P0505 D16Y7 Help Me Please... Running out of ideas

[prodigy803]

Ok to start off I've searched all types of forums and even did the online mechanic help but to no avail.

When my engine is cold and at operating temp I have a high idle (1400 RPM), and an intermittent surging idle at low RPM's (by low I mean when I'm barely stepping on the gas but it's still pretty high on it's own). When I reset the ECU the idle goes down to 1000 RPM but goes back up when the CEL comes back on.

When I first took it to the dealer they replaced my IACV and cleaned my TB. It didn't get rid of the problem. They then recommended me to replace my ECU because it "might" have been shorted out by the old IACV which is causing the fault. Swapped with a used ECU but same issue.

What's been done to my car:

• Replace IACV
• Clean TB
• Replace ECU
• Check for vacuum leaks with Carbon Cleaner
• Check and replace PCV and hose
• Replace ECT sensor (wasn't sure if it was reading correct temp)
• Bleed coolant of air
• Replace Spark Plug and Wires
• Replace Distribution cap and rotor
• Check for vacuum leaks again
• Adjust idle speed setting
• Check throttle cable to ensure slack
• Check TPS sensor output with Scanner (11.0-11.4% at idle expected result approx. 10%)

I lost faith in the local dealership with the explanations they were giving me. I might not be as car saavy but I'm not a complete idiot, I can read a service manual too...

I went through the flow chart again on the service manual for the P0505 fault but I keep going in circles. What else can I check.

The other possible causes I have yet to check are:

• TB improper adjustment
• Intake manifold gasket leakage
• Intake air hose loose leakage

Not exactly sure how to check those. The TB, what adjustments are there? For the IM doesn't that check out when I spray the crap out of it with Carb Cleaner with no change in RPM? The Intake air hose it does't look loose and the hoses look decent. Any help would be great, I'm running out of ideas.

Also, the timing belt was changed about 3 years ago so I'm pretty sure it's still good.

 

[RonJ]

Here's where always to start when P0505 is thrown and the idle speed is high or surging:

When the engine is fully warmed up and high idling, remove the air intake system and then use your finger to cover the hole inside the throttle body leading to the IACV. Does the idle speed drop low or does it still idle high?

 

[prodigy803]

When I cover up the lower port the idle speed will drop from ~1400 to about 1000-1100 RPM.

 

[RonJ]

You have an intake air (TB or IM gasket) leak or vacuum leak. Also check that the throttle cable is adjusted properly with a little bit of slack.

 

[prodigy803]

You have an intake air (TB or IM gasket) leak or vacuum leak. Also check that the throttle cable is adjusted properly with a little bit of slack.

Vacuum Leaks: Aside from spraying carb cleaner by the vacuum hoses and looking for a change in RPM is there a different way to look for a leak? I've sprayed carb cleaner already and I didn't see or hear any noticable changes.

TB or IM gaskets: Sorry for sounding like a scrub but what am I looking for if it's a leaking gasket?

Throttle Cable: How much slack are we looking for because I can literally just unloop it from the throttle link at the closed position. Is that too much slack? lol

 

[RonJ]

Vacuum Leaks: Aside from spraying carb cleaner by the vacuum hoses and looking for a change in RPM is there a different way to look for a leak? I've sprayed carb cleaner already and I didn't see or hear any noticable changes.

Unplug all vacuum hoses and cap the IM nozzles. Does the idle speed drop?

TB or IM gaskets: Sorry for sounding like a scrub but what am I looking for if it's a leaking gasket?

If you cover the top of the throttle body with your hand, does the engine die?

Or just replace the TB and IM gaskets and torque the nuts and bolts to spec.

Throttle Cable: How much slack are we looking for because I can literally just unloop it from the throttle link at the closed position. Is that too much slack? lol

Are you able to manually close the throttle plate beyond where it is when the engine is idling?

Have you or anyone else ever adjusted the throttle stop screw? This should never be done.

 

[prodigy803]

I'll give the first two suggestions a go as soon as I'm able. As far as the throttle cable, while the engine is idling I cannot close the throttle plate beyond where it is while idling (given it already looks closed from my perspective). Also, as far as I know the throttle stop screw has never been touched.

