need help with a scan tool

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That one claims live data and live data graphing. I don't have that exact model, but a similar one from HF with data and graphing. Very handy for looking at how the engine responds to various conditions.

It may also be possible that you are getting "pirate air", or air that slips in through a leak upstream of the throttle plate but downstream from the filter and MAF. This may not cause the same drivability issues as a vacuum leak, but will upset fuel trims and fuel economy.

What symptoms are you seeing? High idle? Rough running that improves with more throttle?
 
You'd have to check their website's FAQ to see if it is offered for your vehicle, but if Live Data is offered for your application, the Bluedriver Scanner is an awesome tool to have. It's 10 dollars more, but offers bluetooth that allows you to pull up the information on your phone.
 
It's a rough idle when in gear and hot. (Most noticeable at a stoplight). It improves with throttle.

In neutral or park, rpm increases a bit and the feeling goes away.

If you are interested, here is what I have done:

- replaced 2/3 motor mounts with no change. (The third mount looks ok)
- cleaned the throttle body
- replaced valve cover gasket
- also sprayed around lines / gaskets with water and carb cleaner but don't hear an idle change.

I'm thinking it could be a master cylinder / vacuum pump. (bad master cylinder would explain why the vibration is so bad at a light with the brake on - my theory anyway, as braking has seemed to deteriorate in the last few years). But before I go replacing parts, I want to see the fuel trims.

Thanks.
 
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What Donald said.

I have an old Samsung Galaxy S3 phone that I wiped and installed Torque Pro on. Torque Pro costs $4.99, and will read most Bluetooth OBD-II adapters fine.

I bought an inexpensive adapter on Amazon for about $13. This Adapter - VeePeak Bluetooth OBD-II adapter

I also got a magnetic-mount vent-clip phone holder for about $8. Holds the phone amazingly well.

The setup as a whole works great. Here's a shot of it mounted:

full-64489-6402-phon.jpg


I typically leave it on this screen to get a second set of info while I drive, but I have other screens setup to show Long Term and Short Term Fuel Trim, O2 sensors (pre and post), Spark advance timing, Vacuum sensor, EGR %, etc..
 
wow - cool. only problem is that I don't have Android. I will have to look at the apple versions....

thanks - that is much cheaper than my pick.
 
That's a nice unit for the money. Made by Innova who makes some good products.
 
Originally Posted By: zzyzzx
I would be using a MityVac to check for vacuum leaks.


at the brake booster you mean?
 
Originally Posted By: Chester11
It's a rough idle when in gear and hot. (Most noticeable at a stoplight). It improves with throttle.

In neutral or park, rpm increases a bit and the feeling goes away.

If you are interested, here is what I have done:

- replaced 2/3 motor mounts with no change. (The third mount looks ok)
- cleaned the throttle body
- replaced valve cover gasket
- also sprayed around lines / gaskets with water and carb cleaner but don't hear an idle change.

I'm thinking it could be a master cylinder / vacuum pump. (bad master cylinder would explain why the vibration is so bad at a light with the brake on - my theory anyway, as braking has seemed to deteriorate in the last few years). But before I go replacing parts, I want to see the fuel trims.

Thanks.



I'm all for you buying a scan tool & learning how to use it! But.....A good diagnostic tech can figure out your issue very quickly. Case in point about the master cylinder causing driveability concerns....Probably not your issue unless your losing brake fluid? You can usually HEAR a ruptured brake booster diaphragm.

Make/Model of the vehicle?
 
Originally Posted By: clinebarger


I'm all for you buying a scan tool & learning how to use it! But.....A good diagnostic tech can figure out your issue very quickly. Case in point about the master cylinder causing driveability concerns....Probably not your issue unless your losing brake fluid? You can usually HEAR a ruptured brake booster diaphragm.

Make/Model of the vehicle?


2007 Mazda 6i (2.3).

Yep - understand, it's an older car that I kinda like messing with. No leaks, but I did find out that the in line check valve seems slightly restricted (it sounds a bit like a trumpet and not an easy flow). It appears that I have to replace the entire hose, which is $94! Mazda parts are somewhat challenging to find, but that is crazy. I also posted on a Mazda specific forum to see if they had ideas. I would hate to make a junkyard run for a hose.
 
The check valve just needs to flow one way & check the other way, The vacuum signal the engine makes is very strong so what seems like a restriction to you isn't.....Engine vacuum will easily overcome the check valve spring pressure.
 
Originally Posted By: clinebarger
The check valve just needs to flow one way & check the other way, The vacuum signal the engine makes is very strong so what seems like a restriction to you isn't.....Engine vacuum will easily overcome the check valve spring pressure.



that's what I was thinking - but thanks for confirming. I'm running out of places to look - so it might be time to just deal with it. what has me stumped is the RPM drop that occurs when you press and hold the brake for about 5 / 7 seconds. it feels almost like a downshift, but happens at a dead stop also.
 
Remove the booster hose from the intake manifold, plug the port & retest....Be careful as you will NOT have brake assist!!

