1998 Mazda 626 Mazda 626 RPM misbehaves + smell

Tiny
FDQX
  • MEMBER
  • 1998 MAZDA 626
  • 4 CYL
  • FWD
  • MANUAL
  • 140,000 MILES
I asked for help some months ago, but my car still doesn't work any better.

The prologue: http://www.2carpros.com/forum/1998-mazda-626-engine-dies-when-pressing-clutch-vt232363.html

The main problem is still the misbehaving RPM when I press clutch or let the gear to neutral. All the other problems are still there.

I have noticed something during these last months though:

- When using clutch, f.e. clutch pedal pressed when at traffic lights, sometimes a horrible smell comes from the engine bay. If I let off the clutch, it stops. It's worst when for example trying to get over some obstacle or when trying to get off the snow. The smell isn't any fluid.
- Sometimes when accelerating very fast, something (metal?) kind of "bangs" on the engine bay, and the car could WORK FINE for several days.
- The neutral gear switch gives weird readings, the whole engine electrical system was checked and everything else was OK.
- The alternator voltage has been measured while driving for several hundred miles, it's 14,5V steady. When idling, it drops to 13 slowly. Alternator was also checked with oscilloscope and it was OK, so I don't think it's the problem.
- The engine temperature meter is just below the center point, not right at the center.
- Throttle body, TB gaskets, TPS sensor, IAC valve and EGR were replaced.
- Sometimes the car doesn't find the idle RPM, the needle in the RPM meter just moves from 0 to 1000 and the car sounds like it's dying. BUT when I give it throttle almost to the redline, it finds the idle.

I don't think the problem is related to engine electrical, since the whole system was checked, the only malfunction was the neutral switch, but it was replaced and still doesn't give right readings.
What should I check next? Clutch? Fuel system? Cooling system? Exhaust?
What can cause that smell? It's not the famous rotten egg smell, but as horrible as it is.

There are no diagnostic codes present anymore.

Thanks in advance.
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Monday, April 13th, 2009 AT 9:59 AM

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Tiny
KHLOW2008
  • EXPERT
Hi fdqx,

Thank you for the donation and coming back to us again.

In your previous posts you have provided a very comprehensive report of the diagnosis and tests and after reviewing them, I have the following conclusion.

1. Crank pulley is bad. The harmonic balancer has detached itself from the main pulley and when accelerating, the alternator is running at a slower speed as the outer pulley ring is slipping on the main pulley.
This is consistent with the symptoms described.

" 3) Some belt makes whining noise; gets worse with RPM to a certain point when it stops. "

The above would result in insufficient charging.

2. The crankshaft thrust bearings are worn resulting in excessive crankshaft side movement. This would explain the clutch pedal kick back when releasing it.

It would also affect the idling when clutch pedal is depressed. At low rpm if the crankshaft is moving sideways too much, it would cause stalling. This would also cause the vibration.

The smell emitted should be burning rubber of the slipping harmonic balncer.
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Monday, April 13th, 2009 AT 2:55 PM
Tiny
FDQX
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Thanks for the quick reply.

Where is the harmonic balancer? Inside the crank pulley?
Is there also one on the other side of the crankshaft?
I hope they are outside the engine, so the engine doesn't have to be opened?

I take the car again to the repair shop on thursday, so it would be helpful to understand what I want them to check :)

Also, you referred to my earlier note:
" 3) Some belt makes whining noise; gets worse with RPM to a certain point when it stops. "

I actually located the noise to the alternator itself; goes away if I pull out the alternator connector. The alternator works OK though now, so I actually don't understand it either.
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Monday, April 13th, 2009 AT 4:15 PM
Tiny
KHLOW2008
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The crankshaft pulley has 2 rings, an outer and inner. It is fused together with a rubber damper to reduce vibrations. If you remove the crankshaft pulley and check the part where the alternator belt seats, just below it would be the rubber.

Other side of crankshaft would only have a flywheel which is just solid metal. Some other makes would have a 2 layered design but not yours.

Pulling out the alternator connector would reduce the load on the alternator and this would reduce the alternator weight on the belt. With less weight on the crank pulley, slipping and weight is reduced thus the noise would be reduced or does not appear.

Under such circumstances, if you test the charging rate, it would most probably provide you the correct rate and when full load, ie with all electrical component working, the rate would most likely drop to battery voltage.

If you use a timing light to check the timing, you would notice the timing mark not staying in a fixed position. It would be moving away and it would seem to be slower than the crankshaft.

Tell the mechanic to check
1. Crankshaft pulley. Use method desribed above.
2. Crankshaft end thrust. To check this, it would be easier of you remove all the external drive belts.

You would need an assistance. With engine off, put you hand on the crank pulley and depress the clutch pedal, do you feel the crank pulley moving? Release the clutch pedal and push hard at the pulley nut as if to make the pulley go in.
Depress clutch again and feel if the pulley is moving.

