Mazda Vibration in Gear

I posted this on mazda626.net.

I have a 97 626 Automatic 4 cyl. Why does the car vibrate when I'm stopped at a stop light and the transmission is in "Drive"? The vibrations goes away when I put the transmission in neutral or park. I'm trying to figure out whether or not the problem is due to cracked engine mounts. I see a crack on the passenger side top mount, but I can't see whether there's any cracks in the rear firewall mount and driver side top mount (near the battery).

I have read some posts from people with similar problems and suggested solutions.

Some posts say the problem is bad idle. My idle speed in park or neutral isn't noticeably less than the idle speed in drive. I revved the engine up to 1000 rpm in park/neutral and the car did not exhibit more vibrations. So I don't think it's idle speed related.

I've also connected a vacuum gauge to the PCV valve vacuum hose and didn't see anything abnormal. The needle was steady. Perhaps I should repeat the vacuum test and put the car in drive with the brakes applied?

So I suspect the engine mounts are the culprits, but the rear one and driver side top one is hard to inspect and to take out. If I just replace the top passenger side one, I'm not sure if that will help or not.

Damn idiots in class

I don't claim to be an expert in auto repair, but I know enough to figure who is a fucking idiot and who knows their stuff well. I hate it when these fucking idiots in class start tinkering around my car without my consent. I don't mind helpers, but I hate unsolicited help from people who are likely to do more harm to my car than me.

1. There's always a guy who always floats between various groups in the class. He helps a little bit, but always disappears when it's time for cleanup. He also liked fixing other people's car without their person or presence. He replaced a PCV valve on another guy's car when the owner briefly stepped away. The owner wanted to do it by himself. In another case, he broke the spark plugs or wires on another car. I gave him the evil eye to keep him away from my car.

2. This old guy in another class came to watch me do an alternator test. He had some strong ideas on the direction of current measured by the VAT-40. I politely disagreed with him and tried to ignore him. But the old fart didn't take the hint. Instead he started probing around my car. I told him to stop and go away.

Fixed Saturn shifter bushing!

I used a C-clamp to push the bushing onto the ball joint of the shift lever. I didn't think it was too difficult, but my dad couldn't do it because he had trouble twisting his body into the right position.

After cleaning up and putting the console back together, my friend and I went on a drive to fully recharge the battery. The battery had enough power to crank the motor after one month of sitting in the garage. We drove up Doherty road up to San Ramon. Doherty road had little traffic and it was perfect for test driving the Saturn after being out of service for two months.

Mazda 626 service items

1. Retest Alternator - I'm still getting inconsistent readings. 20A on alternator cable with no load is weird. Alternator is probably marginal.

2. Test Front Struts - n/a


edited after 11/22 class

I just don't get these kids..

who modify their cars to such an extent that it's become unreliable and needs constant tinkering. Some of these same kids drive like "ass-hats". They think nothing of doing clutch dumps at redline, burning up the clutch, shifting at redline on a regular basis, blowing up the engine, street racing, and driving recklessly on mountain road thinking that they're Takumi of Initial D.

My question is how can they afford to abuse their car? If you had to work hard to earn money, would you blow it away like that? I've noticed a Lemmings or sheep-like mentality among these car nuts. Once something is deemed "cool", everyone wants to get it. The standard for coolness for the import is "JDM-tite yo". WTH do they spend several thousands of dollars for a tired engine or transmission from Japan that has no verified mileage? On top of that, they need to buy the ECU and do all the wiring to get it to work. And then the ECU needs to be retuned to accept the lower octane gas in the US, especially in California (91 Octane max). Such non-ODBII ECU's will not pass smog tests in certain states.


Case 1: Car catches on fire after street racing. Car has aftermarket fuel rails, pumps, turbo, and modified engine management.

Case 2: Car engine blows up after driving near redline for most of its 80K miles. Just 80K miles!

I'm not against modding or performance driving. I like doing things in moderation.

VAT-40 Amperage scale

When I did the alternator test on the Subaru with the help of other students, I suddenly realized that I had been reading the wrong amperage scale on the VAT-40 for the entire time in the class!! There is a red and blue amperage scale. The VAT-40 has a rotary switch to set it to different modes. In "Starting" mode, the correct amperage scale is the red scale (0-500A). In "Charging" mode, the blue scale (0-100A) is the correct one. I had been doing the alternator test with the VAT-40 set to the "starting" mode and reading the blue scale. So when I thought the amperage was 20A, the alternator was really putting out 100A. I should have set the mode to charging and read the more detailed blue scale.

I think the Mazda's alternator is probably ok. I'll remeasure it next week.

The Subaru alternator put out about 80A at 14V and 2500 rpm. Spec was 65A or more at 14.1V. The front mounted alternator allows easy access to the thick B+ cable, so I clipped the current probe onto that cable.



