linenoise

iTrader: (1)

Background:

The idle on my 94 R2 has always been a little wonky, but not so much that it really bothered me or motivated me into action. I had the TPS screw adjusted a long while ago so that the idle sat around 700 rpm and when the AC was off it was fairly rock solid, occassionally fluctuating/fluttering between 700 and 800. If the AC was on the average RPM would rise to around 900 and would occassionally flutter between 900 and 1100 or so. Usually this would happen when the car had first been started and would eventually lessen or go away as the car warmed up.

New Problem:
I was pulling into a parking spot this morning at work and I noticed that when the clutch was depressed it was idling around 1500 and bouncing a bit. I was mid turn when this started happening and I shut the car off when I got into the parking spot. I made a mental note that this was odd behavior

Lunch time comes and to my dismay the problem is now aggravated: When the AC is OFF the idle bounces from 1000 rpm to 1500 rpms. If I turn the AC on the idle climbs and is steady around 2300 rpm! Turn the AC off it falls to 1000 and bounces to 1500. On and it climbs back up to 2300. WTF!

Some potentially important factors:
1) When I started the car for lunch I noticed that the gas level was as close to empty as I had ever let it get. Usually I fill the tank when it reaches 1/4 above empty, in fear of the fuel tank baffle issue. I've never really investigated whether this is a problem that exists with 94 R2s, but I thought I should do it just to be safe. Evidently I wasn't watching the gas over the last couple days and it fell below 1/4

2) I have a battery miniturization kit, using an oddysey 680 battery. I've always wondered if the erratic idle with the AC on (more draw) is due to the small battery, or alternator fatigue, or both.

3) I changed the plugs and wires about 2 months ago. I don't think this is related, but I'll note it anyway

4) other than the annoying idle, the car boosts perfectly (nonseq) and runs strong.

5) I don't have a PFC, I have a piggyback eprom-based XS Engineering ECU that was burned by XS engineering based on the modlist. My AF meter shows the car running rich, which is the same as it was prior to the problem becoming exaggerated

6) I recently (1 or 2 weeks ago) switched to 20w50 from 10w30. My oil pressures went up under WOT, at least when my flaky oil pressure sensor was cooperating.

7) I don't have an airpump, and the car is fairly well modded. My mod list:

Engine:
PFS cat-back exhaust
Pettit Racing air-intake
Pettit Racing power pulley
ASP Racing medium intercooler
XS Engineering ECU
Removed plastic coolant overflow tank
N-Tech Engineering BMK (Battery Miniaturization Kit)
Crane HI-6 ignition amplifier
MGK spark plug wires
NGK Platinum spark plugs (all 9's)
Bonez stainless steel downpipe (ceramic coated)
Bonez hi-flow cat
Non-sequential twin-turbo conversion (with ported wastegate and ceramic coated manifolds)
Apexi Super AVC-R electronic boost controller
Air-pump removed
EGR removed
Many polished engine components

Suspension:
PFS front and rear sway bars
PFS progressive rate springs
Koni adjustable shocks

Drivetrain:
PFS 4.33 ring and pinion kit
Mazdatrix Short Throw Shifter
Center Force Dual Friction clutch
9.5 pound flywheel
17" Konig Villain wheels (17x8, 17x9) fully polished
Yokohama AVS Sport tires (225/45/17, 255/40/17)

Instruments:
HKS boost gauge
HKS EGT (exhaust gas temperature) gauge
HKS oil temperature gauge
Tri-Point Engineering air-fuel ratio meter
Injector Duty Cycle display (via Apexi AVC-R boost controller)


Any help or pointers will be greatly appreciated!

Thanks,

Colin

revvvin7

It must be your PFS progressive rate springs. I would take a look at those and make sure they don't have any leaks. lol


naw make sure you don't have a vacuum leak somewhere or maybe a blow gasket in your throttle body or upper to lower intake manifold.

twinturborx7pete

iTrader: (3)

Exactly, make sure you don't have any gaskets leaking or any other type of vacuum leak. The symptoms you described point to a vacuum leak. You can also test out your TPS to make sure it is getting the correct voltage if you are unable to find a leak. Check the couplers on your intercooler as well. Also check your Blow off valves for a leak.

As for your regular idle, you can always adjust the idle screw on the throttle body if you would like to raise or lower your idle manually. I have mine sitting at a nice steady, shake free 800rpm.

luis@champions-motorsports

check your tps voltage range make sure the voltage is with in specs.. .at closed possition it should be at .75 to 1.25 at wide open it should be at 4.8 to 5. volts...
look at your block off plates specially egr...(look for big vaccum leak).

we had one come loose once and car was doing same exact thing..

also if car still equipped with iac idle air control unit my be completely bad at first when they show signs of going bad units are not as anoing,,once they get worse they become very anoing...loping idle...
last thing if ecm set up is programable check idle map it may be to fat at idle and causing a lean rich movement and causing idle to fall and raise fall and raise..

linenoise

iTrader: (1)

Those two 3/4 inch metal tubes that are left over after a airpump delete: The bottom one is capped and the top cap has evidently fallen off (I can see where it fell off, but the engine is too hot to reach). Possible cause?

linenoise

iTrader: (1)

nope, that wasn't it

linenoise

iTrader: (1)

found it! one of the vaccuum caps had a hole in it. I found it by spraying a little carb cleaner and listening for idle change. Thanks everyone!