Engine Problem?

MX94XM · Post by **MX94XM** » March 3rd, 2005, 8:16 pm

Ok, here's my problem. I have a 1994 Mx-3 and as of late when the car is started and running, whenever i begin to brake to stop for a light or stop sign or whatever reason. my rpm's go below idle as if it were about to stall out. it doesnt fully stall, it just shakes as if going to stall.... i am not sure what the problem could be, a friend suggested it may be my timing is messed up or something. but if anyone has any information, ideas, or anything helpful to say let me know, its driving me nuts...

thanks,
Josh

mazdubber · Post by **mazdubber** » March 3rd, 2005, 8:20 pm

I assume it's a GS (V6). It might be something as simple as the need for a tune up. Air filter...clean up the throttle body. I wouldn't be too concerned if I were you.

relisys_3200 · Post by **relisys_3200** » March 3rd, 2005, 8:23 pm

be sure to check your ribbed intake tube for cracks...could be leaking air

Tunes67 · Post by **Tunes67** » March 3rd, 2005, 8:31 pm

My 94 RS does something similar.. though not as drastic.. When I hit the brakes.. my dash lights dim and my engine RPM drops almost to 500. It used to make my head lights dim as well. I am currently upgrading my ground straps and this has made a noticable difference. I am still in the process of troubleshooting this situation though.. but on my ride its definately electrical in origin. I have two more ground straps to make this weekend and I am going to get the alternator load checked. (already load checked my battery and its ok) This situation is aggrevated if more electrical load is applied. If the wipers are on, my stereo, heater, rear window defrost or Highbeams.. the more thats going the lower the idle drops.. it always rebounds back up though.. Besides the engine bay ground straps.. I also plan to find where the rear light assemblies ground and clean that up as well.

Tunes67

MX94XM · Post by **MX94XM** » March 3rd, 2005, 8:57 pm

alright, im with you on the whole lights dimming thing, cause my car does the same... im beginning to think it may be my speaker and amp draining a bit too much from the battery... my alternator went bad and i have a new one now... so im not sure if the ALT. is a possible prob.

And another thing with my engine is until recently, when i got the new alternator, i was going through about alternator belt about every month & a half, they would squeel horribly and when it got to a certain point it would snap off. it still rarely does it with the new ALT. so im now accusing the pulley system of being bad. could it be it??? again any info would be much appreciated

thanks,
Josh

userAttila19 · Post by **userAttila19** » March 18th, 2005, 10:06 pm

Hey man; your alternator situation does'nt sound good. I have the same stalling and power drain problem; it got progressively worse until the car just kept stalling. I replaced my alternator with a brand new Bosch ( $350.00 CAD) and now if fine.. Maybe go to someone else to get you alternator belt changed, maybe consider getting a new one (make sure not rebuild - unreliable). Good luck..
(BTW: I had a stalling problem before all of this also; and it did'nt only stall but the rpm's were all over, up and down. That was becuase of miss matched vaccum hoses on the air box. Make sure to check that thise are connected correctly)..

Tunes67 · Post by **Tunes67** » March 18th, 2005, 10:37 pm

I have additional information that I will post this weekend... I took my car to a automotive electrician.. the outcome is still pending a few more tests. But in my case the Alternator & voltage regulator have checked out fine. Battery has been load tested and is good. I dont want to post yet on the details I have gathered until I have a definative answer to the issue. Right now.. even with this electricians help we are still speculating. Btw.. this guy is really cool and has been doing this kind of troubleshooting for 29 years. He tested all the major circuits he could get at without removing or hacking into the wiring harness. He gave me a couple of "Experiments" for me to try and then to call him back with the results. Within the week I am hoping to have this issue resolved and will post all the steps I and the electrician have done to track this down.. as well as the fix. Cheers.

Tunes67

atlantamx3 · Post by **atlantamx3** » March 18th, 2005, 11:27 pm

Check your compression.

I bet you have a burnt valve on Cyl #3.

Tunes67 · Post by **Tunes67** » March 18th, 2005, 11:53 pm

Ha ha.. your a laugh riot.

machinehead · Post by **machinehead** » March 20th, 2005, 9:00 pm

Check this out. you were haveing the engine stutter thing. i do not think it is anything to do with the engine. I had the same issue your talkin bout and i got a brand new engine and transmission dropped in my 94 MX-3 and it still does this. Here is what I did. i went and bought a feul filter because i felt there was not enough gas getting to the engine due to the idiling. i put new feul filter on and it has not shaken since, get a feul filter dude, if it still does it you may have damage to the feul pump. your car is not getting enough gas, until you give it gas.

atlantamx3 · Post by **atlantamx3** » March 20th, 2005, 9:27 pm

Tunes67 wrote:Ha ha.. your a laugh riot.

Laugh all you want- but I am serious. Many people w/the SOHC and the low idle thing have had their compression checked and have Low compression on #3.

Tunes67 · Post by **Tunes67** » March 21st, 2005, 3:24 am

Laugh all you want- but I am serious.

