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View Full Version : Need SR Gurus Help: Unstable Idling, High Boosting and High Temp


dongoesby
10-06-2009, 11:03 AM
Didn't get much from last post. Hope to get some on this one. So after making the SR run last week, I took the whole week for careful driving for trials and errors, I've found that making the motor to run right is even harder to just make it run. The motor now has funny idle, high boost and high exhust gas temperature.

The motor is a stock s14 zenki SR and has following upgrades:
all rubber hoses replaced (including fuel lines, heather hoses, and vacuum line; removed one of the factory vaccum line with stock boost restrictor valve)
all gaskets replaced (except headgasket and internal stuff)
NGK Copper spark plug
z32 fuel filter
tomei ras
tomei manifold
hks actuator
s15 smic core
greddy oil pan
taka turbo lines w/ oil restrictor
exedy lightweight flywheel
nismo thermostat
nismo engine/tranny mount

The swap was opt to be reliable and easy for first-timer who never done swap before like myself. Most procedures were done by per FSM and forum suggestions.

Besides I know the lifters are making tapping sound and needed to re-prime, the motor starts, runs and maks boost.

1. The idle now is fine and stable at ~900rpm, but for every 1 min or less, the idle drops a little and start jumping up and down from ~500rpm to ~800rpm) for about 5 secs. It sounded like the motor is breathing very difficult. Then it goes back to normal at 900rpm.

If I tap on the gas, it would go away faster. My defi boost gauge is reading vacuum around -60kpa (-8.7psi) at idle, and the needle isn't stable. It shakes tiny by few mm. When the idle jumps up and down, the boost gauge needle would jump up and down too.

There should be no vacuum leak since all the lines were replaced and all the IC pipes are tighted down with new screw-on clamps. But I can't be sure. Any chance it causes bad ground? Or bad stock recirculating valve? I know mine is not making any sound.

checked TBS is within spec
ajusted IVAC, helps but only a little

2. I have mounted the egt sensor at DP, less than an inch after turbo. The defi egt gauge shows around 800F at idle; 1000F when cruising 45mph; 1200 F @70mpn. When half throttle boosting, it reads 1430F, and boost reads around ~80kpa (11.6psi); However, when WOT, the egt jumps to scary near 1630F and the boost holds steady at near 1bar (14psi). I assume the engine is running lean after 12psi and cause the rocking high 1600F? I see there is little dried water mark on the blue AN fitting installed on the turbo housing. Burning tiny bit of coolant would cause high turbo tempt? How can I make the EGT temp go lower?

I hear the turbo spools really quick @ ~2300rpm and makes boost @~2800rpm. The gas mileage is around 24mpg. I don't feel too much power on 1st gear, but it is really pulling from 2nd and on. Are these normal?

3. The motor is simply stock with SMIC and stock boost soleniod. I have very little clues on why it is running 14psi. According to the HKS actuator manual, 128mm length is 11psi, making it shorter 122mm is ~14psi, so longer is making it run lower boost. I did not follow the 128mm length because it was too short to install onto the turbo. I've adjusted it to the length where I can fit it onto the turbo, which is a lot longer than 128mm.

The vacuum line route should be coorect too. Any idea why it is running much higher boost than stock 7psi?

4. At any gear if below 3krpm, stepping on the gas would make a subtle backward and forward driventrain knocking. Very much when you first time learning to drive a stickshift, and the car reacts violently when you release the clutch too much too fast. Is this a common sign of SR being lack of torque since it never happens to my old mighty KA?

I have a custom new clutch, it is a kelvar clutch disc with dual diaphragm pressure. As for today, I have yet to be able to move the car smoothly from a stop in 1st gear. Of course, start with 2nd is much more challenging than my old KA. And it still makes the drivetrain knocking sound. Any idea? Worn out differential bushing or it just a chatter from my nismo LSD?

Please feel free to help out.
Thank you so much!

