Can someone walk me through the procedures?

[diesel research]

Its not a regular rythmic misfire you can pinpoint to one bank of cylinders then?

Does it seem to shift around when the motor idles?

No, and yes a little, sometimes. It is definitely on my one and only bank though.


Since things are different in europe, I will show you the typical tool I am speaking of.

Many of our cheaper quality autoparts stores even offer a "free" diagnostic service. They use one of these, pull codes, and sell you a new sensor, some filters, and always an 02 sensor on top of the others. Then they try to sell you some trick triple platinum bosches.

In manner cases I (or the DIYer) may not actually own said tool. The codes may have been pulled from such a discount store, and now I am on the hunt to try to fix it.

In a few cases, said owner may have the privy of access to a slightly better tool, BUT only knows how to pull and clear.

 

[richfinn]

Its a 4.0l/4.7l Jeep with the dizzy mounted on the right side of the motor??

 

[richfinn]

Hypothetically of course

 

[Stick]

This is a GREAT suggestion, but you should explain why? and if you would do this with every car or only certain symptoms or codes?

It's my first step with any sensor related driveability problem. I'd worry far more about the Cam sensor code than the misfires, because the Cam sensor often provides timing for the fuel injection, so if that's off it could be the source of the random misfire.

Modern computer systems are *very* voltage sensitive, often .1V is enough to cause a problem. Being that the computer is expecgted to provide a stable 5V reference voltage on the Cam sensor signal, if it doesn't provide that then the output will be off. Sometimes it's off enough to cause a no-start, other times it might just cause a driveavbility problem.

It's not always a battery problem either, which is why I suggested at least a basic charging system test. I checked the shop mail today, and Motor Magazine has a decent article on battery testing. Motorage has another good article on charging system analysis, he uses a scope in the article so it's not really relevent to this discussion other than to show another way to look at things.

 

[richfinn]

It may be the crankshaft position sensor and not the Camshaft position sensor as your crappy code reader claims, does the rev counter needle flicker along with the misfire??

 

[Stick]

If the DMM does frequency it can at least measure switching rate. Not a substitute for 'scope but better than nothing.

I generally see failures in voltage levels or the timing of the output rather than frequency. I'm not so sure checking frequency is the greatest check. Like you said, not a substitute for a scope, but better than nothing.

 

[richfinn]

I think its the crank sensor in the bellhousing thats failing

 

[diesel research]

Its a 4.0l Jeep with the dizzy mounted on the right side of the motor??

What it is, is not important to the discussion. I have intentionally left out a few details, because that encourages people to throw out "common known parts" list at me. That's troubleguessing, not troubleshooting. At 200,000 miles with no engine management parts being replaced, it could conceivably be anything, so the common failure stuff doesn't fly.


Both of the following are for real:

You can fix a problem without a labscope.I went to a class on CAN vehicles and the instructor showed how to fix a car in 2 minutes which can be done.I know what parts go bad commonly on certain vehicles.

Ok, let's try this one last time before I assume you have absolutely no reading comprehension or common sense...



I never said that you can't fix a problem without a labscope, in fact I just said "I don't think I could do the type of diagnosis I do on a daily basis without a good scan tool capable of graphing live data. You may or may not need a scope to back up that diagnosis, it really depends on what the failure is. It's certainly one more tool in the toolbox to help figure out problems though."

You've mentioned that same class on CAN vehicles a couple of times. Either you didn't get much out of it, or it was a poorly run class if they are teaching pattern failures as a diagnostic tool. I'd love to hear what it takes to fix a vehicle in two minutes, so if you can do that why don't you share the knowledge?

You talked about a '99 Expedition that you put coils on. Installed one, "fixed the problem", and then it came back the next week with another dead coil. I guess you got lucky that the customer came back, in the case of the video the vehicle had been to several shops because it was not fixed, likely because they were relying on pattern failures and not diagnosing the problem the first time. To me it makes more sense to do a complete diagnosis and prevent comebacks or worse, losing the customer to another shop because I couldn't fix the problem the first time.

I prefer being able to know for sure what the problem is, and what I need to do to fix it. Certainly there are methods of diagnosing something like a misfire without a labscope, the first video is proof of that. But even if you've got a whole shelf of known good parts for "what parts go bad commonly on certain vehicles", you are still eventually going to run across the non-pattern failure eventually.

So, I've got a couple of questions for you:

1. How do you know what parts are defective on the spot without checking out the rest of the system? What if there is more than one defective part?

2. What do you do in the case of a no-code misfire, or something such as a P0300? Where would you start?

3. Who pays for the parts if what you installed doesn't fix the problem? The customer? Do you return them to the parts vendor? Do they go on the shelf with the rest of the known good parts?

1: know it happened to the same make and model

2: Pull a spark plug and check that first.If the plug is good,the coil is bad.

3: Know the customer very well of the expedition and he has not come back with it running bad.This customer payed for the parts and was satisfied with the work
Fords have problems with coils,DPFE sensors,mass air flow sensors.Ford's Fuel pumps are pretty much built very well and don't have a problem with fuel pumps.

