89 Honda civic dx

My civic is automatic and my problem is that when the motor is hot and you
come to red light and stop. When the is in any gear except for park or
neutral the rpm drop down to about 250 and the shake really bad. I have
chage the pcv and the o2 senor. But this problem is still thier. I have
checked all vacuum hoses and they look fine. anyone have any ideas as to
what is wrong here.

 

any codes on the computer? timing belt changed recently?

things to check:
ignition system, plugs, leads, distributor cap, etc.
idle air control valve.
ignition timing/valve timing - if the belt skips, a common thing if the
belt was done by someone who doesn't know how to tension properly, both
valve and ignition timing will be messed up with the symptoms you describe.

also run injector cleaner through it.

 

If it's only doing it when hot, I'd still suspect a vacuum leak, possibly in a
diaphragm. I had a leaky vacuum-advance diaphragm on my carbed '87 Accord that
was causing weird problems and was really hard to track down because it didn't
make any noise when leaking - I only discovered it when I pinched off the hose
and the idle smoothed out. Try going through your vacuum lines and pinch them
off - GENTLY - one at a time, starting at the carb/manifold and working outward.

On a newer car I might suspect low coolant or bad coolant temp sensor, but I
don't think a car that old (ODB-I) relies that heavily on that sensor input.

 

89 civic is all electronic - no diaphragm.

obd0 - and it relies heavily on sensor input!

 

I didn't mean that one SPECIFICALLY, I was just using that as an example... a
vacuum leak could still be in another diaphragm, where it's not audible.

Read carefully: "...relies heavily on THAT sensor input".

Newer cars can suffer poor running if the coolant-temp sensor is giving them
incorrect data because the temp figures heavily into things. In an '89, I doubt
it's used quite so much.

 

no, they use it the same. there's not much difference between obd0 and
obd1, other than transition to a broadband oxygen sensor.

 

I have an 89 hatchback but with a 4 speed.It get the shakes when more
electric is drawn using the head light ,or the heater fan.Just the added
load of the demand on the alternator,slows the idle down and it shakes.But
it has always done this.