I have a 94 ex with a b18a1 swap. 5spd. PR-4 ecu. When I unplug the map sensor plug, the rpm shoot up to about 1800 rpm. Is this right? I am trying to find the culprit of an idle issue. Car runs fine other then the idle dropping real low before comming back up to where its supposed to be. Done all the iacv cleaning and adjusted fitv. When I cover the fitv hole in the throttle body I get no change and same with the iacv hole. Rpms drop but still surge a little and still does the idle drop thing. Anyway, just trying to cover some questions you guys may have.

 

Forgot to mention. No cels unless I unplug the map sensor of course.

 

so no one has ever done this?????

 

Have you tried unplugging your IACV when the car is idling?

 

I just did that. It dropped the rpm but the slight flux was still there and also if i rev it up even a little it drops like its gonna die but doesn't. This also happens when driving. Push in the clutch at a stop and it will drop and pick back up.

 

Ok. So...
Unplug iacv- idle drops a bit but still surges just a little like it normally does and still does the rpm drop thing.

Map sensor- unplug and idle goes up to 1800 rpm and runs like crap. Did the voltage test with the multimeter like ron describes and its seems to test fine.

o2 sensor- I unplug this and the rpm picks up just a little and smooths out. Also no rpm drop when I rev it. Seems to run a bit smoother also.

Could this be the problem? I know it puts it in closed loop mode so I am not sure if this is a good way to test this.

 

o2 sensor may be faulty. Is the ignition timing dead on?

 

Yes it it. I have checked it multiple times and hondoctors have also checked it.

 

what the hell? How bout get technical with this. At idle, check the voltage from the map sensor signal wire. You should see approx .8 to 1.0 at idle with 19-21hg of vacuum. The o2 sensor you can back probe with a t-pin. Hold the rpm at 2k and it should fluctuate from roughly .2 volts to .8 volts.

Also, a/f ratio problems can cause rough idles just to let you know.

 

I will try this tomorrow. Thanks for the info.

 

My car idled jumpy and dropped way down when I pressed in the clutch also, until I set the idle speed screw.

 

I have the idle set per honda specs and per honda procedure. The wierd thing with that is I have to have the idle screw backed out kinda far....Or at least I think its far.... And it will only go up to like 400-500 rpm max when set like this. I don't think it could go out any further without running into problems. I went through the throttle body and replaced the idle screw and oring, cleaned it really good and put new gaskets on everything throttle body and intake manifold related. It didn't help. I still have the factory paint on my tb throttle stop screw so I don't think its ever been messed with.

 

ok.... so i tested the o2 sensor and this is what im getting. With my meter set at 20, I get a reading like this 0.00 i hooked it up when warm and at idle I fluctuate between 0.05 and 0.91.... If it set my meter to 2000m, its read like this .000 i get a fluctuation between 058 and 913. Of course these numbers are not constant. Its just the lowest I saw it go and the highest. Now at 2k rpm I get 0.06 to 0.91. Meter set at 2000m I get a reading of 070 to 918.

This seems like it might be out of spec to me.... What do you guys think?

 

With the engine at 2k rpms, the o2 sensor is supposed fluctuate from roughly 200mv to 800mv roughly 3 times every 100milliseconds.

It supposed to fluctuate in order for the cat to work. Only check when car is warmed up

 

The car was warm. These are the readings I got.

 

If your readings when warm was 600mv to 900mv then you are running slightly rich.

 

If your readings when warm was 600mv to 900mv then you are running slightly rich.

 

Its not 600 to 900. Its at 050 to 900 mv. I think its lean. My plugs have been in this motor for a year and they honestly look like they just came out of the box. Would this be an o2 issue or something else??? Its all basically stock.

 

Sounds like a bad IACV, or since it's a PR-4 ecu - incompatable IACV. If you unplug it or plug the hole, it should immediately drop to 400-500 rpm with no flucuation. The 92-93 tegs use the obd-1 IACV, but the 90-91 use the obd-0 IACV. Any OBD-1 iacv that fits (it's specifically a p28 P/N) will work.

The 50-900mv flux is normal, that covers about 14.2-15.2:1.

 

ok. I will check this asap. I will post the results as soon as possible.

 

So I checked that out. If i plug it with my finger for a few seconds and release it, it fluctuates. It revs up when released and then drops to catch itself. I have an intake manifold on it from a 96 ls wich is obd2 I believe. My pr-4 ecu is obd1. My iacv part number is P20 i think. Its worn off a bit.

 

When you plug the hole in the throttle body that goes to FITV does it have vacuum? If not you should replace it the adjustment is only temporary and not very accurate.

 

the fitv is working correctly.

 

Im pretty sure its the iacv. Im looking into getting one now. I will update the results.