Hey guys. Here's the deal. Car is running a Type R motor. Air/Fuel is perfect up until the car reaches full warm. Once this happens, the car begins to run lean. It fluctuates between 14.5 and 17.0 during normal driving. No hard acceleration or anything. This is with the A/C off. If I turn the A/C on, those numbers jump by about .5 across the board. Also, during this, the factory temperature gauge bounces around from middle to cold. It actually moves with the rpm's sometimes. Like a tach would.

Do any of you have any suggestions?

 

Is this tuned? And it started doing this when? Also, list the car specs unless you want the thread locked.

 

Yes. Was dyno tuned by a local shop using my Hondata S300. It was tuned last summer and ran fine, with no problems like this. This has just started in the past month or so.

 

Car Specs:
EK Civic
Type R Motor
Hondata S300
Intake, Header, Exhaust

 

Recently my wideband exhibited similar behavior. It turns out one of the zip ties I used to secure it in the engine bay broke and the wiring found itself being worn away against the power steering pulley.

If it's not a wiring issue I'm going to have to go with your tune. Tuned cars run differently in hot and cold weather.

 

You get what you get on forums.

Sounds like the thermostat is bad.

 

Maybe the ECT sensor as well. That can affect the running condition, simple to test it.

 

Could you guys elaborate on your thermostat and ECT theories? How could they affect the lean issue?

 

Engine temperature plays a big role in how the fuel trim is determined by the ECU. Your fluctuating coolant temperature indicates a bad thermostat and/or air trapped in the cooling system. Start by replacing the thermostat and bleeding the cooling system.

 

As for the gauge bouncing I am thinking the sending unit can be bad. That is right next to to the ECT sensor, the sending unit is 1 wire.

 

there's more than one you know

 

Thank you. That is a good explanation. The Spoon thermostat is only about 2 years old.

@Wrona.........really dude? I'm pretty sure we all know that there are multiple types of Type R motors, however, that is not relevant in this matter.

 

Also, for clarification......the temp gauge will sit right around half when the car is warm, and then as i accelerate, it lowers down to cold, then jumps back to middle between shifts. Then starts again as I accelerate in the next gear.

 

Top off the radiator and reservoir with coolant and then bleed the cooling system (as detailed in your Type R service manual).

 

Update: All of the cooling system components and sensors seem to be functioning properly. However, a friend told me how to "burp" the coolant/radiator. I did have an excessive amount of bubbles come out of the radiator. I let it run for about 40 minutes, and finally shut it down. There were still bubbles coming up. Drove it that night, but it was so cold out, that the car never reached temperature. (Go figure). Should be a little warmer later this week. I'll report back then.

 

With it cooling off when you accelerate thinking you are building more pressure in coolant system that is making the thermostat open early and when you are at idle it holds its self closed would replace the thermostat, and if it didn't reach operating temp when it is cold out side the thermostat is bad as well it is to stay closed until you reach operating temp if it isn't reached it is opening too soon

 

So cold out the car never reached temp? I've driven my Civic in -10F before, and it'll still get up to temp. Did you change anything in the cooling system? Have you tried replacing the thermostat, like three people already said?

 

Sounds like thermostat to me but if you want to check the sending unit

http://www.autozone.com/autozone/rep...00c1528008bb85

What are you looking at to gauge the af ratio?

 

does the car actually run bad?
the temp gauge moving around like that sounds like a ground issue.

 

By the way, it will take longer at idle for the temp to go up, as you drive the temp will rise much faster.

 

If you drove around outside in cold weather and the engine never warmed up, it sounds like your thermostat is stuck open. I've driven around in sub-zero temps and the engine always warms up, the only times it hasn't was when my thermostat failed open.

Not to beat a dead horse here, but I'd like to know what "Type R" motor you have... B18C5? B16B? K20A2? K20Z4? It's a nebulous term that can apply to multiple generations of motors, and depending on how difficult the swap was you could have a swap-related problem masquerading as a normal engine problem. Telling everyone exactly what engine you have lets them rule things out.

 

Change your thermostat, mine was doing the exact same thing and I just fixed it by doing the thermostat.

 

Check for exhaust leaks, any pin sized hole or small leak before or after a wideband will trigger it to read leaner than normal.

 

Sorry, let me clarify what I meant. The car would reach temperature at a red light and such, but then as I started to move (less than a 1/4 mile down the road), it would begin cooling off again, and therefore not be at the temperature that the problem occurs.

As for replacing the thermostat....I replaced it with a Spoon thermostat not quite 2 years ago. Besides that, I did check it when I was burping the system, and it was functioning properly.

 

The car actually runs great.

I thought that about the temp gauge, except that it ONLY occurs when the car reaches full operating temperature. If it was a ground issue, I would think that it would happen all the time, or at various temperatures.