Hi guy's

We have a 1990 Honda Integra and for some reason when were changing between gears as your driving, the revs drop too slow? they aren't dropping fast enough for the gear change?

So if i rev to say 3000RPM when i clutch to go up to next gear iv'e nearly got to wait about 3secs before the idle will drop back down to an acceptable level for the change.

 

Do you have a lightened flywheel?

 

No car is stock

 

I don't understand the question, when you clutch in the engine isn't even connected to the transmission anymore so it's RPM should not affect gear changes.

 

Too slow? Clutch not fully disconnecting its self?

 

The revs are not returning to an acceptable level to change into the next gear

So for instance when i rev to 3000RPM and then go to change to another gear the revs stay at 3000RPM for way too long, i have to wait for the revs to drop before changing into next gear.

 

Sounds like a clutch/flywheel issue

 

CMC/CSC/pressure plate related we can bash the heavy flywheel all day but it's extremely rare something would go wrong with the flywheel to cause this.

 

Good point! check the CMC/CSC! your CSC might need to be replaced or lubed with grease.. or your really low on fluid or have air in the line.

sounds like the clutch is not engaging.

 

No i don't think you's are reading the post properly

Your in the car and about to take off down the road
you change from 1st to 2nd with RPM at 3000RPM, you push clutch in to go for second gear but RPM"S are still at 3000RPM, and take about 4-5 seconds for revs to drop enough so you can change into second.

Next you got to change from 2nd to 3rd gear with RPM's at 3000RPM, then again you have to wait 4-5 sec's for revs to drop enough before you can select the gear,

Next you go from 3rd to 4th and once again your waiting 4-5 secs for revs to return to an acceptable level so you change into 4th.

There is no clutch issues!

Understand now?

 

lol ok...

 

lol do you even know what the only part that connects the engine to the input shaft is, wait for it.... the clutch! the flywheel doesn't reach the input shaft save from where it rests on the pilot bearing. It's your pressure plate or the hydraulic system, if you really think it's non of those. changer the cluster since you KNOW it's not the clutch/system why even make a thread.

 

The OP has a 1990 integra. They didn't come with a hydraulic clutch, they use a cable system so any mention of a cmc/csc is irrelevant. I guess it's a possibility that the cable could be misadjusted (too loose) but based on the info he's provided it doesn't sound like the most plausible scenario.

On the 90-91 intake manifolds there are extra parts that honda did away with for all the subsequent B series models. Those parts are the air boost valve and dashpot valve and their purpose was to cause the rpms to drop more slowly during release of throttle conditions (ie: shifting). Although it's not very common that they fail it's definitely the first place I would start troubleshooting a condition like this. They basically create a mechanically controlled vacuum leak which keeps the rpms up briefly with the throttle plate closed.

If those check out ok, I'd remove the intake and visually verify that the throttle cable is fully closing quickly as it's supposed to. A weak throttle return spring could possibly cause this issue but I find it less likely than the dashpot/air boost failure.

OP, if you are at idle and rev the engine up to 3k does it create the same delayed rpm drop or is it only while driving?

 

no it seems to return reasonably fast if you rev from idle but returns slow when driving

 

Did you buy the car with the current symptoms or did they start suddenly out of the blue, immediately after a repair, or progressively became a problem?

When you rev it at idle and let rpms drop are you doing it in nuetral or in gear with foot on the clutch? If it was a dashpot/air boost/throttle spring problem it shouldn't matter if you were shifting between gears or revving at idle, it would hang up and drop slowly regardless so now that sounds more unlikely.

How is your clutch pedal engagement/disengagement? Right at the floor? Near the top?

 

Is this happening only while driving and changing gears? Or at stand-still as well?

From what I understand, the accelerator is not coming back to its idle position quickly. If I understood it correctly, check if the accelerator wire is freely able to move till the intake. Also check if the spring on the intake has not lost any tension (what rollinmyda has also indicated).

 

The throttle dashpot check-valve is defective and is not bleeding-off vacuum as quickly as it should. This has the effect of holding the throttle open too long.

It's #18 in this diagram:


To test my hypothesis, temporarily remove the valve from the system and see if the problem goes away.

 

That's exactly what I was thinking until he said that it dropped quickly when revved at idle.

Where you at OP?

 

He didn't say "quickly", he said "reasonably fast". This may or may not be a perceptual thing: When there's no urgency to get into the next gear, the lack of idle-drop may not feel as bad.

Anyway, it would cost the OP exactly zero to remove the valve from the system temporarily. If that doesn't help, he'll know right away and can then look for other culprits.

 

^ Good point

 

I'm thinking either the ICV is keeping the engine from dropping to idle, or possibly the throttle plate is dirty and leaking, or some other idle related issues. What happens if you rev it out to 5K+, does it still take too long to drop?