The accurate way to do it is to attach a dial gauge to the crank pulley central nut to gauge the amout of movement.
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Tuesday, April 14th, 2009 AT 6:39 PM
Tiny
FDQX
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The crank pulley as well as the end thrust were checked, and they were OK. The clutch is now opened, and there was nothing else that the clutch plate smelled horrible. It looked fine, though. New plate is now ordered and will be fitted at the beginning of next week.

What should I do next if the clutch replacement doesn't help?
The problem can't be big, since sometimes the fast acceleration makes the car work fine for a few days. Can something be clogged or something?
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Friday, April 17th, 2009 AT 2:49 AM
Tiny
KHLOW2008
  • EXPERT
Now that the trans is off, recheck the crankshaft end thrust. Remove all crank pulley drive belts first.

How was the crank pulley checked. Was it removed to be visually inspected?

If charging rate and battery voltage is irregular, the idling issue would happen. If it is mechanical or vacumn, it would be more consistent, not happening sporadically.
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Friday, April 17th, 2009 AT 8:10 AM
Tiny
FDQX
  • MEMBER
The pulley was off the car, I inspected it myself too and didn't notice anything unusual. The rubber looked like new.

The end thrust was checked when the pulley was off. I pushed the clutch pedal following mechanic's instructions but he said there was nothing wrong.

Let's see if the new clutch plate changes anything.

I just can't understand myself, why sometimes fast acceleration makes the car work fine for a while. When the fast acceleration thing happens, the car first seems to lose the power, and then it goes off like a rocket after something on the engine bay bangs once. The bang is very loud and metallic, you can clearly hear it while driving (can't be anything but clutch?).
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Friday, April 17th, 2009 AT 10:17 AM
Tiny
KHLOW2008
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Once the clutch is depressed the crankshaft would be in pushed forward position. Subsequent depressing of the clutch would not show any side thrust. Pry the flywheel to get the crankshaft back to the rearward position, repeat the action a few times to confirm.

Reinstall pulley and try prying it to check thrust, ie do on both ends, take care not to damage the pulley.

Crankpulley dampers sometimes looks good. Try unseating actions, as if trying to press the outer ring out of the inner rings to confirm.

Clutch might cause power loss if it is slipping but it would not emit any abnormal noise. The loud bang is weird. Apart from it, is there any other abnormal noise from engine, such as knocking noise during acceleration, similar to worn con-rod bearings or excessive vlave clearances?

Does the abnormal noise appears during or immediately after releasing of cluth pedal or does it happen long after releasing of the clutch pedal?
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Friday, April 17th, 2009 AT 3:10 PM
Tiny
FDQX
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"Crankpulley dampers sometimes looks good. Try unseating actions, as if trying to press the outer ring out of the inner rings to confirm. "

We actually tried that.

The bang-sound has appeared only three times in last six months, there is only a single "bang" when it happens. The engine or tranny also "kicks" when something bangs.

Those three times have been very similar. Everytime I was at traffic lights, the car started to smell bad, and when the light went green I accelerated very fast. The car seemed to have lack of power (hardly moved), but after about 100 metres something banged, the engine power was back, the RPM behaved like it should, the car didn't vibrate at idle and the clutch and gas pedals felt right. Always after a few days the troubles come back.

The alternator changes have had the similar effect on car behaviour than the bang.

The engine doesn't do any abnormal sounds, the idle sounds very smooth when listening. Only the alternator noise is very loud (from the alternator itself, not the belt) The engine is a replacement engine with 30000 miles, I can't believe it has failed in any way.
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Friday, April 17th, 2009 AT 3:37 PM
Tiny
KHLOW2008
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I can't think of any other things that can cause the symptoms described so we have to wait for the clutch to be installed and retest or rediagnose.

I would try to figure out if there are any other possible explanaion. Keep me posted.
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Saturday, April 18th, 2009 AT 5:47 AM
Tiny
FDQX
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I got the car with the new clutch plate today. First it worked like a dream, now it stills works decently, but seems like it's losing it (sometimes the RPM drop below 750). Still good to drive now though.

Let's see how the situation develops. If it starts to misbehave again, I think I'll have a go at replacing all the pulleys (crank, water pump, powersteering and a/c).

I thought that what if some of the pulleys aren't correctly aligned? Is there any way to check it without the mechanic? Or should I just remove them all and replace?
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Tuesday, April 21st, 2009 AT 11:48 AM
Tiny
KHLOW2008
  • EXPERT
With engine running, watch the pulley from above or below. They should be moving without any side movement, ie wavy.

With timing light, check the timing mark on pulley. If there is none, mark one yourself and mark keeps moving away from its original point, the pulley is bad.

