Hey Honda-tech. I'm back again with another problem. 2000 civic ex 5 spd d16y8, 132k. I just rebuilt the engine. Honed, rings, rod bearings, timing belt, water pump, ARP studs, and lapped exhaust valves. car started up first try just idled high.

So my problem is, when the car gets hot sitting at idle, it will surge from 1,500-2k rpms fairly quickly (kind of sounds like a hard style beat lol). then when i give it some gas to get moving, the car will buck and surge pretty bad until i give it more gas (3k rpm range). after that it accelerates fine. when the car is surging or bucking i smell a really strong gas odor. I think from the engine bay. no noticeable leaks. went to autozone and got the codes checked. P0505 was thrown twice? i replaced intake mani gasket and throttle body gasket when i rebuilt it. I tried spraying water around the manifold gasket and tb gasket area, didn't see a change in idle. then i plugged the hole inside the tb and the idle smoothed out and lowered. when i took my finger off i could hear the air getting sucked into that port. there is only one hole on the inside of the tb on my car. i unplugged the map sensor and the car died. normal? unplugging the tps didn't do anything. when i unplugged the IACV it made the surging and bucking start, but plugging it back in didn't stop it. Is the IACV gone? the tb gasket sort of blocked an air hole but only a little. maybe the gasket is wrong. but this only happens once the car is hot.

I did bleed the cooling system multiple times. at first the air bubbles weren't really stopping. so i thought my hg may have been leaking. I then did a comp test (c1-194 c2-195 c3-195 c4-210) and rechecked the head studs torque to 60 ft/lbs. i bled it twice after that and the bubbles stopped (there were still some tiny bubbles and i'm not ruling the leaking hg out yet). Did my IACV just crap out on me during the rebuild? I feel like it is something else. as of now the car still is idling kind of high 1-1.5k. when i come to a stop it will surge slowly a few times then settle around 1k. the higher compression on cylinder 4 was like that before the rebuild too. comp before i rebuilt was c1 -160 c2-190 c3-190 c4-210. the cylinder walls were washed out and the ring gaps were way off. had a lot of blowby/burning oil.

Thanks for the help.

Edit: I just tested the TPS. 0.5 close and 4.5 full throttle.

nicely glazed cylinders.
rust from my gas tank made its way onto the top rod bearings (see previous threads)
my first hone. not ball hone.
ARP ftw.
pretty much all back together.

 

Check all your sensor plugs by wire color. The 2 wire and 3 wire plugs have no physical keying, so they can be plugged into the wrong things.

A 2 wire IACV has a spring making it fully close off the flow with no electrical drive. So if you unplug the IACV the idle should drop to less than normal, like 450 rpm, because the engine can't get air. If it keeps running fast, you need to find out how the air is getting in.

 

Alright, i checked the plugs on the car but I'm pretty sure i got everything plugged in right. all the wires want to go back to where they were. BUT, i unplugged the IACV when idling and it didn't lower the idle at all (idling at 1.2k). when i plugged it back in the idle went up. and then when i plug the hole on the throttle body the idle will smooth out to normal ~800 ish. I'm guessing its the IACV, the ECT, or just a vacuum leak somewhere. the old intake mani gasket was a fel pro, and i replaced it with a gasket i got out of a rebuild kit. i checked the bolts on the tb and intake mani, besides the lower bolt on the intake. I'll get some carb cleaner and try spraying around the intake. Thanks for the help.