On a side note, I decided to plug in my scanner when I was heading out to lunch and my idle was sitting at 1200 RPM while it was warming up and at 950-1000 RPM when it was fully warmed up. Still high IMO but when I was at a light it was at 700 RPM. Why is it perfect when stopped in drive and high while I'm in Park. I cleared my CEL so let's see when it pops up again.

Thanks a lot for your help RonJ. I should've came here sooner than to waste my time at the dealership.

 

[RonJ]

How and when did this idle problem start? Before you purchased car?

The idle speed should only be measured with the transmission in park or neutral. It's normal for the idle speed to drop when the transmission is in drive -- higher engine load.

 

[prodigy803]

The problem actually started about a month or so ago, I was on my way to work one day when my CEL came on and at stop lights my engine would stall. My cars A/T so I was a little confused and I had no clue what was going on. Took it to a garage on base and they adjusted my idle just so it wouldn't stall out and told me to go to Honda because they had no clue. I'm not exactly sure what the fault codes were when it started because I didn't have a scanner at the time and the dealership didn't really give a detailed description of the issue.

So the problem kind of evolved from a stalling issue to a surging idle to the high RPM that I have now. The surging idle appears here and there but not as often as before. Maybe what I've been doing to the car's been helping a little bit, who knows. But when my car idle surges, whenever I step on or release the gas pedal the car jerks.

 

[prodigy803]

Unplug all vacuum hoses and cap the IM nozzles. Does the idle speed drop?

Still have to do this one, currently researching the different vacuum lines that go into the IM. Any suggestions on what to cap the nozzles with?

If you cover the top of the throttle body with your hand, does the engine die?

Or just replace the TB and IM gaskets and torque the nuts and bolts to spec.

The engine died when I covered the top of the TB. Does this mean that there are no leaks in the TB and IM gaskets?

Are you able to manually close the throttle plate beyond where it is when the engine is idling?

Have you or anyone else ever adjusted the throttle stop screw? This should never be done.

I checked the throttle stop screw, there doesn't appear to be any clearance from the screw to the throttle link. I also can't manually close the plate while it's idling, is that a good thing? I adjusted the throttle cable to the service manual specs leaving only a little bit of slack.

 

[RonJ]

My guess is that the guy at the base garage may have tried to solve your idle issue by adjusting the throttle stop screw because it sounds like you went from a low idle problem to a high idle problem after he worked on the car.

Can you source a used D16Y7 throttle body?

 

[prodigy803]

It'll take me some time but I might be able to borrow somebody's TB from their car lol...

 

[JohnS.]

I had this exact CEL code for something like a year, maybe longer. I fixed it by adjusting the idle via idle screw on the throttle body. I did not adjust the idle like the manual says to (unplug IACV). I simply just turned the screw without touching anything else.

It may not fix your problem but it might be worth a try?

 

[prodigy803]

My guess is that the guy at the base garage may have tried to solve your idle issue by adjusting the throttle stop screw because it sounds like you went from a low idle problem to a high idle problem after he worked on the car.

Can you source a used D16Y7 throttle body?

I'm waiting for my friend to hook me up with one of the shops here that work on a lot of Hondas to see if they have a spare I can test my car with. I don't see a lot of EK's running around this island but hopefully I can get one. Is there any other options in case I can't get one to test?

I had this exact CEL code for something like a year, maybe longer. I fixed it by adjusting the idle via idle screw on the throttle body. I did not adjust the idle like the manual says to (unplug IACV). I simply just turned the screw without touching anything else.

It may not fix your problem but it might be worth a try?

I wish it was that easy for me I tried to adjust it but it only brought my idle to 1000-1100 RPM.

 

[JohnS.]

I wish it was that easy for me I tried to adjust it but it only brought my idle to 1000-1100 RPM.

Even when you reset the ECU to eliminate the CEL, your car still idles that high? Is your idle screw all the way in?

 

[prodigy803]

Even when you reset the ECU to eliminate the CEL, your car still idles that high? Is your idle screw all the way in?

I reset the CEL with my scanner and the idle is still the same 1K RPM, and yes my idle screw is all the way in.