jwest1150

So, been running into this problem every so often. I understand that people are having problems with the idle surging, etc. However, I see that a select few have the problems I'm running into in conjunction with the idle surging.

The car is a 1999 civic EX, stock d16y8.

Symptoms include the following:
First is of course the idle surging. This happens after roughly 20 minutes of driving. Car idles at 1500, then giving a bit of gas causes the idle to fluctuate from 1500 to 2000.
Once the surging kicks in, the car begins to lose power at an extreme rate. Ill be on the freeway going around 65 in 5th, left go of the gas, which causes a slight jerk, and power drops instantly; almost like I'm pressing the brakes.
This loss of power goes hand in hand when in first gear. If I begin to slow down while in first gear (around the 3000 RPM band, and below) the car begins to jerk extremely, causing the car to either stall, or jerk back and forth with tires screeching.

So far I did a thorough cleaning of the IACV. After I reset the codes the check engine light was gone for 2 weeks along with idle surging and loss of power. Just recently it came back on again.

Can it be a bad IACV? I have this idea that a bad IACV wouldnt cause an extreme loss of power. I need help deciphering the problem.

Thanks a lot in advanced!

EJ8_Man

Sounds really violent. You should replace your IACV and see if that fixes the issue.

Loss of power could coincide with a loss of airflow to the engine or loss of gas to the engine, what's your fuel pressure like? How's your air filter look? How do the spark plugs look?

I remember growing up I saw this happen once when someone left their gas cap off on accident. But it was a 1977 Chevy Pickup, not a Civic. Perhaps air in the fuel lines.

jwest1150

I'm thinking about replacing the IACV. My only reason for holding back on that is if that would cause a strong loss of power?
Haven't checked the air filter. I'll take a gander, and the same goes for the spark plugs.

Fuel pressure not sure either. I haven't really gotten into diagnosing yet just getting some ideas on where to start.

Former User

Did you recheck the codes? Still only P0505?

When you are having the idle problem, what happens to the idle if you unplug the IACV?

jwest1150

Well, its been awhile and I have been having trouble replicating the problem. The minute the car shuts off, the idle issue disappears.

I decided to replace the IACV with a used one, then cleared the ECU. After around 40 miles of driving, working smooth and perfect, the check engine light came on and the hard power loss showed its head again.

Should I look into replacing the IACV with a brand new one? I am trying to get my codes checked, and am hoping to see if anything new pops up. Aiming for tomorrow.

chueymuas

i had the similar problem. mine was when i was driving for a while, my car would start to jerk and would the idle would fluctuate. my problem was the tps. good luck on finding the problem.

jwest1150

Thanks. going to change out the TPS and work from there. Out of curiosity, does it matter what the brand is? Ebay is selling a TPS for about 20 bucks, whereas autozone is selling for 40. Any difference?

Former User

Code?

jwest1150

same code; p0505.

I noticed that the sluggish/loss of power happens when its warmer outside, as opposed to being cold. For instance, during 80s-90s, power loss can happen often. I usually restart the car, and sometimes it will work for awhile (a couple miles give or take) before the problem shows up again.

In regards to the TPS, should I go with the cheaper ebay or autozone for 20 more bucks? Do they make a difference?

Former User

Did you pull the code or just assume it was P0505. Prior to this, was the ECU reset to clear old codes?

Before you replace the TPS, check its output voltages at closed throttle and WOT.

Also test the resistance of the ECT sensor when the engine is fully warmed up. It should read 200-400 Ohms.

jwest1150

I checked. And before when the light first came on, I cleared the ECU. Then the light came back on, swapped IACVs and cleared the ECU.

Hate to sound ignorant, but could you point me into the direction on how to check those voltages? My technical knowledge is not that deep.

Former User

Keep the TPS connector plugged into the TPS and back probe the Red/Blk (+) wire and Grn/Blk (-) wire at the rear side of the TPS connector to measure voltages. Do this with the throttle fully closed and wide open and you should read about 0.5V and 4.5V, respectively.

jwest1150

Thanks a lot. Going to go get my hands on a multimeter and post results after.

jwest1150

Alright so plugged the multimeter in and at no throttle got a reading of .54. At full throttled got a reading of 2.12

Are these readings accurate? An indicator of something?

Thanks.

jwest1150

I take it the large difference between 2.12 and 4.5 at full throttle could mean my tps is bad?

Former User

Yes. Replace the TPS.

jwest1150

Sounds good. Just ordered the part, and will post results after.

Thanks a lot.

jwest1150

And I'm back. The engine light went away a day after my last post. The light along with all the symptoms never returned until last week. Odd because the car was running flawlessly since then and just decided to return to me.

So, I replaced the TPS and the IACV and yet am still getting the same problem. The idle surging is coming along quite often now.

What are my other options? Am really stumped right now.

Thanks again.

jwest1150

So, small update.

Noticed I have a small coolant leak coming from one of the hoses leading to the IACV. Seems to be a small tear. Going to replace the hose obviously, but would this cause a code to be thrown?

Thanks.