECU was rebuilt, I may not have "re-set" it properly. Someone told me that you must not only disconnect the
battery, but you must wait 20 minutes. THEN, with the positive connected, you must "tap" the negative post connector to the negative
battery post lightly a couple of times. He said that's the only real way to properly re-set the ECU. All I know is that I did this and it DID
make a difference. The revving stopped. The car ran like crap for several miles as the ECU was likely re-interpreting the new data while
I was driving. But, it worked!
3) I also made a very minor adjustment to the throttle cable because I found the idle to be a bit too low. I may have moved it the width
of a nickel, but that's all it took.
I hope this is helpful to someone else down the road.
11-06-15, 12:06 PM
#34
My car had this same issue last night. I own a '95 SC300 manual, and after a 1.5 hour commute, the revs started bouncing up and down when I got home. I shut her down and attempted to start it back up. It would crank over, but the revs continued to bounce up and down. Of course I lost sleep and couldn't wait to try it again this morning. I started the car which seemed to have a normal idle. I let the car warm up to a normal operating temperature, and all is well. I'm thinking about starting at the TB and IACV this weekend, and search for a small vacuum leak that might be developing. The ECU issue has crossed my mind, and I could kick myself because I owned a spare unit several years ago and sold it to another member.
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