I have a 99 Civic Ex with an OBD1 b16a swap. I just changed the oil and the alternator, ps, and ac belts today. I started the car afterwards and it revved up to around 6k rpms. I shut it down right away obviously and looked everything over and everything seems to be hooked up and in good condition, I didn't touch anything besides the belts and doing the oil change anyway. Any ideas what would cause this? I don't think a vacuum line would cause it to go that high and the throttle cable seems to be functioning normally. It does have cruise but the cruise control components all look fine as well. The car idled fine and started fine today before I did anything. If anyone has any ideas that would be awesome, thanks in advance.

 

Check whether the throttle cable is adjusted too tightly or is binding.

Also check whether the throttle body is dirty, causing the throttle plate to stick open.

 

also take off the intake hose...if you hear a heavy vac sount might want to check your FITV locathed under the throttle body...had this problem with my 93 project and this fixed it

 

Could an FITV or IACV problem cause it to rev that high? If so how do I know which one? Here's a pic of the throttle body, is that the normal amount it should be open and is it too dirty?

 

It's hard to see. Can you push the throttle plate closed any further than it is when it revs to 6K rpm?

If you cover the top of the throttle body with a wood block, can you kill the engine?

 

I can push it further shut than it is but when I let go it goes back to the same position. I may try the wood block thing when I have a friend that can help but I'm afraid to leave it revving that high long enough to get out and put the block on when the engine is cold after an oil change. If I put the block over the coupler and it doesn't kill it I assume that would mean I have a huge vacuum leak somewhere?

 

Sounds like the throttle cable is adjusted too tightly. There should be about 1/2" of free play in the cable.

 

Yes, a LARGE vacuum or intake air leak.

 

Thanks I'll see if I can adjust it. What would cause the throttle cable to need adjustment all of a sudden? I moved the PS pump out of the way near the back of the valve cover when I was doing the belts but I don't think it was hurting anything.

 

Throttle cable is adjusted fine. I tried unplugging the TPS yesterday and it did the same thing. I let it go a little longer and it actually didn't stop revving till about 6500-7000, then it stayed about there. Today I'm going to spray some carb cleaner around the intake manifold gasket and maybe some vacuum hoses just in case there's a vac leak somewhere. If I don't find anything I'll try to remove and clean the IACV most likely. I thought my car should have an FITV since it's an obd1 swap but it doesn't, not sure what's going on there. Any other ideas?

 

If the throttle body is covered with a wood block the car still runs and idles as far as up to 6k still, idk what's going on. I don't feel comfortable letting it sit at that rpm for long so it's hard to diagnose it. Can a throttle body or intake manifold gasket just randomly blow out and cause a leak that huge? Or can the IACV cause it somehow?

 

Back from the dead! Lol but my car just revs and keeps revving after starting and I Did disconnect the brake booster to the intake manifold. My tb is closed completely and I'm positive my thrttle cable isn't locked up.. idk wtf is going on. Started doing this after a wire tuck but I only cut wires for lights nothing cut wire wise for the motor

 

wonder if the OP fix the issue

 

I did, I tried readjusting the throttle cable again just in case and that fixed it, been working fine to this day. I'm still baffled as to how the throttle cable got tighter when I didn't even touch it. Haha. The only thing I can think of is the power steering pump getting set on it when I moved that out of the way and that somehow messing with it? I'm just happy it was something easy to fix.