GSXRJJordan
10-06-2009, 02:55 PM
1) Vacuum pressure is measured in 'inches of mercury' typically, "inHg", so doing the conversion from 60KPa gives you ~18inHg, which is good solid vacuum for idle. I don't know why it would search for idle, that's strange. I'd start by cleaning out the IACV by removing the plastic adjuster screw and throttle body coupler, and spraying a bunch of carb cleaner in there.

Is there a reason you suspect grounding to be an issue? Is your harness damaged?

2 and 3) It definitely sounds like you're running hot, and overboosting. If you remove the OEM boost control solenoid and hook the wastegate up to the throttle body directly, that'll tell you what your wastegate's set for.

4) Your motor mounts, trans mount, or differential mounts (or all 3) could be worn, which can all add to drivetrain lash. What else did you change when you did your swap?

SR_Vlurs
10-06-2009, 03:27 PM
you did change the motor mounts correct?
and clunk sound could be the lsd which is normal on them

dongoesby
10-06-2009, 03:43 PM
1) Vacuum pressure is measured in 'inches of mercury' typically, "inHg", so doing the conversion from 60KPa gives you ~18inHg, which is good solid vacuum for idle. I don't know why it would search for idle, that's strange. I'd start by cleaning out the IACV by removing the plastic adjuster screw and throttle body coupler, and spraying a bunch of carb cleaner in there.

Is there a reason you suspect grounding to be an issue? Is your harness damaged?

2 and 3) It definitely sounds like you're running hot, and overboosting. If you remove the OEM boost control solenoid and hook the wastegate up to the throttle body directly, that'll tell you what your wastegate's set for.

4) Your motor mounts, trans mount, or differential mounts (or all 3) could be worn, which can all add to drivetrain lash. What else did you change when you did your swap?

Thank you so much for answering my pm and giving help on my thread.

1. I cleaned the IVAC prior the swap. Sprayed "mean-green" then water and air dried for 3 days. I will clean it again w/ carb cleaner and see what happens.

Which plastic adjuster screw are you talking about? There is only a metal one I'm using to make the adjustment.

The harness was a mess and got repaired by a forum member here, mestizo. I'm impressed by his knowledge and the harness should be good. I'm trying to figure out all the possible errors. I can't be sure if it is my installation error.

I found the fast idle cam might be malfunctioning. It was fine when I adjusted it by per FSM two days ago. Idle the car for 10min, lossen the adj screw and let it went down to the "shorter line" (lowest point). Then when the engine cools down, it went back to "longer line" (highest point). However, today i found the lowest it would go is between the highest and lowest point, meaning it does not go far down. Anyways, I don't think this FIC would cause idle jumping so rapidly within 5secs every 1 min.

2 &3 I will route the vacuum line that way and give it a shot today.

4. Besides engine mount and tranny mount are replaced with new Nismo ones, I have new flywheel, clutch kit, factory TOB and nismo pivot ball. The diff, however, is still old rubber.

Is the lack of torque symptoms I have common for SRs? I'm very worry because it's been more than a week and I still can't move the car smoothly from a stop in the 1st.

GSXRJJordan
10-06-2009, 04:09 PM
Is the lack of torque symptoms I have common for SRs? I'm very worry because it's been more than a week and I still can't move the car smoothly from a stop in the 1st.

No, SR's actually have quite a bit of torque, especially for a turbo 4cyl. I could start mine in 2nd easily, and 3rd with some serious clutching.

A 'lack of torque' is perceived as a lack of power, meaning you have to rev it a bunch to get it to move... it doesn't seem like that's your problem. It seems like you're experiencing some drivetrain lash (clunks when you engage and disengage power) which are symptoms of loose mounts/mounting bolts, ring and pinion damage (worn out differential gears), or damaged driveshaft/tailshaft. If you can eliminate the differential as a possible cause (i.e., it didn't have this problem before, and the diff hasn't been changed) then it'd be logical to think that the problem came from your installation of the motorset.