Try with full electrical load, ie with headlights, AC etc.
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Wednesday, April 22nd, 2009 AT 9:06 AM
Tiny
FDQX
  • MEMBER
Well, I used the timing light and everything seemed to be OK, 8-12 degrees without headlights and 10-14 with lights on. The pulley didn't make any side movement.

The car works well if headlights and rear defog are off. If either one of these is on, the RPM misbehaves.

If I pull the alternator plug out, the car works great, even when lights and rear defog are on. This is the third alternator I have tried, I can't believe every one of them is broken? This one is ORIGINAL rebuilt unit.

When the alternator is disconnected, the engine temp meter needle doesn't rise to the center point (it doesn't with alternator connected either, but goes higher). CAN THIS HAVE SOMETHING TO DO WITH THE WATER PUMP THAT IS ON THE SAME BELT AS THE ALTERNATOR?

As soon as I connect the alternator, it starts to make the noise, the car starts to vibrate and the RPM goes under 750 when I release the gas pedal.

Now the car is quite in pieces; I have dismantled the whole interior to check every ground point and every combination connector and have found nothing. I also tried to add extra ground cables from battery - to the headlight grounding points.
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Wednesday, May 6th, 2009 AT 2:10 PM
Tiny
KHLOW2008
  • EXPERT
Since timing mark are available, the crankpulley should be ok.

I would suggest testing the charging voltage and output with and without load.

The symptoms and tests done indicates a fault with the alternator.

Since all the alternator replaced were rebuilts, I would not discount the possibility of them being the cause. Personally I have ever tried 3 rebuilts on my own car and all of them had a problem, though it is a Honda.

Btw what is the engine type that you have on your vehicle?
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Thursday, May 7th, 2009 AT 12:41 PM
Tiny
FDQX
  • MEMBER
The engine type is FS.
I'd like to get a new alternator, but here even the importer can't supply brand new one when I asked (!).
Only chance to get a new one is to buy every part of the alternator separately and assemble it myself, and it costs a bit too much for me.
The next thing I think is that I try to insert a new cable from alternator to the battery. Might take a few days.
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Thursday, May 7th, 2009 AT 3:16 PM
Tiny
KHLOW2008
  • EXPERT
Only 2 items from the alternator would cause the problems indicated.
1. Rectifier assy.
2. Voltage regulator.

The others would not cause the noise and if any faults, visual inspection and test can be carried out to confirm the peoblem.
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Friday, May 8th, 2009 AT 11:59 AM
Tiny
FDQX
  • MEMBER
I took the alternator to the test bench and it immediately broke down (gave over 20volts), so I had to get new one.

New, tested original alternator from scrapyard installed now. I drove 4 times today, here are the results:

Drive 1)
All the symptoms are there, but the alternator didn't make any whining noise.

Drive 2)
Worked OK! Absolutely no faults, with some electrical load (lights, A/C)

Drive 3)
All the symptoms are there, also the whining noise from the alternator appeared. Electrical load totally made the car lose idle for several seconds.

Drive 4)
Worked OK, but the alternator noise was there, not so much though than drive 3, behaved OK also with FULL electrical load (headlights, rear defogger, AC, stereo etc).

Test Drive 2 and Drive 4 were started with warmed up engine, 1 and 3 with cold engine.

I think some sensor must read some information wrong.

I looked at the crankshaft position sensor. The workshop manual said that the resistance between pin A and pin B should be 550 kilo ohms, mine gave 620. Is this OK or should I replace this part? It's quite expensive.

I tried driving without the knock sensor and the camshaft position sensor, no difference.

When the engine is warm, the needle in the meter stays a bit below the center point. Is this OK?
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Monday, May 25th, 2009 AT 3:02 PM
Tiny
KHLOW2008
  • EXPERT
The crank sensor resistance range should be between 520 to 580 ohms at 68 degrees F. If the testing temp was not at 68 F, test again when engine is cold.

Seems strange that you are having different readings each time. One of the reasons could be the idling speed, when cold, the rpm would be higher.

The rpm gauge first line indicator is 500 rpm and if idling speed is above the next 2 line, it should be correct. Try adjusting the idling rpm to 1000 and retest to see if problem goes away.
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Tuesday, May 26th, 2009 AT 1:34 PM
Tiny
FDQX
  • MEMBER
I have tried to set the idle around 1000rpm (also 800, 900 and 1100), but the car idles very rough. Also there's way too much vibration especially if the idle is 1000 or 1100. The workshop manual says the idle should be between 550 and 750, currently it is around 725 and it is the best of the alternatives.

Now, though the RPM have behaved mainly OK for the last few days, I still notice one thing:
When I stop, no matter how long ago I have let off the gas, the RPM notches a bit when the car STOPS. How does the car know when it is on the move and when it's not?

