2002SilverMiata

First, this is my build: https://www.miataturbo.net/forum/t27300/
I have a 2002 Miata with Begi S5 and Xede. I am still in the tuning process, but I have a new issue now:
I drove the car over the last few days.. it would hesitate and die coming up to a stop.. things like that, that should be fixable with tuning (I hope).
Tonight, after driving back from a 50 mile trip, I stopped and the engine was revving at 1500-2000 rpms without any throttle. I blipped the throttle, still came back down to that same area. I would oscillate in that range for a few moments, then stabilize at 1700-1800 rpms.
My first thought was the 'patched' MAF connector I had to deal with but that checked out fine. Then I thought it could be the TPS connector which had a crappy soldering job (by me ), so I cut it off, patched it and checked connectivitiy and it was fine. Started the car, still did the same thing.
I connected the Dynoscan and that showed the Absolute Throttle Position at 0% even with the high rpms. When I applied throttle, it did not indicate much change in Absolute Throttle Position, but the car did rev up... I also had the following trouble codes: P0102, P0123, P0505 and P0171 on the Dynoscan.
P0102 - MAF Senso Cicuit Low Input (I disconnected the connector while car running, probably triggered that one)
P0123 - TP (Throttle Position, I think) sensor high input.
P0505 - IAC circuit fault / Idle control system malfunction
P0171 - System Too Lean Bank 1

I checked all the vaccuum hoses, electrical connectors..etc. and everything was fine.
I did not check intercooler tubing in detail, but from what I was seeing, those were OK too. I could not raise the car tonight, but I will tomorrow if I need to check any of that out.
My mechanical and electrical skills are limited so, I have no idea what to do. I left a message for Stephanie to see what comes up with.
I NEED HELP

Ben

iTrader: (33)

Lean = high, oscillating idle. Don't know if the P0505 is the cause or the effect here.

My car wanted a few extra degrees of timing around idle to prevent stalling when coming to a stop.

2002SilverMiata

I will reset the DTCs and see which ones show up again and report back. I think initially I got the P0123 code only but I disconnected and reconnected sensors in the process probably triggering everything else.

2002SilverMiata

I cleared the DTCs and I did not get anything again, but the car is still doing the same thing. Here is a screen shot of the Dynoscan:



After the ride, when I released the throttle, the car would going up and down between 1500-2100 rpm and the AF meter was showing between 14-18 with these cycles. After 10 seconds, it would idle at what you see in the screen shot.
Any ideas?

2002SilverMiata

If anyone uses Dynoscan, here is a link to the log of the last ride:

http://cid-57a2a05488d82ba9.skydrive...march142009.ld

That was mostly on the highway, to check if the throttle position does reach 100% and it does . I'm sure that explanation wouldn't fly with an officer, but it was a test, seriously .

Ben

iTrader: (33)

dude...
it's either
too lean
has a vac leak
needs more timing
iac is inop

or a combination of the above (keeping in mind that lean is the effect of vac leak or inop iac valve)

2002SilverMiata

It could be lean and I tried a new map Stephanie provided tonight (still ran lean, but not as lean as the previous map).
To make sure there is not a vac leak, I went through all the intercooler tubing and any vac lines to the intake manifold... everything is OK.
Stephanie's new map shows less timing at idle (if I'm reading it correctly, numbers were 6.0 in previous map, now 4.0), so not sure about that one.
IAC inoperable? I guess I don't know how to check, but if it the one on the throttle body (I thought that was throttle position sensor), then when I disconnect that, I get an increase in rpms, when I reconnect it, rpms go down to where I started (still too high).
I messed with the idle adjustment screw, it was already almost completely closed and did not help too much.
Tonight, after the new map and all the checking, the rpm was around 1400-1500 (less than the previous time at 1700-1800. Also, when A/C & lights were on, rpm dropped to 1200-1300.
How do I check IAC (where is it too?) and what do I do if it non-functional? If there is something else I should consider, please let me know.
Thanks.

Stephanie Turner

It is very typical that it will idle high when running lean. However, this car went from stalling to idling too high on the same map. So that indicates, some type of mechanical problem. It is pulling in air from somewhere.