Other completed tasks:

Tire rotation
CV boots inspection

I noticed some tissue stuffed into the exhaust pipe near the junction of the left and right exhaust manifolds. I took a picture of it and will ask the dealer mechanics about it.

Measured specific gravity of battery cells. The results seem to vary depending on how much electrolyte was drawn into the hydrometer.

Update on Saturn, 626, Subaru

Saturn:

My dad removed the broken shifter bushing. He used a screwdriver to pry it off the ball joint at the bottom of the shift lever. My dad installed the bushing onto the cable but couldn't get it on to the ball joint. I loaned him some small C-clamps to finish the job.

Mazda:

Parts that should be fixed or replaced soon:

1. Leaking driver side inner CV boot. Perhaps a new clamp would fix it.
2. Alternator isn't really up to spec. Redo VAT-40 test
3. Add more windshield wiper fluid. Done 11/18
4. Radiator cap 16 psi

Wish list items:

1. Front struts R/R
2. Top engine mount R/R
3. Rear and Left engine mount remove and inspect.
4. Clean up grounds/ground wires
5. Test O2 sensors
6. Clean MAF, IAC, throttle body

I've very reluctant to disconnect the battery again because I'm not confident that the ECU will consistently overcome the rough idling/stall problem. Also since this is my wife's car, I don't want to deal with the flak "you messed up the car again!". But I need to disconnect it to replace the alternator.

Subaru:

Tonight, I'll rotate the tires and figure out a way to remove the spark plugs. The trick is to find the right set of extensions to access the spark plugs. I wonder if the Gear Wrench racheting wrenchs would be useful here.

If there's time, I'll do a battery and alternator test.

Mazda 626 passenger side CV joint

This is the passenger side outer CV joint. The leak appears to be a slow, old leak.

Mazda 626 driver side CV joint leak

I took this picture on 11/8/06 of the inner CV joint boot two weeks and about 200 miles after I had wiped away all the grease.

Mazda 626 Update

On the day of the class, the idle problem improved all by itself. The car no longer stumbled while stopped at a traffic light. Also when I put the car into Park, the engine did not always stall out.

The instructor said that the ECU may have needed several ignition cycles to relearn its "operating parameters" for the specific car. When I disconnected and reconnected the battery, the ECU probably reseted itself and used factory defaults. Since the car is old, the factory settings could have lead to rough idle characteristics.


MAF sensor

I took out the MAF sensor and it had some carbon deposits on the front side. I didn't clean it because the instructor said MAF sensors are very touchy and sometimes cleaning it will make the probably worse.

IAC valve

The IAC valve is actually a stepper motor controlling a valve which bypasses the throttle plot. The computer adjusts the valve opening to vary the idle speed. The idle speed is increased when the engine is cold, when the A/C is on, when there is a load on the alternator, etc..I measured the IAC valve motor resistance - 9 ohms, which is within spec.

Distributor cap

There was some carbon around the contacts, but no shorts.

Spark plug wires

Measured the spark plug wire resistance
#1, 24", 7.03K
#2, 21", 5K
#3, 18", 6.2K
#4, 15", 4.08K

All wires are about 3K less than spec (16K/40"). Is this bad?

Ignition Coil

Primary side resistance was too low to measure with my DMM. I was unable to get a secondary side resistance measurement. The secondary output post is coated with a white dusty film. I cleaned it up with some sand paper.


Driver side inner CV joint

The grease leak is coming from the seam between the boot and metal shaft. I'll take a pic next week.

Subaru

I'm here at the dealership for a free oil change. Yes there's free wireless internet here! They are also replacing the driver side window weatherstrip under warranty. The weatherstrip doesn't adhere completely to the window near the back and as a result I can hear wind noise while driving above 70 mph. I hope this will fix it.

Removing Water Pump Pulley Bolts

A few months ago, a friend and I replaced the water pump in my Saturn. The biggest problem was figuring out how to remove the three bolts on the water pump pulley. On saturnfans.com, I found several methods:

1. Use a strap wrench to hold pulley while breaking loose the nuts.
Somewhat useful.
It was hard to hold on to the strap wrench while I applied torque to loosen the bolts. The wrench would have been more useful if it had a longer handle and better self-locking mechanism to lock the strap.

2. Keep the accessory belt on the pulley to provide resistance.
Useless.
The belt could not prevent the pulley from turning.

3. Jam screwdriver between two nuts and the frame.
N/A.
I couldn't see how this would work. The nuts have such a low profile that it was impossible to keep the screwdriver against the pulley nuts.

4. Use a wooden wedge.
This worked. I inserted a wedge between the pulley and subframe or crank pulley. Then I was able to break loose the pulley nuts.