Grant01

I am still trying to determine what is causing the idle woes on my 92 JDM FD. I'm eliminating different things and I've come to the conclusion that the reason for all the idle surging was I was outside the bounds and it was retarding timing.

So now if I set the idle using the ground and ten with all accessory and power off I do not have a single issue. But as soon as I turn even the Park lights on the car stalls or can barely stay running. I can easily adjust the idle up to compensate for the headlights and air conditioning and anything else, but of course as soon as you turn that stuff off the idle then goes up and starts surging very badly. It seems the car cannot compensate for the headlights or air conditioning by itself it seems.

The FSM is completely useless on this topic as I do not have the el unit. I am at my freaking Wits End I'm trying to get this to run right. I swear I am 20 hours in trying to figure this out.

Things I have done so far. Adjust a throttle position sensor each time I adjust the idle, clean the idle air control valve, replace the idle air control valve gaskets, validated air leaks, cleaned and tested the idle air control valve adjusted the wax rod, checked grounds, replaced the dash pot, check the alternator and its reading 13.8 volts. When you turn the headlights on it drops for 13.5 due to its extremely low idle when set correctly. With the air pump unplugged, the car get the correct idle blip and runs far more correct

Below is a video to show exactly what's happening

https://youtu.be/8mWIGC1AWAQ

Grant01

https://youtu.be/8mWIGC1AWAQ

alexdimen

iTrader: (13)

Watched the video. Your car is idling fine. I didn't see any of the symptoms you describe above. Especially for not having an electric load sensing unit (why doesn't it have one?). I'm assuming that's what you meant by "el unit".

It settles out at 850 right off the bat. Then it fluctuates for a bit with the lights on ~200rpm and settles out again. I wouldn't call that surging. You could try bypassing a little more air with the bleed screw under the TB elbow to alleviate that.

What have you been using to adjust the idle? When I think of idle adjustment there are the hard adjustments and then the idle points set in the ECM. If you have a PFC there are several setpoints based on A/C and electric load.

Grant01

Any idle drop for engine load is not correct, and it stalls when driving. JDM cars don't have EL units, it's all in the ECU. No amount of air I can add fixes the fact that the RPM isn't supposed to drop. Also when I add more air the non loaded idle begins surging.

I have been primarily using the AAS screw underneath the throttle body. When I set this I use the jumper from ground to 10. I have tried adjusting the large idle screw off the front of the engine where the cable hooks up and when I do that I adjust a TPS to measure exactly one volt at idle.

I also hooked up the vacuum gauge today and was measuring at 900 RPM idle measuring -18 inches. As the cooling fans kick on the engine load would cause hunting and vacuum would drop to 10-15 and hunt all around

alexdimen

iTrader: (13)

OK. You don't have an EL unit, but you can still check your other inputs: PS switch, AC switch, Neutral/clutch switch, etc.

The front screw you mentioned is not an idle screw - that is the throttle adjusting screw. Tampering with that along with the secondary throttle adjusting screw can really mess up the idle in my experience. I attached an excellent document that tells you how to get your TB set up back to stock settings even after being tampered with - something the FSM doesn't provide.

Grant01

Thank you for the document, I have it set essentially like that right now, but I will follow it step by step tonight and report back. I was adjusting the tas before, trying new adjusments, but set it back to basically to barely touching. Perhaps it's still too aggressively screwed in? We will find out

One thing I did not, is the second set of secondary butterfly's that are actuator controlled are always open, I have yet to see them close at idle. What is their purpose and should the be closed at idle?

Grant01

A couple of videos after resetting the idle per the directions.

The first video has the air conditioning on, but the compressor unplugged to simulate and idle increase without the load as well as headlights in such being on

https://youtu.be/zUjaUJZ6um8

The second video is with the AC compressor on and then various load being turned on

​https://youtu.be/oJIovK1meN0

Bottom line to these videos is adding fuel (propane) makes it run better. also not shown in the video with the propane feeding the engine it will auto idle bump without any hiccups when any electrical load is applied. If memory serves me correctly this would indicate a vacuum leak, correct?

