If your timing was off, what symptoms might you experience, particularly at idle?

 

Backfiring and or stalling out if its really bad. I'm sure theres more

 

That's cool.

Anyone else? Could bad timing make your idle be high and bounce rhythmically?

 

sounds like a misadjusted TPS.

 

Or a combination of things.. Bad TPS, bad Timing.

You got to get your idle down to 800 or so in order to make an accurate timing adjustment...

Jarrett

 

Mine quit bouncing when I changed the O2 sensor.

I have a thread about fixing my Idle, might have some info
that could help.

 

Bought a timing light and shined it down at the pulley even though I know I can't set it until I can get it to idle. The mark showed up to the left of the pin about 1", maybe a little less, when the RPM's were at their peak (around 1600) and during the deceleration part of the bounce I can see the mark work its way back toward the pin. I know timing is supposed to advance at higher RPM's, but does anyone know how far left I should expect to see the mark at about 1600 RPM?

Hmmmm.. o2 sensor. I think the line coming from my o2 sensor is grounded out somewhere. No continuity between the sensor and the line at the ECU anyway... I'll try bypassing it tonight. Still, I didn't the the O2 sensor could cause a bounce, especially since it doesn't operate at idle (I think)?

 

Just how high is the idle when left alone????? O2 is supposed to be out of the loop at idle.

Try jumpering your initial set coupler and see if that changes the idle. I'd try next for sure. The initial set coupler should eliminate any outputs from the ECU that effect idle. Things like the bac etc. Yep. Jumper that initial set coupler right now and let us know what happen.

I suspect a vacuum leak of some sort. Could be a vac hose or a leaking intake gasket. A can of starter fluid sprayed around the intake and hoses will make the engine revs change when the fluid hits a air leak.

Another thing is the injector grommets located at the bottom of each injector. If not seated properly they will cause a air leak and a pulsing engine.

Again....what rpm is the engine at when fully warmed up and left to idle on it's own?

 

Retarded igniton timing on idle will cause the engine to idle really low or not at all.

Advanced ignition timing on idle will actually help cranking and will tend to idle higher, unless we're talking about 10+ degrees.


-Ted

 

Hailers - When fully warm and left alone, my RPM's bounce between 1300-1600 at a rate of about 1 bounce per second. Whether that qualifies as "idling" I don't know.

I have sprayed around everywhere I can reach with starter fluid and can't get the engine revs to change definitively, at least not to the satisfaction of my novice's ears. Is it possible those grommets are out of reach of my fluid spraying?

The reason I kind of doubt an intake leak is its history just before I bought it (I bought it with this idle problem.) It went into IdiotMechanic#1 after developing a problem where the RPM's would skyrocket as soon as you started the car. After Idiot#1 was done with it, it wouldn't start at all, and the owner brought it to Idiot#2, who replaced the CAS and either A:fixed a loose pin at the ECU or B:replaced the ECU because they left the window open while the car was on their lot and the passenger floor area flooded. If B: is true, then whatever that box next to the ECU is may have been trashed by water, too. Also there's still the mystery of my pin 2C, which does not connect to ground like it's supposed to, but goes off up into the harness somewhere, and, when disconnected and connected to another ground, makes the car unable to remain started. (Sorry for the long rant, but I figure one or more of these details might be a red flag.)

Oh, and on the deceleration part of the bounce, sometimes, something by the driver's feet beeps. So I get *vroom*beep*vroom*beep* etc.

I will jumper that initial set connector soon as I get home and post an update.

Meanwhile, anyone know how far to the left of the timing pin the leading mark should be at 1600 RPM's on a car that doesn't have problems and has correct timing?

Thanks, appreciate the help.

 

2C goes up into the harness..........and is mechanicaly spliced with two other ground wires that are terminated under the dymanic chamber/ throttle body/whatever you want to call it. It's grounded with a ring connector that is bolted to one of the housings.

1300 is not a idle. It's a rampage. Idle is around 750 plus or minus a touch. You can't set the timing as the car is right now.

I saw one car who's bac was stuck open that did what you say. It's a mystery to me what is wrong.

 

Should the idle adjust screw on my BAC not do anything at all with my RPM's the way they are? Because it doesn't do anything. If it should do something that might mean that my BAC is junk.

Dammit, I need a spare TII sitting around just to troubleshoot this.