I've checked the alternator voltage every day, it's good (14, 3V steady at idle not depending on the electrical load, battery 14, 6V)

I also thought the catalytic converter, since the old engine gave the blue smoke. Can that cause all the problems?

The workshop manual said that the power steering pressure switch should give following readings (wire harness connector disconnected).
Steering wheel straight -> Under 1, 0V
Steering wheel fully turned -> B+ voltage
I got nothing on my ohmmeter. The meter works fine, tested it on the battery afterwards. The P/S works OK though. When wheel is fully turned on idle, the car almost stalls.
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Wednesday, May 27th, 2009 AT 9:54 AM
Tiny
KHLOW2008
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When power steering is being turned, the pressure switch is to let the ECM knows there additional load and adjust the idling speed accordingly. Snce signal is not present, the ECM does not know of the extra load so will idling would drop.

Either the switch is bad, power is not getting to it or signal is not being sent to the ECM.

We have been on this for a long time and a lot of repairs and parts been carried out. Let us do a stock taking so that we do not confuse each other.

I would like you to relist all the present problems and we can go about without being confused.
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Wednesday, May 27th, 2009 AT 6:32 PM
Tiny
FDQX
  • MEMBER
First of all, thank you for your patience with my car.

I was thinking of relisting the problems also.

The problems present are the following.

1) It is impossible to change between gears 1, 2 and 3 smoothly (car loses power of something when clutch pressed in). This problem is not present when electrical load is turned off.
2) When I either press the clutch or let the gear to neutral, the RPM sometimes drop too low (under 500) and then goes up
3) The car vibrates at idle. Nowadays when driven a short while, the problem goes away (before the problem wasn't there when the car was started, but after a little driving)
4) The alternator (not the belt) makes whining noise that increases with electrical load or with RPM to 2500RPM, then disappears.
5) There is actually no deceleration, impossible to stop the car without brakes when in gear (tries to go forward). When in 2nd gear, the car goes 15mph without touching the gas pedal, won't stop it goes uphill. I actually drove like this around a block several times in a row, it just keep moving.
6) Occasional slight smell of some fumes (fuel? Sulphur?) While driving, and after driving.
7) When the car stops moving, the RPM makes a little notch (750->600->700)
8) The engine temperature meter needle stays a bit below the center point, I remember it was at the center with the old engine.

Last August the engine of the car was changed (only the engine, all supplements were from the old engine), since the old one leaked oil into the exhaust system. I noticed the symptoms 1) and 4) before the engine change (possibly after the first time the battery had been disconnected for a longer while, ECU failed relearning?).

Before the engine change couple of the passenger side front wheel's bolts came off while driving, resulting in destructing the wheel and excessive vibration while driving (broke something?)
All worked OK after I changed the wheel.

Other problems came after the engine change, where again the battery was disconnected for a few days. The problems also include stalling when coming to a stop, but this hasn't happened since last October. The awful smell mentioned in this topic hasn't appeared after the clutch plate change.

The list of replaced parts so far includes:

Battery
Alternator to battery wiring
Battery to ground wiring.
Battery negative terminal
Alternator and P/S belts
Alternator (4 times)
IAC control motor
EGR valve
Fuel injectors and fuel pressure regulator
Camshaft position sensor
Air filter
Spark plugs
Ignition lock
PCV valve
Camshaft pulleys
Clutch plate
Neutral gear switch
Throttle body gasket
Clutch release cylinder

I have also cleaned the IAC valve and the throttle body. I also tried new spark plug wires without any change. I have also put both injector cleaner and valve cleaner into the gasoline without any results as well as tried higher octane gasoline.

The brake cleaner has been applied to everywhere in the engine bay to find vacuum leaks or inspect the intake manifold gasket, doesn't affect anything.

The timing belt has been checked several times, it's correctly placed.

I've tried to change the idle speed, doesn't help.

The engine/emissions wiring harness has been tested from every pin of the ecu to the sensors, all OK. Also extra ground wires added to the headlights and engine. Every grounding point of the car visually inspected.

Some mechanic said to me that my ECM/PCM might be broken. I can't believe this since the car sometimes does work. The new ECM/PCM costs 1800 euros (way over 2000$) here so I can't afford to "test" a new one, I need to be sure of it being broken before buying a new one. An ECM from the scrapyard is impossible to fit the car due the immobilizer.

The power consumption of the car is measured by an electrician, with full load 35A. The battery voltage as well as the voltage from the alternator is OK.

The car works occasionally fine. There are two reasons which sometimes result in the car working fine:
1) Driving without any electrical load
2) After a fast acceleration.

Well, it's a long list but that should be all. When the car sometimes works fine, I'll be sure to make another donation.
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Thursday, May 28th, 2009 AT 1:05 AM

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