MX-3.com

Hi, I just signed up to this site so that I could maybe get some help & advice for my 1992 V6. When I bought it I had a 140pt. inspection done on it, and noted to the mechanic that there were some surging issues while the car is warming up, and somewhat randomly afterwards.

Since the car was parked for 3 years before I bought it, there was no antifreeze in it, which the mechanic said COULD cause some surging. After putting in antifreeze & about 2 grand worth of other work (timing belt, water pump, alt belt, valve covers & gaskets etc.) the car runs great, but the surging still happens and occassionally the car stalls as it tends to bog down after it surges.

I am thinking this is the O2 sensor, but I am not sure as i've never dealt with that type of problem. Seems to be pretty common on these cars though, as I see lots of discussion about the O2's, but wasn't sure if this was my problem.

Oh, and the other thing I wanted to ask about was should the RPM's slightly climb when I engage the clutch & put the car in gear?? The surging occurs quite often when I engage & put it in gear, wondering if maybe its as simple as a clutch adjustment. (Also happens without the clutch being engaged though)

What i'm wondering is how do I determine what the problem is, and how much will it be to replace it if it is the O2 sensors? Unfortunately I don't have the tools & will likely have to take it to my mechanic.

Please help me out! I would love to do the work myself if its not too hard. I'm a chick who likes to work on cars, but only has minimal knowledge of engines.

Thanks....

Hehe, welcome to the site! Nice to see that "chicks" love these cars as well. Now to that problem of yours: I don't have the slightest clue, although I think that it should do that thing when you change gear. Mine does the same (also a '92)...

Nice to see that someone pays attention to these cars! c",)

Thanks! I absolutely LOVE this car, and have always drooled over them. Finally could afford a new car, so the search was on for the MX-3.

I was thinking the slight rev when you put the car in gear was normal, so i'm glad you confirmed that.

However the surging i'm referring to is about 500-1000 rpm surges, which sometimes on the downswing bog the car down to the point that it stalls. It just seems to me that its not getting the air.

Perhaps I ought to enter mycar in this registry hey?? Need to get some pics of it.

Try and test your engine for codes by jumping ten and gnd and see if that tells you anything. Follow these instructions
http://www.mx-3.com/ubb/ultimatebb.php?ubb=get_topic;f=23;t=000005

Thank you! Hopefully I will be able to run these diagnostics tonight. Will keep this thread updated with what I find in case I need more help. Much appreciated!!

The rise in revs is intentional, and comes from the action of clutch and neutral switches.

The bogging down is more likely to be caused by "too much" air, i.e. unmetered air getting in through a leak in the induction tract downstream of the VAF. Most common cause is a crack in the "accordion" hose between the VAF and the throttle body.

Wow, thanks for all the help. I likely wouldn't have thought of that. Will check out both avenues!! My ultimate goal is to make this car brand new again.... now if only I could turn the speedo back a few thousand k.....

To elaborate a little more - when I start the car it revs at about 2000rpm for the first minute, then goes down to about 1500rpm. Longer you leave it idling, the lower the revs get. I used to have an old Escort that did this to help warm the engine up faster, but it didn't go up to 2000rpm, just 1500.

So, when I take off in first gear (i'm a "stick chick" ha ha) it seems to have more punch than it should, ie: when I let off the gas the revs stay up there for a bit before slowing, and the first couple of shifts, up or down, the revs climb when I push the clutch in, before falling back down to normal. After a little while it stops doing this, and idles at a fairly normal 500rpm, with small surges happening. After even longer the surges stop too.

Maybe this will help someone better understand what i'm trying to describe.

The help i've already received is pretty valuable i'd say, but this paper clip diagnostic test does sound a little risky. Is this a regular practice? Should I be holding that paper clip with a pair of rubber gripped pliers? Is it something thats commonly used??

Is the car properly warmed up when it is doing this or not?

remember when the car is cold it will rev a little higher at idle until it warms up.

yep, its worse when its cold, but it still does it when its warmed up.

Idle speed when warmed up, with coolant fan off, should be 640 to 700 rpm. 500 is too low, maybe a sign of lean mixture due to vacuum leak, but may just need adjusting. Initial start rpm of 2000 sounds ok if it's really cold weather.

The engine does set a higher idle speed if it thinks you're about to take off (not in neutral, clutch pedal pressed) or changing gear. If you stop at the lights, it will wait maybe 10 sec. before lowering the idle to 670+-, in case you're doing a quick takeoff. As I said, it gets this information from the neutral and clutch switches.

Other (than a vacuum leak) possible causes of surging:
Bad contact in VAF sensor
Poor spark
Over-rich mixture due to fuel evaporative system malfunction
Low engine compression

The paper clip method of grounding the TEN terminal carries no risk and does not require insulated gloves or tools. All it does is apply ground to the test terminal to signal the ECU to output fault codes. The paper clip is at ground, so the voltage is zero, and no current is drawn. Using a paper clip may sound "informal" but is a common practice - a Mazda dealer will use a special test set, but it does exactly the same thing.

<small>[ September 21, 2004, 05:43 PM: Message edited by: IanL ]</small>

Originally posted by J-Bird:
To elaborate a little more - when I start the car it revs at about 2000rpm for the first minute, then goes down to about 1500rpm. Longer you leave it idling, the lower the revs get. I used to have an old Escort that did this to help warm the engine up faster, but it didn't go up to 2000rpm, just 1500.

So, when I take off in first gear (i'm a "stick chick" ha ha) it seems to have more punch than it should, ie: when I let off the gas the revs stay up there for a bit before slowing, and the first couple of shifts, up or down, the revs climb when I push the clutch in, before falling back down to normal. After a little while it stops doing this, and idles at a fairly normal 500rpm, with small surges happening. After even longer the surges stop too.

Maybe this will help someone better understand what i'm trying to describe.

The help i've already received is pretty valuable i'd say, but this paper clip diagnostic test does sound a little risky. Is this a regular practice? Should I be holding that paper clip with a pair of rubber gripped pliers? Is it something thats commonly used??

As far as the paper clip thing goes it is alright to do this it wont hurt your car in any way. (that is of course if you do it right just make sure you jump the right pins together) I have done this a couple of times to get codes out of my car. Reading the codes is a little tricky but just read the faq about it and it should be a breeze. Good Luck!!

Thanks again, all of you have been very helpful!!

Unfortunately, the surging has nothing to do with my clutching, if it was me bogging it out & not realising it, then I would say i'm not fit to be on this website, let alone driving!!

it is definatley a vacuum leak because i had the same thing on my mx-3 gs so check your vacuum lines but it will most likely be a crack in your plastic intake so try bending it to make the cracks appear but it will most likely be in the spiral looking thing cuz that's where my leak was so i hope this helps.

Ok, I've done a diagnostic & also changed the plugs on my car. First of all, some of the plugs were pretty oily, other than the head gasket, what could be causing that??

The diagnostic gave me what I interpret to be an 08 and a 22. 08 being the VAF, which was assumed in why the engine was surging. I can't find any cracks in the accordion hose though. At least nothing glaring.

22 isn't on the instruction page I had, so either its a 10 & 12, or someone needs to please tell me what a 22 is.

Thanks!!!