If your running at speed....Applying the brakes will unlock the torque converter.
Trying idling at a stop light with the parking brake instead of the service brakes & see if it improves.

A scan tool would help you see if the actual idle speed is lower than the target idle speed. I would also take a closer look at the old mount that looks good!
Take a floor jack with a thick piece of rubber & take the weight off that mount & see if the vibrations go away.

Mounts can visually appear OK but be collapsed internally, Does the engine torque on this mount in drive??
 
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Originally Posted By: clinebarger
Remove the booster hose from the intake manifold, plug the port & retest....Be careful as you will NOT have brake assist!!


Did this after doing the test below. There is a slight improvement but the chug is still felt. RPM still drops when pressing the brake.


Originally Posted By: clinebarger
If your running at speed....Applying the brakes will unlock the torque converter.
Trying idling at a stop light with the parking brake instead of the service brakes & see if it improves.


Did this. It does improve. The rpm drops when you press the brake and hold - this made me think it was the booster or check valve. By the tach, it drops to 500rpm, idle is 750 according to my shop manual.

Originally Posted By: clinebarger
A scan tool would help you see if the actual idle speed is lower than the target idle speed. I would also take a closer look at the old mount that looks good!
Take a floor jack with a thick piece of rubber & take the weight off that mount & see if the vibrations go away.

Mounts can visually appear OK but be collapsed internally, Does the engine torque on this mount in drive??


The motor visibly moves when in gear. I probably should just replace the passenger side mount. (Supposedly it is fluid filled and leaks when it goes bad. I did have an oil leak from a loose filter cover - so I may have missed the leaking fluid.) Long story short, aligning the transmission mount was tougher than expected, and I stripped a bolt - which needed a helicoil, and a trip to junkyard to find replacement bolt. Learning experience, but I'm hesitant to work on the last mount (which is on the other side of the motor) until I'm sure I fixed the cause.

I really do appreciate the help. I think I'll pick up the scan tool and confirm the RPM changes again at temp.
 
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So if anyone is still watching, I pulled vacuum at the booster. It appears to drop about 1 psi after 5 minutes. (20 to 19). I'm using a cheap Harbor freight brake bleeder, so this may not be a significant drop.

If I touch the brake (after pulling the vacuum back up) it drops about 10psi. This is normal based upon what I read online (see below).

The only interesting finding is that vacuum drops very unevenly if I press and hold the pedal for 30 seconds. (See number 4 in the link below).

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjFy4KFh_zaAhXkuFkKHRQZBV8QFggpMAE&url=http%3A%2F%2Fssbrakes.com%2Fattachment%2F85569-Vacuum%2520Brake%2520Booster%2520Testing%2520and%2520Diagnosis.pdf&usg=AOvVaw2UiiDJH-3xHq0JIaEgrm0E

I'm still not convinced the booster is the issue - because even with the vacuum line blocked and disconnected from the booster, I still have a idle drop in gear. This leads me to looking at disconnecting the brake light switch. If this fixes the problem I would have to look at the trans, engine computer doing something nutty, or some crazy ground issue?

(I still have not replaced the remaining mount either).

Not ready to give up yet, but close.
 
Originally Posted By: Chester11
I still have a idle drop in gear. This leads me to looking at disconnecting the brake light switch. If this fixes the problem I would have to look at the trans, engine computer doing something nutty, or some crazy ground issue?

(I still have not replaced the remaining mount either).

Not ready to give up yet, but close.


Idle drop in gear is normal! I would replace that engine mount first.
NO piston engine is perfectly smooth at idle.....We like to talk about how smooth Inline 6'/8's, V12's etc are WITH rubber motor mounts! Inline 4 cylinder engines are probably the worst for vibrations/harmonics.


Published Idle Speeds are not to be trusted as they do not apply to any adjustment that can be made without ECM Calibration changes.
Your also going by the cluster mounted Tachometer which is more of a novelty item in most cars.
 
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I hear you and hope you are right. To be clear, the idle drops in gear, and then drops further (near stall to the point where the dash shakes) when the brake is pressed. That said, I'm ordering the mount tonight.

My concern is that if I replace the motor mount (like I did with the others) and don't fix the underlying issue - I'm just wasting money on parts.

I hear a hiss - like a leak - but just can't find it. I'm wondering if there is a line I am missing. I've sprayed just about everything.
 
I'm not all that familiar with Mazda's, I see the occasional Tribute which seems more Ford than Mazda.

With the Throttle Blade used for IAC duties.....A slight hissing is normal.

A vacuum leak big enough to cause driveability issues should set a Bank 1 system Lean DTC (P0171).
This codes set criteria is usually WELL WITHIN the ECM/Fuel System's ability to compensate.

If the Idle RPM is in fact really low/unstable/uncontrollable.......I'm surprised you don't have "Random Engine Stall" issues?

The last thing I want you to do is throw parts at a problem, I'm helping the beat I can with the data given,
But.....I have have seen/witnessed folks spending thousands of dollars chasing down a vibration caused by a bad/collapsed motor mount.
 
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