severvip

Idle Problem

25 posts in this topic

I have a 4cl 98 626, and I've had an idle problem for the last 6 months or so, I've tried and tried but I can't pin point the source of the problem. The problem is whenever at idle speed, the idle speed fluctuates. Usually going up and down between 500 and 750, causing the car to shake violently. The fluctuations get worse the longer the car sits at idle speed, and eventually causes the car to die. If pulling up to a stop light that lasts for more than 30 seconds the car will die. I've received one code the first month the car started doing this, stating Fuel to Lean. That code disappeared eventually and I haven't received any codes since.

Now like I said, I can't pin point the issue, but I've tried quite a bit in my quest to fix this car.

I've looked at and inspected all the vacuum hoses numerous times and I can't find any holes or cracks in any of the vacuum hoses. I replaced the timing belt because I heard from somebody it could be a timing issue. While working inside the engine I put new seals on all the valves and re-shimmed the lifters. I replaced the valve cover gasket when I did all that just incase it was leaking. None of that fixed my problem.

I've replaced the 02 sensors and Fuel Filter. I've cleaned the MAF, IAC, and injectors. But still no luck.

I replaced the spark plugs with the proper NGK spark plugs. No luck. I've changed the gap setting from .29 to .32 to .44 and everywhere in between, but it still has the idle problem. Speaking of which, what is the proper gap setting??? Oreilly Auto Parts told me .29 Autozone told me .44 Mazda dealership told me .32 Chiltons books say .44 so which is it???

So any ideas on what could be causing my idle problem. A friend suggested it could be a piston problem? Is that it, or have I overlooked something else. Please any ideas?

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If somebody on here can tell me what the problem is and how to fix it. I will pay that person $30.00. I'm dead serious, I'm that sick of this problem.

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Have you tested the IAC? Or just cleaned it? Test the thing & see if it's reading to specs.

Check your fuel pressure too, might not be right.

Spray carb cleaner around the intake manifold gasket & throttle body gasket while the vehicle is running. If it starts to rev, replace the gasket.

Also spray it on all vacuum lines to see if that will cause the engine to rev, if it does, replace the lines.

Do you have anything on when this is happening? Like the radio, a/c, lights, etc? Or does it happen weather or not anything else is on?

If it only happens when you have something else on, then you have a load issue. Something is drawing to much or the battery/alternator is unable to handle/provide enough for it.

Check & clean all you grounds. You can add extra grounds to help.

I know you said you cleaned the injectors, but did you test them to make sure they are not leaking & are they spraying properly?

Maybe you need new plug wires &/or coil pack.

Sorry got to go now, got some work to do to finish, but I'll be back, mwhahahaha.... Good Luck

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When I tested and cleaned the Injectors I had it done at a shop around here, they said they were fine. Yeah I did test the IAC also, and just to make sure the IAC worked I purchased one over at Autozone, cost 400. Put it on and the car still had the idle problem so I returned it and got my money back. As for what I have turned on when it does this, I've tried turning everything off and it still has the problem, it doesn't seem to matter what I have turned on or off. Oh and yes I did clean all the grounds but still no such luck, I haven't added any extra grounds, so I might try that.

As for adjusting the throttle cable, I did that and it raises the idle a bit, instead of shaking violently between 500 and 750, it shakes violently between 750 and 1000. It doesn't die at every stoplight now, but the idle problem is still there.

Oh again, what is the proper gap setting for the spark plugs, or does nobody know???

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Almost sounds like a bad motor mount.

Motor Mount how would that cause an idle problem?

You said "it shakes violently" at different rpms. I would imagine that if a motor mount was bad, the engine would shake violently just as you mentioned.

I could be way off but I have seen other vehicles exhibit the same or like symptoms from a broken motor mount.

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If you have a shaking/vibration problem, mounts would do that. But you also said your idle was going back & forth between 500-750 rpms & it has died. Unless you had the a/c on when that was happening, idle will drop when the compressor comes on for a second. That is normal. But it shouldn't cause it to die.

So I would rule mounts out due to what you have said. But it still doesn't hurt to check your mount to see if they are split. Which I would say yes if the previous owner didn't take care of that.

So the shop told you the injectors are good, did they check fuel pressure?

Did you adjust the throttle plate sitting position? That would cause it to behave erratic. That adjusting screw should never be touched, unless you know what you are doing.

For some weird ass reason, pretty much all aftermarket replacing parts for these cars seem not to work right. I have no idea why, except for they can't build products with good quality like in the good old days. But, whatever. You do get lucky once and awhile and do get a working aftermarket part.

