CharmCity

Last night My idle started surging up and down ~1500-2000 rpms.. whenever I am stopped, or the clutch is pressed in.. I have had cold idle problems in the past but that was only a 500 rpm surge.. any ideas on what could be causing this? I tryed starting my car this morning, and becuse the engine was cold, it went all the way up to 3500-4000 then down and up and I shut it off.. I checked the codes since my light has been on for a long time and it's the same two codes that have been on there for a while(vtec pressure,O2 sensor).. so it didn't give me any new codes.. Any help would be appreciated.. OH and I jsut replaced the MAP sensor with another used unit.. could that have good bad? Thanks a lot!!

splitime

not sure what motor this is on, that type of info could help. But someone around this area had the same problem recently, and had fixed it. He had a broken Fast Idle Valve, the unit attached to the bottom of the TB on his jdm GSR. Not sure if this applies to your car, but its something to check.

inarush168

don't know what car and engine you got, but make sure you didn't set the idle too high on honda's . I use to have a prelude and if i set the idle too high at the throttle body, i would have idle surge all day long. or it might be the map sensor also. a very common problem that i see on eg civics

CharmCity

It's a 94 si with a stock motor.. The idle setting should be fine.. i've never had to even set it before.. it's always been perfect at 750.. also when I press the gas in lightly it kind of like jumps.. or bucks.. but if I press it in more, or if I press it in fast it drives fine.. i've never had a similar problem like this before.. I am leaning towards a map sensor.. but I have no idea what the car will act like if that is bad..

Quetzolcotl

try resetting the timing. can't remember exactly how to do it its either turn car on and let it fully warm up (2 fan cycles) and then turn on everything (headlights, hazard lights, stereo, a/c, rear defrost, stereo, everything) and let your car run for 10-15 min. this resets the ecu engine timing and worked for me. if its not that its the same process but from a cold start instead of full warm up.

BlackDeuceCoupe

Yep! That's the most likely candidate, otherwise known as an 'IAC' or Idle Air Controller.

One other problem that you see a lot is when someone flushes their cooling system or has the system open to replace a coolant hose or whatever. If you don't get all the air out of the radiator and heater core and all the hoses, sometimes an air pocket will remain where the engine coolant temp sensor for the ECU is located. When this happens the ECU will not know when the engine is total warmed up 'cause it isn't getting a signal. This can cause the engine idle to vary up and down erratically too.

pennies_hatchie

iTrader: (1)

bump..
i got the SAME problem in my 94 gsr...
checked the iac and its working correctly (checked by unplugging and plugging it back in, and it changed the idle when unplugged and went back to the same when plugged)

bump for more help

cb9sir

the fast idle valve and the IAC are two different things. the fast idle valve is on the back of the throttle body. its a little metal plate held on my two 8mm screws.

there is a plunger vaccum inside that if it comes loose you will get way too much air at idle. it will make your engine purge pretty bad. mine woudl go from about 1k to 3k and then when it warmed up it woudl idle about 2k or a little above.

pull the plate off and start up the engine. put your thumb over the vaccum plunger and see if the idle immediately drops down. if so you need to screw it in so its tight. problem solved. good luck

pennies_hatchie

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91wagonsir &raquo;</TD></TR><TR><TD CLASS="quote">the fast idle valve and the IAC are two different things. the fast idle valve is on the back of the throttle body. its a little metal plate held on my two 8mm screws.

there is a plunger vaccum inside that if it comes loose you will get way too much air at idle. it will make your engine purge pretty bad. mine woudl go from about 1k to 3k and then when it warmed up it woudl idle about 2k or a little above.

pull the plate off and start up the engine. put your thumb over the vaccum plunger and see if the idle immediately drops down. if so you need to screw it in so its tight. problem solved. good luck </TD></TR></TABLE>

i was just going to say, that im thinking its the Fast Idle Thermo Valve...will check and update later. thanks

stevey

Check for air leaks around the intake manifold and TB... Spray some WD40/carb cleaner around them and if it bogs down or idles up, then that is where the leak is. I had a leak at my intake manifold gasket and this helped me find the leak and fix it..

pennies_hatchie

iTrader: (1)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by s7e &raquo;</TD></TR><TR><TD CLASS="quote">Check for air leaks around the intake manifold and TB... Spray some WD40/carb cleaner around them and if it bogs down or idles up, then that is where the leak is. I had a leak at my intake manifold gasket and this helped me find the leak and fix it..</TD></TR></TABLE>

tried that, but there's only so many vacuums on the sk2 IM...and they're all accounted for.
tried the FIV and screwed it in tight...still the same results.
so i decided to try another gsr TB and still the same results.

now im all out of ideas, the IAC works, the TPS, MAP, FIV all work as well (did voltage test and plugged and unplugged them and they all work)

check for vaccum leaks and there's none to be found.

i have a new TB gasket, new IM gasket, the IM was torqued to factory specs.
burped the cooling system as well, reset ecu and no code except CKP (54) but im running a 2000 si ecu, which is detecting obd2 stuff.

tried the wd-40 idea, still no leak. i have no idea whatsover, and ive tried everything possible. any other thoughts?