Hey everyone, I've been having some strange issues with my 93 GS/SE lately. Car runs like a top, never had a major hiccup, she's overall in fantastic shape. However, in the last couple of months I've been getting an intermittent issue concerning first gear starts. I can get the car into first from a stop with no problem, try to move and unless I play with the gas and clutch just right, she wants to die out (or take a severe drop) around 2-3k on the tach. I originally thought it was a clutch issue so I had a local Mazda mechanic I trust take a look at it. Said the clutch was fine, I would be seeing issues in all gears if that were the case. When it starts to die, if I clutch in partial and give it more gas to comp for the drop in rev's she stays on (i never let it fully die out if i can help it). I just cleaned out the TB with some seafoam spray and checked the air intake/filter/piping and did not see anything out of the ordinary. Can not find any vac leaks, no abnormal sounds under the hood. Both VRIS's appear to be activating at their proper times and nothing is sticking. Took it to Advanced Auto and had the charging system tested, no issues there either. Once I am past first gear, everything acts normal for the most part. All gears pull decently strong, can get up to speed with no real issues, highway she coasts perfectly.
I've checked just about everything I can think of. I am at a loss here. Thoughts?
PS: I have a printed copy of the FSM and checked the troubleshooting area for this issue, I have no CEL codes when jumpered and have not been able to test the individual sensors as of yet. TPS maybe?
I believe there is a sensor when you press the clutch and put it into first gear.
This sensor lets the ECU know that the car wants to move soon so the ECU will slightly raise the revs.
Perhaps this one is broken.
Yeah, that part is working. I go from around 700 rpm's at idle in neutral to a little above 1000 when in gear but not moving. Did not know it was a sensor though, thought that was vac/solenoid actuated. Let me clear something up as I realize I didn't mention this before: this happens ONLY as I am letting out the clutch. Feels like when it starts to grab, it grabs TOO much and tries to halt the engine. I am not letting it out too fast, actually very slow and typically have to press in a little whenever it tries to choke to avoid the resistance shutting her down.
Before doing anything else, I'd start with a full tune up. Spark plugs, wires, distributor rotor and cap, PCV, and seafoam mixed in the gas. If that doesn't work, report back, and we can look further.
And post a pic of the spark plugs while you're at it, so we can see how the car is running.
Did a full tune-up about a month ago just after this started happening. Changed the plugs with fresh Denso's, wires were a new set of NGK's, dist cap, dist rotor, checked the PCV it's working (not very old), and I run seafoam about once every two months with a full tank of 93 grade octane pump gas. I was thinking about pulling the plugs tomorrow and inspecting them and also doing a compression test while I am at it, just to be sure. I live in a very hot climate during the summer time, central North Carolina, average temps lately have been in the triple digits and humidity is insane most days. Even writing this right now, it's just before midnight and the temp outside is 87.4F with a heat index of 97.1F. Not blaming the heat though, car ran great last summer with similar conditions. I do notice some light pinging from time to time taking it up a hill in a low gear but typically buying better gas solves that without much issue.
I'll post pics tomorrow if I can tolerate the heat long enough to go work on her.
Do you have your IAC disconnected? If not, I'd recommend you test it. I don't remember how off the top of my head, but searching on here should yield good answers.
When you're having a hard time starting, do you find yourself holding the clutch in too far and over-revving to compensate for the near stall? It will cause your clutch to slip a little, but it lets you get the car moving... If so, I'd definitely look into the IAC.
YES! That's EXACTLY how it's acting. I could not find the right words to describe exactly how it was behaving but I think you've just hit it pretty good there.
Before you check the IAC, since it is harder to check, someone above mentioned checking the Neutral Switch on the trans, but didn't give you the part name to look for. It adjusts idle based on the clutch poition (is an on/off swtich, or in electrical terms a open/closed switch) and helps with the described start and also catches the revs from falling too low when you release the clutch suddenly. If the revs stop pretty close to normal when you get out of gear quickly then the Neutral switch is probably ok and just go to the IAC checking.
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If you're having a hard time driving the car and happen to need it(for school, work, etc.) on a daily basis, you could raise the idle a little to compensate a bit. You'll burn more gas when the car's idling, but it will help you avoid stalling(and your clutch slipping). I actually run my idle a little high because my IAC is disconnected at all times, it was causing a ridiculous idle surge and I haven't replaced it yet. My idle is ~850 when it's warm out, and drops to around 700 at night.
+1 on the IAC.
The fact that your idle is going up when you put your car in gear tells me your neutral switch is good, but it never hurts to check anyways.
Thanks again for all the suggestions guys, unfortunately earlier this morning I had to pay a visit to my doctor who sent me home loaded up on meds due to a rapid case of bronchitis that is whooping my butt.
I have been driving the car as usual, just having to use a lot of patience to compensate for the issue when getting moving. It's not totally stopping me just being severely annoying (and make you look like a fool at a red light )
MrMazda is right, I've been manually overcompensating for the glitch by applying more gas and it IS causing clutch slippage which is even more annoying. How bad is this going to screw up my clutch in the long run? Also, with those switches mentioned, do they control fuel rate at all? It feels like it's cutting out fuel when it does this, very hard to get the rev's up again occasionally.
I wont be able to go look at it anytime soon due to illness but I will take a look at all of this and post back when I find anything.
Actually, the ECU will increase your fuel delivery when you get in gear, together with opening the IAC, to get more air. My guess is you're getting more fuel, but the IAC is not letting the extra air through, which is causing the engine to run rich, until you apply throttle.
Either way, it's nothing serious, so relax and get better. You will have plenty of time to take care of it.
About the clutch, don't worry. Clutches are unbelievably rugged.
Ahh, feel better soon! I know how mouth/throat related things can go downhill fast, and how much it can take out of you! You'll pull through it, and the car will be waiting for you when you do! =)
You might have success with increasing your idle for now though, to at least make driving a little more pleasant. I assume you know how to do that already, but if you don't there are quite a few guides bouncing around the forums.
I second the clutch strength statement, and honestly if it's not the OEM clutch... it will probably outlast the transmission That's a little dry, but it's been known to happen... Don't let me discourage you, you'll get it fixed in no time!
I want to hammer on the idle speed point though, it will seriously make it bearable until you can fix it right! I drive with my idle high every day, and honestly I got used to it pretty quickly. =)
So, let's say that the IAC in my mx3 is the issue here. Can't say I'm 100% familiar with the part as I've not had to mess with it before. Is it possible to repair one or would it require replacement? Been looking at prices online, not finding one very cheap.
Is there a website anyone knows of that gives more detailed information about this part/system in general so I can get a better understanding of it's function? My engineering mind wants to know more
Short of unplugging it, is there anything else that can be done? What sort of effect will disconnecting it have over all?
Looks like I should finally get around to fixing the exhaust on my RX7 and drive it for a while instead
The IAC is just a valve activated by a solenoid. When open, a measured amount of air can bypass the butterfly valve, and, combined with some extra fuel, it raises your idle.
Sometimes you can fix it, sometimes you can't. If the solenoid coil is in good shape, most times the problem is the valve got stuck (thanks to the gunk deposits created by the EGR and PCV systems). If that's the case, all you need to do is clean it up, until, upon applying power to the solenoid, you can hear it click, clearly.
)
That's a little dry, but it's been known to happen... Don't let me discourage you, you'll get it fixed in no time!