Dekorum

What would cause such a low idle upon start up when the engine it completely cold? In the mornings when I start up my car the idle is VERY low and it takes a long time (a few minutes) for the idle to notice that the engine is cold and raise the idle up. I am pretty sure the car should idle at around 2k RPM right away. My idle never even goes that high, after a couple minutes it will start raising up to 1600 RPM for a couple seconds then quickly warm up my car at around 1100 RPM (close to the normal warm idle). During the first few minutes of the idle being low, if I give it too much gas it will eventually drop the idle low again and kill the engine. When I am backing out of my driveway in the first few minutes, I have to be careful not to give it too much gas. It is also around 15-25 degrees Fahrenheit outside currently. I don't remember this issue happening when I lived in warm Florida, but I could be wrong (this is my first winter up north).

Any help would be greatly appreciated. I have a 96 spec JDM B18C swapped into a 92 Civic hatch. The engine was just completely tuned up 2 months ago (plugs, wires, cap, rotor, fuel filter, new IACV, clean TB, new PCV valve).

TomCat39

The B18C may be different but on the stock engines it's about 750 RPM for warm idle and 1500 RPM cold idle.

As for your issue, I would think it has to do with the ECT sensor. There is a series of tests you do to rule out the ECT or any shorts to do with that system.

The FSM for the B18C1 can be found under 94 Integra. I believe it should be pretty close to the B18C to be able to trouble shoot through your various sensors.

Dekorum

But how long does it usually stay at 1500 RPM? I would think longer than 30 seconds, when it is below freezing temperatures outside.
(FYI, I replaced the ECT with a new OEM one 6 months ago for preventative maintenance)

TomCat39

My stock D15B7 stays at 1500 rpm for several minutes before starting to drop (1200, then 1100, then 1000) when it's cold out. And our cold isn't below freezing like yours is now.

It's an aluminum engine, it takes a real long time to warm up when it's really cold out. You're cold enough to almost warrant using a block heater.

averyvm

iTrader: (1)

I believe there is FITC Fast Idle Thermo Valve on these engines that change the idle depending on what the temperature is. I has a coolant line running through it. I would make sure that this unit is operating correctly.

Dekorum

Type R's have no FITV.

TomCat39

What about the IAT? Maybe it's giving a reading of hot air in the intake?

Did you clean the TB before or after installing the new IACV?

Also did you remove, clean, and then install and calibrate your TPS?

averyvm

iTrader: (1)

My mistake then.

Dekorum

I am not sure how the IAT can be reading hot air.

I cleaned the TB two times right before I got the new IACV (I cleaned enough gunk off my throttle plate that my idle was too high and I thought I needed a new IACV when actually I needed to adjust the small allen head screw under the throttle bracket).

When I did this, I took off the TPS and I realized they don't sell a gasket for that sensor so I decided to put the cover back on and recalibrate it. First I did an analog recalibration with my multimeter and turning the torx screws. Then I digitally calibrated to provide compensation to make the calibration better, using SManager for Hondata S300.

TomCat39

I was thinking a bad sensor for the IAT, but really, I don't think that would have the behavior you are having.

And it seems you went to town calibrating your TPS so that kind of rules that out.

It's not very likely but maybe you got a bunk IACV. Did you keep your old one? I might try cleaning the old one up and putting it back on and see if that affects anything.

I'm not sure if you should have tweaked the allen screw under the throttle bracket.

You might have to go through the set idle procedure. That might be the issue. I'm thinking that screw is the idle adjustment screw but not sure. Car wants to idle fast to warm up but you set your idle dangerously low kind of idea.

All sensors seem to be new or are re-calibrated, so that only leaves that screw as the odd man out. At least so far as you have mentioned.

Dekorum

Hmm you might be right. Going through the set idle process is such a pain to me, because it never actually changes anything. I have done it hundreds of times, and that's why I resorted to tweaking the allen screw under the bracket. The set idle adjustment screw is a flat head screw on the front/side of the throttle body. I can never really get this thing to turn any more tight, I guess it is all the way tight. It only seems to be able to unscrew a little bit and tighten a little bit.

I think that I never needed a new IACV when I got mine. I had cleaned my old one a few times, and got one from the junk yard and cleaned it a few times, and nothing was changing with my high idle and occasional idle surges. I got frustrated and spent the $260 on a brand new IACV (yeah I know, no one ever does this, but I was desperate). This didn't change much, and then I found out about the allen screw and adjusting that was the only thing that dropped my idle.

Now that I reset it since then (2 months ago), all seemed to be fine until I moved up north and I am experiencing very cold temperatures for the first time outside of Florida.