You can try to get an IAC from the dealer & see if that will work. And I know how dealers are on SOP, you can't return them or if you can there is like a "15% restocking fee." Which is bull.

Did you test the MAF. And like 97Mazda said, do a compression/leak down test. Have you try spraying carb cleaner on the gaskets/hoses like I mention before yet?

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Raziel

I did do a compression leak down test once, it wasn't loosing compression in any of the cylinders. It would build up and stay up, but cylinder 3 didn't build up as high as the others. It was like 10 pounds lower than all the others. I asked somebody about that before, they said that was normal for cylinder 3, or it was still within normal parameters or something.

I have sprayed carb cleaner directly into the Intact Manifold, and I've sprayed it directly into some hoses, but that's never done anything. I'll try again, see if it causes any reactions or something. I've checked the MAF, I didn't go buy one and see if replacing it fixes it like I did with the IAC, but I did check it. The Ohms were within the normal operating parameters. I may buy one tomorrow and see if I get any different results, but I can't imagine I would.

I'm taking my car to Mazda on Friday, have them run an complete engine diagnostic. If I can't fix it by then. Right now it doesn't look like anybodies getting the 30 dollars. If I spend 80 for an engine diag, yall can forget it.

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First, easy test of IAC valve by dis-connecting electrical connection. Your idle should change (go down) if IAC is working.

If your idle still fluctuates, even if connection is un-plugged, then your problem is maybe something else. Note: A dirty or improperly assembled (after cleaning) IAC valve still could be part of the problem.

If you changed the idle (set by manufacturer) then you will need it re-set by qualified people/garage equipment.

Question 1: Was your car running properly before you noticed the problem with idle?

Question 2: Did you have work done to your car that may have started/caused the idle problem?

At proper idle, 700-750 rpms.....no fluctuations (in 'Park', warmed up, no load 'ON').

A dirty EGR valve/system could also cause idle problems....try Seafoam treatment to your car (gas tank and brake booster or PCV vacuum hose).

Add extra ground wires to electrical system.

I use NGK G-Power #7090 BKR5EGP (pre-gapped; platinum) spark plugs and works great for my 98' LX.

And 'yes' broken motors mounts can cause 'shaking' but irradic or fluctuation of idle rpms....maybe....check mounts any ways.

Good luck!!

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MazRedMan If I disconnect the IAC valve the car dies almost instantly.

Now to answer your questions, this problem happened suddenly, it just started idling rough one day.

About a month before that I replaced the Master Cylinder and one brake line, but I can't imagine the Master Cylinder would have caused this, plus that was a month before the problem all of a sudden started.

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Hi,

Couple of suggestions

Test the PCV valve for 2 things;

1) That it is pulling a vaccum when disconected from the rocker cover (put your thumb over it)

2) Verify that the one way valve is operating correctly by blowing through the rocker cover connector (should be flow) and then from the other side (should be no flow)

Have a look at the condition of all of your air intake system.

ie, no loose hose clamps, nothings popped of at the bottom or there are no splits in the ducting. Is the air filter clean and is the box clamped down properly

A long shot - but crank angle sensor?

good luck!

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And you guys never mentioned one thing - coolant level.. Mazda's idle depends on coolant level.. if it is only a few mm under the Normal, it keeps fluctuating.. So check that.. I had the same thing with my GE, it did the same thing and after i filled it, it stopped.. Also, when you recently replaced the coolant, it might have air bubbles still left in.. but if the radiator's valve is working, it should let the air out by itself, also you would notice high temp. on the dash..

Another possibilities -

*engine mounts - heavy vibration in the chassis, but not the reason for dying..

* if it dies, when you hit the brake pedal, it is the vacuum membrane in the brake distributor.. Or a massive vacuum leak..

*check the spark plugs and replace them if necessary.. factory suggestion is NGK BP6ES (same as V6's) should be a 16 dollar investment..

*spark wires - hardly ever.. only when you have trouble cold-cranking..

my other guess would be fuel filter, AFM.. but i guess you've already cheked those..

This fluctuation also happens, when your temperature sensor is dead - thi causes the ECU to turn on the "Save power" mode and does not work properly..

Someone mentioned a distributor malfunction.. but the I4's distr. doesn't break that easily..

Hope this helped..

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Don't spray it inside of the intake manifold and hoses. Sprays it on the outside of the hoses & intake manifold area where it meets the engine block(while the car is running). That is where the gasket is. If the vehicle starts to rev when you do that, then you have a poor seal or a split hose(s).