You know, it's weird. When the idle bounces back up from 1300-1600 it feels like it's saving itself from stalling. So maybe my problem is that I'm about to stall and the computer's correcting for it. Maybe the bounce is just incidental, and my real problem is that the car won't stay started without the bounce. If I don't hold the accelerator until it's warm, it will stall.

Going home now. Will update re: initial set coupler in a couple hours.

 

BAC doesn't kick in unless RPM is under 1,200RPM.

-Ted

 

Jumping the initial set coupler did nothing. BAC could be stuck open regardless of what signal it's getting though, right?

 

mY car was doing that but then I got a new tps sensor and everything is fixed... but it could also be somthing to do with the timing,,, I would recomend geting a new tps sensor

 

you can test your tps, there is a how to in the factory service manual. This is very helpful, I thaught that my tps was gone, I tested it and it said it was still good. So i kept looking turned out to be a loose coupler for the FMIC. I know that my situation doesn't help you but it is just saying that getting a new tps isn't just something that you just try... first try testing your existing TPS, then if tests good keep trying and if in the end still not fixed, then it very well may be a minute flaw in the tps... but there is a small chance of that IMHO.

 

the bouncing idle is from a mis-adjusted TPS sensor.

My tps died right after I left the shop... I was pissed but my mechanic put in a used one for free. I maybe left the shop for 5 mins before I had to turn around.

I'm in the process of making a TPS checker and Mazda code checker(including a fuel mixture indicator)

 

******Jumping the initial set coupler did nothing. BAC could be stuck open regardless of what signal it's getting though, right?****** RIGHT. The piston/device inside could be held open with some gunk or what ever. Two 10mm size nuts hold it on along with the water hose. Take it off. Lay it on its back and pour some fuel injector cleaner in it til it's full. Let it sit over night and then exercise it by applying 12v and a ground to the two pins on it. It matters not which pin gets the 12v or the ground. Just make sure when fiddling around with it that you don't short the two wires IN THE PLUG, together ever. That will kill the output from the transistor in the ECU that operates the bac.

It does not sound like a tps problem......because the idle is waaaay up there around the figure you quoted above. It's either a bac stuck open or the throttle plates being held open a touch and not fully closing. Or some other unauthorized air leak b/t the throttle plates and the rotors.

 

About your timing.....go to this site http://www.teamfc3s.org/forum/showth...ghlight=timing

Here's the deal. Turn your engine til the timing marks line up for the Lead mark. Now take the black cover off your cas. Just two phillips screws. Now compare your cas with the one I posted in the above thread. It should not be any different than the picture. At least not off by more than a half tooth. That should get you within just a couple of degress from being spot on.

 

About my TPS: I've already tried changing it and adjusting it. I adjusted it by turning the screw until its resistance at idle position was 1 Kohm (across the correct set of terminals, yes) and within 5+/-1Kohm at wide open. That made the voltages at the check connector almost exactly 12V and 0V, which supposedly means "adjusted."

One weird thing that might further illuminate my problem is that when I unplug my TPS, the car will stay revved at somewhere between 2000-2500 RPM. It's tough to tell if the bouncing is resolved, though, since I can hold the throttle at those levels and there will be no bouncing at that point anyway.

It may be the throttle plates. Rotating the whole assembly in the engine bay, it does feel like it sticks a bit at the idle end of things.

I will clean the BAC tonight and lubricate the external TB moving parts. Is WD-40 good enough for that purpose or is there something better? Can I open up the TB and lube up the inside somehow? May need to check clearances in there anyway - something with yet another learning curve.

 

Oh and I'll try that CAS thing. Youdaman, Hailers.

 

CAS looked exactly like those pictures.

Took the BAC off and filled it as best I could with fuel injection cleaner. Will clean it up and work it around tomorrow.

Also noticed that my first cat was glowing very shortly after starting the car... that was probably like that this whole time. The glow didn't get brighter as it warmed up, if anything it got darker.

 

For my reference when I'm exercising the BAC, should I see that accordion-looking thing move and if so, how much/what should it look like?

I know that's kind of a weird thing to describe in words, sorry..

 

you won't see it move, you'll just hear a click.

Glowing cats usually mean rich mixtures BTW. If the condition is not remedied, you get a melted/fubar cat. not good.

Hugues -

 

The accordion/piston wll only move approx 1/4 inch from full close to full open. Don't expect it to move any further. Normally it works at opening/closing at about 120 hertz. It's always vibrating when the car is running.

Read this article and the part about the bac http://www.teamfc3s.org/info/articles/idle.html