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90 CRX Si
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Discussion Starter #1 (Edited)
Well guys, some of you may recall not to long ago I had a thread about some problems with my build. Well my main concern is my surging idle. So, here's the low down on it.

The car is a 1990 CRX Si with the setup in my sig. I've had the idle problem since I bought the car, its just changed how it acts as i've changed setups. No CEL is beign thrown. Now it will start to idle up and down, probably around 1000-1500, then will drop lower and lower each time until it dies. When i unplug the TPS it idles fine, just a bit high, ~1100, and throw the CEL.

Now, here's a list of things that have been replaced at least once or checked out: ECU, TB, IM, all gaskets, TPS, air in coolant, MAP sensor, IAT, fpr.

All vacuum lines were checked out and several of the smaller ones were replaced during the rebuild. The only thing thats still in the car thats been there from the start is the harness, a couple of vacuum lines, and some grounds. I replaced the VC ground.

I think its in the harness somewhere b/c my temp gauge reads high, like operating temp right after start-up and hot within 5 minutes.

**EDIT** I forgot to add that I checked the voltages on the MAP harness clip according to the Haynes manual. I can't remember which wires it was (I don't have my Haynes with me), but the first test read 7.03V, the second read 5V, and like 3.46V on the third test.
 

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Rising and falling initially screams IACV. But dropping lower each time until stalling is a little weird. Try cleaning the IACV or swapping with a another one if you have access to it. Other than that, you're gonna have to start eliminating vacuum, sensor, wiring, and maybe even ECU troubles.

It's always good to backtrack and check over the easy and simple stuff because it's even easier to make a simple mistake and/or overlook something very minor. It happens to the best of us, more often than we'd like to admit!!!!!!!
 

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90 CRX Si
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Discussion Starter #3
Oh yeah, forgot to add, it's had at least 2 IACV's that have both been cleaned and still does it. All sensors check out, just some voltages to them read off. It's had two different ECU's (stock PM6 when obd0 and my P28 that came from phearable now).

My thing is i don't know where to start on checking the wiring, i suck when it comes to wiring, thats why all my conversion to obd1 was rywire.
 

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Oh yeah, forgot to add, it's had at least 2 IACV's that have both been cleaned and still does it. All sensors check out, just some voltages to them read off. It's had two different ECU's (stock PM6 when obd0 and my P28 that came from phearable now).

My thing is i don't know where to start on checking the wiring, i suck when it comes to wiring, thats why all my conversion to obd1 was rywire.
Even with a conversion harness and a "new" engine harness, you still have alot of under dash wiring, and I'd be willing to bet that's where your problem lies if your getting funny reference voltages to your sensors.
 

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So you have a crower stage 2 cam and a phearable ecu.. does the car run on just a phearable basemap?

Sorry if i failed to read further in your build thread but how far have you gone with regards to tuning?

(something tells me i need to completely read your build thread otherwise feel free to ignore my question.)
 

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...Ok so i did some reading
so now i'm going back to my first question: Have you done any wideband tune eversince you got the car to start?

Coz from reading your build thread, i didn't see any event relating to any form of tuning.
It seems as if your running off a basemap and looking elsewhere to fix your idle problems.

Believe me, a basemap will never be good enough to run a crower cam ---> no matter who made it for you. that's as far as i believe and experienced.

Crower cams are pretty tricky when trying to get a stable idle.
To begin with, you have to lean out the idle afr looking at a wideband.
The low cam lobes are big enough to draw more vacuum to cause the ecu to pig out using the stock map or whatever alterations on the map your "custom chip / chipped ecu" is running on.

If i am correct that you're still running on a basemap, and you are still having those idle problems, then stop looking elsewhere as you have done enough already to confirm that the problem isn't in those other areas anymore.

..then you know what needs to be done next.

Good Luck.
 

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90 CRX Si
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Discussion Starter #8
You're right it's not tuned, but the problem is my car has always done this, ever since I've had in in Oct 05, and i never knew enough to figure it out. That was with the stock PM6 and A6, then my P28 and mini-me, it still surged, now it still does it, it will just keep doing it and die. It doesn't do it all the time but when its not it idles high, around 1000-1100, but i imagine thats from the cam.

Thanks for taking to time to read the thread though. I don't have the money for a Hondata, wideband or anything like that. I'm either going to have to wait until september when i start college back and some scholarship $ back or take out more loans.
 

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98 civic ex coupe
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Might not be your issue but one thing thats quick to check would be the brake booster. Not too common to see but i had a simialar issue in my civic and couldnt find a leak anywhere. We have a machine at work that you can put smoke into the manifold to check for leaks. I couldnt find any with that so i clamped off the line to the booster with the car running and the idle went right to were it should be. Turned out to be a small leak in the diaphragm. Changed the booster and problem fixed.
 

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I was chasing my own terrible idle problems, surging, stalling, idling at 1500 to 2000, bouncing, and just generally idling like crap, all the while throwing code 43 and 41. One B16 throttle body from ebay and a brand new O2 sensor later along with cleaning my IACV and the thing runs like a dream.
 

