Really need some help guys, 2 years after my VVT swap, the car is still about worthless below 60*. Warmed up, it runs great, got the AC features working, very happy.

MS3 basic by REV, 2003 VVT motor with 99 manifold, 2003 injectors. Just as a prelude, I've gone back to the base map 4 times, re-calibrated the 02 3 times, bought a new IAC valve from mazda, cleaned the TB and ports inside spotless, none of which had much of an effect.


The problem:

Below 60* or so, I go to start the car. It catches early (cranking rpm 300), and then instantly bogs, running around 750 at first. It really doesn't sound like all the cylinders are firing properly. Touching the throttle makes the engine chug more, and rpm drop. So it's lean, right? WUE and ASE can be maxed/min-ed, no change. Timing +/- 5 points, no change. Idle cranking duty has been raised, which helps a bit. It runs like this in closed loop idle, bogging away until I can get some heat and RPM in the motor.

Adjusting values create some AFR changes, and it runs slightly different, but the bogging is still there. Trying to drive, you can go wide open and make no power. The car just falls on its face, stumbles, and generally refuses to move. Once coolant reaches 105* or so, I can rev it to 2-3k a few times, and it smooths out and is driveable.



Maybe my 02 is biased, giving me false readings even when "calibrated"? I'm attaching my .msq. I can take a log tomorrow morning (sat at work for 10 minutes trying to get it warmed up so I could come home), but I have to imagine something is beyond fucked up in my tune and may be instantly noticeable. I've been searching and reading for nearly 2 years now and it still hasn't really changed. I'm about at my wits end, I'm about ready to pull the motor out and go back to 100% stock. Any suggestions at all are appreciated.

 

When was the last time you checked valve lash?

 

Head was cleaned, decked, and valves were set at the time of the swap. Maybe 5-6K miles ago? No valves needed replaced, new valve angles cut.



Here's a quick log of the issue, with a few light throttle blips showing how lean it goes. In the next log, I have jumped WUE approx. 100%. Closer to stoich, still too lean for cold idle, it's like I can't add enough fuel to compensate.

 

If there is any issue with the logs, please let me know.

 

Basically, the car is compensating COOLANT based WUE/ASE, but not compensating for the denser air. This has no bearing on coolant temp whatsoever. Perhaps a MAP issue? The car is idling the the same cells it always does. It runs like a champ at 120* coolant temp, the engine shutters slightly, and idles normally around 13/1 afr.

 

Find out what afr you're running at 1500rpm and whatever map row you idle in when cold. WUE is only a multiplication of your fuel table, so if you have a lean cell at a slightly different map reading or RPM (cold should be 1500, warm 1000), then WUE might not be doing enough.

 

Gotcha, will check that tonight (possibly tomorrow morning), when I cold start. I was initially against moving too far off Revs base map, but now I'm about open to anything.


Measured 02 sensor heater circuit, 5.1ohm, so I'm confident it is working and functional.

 

Idle cells for 40-55kpa and cold idle rpm (1200-1500), raised 50 points. Pulsewidth is up to 9ms at idle, AFR hovers around 12.5-13. Literally exactly the same behavior.

If I rev the car (same KPA load, rpm increasing, it continues to go super lean, like 20/1. I added 30points of fuel here, no change at all, not even in AFR. It hit 115*coolant temp, stumbled, and idles perfectly now.

Is this telling me my wideband is bad? How much fuel can I reasonably add? I have 100 points of fuel on my map in idle cells, plus ASE,WUE multipliers. I cannot comprehend that it needs this much fuel, and then when it hits 115*, it's suddenly okay with 40 fewer points.

 

Went back to the pre +50 points of fuel map after starting tonight. Coolant temp at 80*. I can now smell gas out the tail-pipe, and am running in closed loop idle at 10:1. It's never been that rich at idle, always pegged lean, and it was running much better after 10seconds from start.


At this point I have to believe the wideband is bad, and the MS3 is trying to use closed loop idle with bad data. I suppose a new wideband is in order, calibrate, then retest?

 

Why are you on closed loop on an untuned ecu?

Definitely check for fuel and spark when cold, sounds like you might have a dead something.

 

Plenty of tuning done, just all above 60* ambient temp. If the car is above 60* or so ambient, it's 100% perfect. Closed loop idle with ac stuff works fine, street tuned fuel map off the base map REV sent me. Aside from below 60* start, it's basically like it was from the factory. It can be 20* out, as long as the motor is up to 110* or so, it will run and re-start perfectly. Up until now, I basically just had to give up driving the car when it got cool.


My current plan is to use the scope tomorrow to confirm spark output, I know the injectors function, the varying AFR (from 20;1 consistently then 10;1 tonight, on an identical map) makes me thing the wideband 02 is bad.



If I am being ignorant or sounding foolish, please tell me. If I don't have a biased sensor, I feel like I am missing something huge and obvious. I'm a mechanic 40+ hours a week, and looking at the AFRs/vs the pulse width, I cannot comprehend that this car is actually lean.

EDIT: I'll be putting a vacuum gauge on it tomorrow as well.

 

So - the reason why I mentioned valve lash - I had a 99 head, would idle.. okay.. but AFR's fluctuated a bit before it warmed up a little, seemed like I couldn't get WUE dialed in like I wanted. Eventually I read a thread here, and sure enough, my valve seats were cut too thin and I was out of lash until the head warmed up. 2 cylinders were low compression cold, perfectly fine warm. I thought I'd throw it out there because I pulled my hair for a few weeks trying to hunt it down.

 

Perhaps I'll do a leakdown before I leave work once the engine is cool. Thanks.

 

Cold start when well today in open loop. I played with the IAC duty to get it running at a reasonable rpm, then added fuel to smooth it out. About 80* coolant temp it smoothed out.


Are/were my expectations for reasonable adjustments on a base map unrealistic? I don't have a problem making big changes, but when I change duty cycle from 30% to 70%, I'm a bit concerned. Like I said, I'm more than happy to make changes, but some of the sweeping changes I'm making are much bigger than what I would consider "normal" to adjust off of a run-able base map. This is my first aftermarket ECU, so maybe my perceptions need adjusted. I'll try closed loop this evening for the cold start, after I confirm it DOES start with the new changes.

 

With a base map, some of the settings will be close and some won't be close at all. A base map is designed to get the car to crank and run roughly enough to allow actual tuning. It is not designed to be run as is in perpetuity.

 

Gotcha, that explains a lot, since the timing table and VVT stuff seems basically perfect. I messed with the idle screw, idle is happy, but high now. I had run it nearly all the way in, fighting CLI trying to lower the idle rpm. I likely need drop IAC duty now. Fighting closed loop explains my lack of results with wild changes. I will keep re-tuning the open loop stuff, then reevaluate.



I sincerely appreciate all the responses in this thread.

 

put the idle screw back to oem/original position and never touch it again ever

 

This.

 

Idle screw was adjusted last year, OEM position now unknown. At the time, it fixed my high idle issue. I'm expecting to have to tune around that now, since I know they are set at the factory for a specific throttle body assembly.


EDIT: or I could re-set the screw to a factory-ish position - most cars is barely running at 500rpm with the IAC unplugged. For now I'll see how it goes. Hot idle is now perfect in open loop. 125*+ is now basically perfect in open loop.

Hopefully I'll knock out some ASE and IAC crank duty settings tomorrow.

 

Original screw position unknown? Set the car on fire.