If the hose from the brake booster to the engine is split some where, it will give you idle problems because there is a leak. That hoses needs to be seal complete.

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Severvip, since your car dies(stalls) after you disconnect the electrical connection of the IAC valve, then more than likely your IAC valve is still working(....maybe not perfectly but 'ok')and cleaning it can only help.

'Fluctuating' or 'erratic' idle??

An erratic idle (jumps around) maybe more associated with an 'electrical'(poor signals) problem in system of operation.

An fluctuating idle (comes and goes; almost rhythm-like) maybe more associated with a vacuum leak.

So I would spray carb cleaner around your last repair job......master cylinder! Just as Raziel suggested, spray around brake booster/master cylinder connections, hoses, etc..

(Other areas suggested earlier: intake manifold gasket;TB gasket; other vacuum hoses.)

And it wouldn't hurt to check the radiator fluid level, as suggested by Mario, this could also cause your idle to 'fluctuate'....actually your motor/engine is getting a little 'over-heated' and causing your idle to be affected.

Keep this in mind, you messed with the 'set' idle position and this may need to be reset by dealership/qualified garage.(It would seem hard to properly 'reset' idle if your initial idle problem isn't fixed first?? This is why I would never touch/adjust the 'set' idle. I would need this as a reference point for troubleshooting any problems.)

BTW- Our 98' 4I auto have electronic ignition system (coil pack).....no distributor.

Good luck and report back to us what you found out ...if anything.

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I forgot to add, if you still find no vacuum leaks then check your EGR valve or system.

I would first do a Seafoam treatment to the gas tank (with half tank of premium gas) and to vacuum hose of PCV (or brake booster vacuum)to help clean system.

And again... try adding extra grounding wires.

Good luck!!

http://www.mazda626.net/topic/24886-added-ground-wires/page__hl__mazredman

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X2 with checking the coolant level. Also, adding coolant can also be a pain and takes some patience.

Good luck

Larry

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Yea man, I had that same friggin' problem . and boy was that a pain in the a**. i got a new iac and that didnt do the trick , I took it to a mechanic , he made some idle adjustsments on the throttle cable and that did it, try that bro. it should do the trick. good lluck!

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Thanks Everyone for their insite.

 

I too am having the same issue.  But I have different circumstances...  I'll explain briefly.

I have a 1998 Mazda 626 Manual, Standard emissions.  I found out it was a standard emissions and not the low emissions by the letter 'C' in my VIN.  I forget what the other letter is.

 

My engine idle didn't fluctuate. It would almost stall coming to a stop like at a light.  It would almost stall in cold weather and as the weather got warmer, it would actual stall out.  In the rain... It would stall and wouldn't start without standing on the accelerator. 

 

I found out that there is a recall on the 98 Mazda 626 to get this corrected.   You can still get this done, just call your Mazda dealer and they will do it free of charge. 

 

I didn't get this done.  I only found out about this after my engine blew up.

 

As I was saying, On memorial day, I threw part of a rod through the side of my motor going down the turn pike in PA.  In the middle of nowhere.

 

So I had my car towed to the nearest shop and I found a motor in a u pull it yard.  I had the motor shipped and installed into the car. 

 

I now have the fluctuating idle issue.  So I'm going to look into replacing the Temperature senor and PVC value. 

 

My idle speed is really high, so the fluctuation is between 1000 and 1500.  It also stays at 1500 for a minute or 2 and then goes back to fluctuating. 

 

I'll post back here after I get that done.  Good luck and Thanks..

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My 2002 626 I4 recently started idling low and shaking violently when the automatic transmission is in gear and the engine reaches operating temperature. Stepping on the brakes or turning on the AC made the vibration even worse. Giving a little gas to bring the RPM back above 800 reduced the shake significantly. I too looked at plugs, wires, timing, IAC, etc. I finally found that the driver's side engine mount through bolt had come loose and the nut was nowhere to be found. A new bolt and nut fixed everything. Idle is smooth while engine is cold or hot with brakes and A/C on. I hope it will run this well another 112,000 miles.

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Anytime your idle speed drops below 700 RPM you are going to get vibration and shaking.  At 600 RPM and lower the engine approaches stall speed.  You have to figure out why your car has a low idle or fluctuating idle (usually caused by a vacuum leak).  This is why when you give it gas to go above 700 RPM the engine doesn't vibrate anymore (or at least much less).  If your engine still vibrates above 700 RPM then you should look into bad mounts, internal engine or transmission issue.

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650 RPM is the desired idle speed.  His engine was stalling because instead of the cylinders firing exerting energy onto the crankshaft, they were spinning the block instead.

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