h2omusc

I have a 93 Accord 10th Anniv edition with almost 200K mi. When I am on the interstate at 60 mph the rpm are generally 2600. But sometimes it will jump up to 2900 rpm then back to 2600 and go back and forth for a few seconds and then its fine. This typically only happens once or twice a day.

This is seems to be a minor problem since the car seems to be running great but I am curious. My ideas would be maybe an ECM issue or the torque converter slipping (if a 93 has one).

MAD_MIKE

Start with looking for any stored codes. Does your CEL/D4 light turn on when the key is turned to II(ON)? If so, look for the two wire blue connector behind the passenger kick panel. Jumper it with a wire and turn the key to II(ON) and look for blinking CEL/D4 light, record any codes.

Warm the engine up to operating temp, charge all gears for 5-10 seconds(P-D1), leave engine running. Pull trans dipstick, wipe clean reinsert, pull out, check where the level is. It should be within, preferably midway, the hash mark. If the fluid is low or on the low end of the hash mark, the trans may be starving of fluid and dropping out of lockup for a few moments as the pressure builds back up.

When the jump in rpms occur do any other dash lights/gauges do anything? Does the speedometer jump? If you have cruise control, does the rpm still fluctuate with cruise set?

Verify the battery connections are clean and tight.
Verify the battery has a full charge.
Verify the throttle valve cable from the TB to the trans is correctly adjusted. There should be no tension nor should there be any slack.
Check the condition of the converter lockup solenoid, and it's electrical connection for any corrosion. This will be the higher pair of solenoids. With the car off, unhook the wire connector to the solenoids. Using a jumper wire, directly power the solenoid. Does the solenoid operate with a distinct 'click'? If yes remove the solenoid and check the filter screen, it should be free and clear of debris.

h2omusc

No codes. Tranny fluid OK. The rpms do fluctuate when the cruise (and when it is off), it is very random. I don't see any other lights and the speedometer remains constant. The only thing I notice is the tachometer and the sound. It almost sounds like it is downshifting but it isn't because if I manually shift down to D3 it goes up to almost 4000 rpm.

I don't think it's the battery, I just changed the terminals. I'll have to look into the solenoid stuff you mentioned. In the past I had trouble starting occasionally and had code 1 but haven't had any problem since I changed the main relay.

holmesnmanny

Assuming there is no actual change in the engine rpms, just the gauge moving, it could just be the solder joints in the tachometer are going out. If the rpms are changing and you can feel it in the engine then it's possible the ignition control module is acting up. You could pull another from the junkyard and see if that fixes it.

MAD_MIKE

Verify the battery is holding a full charge.

If the change in rpm is only a couple hundred rpm then it most likely is a function of the lockup clutch in the TC. Check your lockup solenoid, and wiring to the solenoid.

If the throttle valve cable is adjusted too tight, throttle input may be sensitive and cause undesired locking/unlocking of the TC.

The way the lockup functions is dependent on a few things.
No lockup occurs with Sol A OFF and Sol B Off
A partial lockup occurs with Sol A On and Sol B Off
A 'half' lockup occurs with Sol A On and Sol B On
Full Lockup occurs with Sol A On and Sol B On along with full pressure built up in the lockup circuit to actuate the lockup timing and lockup control valves. This final full lockup is related to speed.

During deceleration Sol B switches from on-off for smooth deceleration.
TCU relies on the VSS on when to command a downshift. If the VSS is dirty or worn it may cause some down shift issues.
http://techauto.awardspace.com/vss.html

If you have not changed the fluid, try changing it and adding some cleaner such as TRANS TUNE from SeaFoam. If there is any varnish/crud/goo that is interfering with correct operation of the various accumulator valves, this cleaner should aid in unsticking them.

kevinhughes13

Mine does the same exact thing as you describe. I have a 1990 HONDA ACCORD LX F22A1 208k AUTO doesn't really bother me much but obviously it uses more gas and the engine is working harder then it should when it happens. Hopefully we can both find a fix on here. Is yours a auto too? What engine is in the 10th anniversary?

h2omusc

holmes: I can hear the engine revving, it's not just the tachometer

kevin: Mine is an automatic and has a 2.2L L4 engine.

Mike: Thanks for the tips, I'll look into it, but it may be a little while till I get around to it since the problem doesn't appear serious. If I find more out I'll post about it.

MAD_MIKE

Doesn't look like I mentioned to backprobe the TPS.
If it is worn/has a bad spot, this will affect shift/shifting as well.

h2omusc

I finally got around to testing the lockup solenoids. They appear to be fine, they both make clicks and spark, but I've never done this before and don't have anything to compare it too.

I've also noticed the car tends have the problem more often when I'm on bumpy roads with lots of cracks. It's usually fine when I'm on newer smooth roads. I guess that would lead me to believe it's a loose connection somewhere.

You also mentioned the throttle valve cable. That looks pretty tight but if that's the problem wouldn't the vehicle surge in speed slightly along with the rpms going up?

MAD_MIKE

Check for corrosion at the connectors, follow the wiring back up into the main harness look for kinks, abrasion, past repairs etc.

kevinhughes13

Did any of you actually figure this out? I am still having this problem please post if you did figure it out.

h2omusc

Sorry but no I haven't figured this out. It doesn't happen too often and it's a minor problem so it's not a high enough priority for me to keep digging with the other stuff going on in my life. I'll get back around to it I suppose at some point and if I find anything out I'll post it.

ZDOG2KXX

I have a 1990 Honda Accord EX With an A4 engine Auto.The car has been idle hunting and jumping up and down 100-150 rpms when I start to drive without the car warming up, and I can hear it. Is this normal? it stops after a couple minutes of driving, then the gauge only wiggles and is inaudible.

MAD_MIKE

Top of the forum, Accord FAQ, look for how to clean and adjust IAC and FITV thread.