Serious idle problems (2k) and cant figure it out! (hotair,long)

[Datsunboy]

Guys, my car has been idling for the past two or three weeks at 2000 rpm. Not good when shifting to drive etc... it sits at 15 in drive and creeps when your on the brake.

I bought a scantool, and tried to set my IAC. I had NO luck whatsoever, the IACs always started high and worked thier way back to zero in short order. After they hit zero I had no adjustment.

I (somewhat) sucsessfully set the TPS as well, wot isnt set right but its in idle range.

Ive checked the following things, what do you guys think the problem could be?

New ground from battery to body, and block to battery
Cleaned ecu terminals (noticed they are dirty, but wiggled them to no avail)
Spent about two hours jacking with IAC and TPS.
Cleaned IAC out, looked very clean and was functioning.
Set fuel pressure to factory spec
New 02 sensor
Did my best to check for vac leaks.
Whacked the maf, no change, the counts look normal
Checked various and sundry electrical connections

One wierd thing, just for fun i grounded out the IAC per the IAC reset instructins without a scantool, well i got the idle to settle to 1500 in park with IAC disconnected, but when i left it disconnected and pulled the grounding lug out, it sped back to 2k rpms in short order.

Could this be a function of the EGR? Or a bad sensor? Sensors LOOKED normal on the scanner.

Car seemed to be running WAY fat at idle, so i backed the FP way down to factory specs. Got rid of the richnesss and added some pep to the pedal.

If anyone can help PLEASE DO... I am literally scratching my head at this point. IF noone has any ideas, i may do the 87 ecu conversion and hope it helps. If not, no clue what to do!

Thanks - Evan

 

[Steve Wood]

With the car fully warm, in Park, no AC, try setting your iac to about 20 counts. Turn the key off, restart the engine and see if it is still at 20. Repeat until it is near 20.

When you have done this, does the car idle at the right speed?

Have you sprayed carb cleaner thru the tb passages and Iac passages? Have your removed the iac and cleaned it and the passages that lead off it;s cavity?

If you have done all the above and the iac will still not stay set, then you probably need a new iac. Remember, the car has to be fully warm before setting it as it is natural for it to read higher on a cold engine and drop as temperature comes up.

 

[blackbuick87]

Very high idle can also be caused by a severe vacuum leak. Make sure it is not leaking from the base of the manifold by spraying WD40 or something similar around the base and see if the idle changes.
What is the TPS number?

 

[Datsunboy]

Steve, if i can get my IAC up to 20, it usually idles higher than 2000 rpm. I used the technique described on gnttye.org. I will try it again (worth a shot).

I did give everything a (un)healthy shot of TB cleaner.

I did everything when the engine was hot, and in park etc.. i used the gnttype information. Very helpful stuff.

Thanks - Evan

PS.. how much does a new IAC go for?

 

[GNVAIR]

Do you still have the stock cam in there? From what I understand, that could make a substantial difference. Also, if the IAC counts are high, then you might not have the throttle blades open far enough at idle. We just did my buddies car (which has an unknown aftermarket cam) and we couldnt get it to idle below 1000. I am pretty sure the amount of vacuum the engine pulls might have an affect on it. I know that idling at 1000 isnt the end of the world, but the counts were at 175 when we started. It seemed that the lower the IAC counts went, the higher it wanted to idle, so we figured 1000 would be a happy medium.

 

[Steve Wood]

It's been a long time since I bought one so I have no idea...

consider the vacuum leak suggestion above...that will certainly do it.

I swapped injectors not long ago and the car would not idle down...drove me crazy and I got mad and went in the house.

Later went out and started spraying cleaner over everything....suddenly heard a hiss as I walked around the car....pcv hose was pulled loose and gulping air....I felt pretty stupid.. LOL

 

[Datsunboy]

Basically, no matter what I do the iac's make way to 0 way too fast. They dont level out, and when i can get them up, the car idles so high that i just drop it back down again.

This motor is bone stock btw..

I dont think its the manifold leaking, but ill definitely check again.

Keep the good advice coming! - Evan

 

[Datsunboy]

Another fun fact... i cant find the PCV valve ANYWHERE!

Evan

 

[GNVAIR]

Passenger side in the middle of the intake. Follow the thick steel line from the vacuum block on top of the throttle body to where it terminates between the fuel rail and the upper plenum.

 

[Datsunboy]

Upper plentum? LOL Wish i had one! Mines a hotair car

Thanks anyway, i looked on gnttype.org and found the location and the damn thing is NOWHERE to be found. Granted, the idle problem is new, and no pcv is not.

Evan

 

[Datsunboy]

Alright guys here is the latest.

There is definitely NO pcv valve anywhere on my engine. I will be checking schematics and installing one where I think there should be one.

Even when I can get my IACs to the correct realm my idle is sky high.

I did find that my EGR may not be functioning correctly. When i apply vac. to it at idle the idle drops to about 1600 in park instead of 2k.

The scantool said it was requesting EGR, so why did it change the idle when i manually applied vac as opposed to the EGR applying vac by itself? I did do it with like 15psi (prob too high).

I am awaiting my new translator from ramchagers, although I am almost sure this isnt going to cure my problem. I figure eliminating a few variables cant hurt the cause!

I have been as thorough as possible, but having a 2k idle would mean i have one enormous vac leak that i havent found.

Also, when I apply vac to each of the items on the vac. block, only a few hold vac. (excluding egr) is this normal? Or do i have like 10 small vac leaks?

I am preparing myself to snag a new IAC controller right quick as well. I have tried to exhaust all my other options first.

Thanks guys - Evan

 

[Steve Wood]

unfortunately, I am not familiar with hot airs....if there is no pcv but there is a vacuum leak where one should be, the idle will be high.

 

[GNX423]

i had a simiar problem about a week ago. my car actually backfired through the intake (dont know y) but the back fire had bent my throttle plate in the tbody, i dont think that a back fire would make it past the turbo on a haot air with enough force to do the same thing, but its worth checking out the throttle plate to make sure its not bent and its closing all the way.

Just tryin to help, good luck
Mike

 

[WFO]

it sounds like your throttle blade is too far open.i'd get a new iac in there and then back the throttle blade adjustment screw all the way out(thus making most of your idle air come thru the iac instead of past the throttle blade like it is now).

then re-set your tps and iac and see what it does.


later,sean

 

[cturboaddict]

COOLANT TEMP SENSOR

i had the same problem and it turned out to be the coolant temp sensor........ It was only 8 bucks at the local parts store and now it idles fine.

 

[Datsunboy]

WOO HOO PROBLEM SOLVED!

Alright I feel like a complete dumbass here. Somehow, the end of the IAC (pintle) and spring got run out of the end of the IAC motor and fell onto the top of the intake. I dont know how, when or who this happened too (coulda been me). Well, i reassembled it, its still a bit funny but fixed the problem. I got a new IAC tonight and am putting it in later.

Thanks alot guys - Evan

BTW.. i tested whether the IAC was passin too much air by partially blocking the hole the IAC uses.