FIRST POST PLEASE HELP

1992 honda accord lx wagon auto trans

Upon starting at any temp it idles high for 10 or so seconds(normal) then starts to surge at idle. Jumps from 1100-2100 rpms. Idles and runs fine in drive and Reverse but surges in Park or Neutral.

Cleaned IAC, Fast Idle Valve, Throttle body and buttery valve. (The valves and TB were all filthy, now clean)
Checked for vacuum leaks with gauge and carb cleaner. No leaks
Replaced TPS and adjusted to .51v and 4.48v

If I unplug the tps before starting it idles higher and blips faster like a misfire, but it isn't misfiring.

If I unplug the tps after starting then rev for a second the idle stays a little high but stays consistent(no surging).

If I unplug the IAC before or after starting it blips way faster like a misfire.

Engine computer reset several times before and after cleaning different parts and replacing the TPS. No change.

Only replaced the TPS because of when I unplugged it and the idle smoothed out. No change after replacing it.

Haven't done anything with the coolant at all. This idle problem started randomly. Not associated time-wise with any repairs or coolant issues.

 

Take off the snorkel to the throttle body. Start the car and wait for the idle to surge. Inside the throttle body there will be 2 holes. Cover the bottom hole with your finger. Let us know if the idle smooths out.

 

Just plug it? No quick blip of the throttle cable or anything? Whats that telling me either way? I will try in the morning. Thanks

 

The bottom hole is where the fast idle valve (FITV) draws air. Cleaning the FITV may not fix the problem. Plugging that hole with your finger shuts off the FITV. The FITV should draw air when the engine temperature is cold, so you should try plugging that hole when the engine is warm too.

 

no change with the bottom hole plugged but I tried plugging the top and it idled perfect. What's my top hole going to?

 

If the "ports" are the same as the 5th gen's - the upper port is for the IACV

 

The 4th generation accords have a IACV, FITV, and an air boost valve. I can't remember how the ports are setup on the 90-93, because the location of the components are different than the 94-97 accords.

Here is the thread I remember covering the same kind of issue you are having.

Take a look at each valve and trace back where it draws air. They all have to be in front of the throttle plate.

https://www.hondaaccordforum.com/for...354/#post34110

EDIT: Found a picture of the intake. 8 is the air boost, 7 is the fitv, and 13 is the iacv. I think you can take the cover off #8 and #3 and just cover the top with your finger to stop air from passing by.

 

So here is some new data/info. Last night my brother calls me and says the car is trying to accelerate on its own but no real change or super high rpms or reving. Just let off the brakes and it goes on its own even uphill all the way up to 40mph and the brakes are getting extremely hot.

So today I replaced the IAC with a used one from the junk yard. Nothing changed. Could be a bad one from the junk yard but at 30dollars there vs. $160 at oreillys it was worth a try. So with no change with the different tps(new and adjusted) and iac(used) we took off all the sensors/valves and plugged every hole with 3 hands. I plugged the start/high boost whatever valve ports and the fast idle valve ports. One other person plugged the top hole in the throttle body and the ports of the IAC. It idled perfect with all of them plugged. So obviously we are just going to sit on the engine and keep the holes plugged while my brother drives his car. Just kidding.

So with all the holes plugged we let off one at a time to see if anything changed for the good and the only time it idled perfectly was with all the valves plugged with our fingers and the top hole of the throttle body. Even with the valves plugged but the top hole open it surged and idled high.

Help?

 

Plugging the IAC, FITV, and air boost ports should cause your car to stall out due to lack of air. Air is getting into the engine by some sort of vacuum leak.

I'd start by thoroughly cleaning the bore of the throttle body and both sides of the throttle plate with some carb cleaner and a toothbrush. Clean where the throttle plate pivots as well. I would also detach both throttle cables from the throttle body to make sure they are not keeping the throttle plate slightly open.

 

Vacuum leak was my thought with the problem in drive but to me a vacuum leak doesnt seam like a resolution to the surging idle. And the throttle body has been thoroughly cleaned including the butterfly valve. I would take a picture of the inside but i have no clue how to post that. It was filthy when we cleaned it but the valve doesnt really have a gap that some might expect to be the problem. It is open minutely. In all other cars i have worked on the general rule is dont mess with the idle screw or tb setting unless there is a significant gap in the butterfly when closed. I can barely slide a sticky note thick piece of paper through. That has always been my indication that the factory setting is still good. Maybe im wrong with this honda though?

And i sprayed a ton or carb cleaner around everywhere in the engine bay to look for a leak. There was no change in rpm anywhere. I sprayed around every line i could see and all around the injectors and intake manifold(ive seen them leak before).
Also plugged the top hole in the throttle body and idled perfect. While it was plugged had a vacuum gauge hooked up to the capped port just above the throttle body and it stayed steady and moved as it should when the throtle was blipped.

Does anyone have any voltages to check sensor specs. Tcu? I would like to check all the voltages to ensure they are within specs at the sensor plug as well as the input at ecu to make sure a wire isnt shorted on the way to the ecu. I do not have a service manual so if anyone has the correct sensor voltages or test procedures please show me.

Thanks for the help guys.