FearItself

After rebuilding my motor the idle has been a little ackward. When first starting off my car it's normal but after the motors warms up it starts idling above 1000 to 1500, or sometimes going from 1000 to 1500 over and over again, reving all by its self. And a few weeks ago it started idling at 2000 and was constantly boosting atleast 1lb+, even at idling but then that stopped. The flow meter is a little screwed up it dies off and gives me mad fuel cup when I'm about to boost at times, but sometimes it works. Do you thinkt he reason for all of this is my screwed up air flow meter? Or could the throttle be too high...it was before when I first got it...then my mechanic tuned it down. I still havn't figured out where the idle throttle is located underneath the intercooler. If someone could please help me!

tarmac_terror

Right now, I'm also trying to solve the exact same problem on my S5TII. Ever since I got the car, the idle has been getting a bit weird and progressively getting worse. Like, once the engine warms up, the idle would actually increase.

Last week while driving back from uni, once the engine warmed up, I pulled up to a red light and dropped it out of gear, the idle went up to 3K. After giving it a blip to try and reset it, the idle speed just kept jumping around between 2-3.5K. (The fact that I have a little bit of clutch drag didn't help getting it into gear either!). It's been behaving the same way every time the engine warms up ever since.

The manual said that in the case of high idle issues, the first devices to check were the BAC and AWS solenoid valves, since they are the major components of the idle control system (correct me if I'm wrong though...). I removed and checked the BAC solenoid today. The resistance was at approximately 7-8Ω. Although this is below the recommended resistance in the manual (10.7-12.3Ω ), an electrical engineer said that this doesn't matter, since what the resistance should tell is whether or not there's a short in the solenoid and clearly there is not, since it moved when a 12V source was applied. One thing I noticed was that the total travel, when the solenoid going from closed to 'fully' opened, was about 2mm. My first question is does anyone know if this is normal, or if it is supposed to open further?

Next up was the AWS solenoid valve, but I could NOT FIND IT FOR THE LIFE OF ME! I have a Jap import and the manual seems to be American... was the AWS system included in the JDM versions if the S5TII?

FearItself, did you end up figuring out whether it was your AFM that was giving you the problems? The next probable cause in the troubleshooting guide seems to be to inspect the AFM sensor... so I guess that's what I'll be checking out next.

Has anyone encountered this problem before or can anyone suggest what could be causing this?

Any help will be greatly appreciated.
Cheers,
- TT

P.S. I'm kinda glad that the BAC valve seems to be working ok. A replacement from Mazda is about AUS$1K (~US$700)!!!!!!!!!!!!!!

tarmac_terror

Ok before I get flamed, I acknowledge that the idle problem threads have been done to death and that I have searched for similar issues before posting!

Since my last post, I've checked out the AFM and the TPS (as per the factory manual). The AFM appears to be ok, and from what I understand doesn't usually cause problems.

The TPS looks a bit sus (no surprise I guess). The resistance readings were looking a bit high for both the narrow and full range sensors at 0 throttle (engine warm - ~2kΩ ). After using the adjuster screw and the narrow range sensor as a reference, I managed to bring down the resistance of the narrow range to spec. However, when I checked the full range sensor, it was still out. At 0 throttle it's still ~1.2kΩ and at WOT is 3kΩ (mazda references for full range: 0.6-0.9kΩ @ 0 throttle and 3.4-5.1kΩ @ WOT). The adjustment also lowered the idle speed significantly, but it still bounces up and down.

Is there a separate adjustment screw for the full range sensor, or are the two sensors supposed to be adjustable in sync? I couldn't find any reference to separate adjustment, so is it safe to assume that the sensor needs replacing?

Thanks for reading
- TT

tarmac_terror

Ok, so Mazda told me that a new sensor would take 2 months to ship in from Japan, so I hit up a couple of the wreckers today to find a replacement TPS. Used a volt meter to check that the resitances were within spec. So I replaced the original TPS with the one from the wreckers and the problem persists, but at a lower RPM (1000-1500 bouncing)!

Difference is that this time I decided to take it for a drive. The car felt awful! There was no power and it would frequently lose all power instantly, making the car decelerate and jerk forward. I did notice that the boost was way up under just normal driving conditions too.

ANYONE HAVE ANY IDEAS? PLEASE?

Vacuum leak? Another bad TPS?

- TT

eurolatin

this site has some info regards to that issue just search the site and you`ll find it http://fc3spro.com/ and that problem

tarmac_terror

Thanks for the link, eurolatin.

A few more things left to try now before giving up and taking it to a real mechanic!

- TT

Sideways7

iTrader: (7)

Just make sure its a real rotary mechanic, not just a regular one, but I'm sure you already knew that. And try to talk to others that have used them before, too. Just because they know about rotaries doesnt mean they're honest.

tarmac_terror

That's a good point. I'm afraid I'm now at the point where I'm going to have to talk to a mechanic...

I put the original TPS back in and whaddaya know! The power came back! The idle is sitting around an acceptable level now ~1.5K, so it is driveable. I also noticed that unplugging the BAC valve does nothing to the idle speed, when the car is warm.

I'm also starting to find that there are differences between the online factory manual (which I assume is for the american released vehicles) and the JDM cars in the electronics:

- The test plug for the TPS does not exist, thus I can't check it using the 2-light method. There is a 3-pin test plug in the same area, but I'm pretty certain it's connected to the three solenoid valve assembly (Relief, PRC and Switch).
- There is no AWS
- There is no idle control screw on the UIM
- There's no engine check light on the dash, so I don't know how to check for error codes!

Cheers,
- TT

tarmac_terror

Just a bit of an update... as I was stripping the engine back to short block, I noticed a few loose bolts/gaskets and pipes here and there that might have contributed to the poor idle. The most concerning one was the carbon pipe (I think it might have originally been rubber, but I couldn't tell!) going vertically onto the turbo being quite loose. As a result, the vertical section of the turbo (the air outlet I think) was covered in a thick layer of oil, which had to have come from the loose pipe from above... Might be a good idea to replace the pipe!

It'll be interesting to see if the idle problem persists after I put it all back together.

Thanks for reading,
- TT

iSP33D-for-J3SUS

It sounds very much like a vac leak to me. I just installed a cold air intake and I've had an awkward idle after warm up. (Pulsing idle usually, that revs from 1000 to 1500 usually) I'm sure I just need to get in there and tighten everything down extra good.

Cheers,
iSP33D-for-J3SUS