I recently bought a 93 CB7 with its stock F22A1 engine. The car has 225 000 Km (140 000 mi) and was well maintained. The main issue I have with the car is its rough idle. Once the engine is warm, it idles rough at around 600-650 rpm. There are no other mechanical issues with the car and this problem does not affect performance. It is annoying though. Spark plugs are in good shape and I changed the distributor and the wires recently. Does anyone know were to start looking?

 

If you haven't replaced the oxygen sensor you should swap that out first with a Denso unit. Even if it doesn't fix it, it's good maintenance.

 

EGR ports probably need cleaning...

 

The only thing that I can think of is timing?

I used to have a car that did that but it would drive just fine, I adjusted the timing and it was perfect.

Also, The O2 sensor sounds good, I would hook up a scanner and see what the Air Fuel Ratio is reading.

 

The egr system works between 1500-3000 rpms so unless his car is somehow idling higher than 1500 it's not the egr.

 

How do you figure it has nothing to do with the EGR system when OP stated that his idle is rough at lower RPM's and majority of searches about rough idle point toward the EGR valve or ports gunked with carbon? That's exactly what mine was doing and when I cleaned my EGR ports, car ran and idled normal again. "Somehow idling higher than 1500"....you say that like this doesn't happen either. They do idle that high and that's most likely going to be the IACV. Ask me how I know.

 

When a car starts up from cold the egr is completely and totally turned off. The ecu won't turn the egr on until the engine is warmed up. The car never idles higher than 1000 at the highest unless the engine is cold and the fitv is working which is when the egr is off.

Furthermore...

...Not only does he state it happens during idle but he actually states that there are no performance issues whatsoever.

Case closed.

 

I had a similar issue on my 92 and tightening up the slack in the throttle cable fixed it for me. It's the two bolts right under the PGMFI.

 

Oh boy....case closed, huh? I can't win against the residential "expert".

 

OP, I can't tell you exactly what your issue is, but I can tell you my personal experience and what I did to resolve it. Your issue sounds close to what was going on with my Accord and cleaning the EGR ports (almost fully clogged closed, BTW) fixed my rough idle.

Good luck to you.

 

EGR is actuated by positive crank pressure, and has nothing to do with the car being warm or not.

Clean your EGR, it is the most common cause.

 

That post belongs in a Toyota forum not a Honda forum. Honda's don't even use vacuum modulators to begin with.

 

Here's a rough draft of how egr works.

http://en.wikipedia.org/wiki/Exhaust_gas_recirculation
On hondas, egr is ONLY used during 1500-3000 rpms. If you want me to document this lemme know. I'll find it somewhere if you don't want to find it for yourself.

If the egr valve was in fact stuck open it would stall the car immediately. Test it by opening the valve manually with your fingers.

 

Indeed. I have no idea what I was thinking when I posted that ... actually I do, I was thinking EGR is controlled by vacuum, and then it got all tangled with PCV and to much rum.

Regardless, the EGR needs to be cleaned.

 

On some cars it is controlled by vacuum(toyotas)..but on Honda's it's controlled by the ecu.

 

Right, and you expect anyone to take you serious when you're quoting wikipedia?!?!

Yes, post up some documentation so we can all put this to rest, EGR guru.

Please tell me my rough idle solution of cleaning my EGR ports was just a coincidence too....

 

no point in posting anything else ... u cant correct a scoffer

 

Yet...you did. Prime example of douchebaggery.

You can't argue with a self absorbed know-it-all either. You're a clown.

 

I will start by cleaning out the EGR and see if that fixes it. If not I will try the other solutions offered. Thanks everyone for the help.