WTF, OVER?!?!

richfinn, it starts just fine once it fires.

 

[Mr.Nutcase]

If CKP was bad, car would not start.

If you got missfires, try moving the coil to next cylinder.
If misfire moves then the coil is bad.
If the misfire stay in that same cyl, then rule out the coil.
Then you check the fuel sys, then if ok check engine mechanical condition
Wth no service info, diagnosis is worthless.
Also it would good Idea to check for Technical Service Bulletins (TSB)
Technical Service Bulletins (TSB)!!!!!!!!!!

 

[diesel research]

If CKP was bad, car would not start.

If you got missfires, try moving the coil to next cylinder.
If misfire moves then the coil is bad.
If the misfire stay in that same cyl, then rule out the coil.
Then you check the fuel sys, then if ok check engine mechanical condition
Wth no service info, diagnosis is worthless.
Also it would good Idea to check for Technical Service Bulletins (TSB)
Technical Service Bulletins (TSB)!!!!!!!!!!

While I'm sure they empahsized that in your tech school, teach us diyers how to check TSBs.

What service info do you need? I think I have provided most of it already.

 

[Mr.Nutcase]

While I'm sure they empahsized that in your tech school, teach us diyers how to check TSBs.

What service info do you need? I think I have provided most of it already.

Google works wonders.... there many good techs in forums, here ect
Tsb save time.....

When I was 16 years old, I had 1994 Nissan Altima that was making top engine noise, almost like rattle..
I did not know part was wrong, I thought maybe a bad alternator bearing, maybe a bad water pump, or bad idler. Nope..
If had asked in forum, I would found that there was a TSB adresssing the problem.
I asked later on.. It would saved my ***...
The engine was KA24DE, The problem was the guides, solution, get rid of them..
http://www.jonko.com/auto_repair_forums/index.php?showtopic=12663
There is a site i like, It is www.jonko.com.
By the way, I am Alphaman overthere.......

 

[diesel research]

Let me rephrase that. Show me a FREE complete TSB listing, inlcuding the details inside (not just the titles)

 

[Stick]

Again, I believe I see what diesel research is getting at. The responses have been somewhat insightful, but I think most of you might be on the wrong track.

Ok, now that we've got a couple of posts... I believe the point in the OP is that code readers are great for one thing, pulling codes (and maybe as a doorstop). To do any actual diagnostics you are going to need more than just codes. Livedata, mode$06, service info, etc are helpful, but without an understanding of how things work you are just throwing parts and not diagnosing anything.

 

[Mr.Nutcase]

Let me rephrase that. Show me a FREE complete TSB listing, inlcuding the details inside (not just the titles)

http://www.jonko.com/auto_repair_for...howtopic=12663

 

[Mr.Nutcase]

To do any actual diagnostics you are going to need more than just codes. Livedata, mode$06, service info, etc are helpful, but without an understanding of how things work you are just throwing parts and not diagnosing anything.

Agreed,

 

[richfinn]

What it is, is not important to the discussion. I have intentionally left out a few details, because that encourages people to throw out "common known parts" list at me. That's troubleguessing, not troubleshooting. At 200,000 miles with no engine management parts being replaced, it could conceivably be anything, so the common failure stuff doesn't fly.


Both of the following are for real:

WTF, OVER?!?!

richfinn, it starts just fine once it fires.

Make mine a Bud Lite Lime

 

[diesel research]

Ok, now that we've got a couple of posts... I believe the point in the OP is that code readers are great for one thing, pulling codes (and maybe as a doorstop). To do any actual diagnostics you are going to need more than just codes. Livedata, mode$06, service info, etc are helpful, but without an understanding of how things work you are just throwing parts and not diagnosing anything.

We have also established pattern fixes are not reliable, and can be costly.
We have established they are mostly useless, except for some professionals and limited applications (swapping around coils or some wheel speed sensors)


Not once did someone tell me how to check any of those 3 wires leading to said sensor. No one mentioned checking shutter wheel, but icanfixanything was getting real warm.

Reminds me of the guy who had a mt2500 (or I mean access to it) and used it as a code reader. Replaced every sensor in his truck, then replaced the pcm.

When he was connecting the new pcm he noticed the battery feed wire was a bit loose...ouch!

________________

The fault is obviously a fake. I've had a few rads/fan clutches/condensers and a front pinion seal. Well and a cracked power steering pulley. Other than that, no real servious history.

 

[diesel research]

Make mine a Bud Lite Lime

I was kind of worried once you mentioned vehicle specifics (even though they were correct) that people would start throwing more part names out there. Yes, as soon as I said it only has 1 bank it was a pretty dead give away. You do deserve credit though.

As for TSBs, I threw the P0300 in there for a few reasons. It is a "distractor". It is a very common code that could be caused by almost anything! One TSB even tells me to start talking the top half of the engine apart and checking for stuck valves. Of course, misfires are commonly associated by diy'ers with the secondary ignition, so that helps add to the confusion.