If you indeed are serious.. then I apologize.. My first thought was that you were making light of the issue I had with my car when I first bought it.. there were numerous posts on it.. and yes.. I had a burnt valve in #3 cylinder. And while this did indeed smooth out my idle... there is still a electrically related problem. Weather here this weekend sucked and I was unable to work on my car to try out the "fixes" my auto electrician suggested I try. My idle is only slightly effected by the electrical issue.. mainly its annoying.. its not harming anything and the alternator has checked out. But the more load that is applied.. the idle speed does decrease slightly.. though it comes back up.. and it can be slightly rougher until accessories (or load) is decreased.

As for the fuel filter.. was planning on doing that as well.. along with a new charcoal canister.. there is excessive vaccum present when I remove the gas cap. I realize there should be some.. but what is present is more than I have ever seen on any car. Since its a sealed system.. I am kinda assuming the charcoal cannister is plugged up, since that is where its supposed to vent at (supposedly). And while this may indeed help the engine run better.. I doubt it will directly effect the electrical load issue.

Tunes67

Typhoonk · Post by **Typhoonk** » March 21st, 2005, 7:42 pm

Sounds like you got the same problem I had. The idle was good for a bit but as soon as the engine warmed up and went into closed look, it would do one of three things in random order:
1. idle perfectly fine (not too often)
2. idle really low (most of the time)
3. or search for the idle (up and down and up and down)

from my research and testing
1. check the intake for 'unmeasured air'
2. compression test engine
3. clean idle air valve and throttle body
4. tune-up -> wires, spark plugs (gapped to spec), intake filter
5. reset ecu and set idle

if you did those and it still idles funny, messing up your beats, and you headlights. Then it's 95%+ that it's your TPS (throttle postion sensor)

Some learned
Thottle Position Sensor -> it's a variable resistor or a POT. As the throttle is moved it changes the resistance in the TPS. This is what the computer is using to measure your air/fuel ratio.

If it's sticking or is dirty, cause these things do wear out (it's a wiper rubbing up and down), then it can send some funky info to the ECU.

(this is for manual tranny)
Testing TPS
1. detach connector from TPS
2. connect an ohmmeter between the bottom pin (IDL) and the middle pin (E)
3. insert a 0.004 in. (0.1mm) feeler gauge between the throttle stop screw and the stop lever
4. Verify there is continuity between terminals
5. put in a 0.039 in. (1.0mm) feeler gauge, and make sure there is no continuity between the terminals
6. Then open up the throttle wide open and verify there is no continuity again.
7. Next connect the ohmmeter between the top pin (POW) and the middle pin (E)
8. insert a 0.004 in. (0.1mm) feeler gauge between the throttle stop screw and the stop lever
9. verify there is no continuity between the terminals
10. put in a 0.039 in. (1.0mm) feeler gauge, and make sure there is no continuity between the terminals
11. then open up the throttle wide open and verify there is continuity between the termials.
12. If this is not true with your TPS then adjust the sensor (has two screws, then you can rotate the TPS), or the throttle cable.

Also a note I saw on the protege forum -> if you take the TPS off and move it manually and it doesn't move amazingly smooth, then it's messed and should get a new one.

hope this helps

word up.

Tunes67 · Post by **Tunes67** » March 21st, 2005, 8:13 pm

Thanks TyphoonK... Got that for the ATX as well?

I have a spare TPS from a MTX car.. is it the same as the TPS on my ATX car? I do have some of these minor symptoms..

1. idle perfectly fine (not too often)
2. idle really low (most of the time)
3. or search for the idle (up and down and up and down)

But I only notice the effect at all because I am watching for changes.. its so slight (maybe the TPS is just starting to go bad?) that I wouldnt notice it otherwise. There is a electrical problem here somewhere though. When my brake pedal is depressed.. the brake light circuit draws a spike of 25 Amps. This is a 5Amp circuit and shouldnt draw that much power. Only reason it hasnt killed the fuse is because the draw is very short in duration and the fuse doesnt get enough time to heat up and pop. This occurs regardless of whether the car is running or not. When the car is running.. it also has the additional side effect of the idle dropping briefly when the brake pedal is depressed.. though this only occurs if there are other electrical devices operational as well.. headlights.. heater.. RDefroster.. etc.. Thanks again.

Tunes67

Typhoonk · Post by **Typhoonk** » March 21st, 2005, 8:56 pm

TPS Automatic Transaxle test
1. Connect ohmmeter between the bottom pin (IDL) and the second from the bottom (E)
2. 3. insert a 0.004 in. (0.1mm) feeler gauge between the throttle stop screw and the stop lever
4. Verify there is continuity between terminals
5. Insert a 0.024 in. (0.6mm) feeler gauge between the throttle stop screw and stop lever
6. verify there is no continuity between terminals
7. Connect a ohmmeter between the third terminal from the bottom (Vt) and the bottom pin (E)
8. Verify that resistance increases as the throttle valve opening increases
9. with throttle valve fully closed the resistance should be below 1 kilohm and as the throttle valve is fully opened the resistance should increase to approx. 5 kilo ohms. (should be smooth)

But don't say it's bad until you test it!!!