1998 Mazda 626 Mazda 626 RPM misbehaves + smell

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.

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?

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?).

"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.

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?

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.

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.

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?

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.

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.