 

[richfinn]

Very good addition to the topic. Understanding sensors/waveform types could definitely be helpful. Although probably a vast majority don't know what a variable-reluctance, optical, or hall effect speed sensor is, let alone what a waveform is, or what type produces what type.

My crappy haynes manual does identify the 3 wires and their various positions. Hall effect is an on/off switch, although I'm not sure I would want to draw current of a bulb through the tiny switch.

I did tell you (sort of) if you think about it carefully

Was it a Jeep ??

 

[richfinn]

Course it was, never doubted it for a minute

 

[Stick]

How about this one I just had today. Started vehicle up and it had a check engine light. Codes were P0108 (MAP high input) and P0113 (IAT high input), otherwise the vehicle ran fine.

 

[Mr.Nutcase]

How about this one I just had today. Started vehicle up and it had a check engine light. Codes were P0108 (MAP high input) and P0113 (IAT high input), otherwise the vehicle ran fine.

I would check the MAP sensor,
Is this a MAF with IAT sensor?
I would look at PID's
MAF should be close to engine litters. if engine is 2.4, 2.3 grams is ok

 

[Stick]

Again, just like the OP, you've just got the codes. No livedata, etc.

 

[MattT]

How about this one I just had today. Started vehicle up and it had a check engine light. Codes were P0108 (MAP high input) and P0113 (IAT high input), otherwise the vehicle ran fine.

Not sure if you meant MAF or MAP.

Had one a few months back that was throwing MAF and IAT codes on an '01 E-150. Anyways the duct between the MAF and IAT sensor housing and the throttle had popped off and the someone had unplugged the sensors to "fix" it

 

[richfinn]

I would be looking for the reference voltage wire being open circuit on that MAP/IAT if that was OK I would volt drop the grounds.

Are they a combined sensor or seperate?

 

[diesel research]

Since he said MAP, a cut open vref line on MAP would result in a low (0) reading at the sig wire or pcm pin.

A cut open "vref" on the IAT would obviously result in a high reading, since it's a NTC thermistor.

Voltage drop on grounds sounds reasonable, but I am not sure if this particular vehicle uses a single ground point for ALL sensors, or just certain ones here and there? If all used a common ground junction you would have a lot more problems on a lot more sensors. Might not even start up. Definitely should have ECT problems since they often run on exact same parameters as the IAT.

Looking at the mechanical side, high voltage MAP on a working system means low vacuum, or atleast it is not reaching the sensor. high voltage on a IAT typically indicates low air temp. I am not aware of any physical condition that results in both condition.

I am wondering if there is some sort of short to power? (w/o livedata, I would definitely want to look at the 2 raw values on sig lines to see if they are similar/same)

 

[Stick]

I will say this, playing by the rules I got the code definitions from obdcodes.com like I would if the reader just spat out numbers. I also spotted the problem pretty quickly on a visual inspection, and it was easy to verify, but I work on these vehicles all the time.

If you did have freeze frame data it would have been pretty useless.

 

[diesel research]

The windshield wipers hit the sensor?

 

[richfinn]

Alaska? is the sensor frozen

 

[Stick]

I'll go ahead and let this one go since you guys were reasonably close. 4.6L Ford engine, bad connection at the MAF. The section of the wiring harness going to the MAF was routed improperly and pulled fairly tight, not letting the connector engage completely. Vehicle had just been in a couple weeks ago and had a new intake put on it because it was cracked. The harness was probably routed improperly at that point, and the connector likely wasn't engaged completely, letting it gradually work it's way loose.

 

[Stick]

Alaska? is the sensor frozen

It's actually 75 degrees out right now. It's not always snow and darkness up here, we currently have 23 hours of daylight as well, which makes it hard to send the kids to bed at 8:30. "But dad, it's still light out..."

 

[richfinn]

It's actually 75 degrees out right now. It's not always snow and darkness up here, we currently have 23 hours of daylight as well, which makes it hard to send the kids to bed at 8:30. "But dad, it's still light out..."

I was only kidding Stick, I,ve just got back from the USA and was glued to your amazing weather reports waiting for the Space Shuttle launch to be confirmed. It was cloudy in Florida but luckily we saw it for a few seconds.
There were floods and storms though on the TV reports

 

[Busted Bolts]

First start with the basics, fuel, air, ignition, compression, connectors, basic electrical, grounds, corrosion, then look at the possible causes, see if you ruled out any of them performing the basics, be observent, look, listen anf feel (when safe), looked at basic schematics. To many people go to replace parts that didn't need to be done, anyone can change outparts. Buy reference materials to compare. Start simple

 

[diesel research]

First start with the basics, fuel, air, ignition, compression, connectors, basic electrical, grounds, corrosion, then look at the possible causes, see if you ruled out any of them performing the basics, be observent, look, listen anf feel (when safe), looked at basic schematics. To many people go to replace parts that didn't need to be done, anyone can change outparts. Buy reference materials to compare. Start simple

So if you are going to do all of that anyways, basically a code reader is often of no use?