I have a 99 civic it has a Y7 block and a Y8 head. When I first put the engine in it ran fine for a couple of weeks. It then started to have a very bad hesitation. When I first start the car up it will run fine for a couple mins then it starts acting up. If I stop at a stop sign or a red light the rpms will drop almost down to zero. Then when I hit the gas the light will be turning yellow by the time I get through the intersection. If I'm sitting on a hill it's even worse. The rpms will climb to about 4-4.5k before shifting from 1st to 2nd and again when shifting to 3rd(It's an auto). Once it gets moving above 20mphs it will start to do ok it struggles to get up to speed, but as soon as I take my foot off the gas it starts acting up again and becomes more sluggish. I replaced the fuel filter a couple days after it started doing this, thinking it might be clogged. It was clogged up a little, but it still does it with the new filter on. I put new plugs in after I dropped the engine in. What could be causing this problem???

 

sounds like it could be iacv, or maybe a vaccum leak.

 

Checked for a vacuum leak and didn't find one. will the iacv on a y7 work for the y8? cause I have spare parts from a y7 sitting in the garage.

 

im not shure about that? i would assume that if they look identical they would work. im waiting on a answer to that question on my car cause my iacv went out on me. found one that looks the same but the listing says its for 92-97 civic.

 

According to hondapartsdeals.com the iacv from the y7 and y8 have the same part number. So I would assume that they are the same. Thanks for the help cause I need to get this car running. I will give it a shot and try using the iacv from the y7 and see if it works or not.

 

The IACV only affects idling. You could try opening the air screw on the throttle body to keep from stalling, but that might make it idle too fast. Since it doesn't drive properly though, there is more than just an idle problem.

I'd start by disconnecting the fuel injectors one at a time to check that it's not running on 3 cylinders.

And I think it's supposed to rev up to 5K before shifting while you have the gas pedal on the floor. In regular driving (not floored) it will shift sooner.

 

But I'm not flooring it. Cause as soon as you push the gas it starts hesitating and even if you do floor it it does nothing, the rpms just slowly go up til they get to about 2.5k then they shoot up to 5k or higher if you still have it floored if not floored they will start climbing a little faster then before but not like it should.

 

How will I be able to tell if it's running on 3 cylinders by disconnecting the injectors one at a time?

 

Unplug one and see if it runs differently. If you notice a change, that means that cylinder was running until you unplugged the injector. If there is no change then that means the cylinder wasn't running and you have just isolated the problem to that cylinder, which could be a bad injector, bad wiring, bad distributor cap, bad spark plugs, or bad plug wire.

Make sure you only have one unplugged at a time though, you don't want to unplug one then unplug another and then another.

 

k thanks I will try that tomorrow and see what happens. I'm going to see if my father in law has a compression tester and if I can borrow it and check the compression out too.