The MAF code is just an indicator that it is out of tune.
The TPS code does not make sense. Could be the wiring to the sensor.
The idle control circuit could be the IAC. Try unplugging it with the car running. It should stall. When an IAC goes bad, it typically creates and oscillating idle condition.
Stephanie

Mikeymx5

iTrader: (2)

Bad Idle is a sign of a leak in the intake tubing.

I had some problems with idle droop and after pressurizing the intake system I found several leaks even though i thought that everything was tight. An exhaust leak can do this as well surprisingly but that is easier to spot or smell.

My xede settings have the first two timing boxes a 5 degrees and the following at 3 so it about four-ish

My fuel was set really high in the first squares I think like 3 to 3.5 I will have to look.

Remember if you have the xede and 550cc injectors you will idle rich no tuning can fix this, so just tune to where your car will idle smoothly. The factory ECU can only compensate for a 30% injector size change and no piggy back will be able to change that unless it has control of the actual injector duty cycle.....

Stephanie told me that adding fuel can force the car in close loop which is kind of true, but with out knowing what the factory map looks like Im not really sure what the heck im doing in that area when tuning.

Would be nice if someone could make a unit that could adjust the injector duty cycle only at idle kind of like the voodoo box does but in reverse.

2002SilverMiata

I have not had a chance to work on the car until today... today, I really screwed up:
I tightened every T-Clamp on the intercooler piping, and still the idle would not change. I tried to change the idle position screw still idled too high.
So, I tried to search for other ways and went to miata.net. Someone suggested doing the idle adjustment with TEN/GRND jump on the diagnosis box.
Such a simple thing to do (I thought) - Instead I completely fucked up, but jumping GRND to the one next to TEN, I guess B+ from a diagram I saw. The car died almost immediately. I would not start again at all.




I checked all the fuses in the engine compartment fuse box (on passenger side) and even changed the MAIN fuse, still, nothing.
Then, I looked at the XEDE to see if the light is flashing before the car is started (as it should), and there was nothing. I disconnected the Xede and reconnected the stock ECU, still nothing. The car is cranking, but not starting.
Did I fry the ECU? What should I do? I was trying to fix one problem, and started a completely new one!!!
Help please.

2002SilverMiata

I guess it was just a fuse in the room fuse box, marked 'engine'
I did not look hard enough the first time. So, the car is running, still having the idle issue and I think it is from the IAC at this point, but no way to be sure.
So, I took off the Throttle Body/IAC. I used fuel line clamps to block the coolant lines so I don't have to drain all the coolant.
The pictures show what I found, but I have some questions:
1) Is it normal to have oily residue in the intake manifold? If yes, why would it be there? Is there recirculation?
2) Should the throttle plate in the TB have a small gap around the edges? My picture is blurred, but you can see light around the edges? Normal?
3) I found the oily residue also on the rubber tubing connecting the intercooler tube to the TB and in the intercooler tubing... Normal? I have a feeling it is not but I am new to this so I don't know.
4) I tested the resistance on the IAC terminals as the manual suggests and it is 9.6 ohm which is in the range of normal... Is it a sign it's OK or could it still be bad?
5) I don't know what kind of fluid it is on all these parts, but it could be PWS fluid - someone suggested that I have a leak under load from the original build thread I posted (see pictures here: https://www.miataturbo.net/forum/t27300-9/ ). Is it possible for that to get though the turbo rubber tubing and into the system or is more likely oil and from where??

I am currently soaking the IAC and TB in throttle body cleaner and I will let them sit there until tomorrow, then put everything back together and give it a try. I was also looking for a new IAC on Craigslist, on the Classified on this forum...etc no luck. So, I called FM and they have two from salvage, but I won't find out about that until Friday probably.

Here are the pictures and please let me know what you think:

Stephanie Turner

The broken IAB Valve gasket could very well explain the high idle.
Stephanie

2002SilverMiata

I don't think the IAC valve gasket was not broken until I took apart the TB and IAC. The rest of it was stuck to the TB.

2002SilverMiata

Since I have to wait to get a new IAC and have spent the time and effort to clean the IAC and TB with TB cleaner overnight, I thought I would put everything back together and see if things function normally.
I could not find a gasket to replace the one I had torn, so I used Blue gasket maker... Anyone has experience with this?
Anyway, I put everything back together but I cannot start putting load on the gasket until tomorrow (has to set overnight)... we shall see

Here are some pictures: