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Help with waveform analysis. (Read 10,189 times)
J Angell
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Help with waveform analysis.
Oct 16th, 2016 at 1:36pm
 
Hi there everyone.  I am currently trying to repair my car and was hoping for some insight from you guys as to what could be the problem.  It has been to 2 mechanics (including the dealer and so far $1300+ has been spent in parts and labor with no fix).

It is kind of a complicated case, but I will try to be brief.

Car:  2002 Ford Focus ZX5 Vin "3" DOHC Zetec motor with manual transmission.

Problem:  Starts but wont idle and stalls seconds after starting, despite trying to give it gas.  If you start it (and stall it) several, several times so that the engine warms up, sometimes it will run just fine all day until next cold start.

Replaced:  MAF sensor, TPS sensor, Idle air control valve, alternator, pre-cat 02 sensor, spark plugs, spark plug wires, ignition coil (14k ago for the coil).

Exhaust leaks have been repaired.  No obvious intake leak.

When it runs (and it runs very rarely), it runs mostly lean, but at times rich (based on fuel trim numbers).  There doesn't seem to be any rhyme or reason.

***********
The following is what I would like help with, and please correct me if I make a glaring error in my analysis.

This was taken from a recent start / run for a few seconds / then stall:

https://www.flickr.com/gp/138846169@N03/ES190u


The light blue sine wave is the crankshaft signal.  It is a 36-1 tooth and the missing tooth is 90 before TDC.  I wrote in white numbers the degrees before and after TDC.

The yellow is my camshaft signal.  It rises and then falls and then rises again.  Where it first crosses from positive to negative (in the middle of the signal) should be at 22-26 degrees after top dead center from what I have researched.  You can see that mine crosses at around 38 degrees (or about 12 degrees late).

The darker blue hump is a crappy pressure transducer stuck in cylinder 1 instead of the spark plug, so I can see the cylinder pressure and tell where TDC is... it was about $13 on Ebay, so the response time and quality isn't the best, but look where the spike in that hump is:  at about 12 after TDC, which means my TDC is occurring 12 degrees too late.


And here is one that  I cannot explain:

https://www.flickr.com/gp/138846169@N03/0tZn9E

In this you can see my camshaft signal (blue), my spark amperage (purple)​ with cylinder 1 presumably just before the camshaft wave, and the voltage of the #1 fuel injector (yellow).  The two white vertical lines roughly encompass the powerstroke starting from TDC.

Ignoring the fact that my spark is probably occurring too early before TDC (and sometimes I have two ramps like you see in the picture, whats up with that? Multistrike?), check out where the fuel is spraying:  Towards the end of the power stroke and into the exhaust stroke.  I have really tried hard to see where I am messing up in my thinking, but I think it is an accurate interpretation.


I don't know, could be nothing, but the next time I get a chance, I am going to check the timing and see if I can't find anything... I don't get it though, because the timing belt was a Gates that I put on maybe 30k miles ago, with new tensioners and pulleys.  And the fact that I can get it to run (sometimes) if the car warms up enough... Maybe a loose keyway?  What do you think?  Thank you everyone for reading this and for all your help.  You make this a great community.

  Jeff from Virginia
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« Last Edit: Oct 16th, 2016 at 2:37pm by J Angell »  

Spark_vs_inj_1.png (47 KB | 371 )
Spark_vs_inj_1.png
 
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rayray
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Re: Help with waveform analysis.
Reply #1 - Oct 17th, 2016 at 7:59am
 
This is a known good cmp, ckp, ign. The 2 ignition coil ramps is the Multistrike. Unfortunately, there are 2 cams but only 1 cmp sensor.

Ray
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J Angell
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Re: Help with waveform analysis.
Reply #2 - Oct 17th, 2016 at 8:14am
 
Rayray,  Really, really appreciate your help and time.  I am going to study this.  Thank you sincerely,  Jeff  PS.  I wish you weren't so helpful though, because now I don't know what is wrong with my car Smiley  Thank you again.

With your experience and knowledge, do you think my fuel injector is spraying at the correct time?
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« Last Edit: Oct 17th, 2016 at 8:30am by J Angell »  
 
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Mike in St. Louis
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Re: Help with waveform analysis.
Reply #3 - Oct 17th, 2016 at 9:56am
 
Hi J Angell. Are there any trouble codes? Has the fuel pressure, volume and voltage going to the fuel pump been checked? Fuel trims, what were the numbers.
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J Angell
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Re: Help with waveform analysis.
Reply #4 - Oct 17th, 2016 at 10:33am
 
Thank you for asking.  No trouble codes.  Fuel pressure on this car is read on the scan tool and it shows good: 34+ psi.  I have not checked the voltage yet to the fuel pump but the psi shows steady and good, and I hear the pump engage when I turn the key on.  The fuel numbers were all over the place, but if I recall, mostly showed above 10 and probably less than 30.

The spark plugs have been changed, and they have in their very short life turned black and wet with gas.  The exhaust smells of gas when it stalls.  I tested spark with a test light (as well as the oscilloscope) and both showed positive results.  Plugs have been changed as well as the ignition module.  Thank you very much for your time.
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Tom Roberts
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Re: Help with waveform analysis.
Reply #5 - Oct 17th, 2016 at 10:39am
 
J Angell wrote on Oct 17th, 2016 at 8:14am:
do you think my fuel injector is spraying at the correct time?



http://www.autonerdz.com/cgi/yabb2/YaBB.pl?num=1112817999/
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J Angell
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Re: Help with waveform analysis.
Reply #6 - Oct 17th, 2016 at 10:43am
 
Here is a shot of my MAF (yellow) and TPS (blue).  You can see the MAF has three different points where it becomes wide and thick... this is where the car was trying to stall.  During the last of the three sections, you can see the car stalling despite me trying to give it WOT to save it.  I plan on retaking this shot to make sure those spikes are artifact and not real voltages.
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« Last Edit: Oct 17th, 2016 at 10:59am by J Angell »  

TPS_and_MAF.png (49 KB | 384 )
TPS_and_MAF.png
 
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J Angell
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Re: Help with waveform analysis.
Reply #7 - Oct 17th, 2016 at 10:59am
 
Tom Roberts wrote on Oct 17th, 2016 at 10:39am:
J Angell wrote on Oct 17th, 2016 at 8:14am:
do you think my fuel injector is spraying at the correct time?



http://www.autonerdz.com/cgi/yabb2/YaBB.pl?num=1112817999/


Thank you!  I am at work now but will study this tomorrow.
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J Angell
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Re: Help with waveform analysis.
Reply #8 - Oct 18th, 2016 at 12:41pm
 
Thank you everyone for all of your help and time.  I really appreciate it. 

Here is one more photo showing why I think my fuel is spraying at the wrong time.  The darker blue is my #2 compression.  The yellow is my #2 fuel injector.  The pink are my spark ramps.  My car is a waste spark system firing 1-4 and 2-3.  The firing order is 1-3-4-2.  It seems to me from the photo that the fuel is spraying mostly in the exhaust stroke and therefore not getting burnt up.  I know my spark plugs are black, wet, and smell of fuel.

https://flic.kr/p/NacAfS
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Re: Help with waveform analysis.
Reply #9 - Oct 18th, 2016 at 7:30pm
 
J Angell wrote on Oct 18th, 2016 at 12:41pm:
Thank you everyone for all of your help and time.  I really appreciate it. 

Here is one more photo showing why I think my fuel is spraying at the wrong time.  The darker blue is my #2 compression.  The yellow is my #2 fuel injector.  The pink are my spark ramps.  My car is a waste spark system firing 1-4 and 2-3.  The firing order is 1-3-4-2.  It seems to me from the photo that the fuel is spraying mostly in the exhaust stroke and therefore not getting burnt up.  I know my spark plugs are black, wet, and smell of fuel.

[img]



From what I have seen your injector is firing as designed
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J Angell
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Re: Help with waveform analysis.
Reply #10 - Oct 19th, 2016 at 1:48am
 
Thank you so much.  I really appreciate it and it helps me a lot.
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