94 mx3 gs1.8 Drives jumpy lurchy going from stop HELP!

[evaunit360]

Recently I have had trouble with my Mx3. I will start up the car with no problem just like any other day. I put the car into reverse and back out of my spot just like normal no problems. I will then put the car into gear and let out the clutch while giving it gas and I will suddenly drop the rpms if I let the clutch out all the way like I'm going to kill it. I have been driving this car for 3 years every day so I know how to drive it. It will do this ever time from a stop. I like have to keep the clutch pushed in until I'm going fast enough to keep it from jumping/stumbling. It's like kinda violently lurching going slow in first and second. However, when I get going 25ish mph and continue to shift through the gears it will drive like a dream/like normal. I can't seem to figure this out. I changed out my spark plugs and spark plug wires and did an oil change. It only seems to get worse the more times I drive it. I hope I'm not hurting anything on my engine.

So far the only thing I have come to the conclusion is that it's a TPS sensor issue?

What do you guys think?

Thanks

William

[MrMazda92]

It sounds like you have been searching around, that is definitely in your favor!

Adjusting your TPS is an important step in diagnosing issues pertaining to rough idle, stop and go trouble, etc. I would first remove the accordion tubing that attaches your air filter to your throttle body, and inspect that for cracks. If it is original, it will be cracked, the question is how badly. You're looking for an obvious air leak, one large enough to allow unmetered air into the engine. This is less noticeable at high RPMs, and more noticeable at low RPMs, so I suggest adding this to your checklist.

Good luck, and post your results! More info will always help us to answer your questions more thoroughly.

[evaunit360]

If it's Not in gear it runs great. That's why I don't understand though. I can rev it to 7000 and back all day if I wanted just like the day I bought it. It's ONLY when it's in gear and going slow. Highway speed drives just as amazing as the day I got it. I just want to emphasize that it's only a issue starting from the beginning of driving till approx 25 mph and then it's fine...

[MrMazda92]

Does it matter what gear you're in? You specified 25 mph, this is pretty specific... I'd assume 2nd/3rd gear, but it sounds like a low RPM issue to me.

[evaunit360]

Like it wants to take off when I let out the clutch just like normal, then it will just lurch a whole bunch in a strange rythm with you are driving until you get to the later half of second and then by third you are going fast enough to were the problem goes away and it drives great. If I downshift into 3rd and second it won't show the negative symptoms. Strange strange...

[MrMazda92]

Have you tried short shifting by any chance? This could help determine if the problem is transmission related. Try a 1st > 3rd shift at ~4,500 RPMs, but rev-match like normal.

From what you're describing so far, it sounds like either your idle is too low, or your throttle plate closes too far when you release the throttle. This would definitely cause some bucking if you ease the throttle between 1st and 2nd, due to the increased torque over say 3rd>4th.

I'm no expert on this, but without seeing it first hand, that's what it sounds like to me.

I would start with a good throttle body cleaning, as outlined here(4 banger TB shown, process is very similar):
viewtopic.php?f=3&t=42551&p=587830&hili ... tb#p587830

After that, I would adjust your TPS(Throttle Position Sensor), as outlined here in post #5:
viewtopic.php?f=23&t=47561

If you do both of these properly, especially the TPS adjust(can be tedious, I highly recommend removing the throttle body before adjusting!), you will either have a solution or 2 more items to check off the list.

Good luck! =)

[evaunit360]

Thank you very much. I have some time today so I'll give it a shot.

[MrMazda92]

You're welcome! Just remember to post your results, it will help us to better help you.

Mx-3s definitely take some work to get them where we want, but any 20 year old car is like that. I've got 2 of them, and tbh I've spent the last 3 hours working on seatbelt swaps and problems with both cars. Still, it'll be nice knowing that I will never hear that dreaded seatbelt beep again, manual belts are the way to go!

[evaunit360]

Found a little hose that goes the the air filter had been broken off. I don't know what it does but we are trying to repair that connection. Do you guys know what that does?

[mikeinaus]

that goes to the egr

[evaunit360]

Probably why it won't pass smog either...

[MrMazda92]

Blame the EGR anybody? Where did that thread disappear to?

[evaunit360]

I'm assuming that won't help?


I was only 10 points high on my test.

[MrMazda92]

No it very likely could, I was recalling a thread where everybody blamed EGR for everyday problems, even those unrelated to their cars

Sorry for the thread hijack, EGR definitely effects your emissions testing.

[RedAutobotMX3]

All of the info so far has been good and helpful, but as i always like to play devil's advocate, allow me to suggest something totally alternative; a bad motor mount, most likely the one furthest back against the firewall and under the K member. This can simply be diagnosed by looking at the motor as you rev the engine, and if the motor bucks and vibrates hard, this could definitely put a strain on the motor trying to engage the clutch and drive wheels, but would be hardly noticeable while moving and shifting at driving speeds.
GL and HF!