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1998 Honda Accord LX, 4-door, 2.3L VTEC/4-speed auto. While coasting in 3rd gear at a steady 20 mph, the engine and tach pulse about 100-200 rpms. It only happens when the engine is cold. If I apply the brakes and slow down, or speed up and then coast at a higher speed, it doesn’t happen. Doesn’t happen at all when warmed up. If I put it in neutral while it’s happening, it stops bouncing. No MIL. The tranny is filled with genuine Honda ATF, and it’s properly filled (level is in the hatched area). I don’t think the torque converter is locking and unlocking because both the tach and the engine fluctuate, and it’s not a light jerk as if the converter clutch was engaging. It’s more like a light pulsing, but it is noticeable. I’m doubting it’s the tranny, but then again, what do I know. What could be some other causes/items to check/test? The nuts around the intake manifold (just re-replaced the gasket) are snug, the gasket is properly positioned, and everything is in its place. These problems initially only came up after I finished the head gasket replacement several months back. I made especially sure that all gasket surfaces were SPOTLESS and STRAIGHT, that the valve lash was properly adjusted, and that the head bolts were all properly and sequentially torqued to specs. I also cleaned the throttle body and intake manifold. Sorry for the long-winded explanation, but I hope everything makes sense and I just don’t want to tear random stuff apart that is totally unrelated. Thanks again in advance!
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[quote=”CourierMick” post=158483]1998 Honda Accord LX, 4-door, 2.3L VTEC/4-speed auto. While coasting in 3rd gear at a steady 20 mph, the engine and tach pulse about 100-200 rpms. It only happens when the engine is cold. If I apply the brakes and slow down, or speed up and then coast at a higher speed, it doesn’t happen. Doesn’t happen at all when warmed up. If I put it in neutral while it’s happening, it stops bouncing. No MIL. The tranny is filled with genuine Honda ATF, and it’s properly filled (level is in the hatched area). I don’t think the torque converter is locking and unlocking because both the tach and the engine fluctuate, and it’s not a light jerk as if the converter clutch was engaging. It’s more like a light pulsing, but it is noticeable. I’m doubting it’s the tranny, but then again, what do I know. What could be some other causes/items to check/test? The nuts around the intake manifold (just re-replaced the gasket) are snug, the gasket is properly positioned, and everything is in its place. These problems initially only came up after I finished the head gasket replacement several months back. I made especially sure that all gasket surfaces were SPOTLESS and STRAIGHT, that the valve lash was properly adjusted, and that the head bolts were all properly and sequentially torqued to specs. I also cleaned the throttle body and intake manifold. Sorry for the long-winded explanation, but I hope everything makes sense and I just don’t want to tear random stuff apart that is totally unrelated. Thanks again in advance![/quote]
Sounds like to me like a transmission issue. Let me find a FSM and a flow chart for transmission issues.
Alright so I have a very probable cause: brake switch intermittent failure OR an issue with wiring. The reason: that speed is when the torque converter locks up, and if you tap the brakes it disengages. That’s my best guess.
Automatic transmission section of FSM which applies to torque converter lock up is 14-17
FSM: http://www.gvrdeu.org/Honda%20FSM/Accord/1998-2002%20Accord%20FSM/1998-2002%20Honda%20Accord%20SM.pdfModerators, dunno if I can post a link, if not sorry!
I don’t think it’s a transmission issue based on your description. Just to be sure though, are you checking the transmission fluid level with the vehicle running or off? It should be off. If not, it’s likely overfilled.
If you don’t have a D4 light flashing, it’s not likely a transmission problem.
Since this occurred after your cylinder head removal. I’d suspect something with the work you had done. It could either be something that’s not plugged in correctly, something misadjusted (never attempt to adjust the idle screw. It’s sealed for a reason), or perhaps a vacuum leak. Don’t assume you don’t have one, check for them first. I cover that, and other details about solving problems of this type here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Good luck and please keep us updated on your progress
[quote=”EricTheCarGuy” post=158541]I don’t think it’s a transmission issue based on your description. Just to be sure though, are you checking the transmission fluid level with the vehicle running or off? It should be off. If not, it’s likely overfilled.
If you don’t have a D4 light flashing, it’s not likely a transmission problem.
Since this occurred after your cylinder head removal. I’d suspect something with the work you had done. It could either be something that’s not plugged in correctly, something misadjusted (never attempt to adjust the idle screw. It’s sealed for a reason), or perhaps a vacuum leak. Don’t assume you don’t have one, check for them first. I cover that, and other details about solving problems of this type here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Good luck and please keep us updated on your progress[/quote]
I would listen to Eric’s opinion over mine here, but I gotta ask Eric, what makes you think this is not a transmission issue? Have you ever seen the torque converter lock up feature being intermittent at lower speeds? I haven’t ever owned an automatic so I haven’t seen it first hand, my recommendation was from the FSM and an online forum that mentioned a probable cause.
Asking because I want to learn, no offense.[quote=”EricTheCarGuy” post=158541]I don’t think it’s a transmission issue based on your description. Just to be sure though, are you checking the transmission fluid level with the vehicle running or off? It should be off. If not, it’s likely overfilled.
If you don’t have a D4 light flashing, it’s not likely a transmission problem.
Since this occurred after your cylinder head removal. I’d suspect something with the work you had done. It could either be something that’s not plugged in correctly, something misadjusted (never attempt to adjust the idle screw. It’s sealed for a reason), or perhaps a vacuum leak. Don’t assume you don’t have one, check for them first. I cover that, and other details about solving problems of this type here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Good luck and please keep us updated on your progress[/quote]
Eric, I’m checking the fluid level when it’s hot and immediately (or very shortly) after shutting the engine off after a drive.
I do have a P0420 code, which indicates the cat. Could a dirty cat possibly cause something like this? I’m just throwing possibilities out there, see what you think.
I’ll check for more vacuum leaks, but I honestly hope there isn’t. It’s weird because it only happens when cold.
And not sure if it’s related, but there’s another weird quirk going on. While driving down the highway at about 55, I will get a random vibration (think of your smartphone vibrating x3) that just comes out of nowhere. It will last a few seconds and then go away, only to reappear a couple of days or even a couple of weeks later. It’s very sporadic. The struts, ball joints, and tires are all brand new.
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