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Adia's Daddy
2004 Honda Element
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According to our teacher in class today, the IACV is actually working when you have the hunting idle because it is trying to compensate for changes in air coming into the engine. I would look for other sources, especially if you have changed out the IACV a couple times already.

From my understanding, if the IACV isn't working or is plugged, it will choke off the engine and/or cause it to run poorly because it is not allowing bypass air past the throttle plate of it is improperly regulating the air getting by. Case in point, I worked on a 2000 Accord in the shop which would only run on start-up if you touched the pedal a bit to open the throttle. Ended up being a plugged rotary air valve/IACV and it was choking off the car at start-up because no air could bypass the throttle plate.

**EDIT** Also perhaps try checking your fast idle valve and as well the small holes before the throttle plate by plugging them with your finger with the engine running to see how much, if any, air they are pulling past the throttle plate.
 

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Adia's Daddy
2004 Honda Element
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Just noticed now that you replaced the TPS. Are you sure it is adjusted properly? With a DVOM it should read 0.45V (or 450mV depending on which scale you prefer to use) with the throttle plate fully closed. With the throttle plate wide open I believe it should be around 4.5V. If it is out of spec when fully closed, adjust as necessary.

Also, if you played around with the idle adjust screw/throttle plate stop screw, you need to re-calibrate/adjust the TPS to compensate for the change.

We were talking about idle controls in class today actually :D

suggestion.

did you mix the map and iacv wires up?
Is it possible to do that? I thought the harness plugs were different?
 

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Adia's Daddy
2004 Honda Element
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You might wanna go over some of these procedures I picked up from some of the diligent guys at pgmfi.org who've been through a lot and wrote useful stuff for people like us....

I know you have covered some of the steps already. But i'm sure it will help you do a rundown once again and perhaps retry. It sure helped me a lot with my idle issues.

1.) Post-IACV Cleaning Idle Setting:

"It always helps to clean out the IACV with carb cleaner...

Also, reset your idle per these instructions:

Get a digital tach (like on a timing light) - (but don't worry if you don't have one. I didnt lol)
let the car fully warm up (meaning the cooling fan has kicked on and off 2 times)

once warm, jump the CEL (service) connector under the dash.

Unplug IACV's connector.

set idle ~150 RPM below the RPM you have set in the ROM.

once idle is set, check ignition timing... you might have to do this 2 times or more... depending on setup etc. I have seen weird things happen when setting idle sometimes, that's why I set the timing at the same time.

Stop motor.

plug in IACV.

Pull backup fuse from fusebox.
wait 20 sec, put fuse back in.

pull service jumper out for normal operation.

start motor.

it should run perfectly..."



2.) Another approach focusing on the throttle stop screw:

"THROTTLE SET SCREW CALIBRATION

Assuming the program in the ecu is the properly setup for you motor this is how I adjust the throttle stop/TPS/Idle speed on OBD0/OBD1 honda's with intake manifolds and a single throttle body.

Warm up the car.
(addt'l: jump the service check connector)
Turn off car.
Using duct tape block off the holes inside the throttle body that go to the FITV and IACV.
Adjust idle speed screw to about the middle of its adjustment range.
Loosen throttle stop locknut and adjust throttle stop so the throttle body is slightly opened. (note: one made a comment that he adjusts the set screw only enough so that the plate won't press against the throttle bore and cause sticking)
Start car. The car should be idling super high like 2000-4000RPM. (note: depending on how much you adjusted the stop screw to crack open the throttle plate)
Adjust throttle stop so the car idles about 150-200 RPM below spec
Tighten throttle stop locknut.
Adjust TPS to 0.49Volts (note: use Steve-O's procedure on this as it's dead on.)
Set base timing (short service connector if required by your generation ecu, etc.)
Verify idle speed is still 150-200RPM below spec and adjust throttle stop if necessary.
Turn off car.
Remove duct tape.
Reset ecu by disconnecting ecu fuse or battery.
(addt'l: pull service jumper out for normal operation.)
Restart car and adjust throttle speed screw until ideal throttle speed is achieved.
Verify timing again.

The car should idle beautifully and the cold idle up/ electrical idle up should work perfect.

Its a lot of steps but thats how I always do it. It takes like ten minutes when you get the steps down. And a secret I use is when I adjust the TPS is I always take my voltage reading @ the ecu instead of at the sensor to compensate for any possible resistance in the signal wire. I remove the ecu cover and probe the pin inside the ecu that is for the TPS...."

_________________
All comments are for offroad use only. Not to be used upon public highways."


Pay close attention to the TPS calibration part as it goes along pretty close with the idle calibration steps mentioned above.

HTH & Best of luck
 

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I got Bit by the Boost Bug
Bmw 528e
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1,233 Posts
Xotic crx asked me to let you guys also know that its only surging when its stopped,When hes driving it doest do anything,But bump for good guy with a ppain in the ass problem...
 

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95 CX Hatch
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5,910 Posts
I had problems with mine and chased it like you did. I finally just screwed the idle screw all the way in and its been fine since.

 

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I got Bit by the Boost Bug
Bmw 528e
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1,233 Posts
Hey i just got off the phone with him,He said hes gonna try your idea bizzar and he'll redo his vac lines for the third time....i doubt its the vac lines..
 
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