DaleClark

iTrader: (55)

Have you cleaned the ISC? Problems holding a steady idle can be a sticking ISC many times. I've written up many times how to clean it with carb cleaner.

If the ISC is sticking it won't physically go where the ECU wants it to go and you will have surging or wrong RPM.

Dale

Grant01

I have removed it and cleaned the ISC, I also tested it and it opens and closes fine

alexdimen

iTrader: (13)

Did you verify the ISC valve is getting voltage/signal from the harness? You may need a very fast reacting multimeter or scope if it receives a pulsed voltage.

Did you check those other inputs for idle control? The FSM lists a number of others on page F-81 (neutral switch, ps switch) besides the EL unit.

Does the car have any starting issues?

DaleClark

iTrader: (55)

It could be the idle adjust screw under the entrance to the throttle body needs to be adjusted a bit. That regulates the amount of air the ISC gets and has to work with.

I would also check the clutch switch as stated, that will do some really weird idle stuff on the stock ECU if it's bad.

May also try unplugging the ISC and testing the idle - wondering if the ISC is having a problem or something with the wiring to it. If it does the same thing with the ISC unplugged there's your culprit. But, the ISC is pretty hardy and doesn't fail often.

Dale

Grant01

The idle control valve definitely does its job. I unplugged the air conditioning compressor, and then started the car. The idea here was the idol would be bumped, but the load wouldn't actually be changed. with the idle control valve plugged in the car bumped the idle, without it plugged-in nothing changed.

The car has no startup idle issues and zero issues with bumping the idle while on a warm-up sequence. But as soon as the idles down Under full temp it starts acting up.

I'm also going to remove the intake air temperature sensor and clean it. Under a warm run, unplugging it make the car run better. I'm sure it's because it switches the tune to be rich, but it's at least another thing I can do.

I have also adjusted the lower screw several times, and I have checked the voltage from the wiring harness and I get some solid 13 volts or better

DaleClark

iTrader: (55)

I wonder if you have a JDM ECU in your car. Have you ever checked and Googled the part number on your ECU?

The JDM ECU's have like 3-4 wires that are electrical load inputs. US cars use those same wires for emissions so US cars have a separate electrical load (EL) box that feeds the ECU with 1 wire to tell it if there's a load. If you had a US ECU in a JDM car you could have some weirdness. I could almost see the car being imported with a chipped ECU or PowerFC, some one pulls it out to sell and tosses a US ECU they had laying around into the car.

Long shot but worth checking.

Dale

Grant01

I wish that was the case, but the car is imported by a reputable dealer and most definitely would not pull the ECU. But some of the most definitive reasoning I would have is that it did not do is prior to me replacing the motor when I realized it had a coolant seal failure. It does idle bump correctly when it's under a warm up sequence or with the intake air temperature sensor unplugged. Unfortunately with it unplugged it runs so rich it smokes.

I've been driving at the last few days and I've noted that it runs really rough for the first 15 or so seconds of starting. Almost as though it's running on one rotor. It idle hunts and then eventually clears up and idles perfect until you apply load.

cr-rex

iTrader: (114)

What ecu are you using then? Stock? Have you messed with the o2 sensor at all or checked for vacuum leaks? You say it runs better with propane, there's a possibility you could be having fuel pressure issues. Using the diagnosis box, jump f/p and gnd with a gauge on your fuel feed and verify the pressure. There's an o ring at the top of your fuel feed pipe at the fuel pump and if it fails then it basically leaks fuel at the hanger. Like a straw with a hole in it. Low fuel pressure causes a lot of wonky issues. In addition to the fuel pump and o-ring, your injectors could also be dirty. If they're the stock 550 then chances are they could benefit from a cleaning anyway.

Grant01

I couldn't handle it, I went out and I bought a used power fc, it idles and does everything exactly as it should now. The only quirk is coming off of RPM going back down the idle it's hunts around for a few hops. So I have to readjust the bleed screw but otherwise everything seems happy so far

cr-rex

iTrader: (114)

Excellent solution. It's better that way