But to answer the question, yes I have BOTH of my old IACVs and they work well. I am actually looking to sell them.

TomCat39

I don't have the B18C1 manual in front of me at work, once home I will look to see what that allen screw might be. I'm hoping it's not the one that says factory set do not mess with.......

Dekorum

It may be, but I was told by a few people to do it. This is because my high idle would appropriately drop upon pushing the throttle plate closed harder with your hand.

By the way, the B18C type r should be more similar to the B18C5 than the B18C1.

TomCat39

Okay that works, I believe I downloaded the 98 Integra FSM too, the C5 should be in that manual. Will let you know if I discover anything. That is if you don't beat me to it.

Okay got an early out today, will be busy with my wife, but before the night is out I will post all the pages. It goes IACV, FITV (which I don't believe you have), Idle speed adjustment, and then lastly (Cold Fast Idle too Low) is IAT sensor circuit (Intake Air Temperature) for troubleshooting logic.

This is for the 98-01 Integra which includes the B18C5 as well as the C1 and one other motor.

TomCat39

I get the feeling you are pretty well versed in all of this but here is the FSM manual pages of relevance.










Not sure if these help but hopefully. And by the looks of things, I am guessing you adjusted the screw yer not supposed to, the image may tell you better than I though.

Also of note, I assume you have a manual so won't have the FITV but I included the pages in the advent someone with an automatic searches and stumbles across this thread. It's provided for completeness.

Dekorum

Maybe my IAT is messed up somehow. I need to check into this more but I have been so busy.

I realized that if I start my car when its very cold. It will start idling at 700-900 RPM but if I sit there waiting, it slowly increases to around 1200 RPM (as if it is a delayed response to noticing the engine is cold). BUT if I go drive down the road (let it warm up just a little bit, although the water temperature gauge will still be fully cold) then I come to a stop and let it idle, it WILL start idling high (like around 1800-2000 RPM) because it realizes that it is no where near cold.

Yes I guess I adjusted the screw that I was not supposed to adjust. Nothing else was working for me. I even visited Kenny, aka Turbogixxer, and he told me to adjust that throttle stop screw. I had a brand new IACV, PCV, and he looked over my tune to check for gross incorrections, yet my idle was still too high (when the engine was well at operating temperature) and even sometimes idle surge (as if my IACV was failing).

TomCat39

The only thing I can add is I saw a suggestion on the Throttle Stop screw once it has been fiddled with.

In the post they said don't mess with it, if you have, then back it out, then screw it in until the throttle plate just starts to move. Once the plate moves, back the screw out one half a turn.

My other thought is you are using Hondata S300. I believe you can do logging. I would also do all the trouble shooting items in the manual sequentially to rule out wiring and everything else.

Also 1800-2000 rpm idle would suggest the motor either thinks the throttle is partly open, and/or engine is cold.

If I recall, the manual says the B18C5 should be idling near 1800 when cold unlike the typical 1.5 L engine where it's 1500.

Dekorum

Exactly right (on that final comment).
I believe my engine is correct in its idle after I drive it for a little then let it idle again. This is all leading me to believe it is just a delayed reaction that my car is having, to the cold weather. I have no idea what this could mean that needs fixing. It is almost like my engine doesn't realize it's cold because it's TOO cold, but once the engine temperature is past a certain threshold (lets say 30-40 degrees F) then it will start behaving like a cold engine should.

On the other hand, I do not believe I will mess with that throttle stop screw anymore. I am pretty sure I adjusted it meaningfully and as perfectly as you can. My cold and warm idle (while in Florida) were perfect after my adjustment.

TomCat39

Up to you.

If it were me, I'd start with the car being cold. I'd adjust the throttle stopper screw so that the plate just starts to move, then back it off the half turn and lock it down. After that, I would then calibrate my Throttle Position Sensor to be .48v when the throttle plate is in the closed postion. I'd then measure the WOT to know it was within spec of 4.1v-4.8v.

After that, I'd do the full set idle procedure. Then I'd follow the procedure for the IAT. I'm only skipping the IACV being you have a brand new one. I'd still test the wiring between the IACV and the ECU.

After all of that, if there was still issues, I'd start logging to see if it gives any clues. Being you are not a stock ECU, that makes things more complicated if it boils down to an ECU issue.

You would find out if it's an ECU issue being you'd be testing for various voltages reaching the ECU thus ruling out bad wiring to the ECU.

Summary: I'd start at the top and redo everything, starting with returning the throttle stop screw as close to factory as we possibly can.

But, that's just me.