http://www.wellsve.com/ This video demonstrates how to diagnose a sticky poppet injector utilizing scan tool and 5 gas techniques. The upper and lower intake…
Chev / GMC misfire running rich diagnosis and replacement
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Hey man can you check my video out n see if you can give me any pointers please and thanks
my 2001 bravada when first turn on misfire in 1,000 rpm. and when is warm stay doing it. is only in 1,000 rpm the motor run can ruft. any ideas. can helppppp thanks.
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good job keep up the good work
Yes, you must have a scan tool to check timing. To be able to ajust the distributor we elongated the mounting hole a little. Connect scan tool and turn distributor if needed.
Mark Hicks
Wells Vehicle Electronics
The reason I ask is there really is no play to allow for any rotation due to the hold down clamp being slotted to and from the hold down bolt, instead of being correctly slotted for distributor rotation.
Hi,
GREAT video! Thanks to you guys I just did all this to my ’01 blazer (intake gasket replacement, upgraded MPFI spider, etc) Now, I will need to do CMP retard as shown around the 8 min. mark in your video. Can you elaborate how this is done? Is it that you hook a scanner to it, check where its currently at (say -5), loosen the distributor and rotate it like a clock forwards or backwards until the -5 becomes 0? Continued in next comment…..
Thank you for the kind words. Means a lot to us!
Mark Hicks
Wells Vehicle Electronics
Great video!
Correct!
Mark Hicks
Wells Vehicle Electronics
That is the spider injection correct??
Thank you for watching. Your comment really means a lot to us!
Take Care,
Mark Hicks
Wells Vehicle Electronics
Thank you for your great videos and awesome products.
Thank you for the kind words. I wish we could take a look at your vehicle too.
Mark Hicks
Wells Vehicle Electronics
Great video!! I wish you guys had a workshop in Bahrain where i live! Truely speaking Its a very nice video with a very important lesson to learn “Get it right the first time” Unfortunately i cant bring my car to US to you amazing fault detectors to be diagnosed! Very well done!!
You are right it is a calculated value. Love the idea of measuring before combustion. In a round about way it is what we are doing now by measuring the amount of air coming in etc. But to measure just prior to combustion would be perfect. Never say never!
Mark Hicks
Wells Vehicle Electronics
It seems to me that misfires cause the 5-gas analyzer to display a false air/fuel ratio. I believe that it is a calculated value. It has to be unless you drill a hole in the combustion chamber and stick a 5-gas analyzer probe into that hole to measure pre-combustion gases (since the term air/fuel ratio describes a condition before combustion). I wonder if there will ever be a time in the future where cars have a 5-gas analyzer probe built into the combustion chamber.
You remind me of someone I know very very well. I have a feeling someday you will be on this end of the questions. The book is absolutely correct! Keep it up I can tell you really love what you are learning. If you have find yourself in Wisconsin I would be honored to take you on a tour of our facility. Keep reading!
Mark Hicks
Wells Vehicle Electronics
The book I got from the Pennsylvania Department of Transportion says “. . . This is why CO is such a good rich exhaust indicator.” It also says “CO2 indicates combustion efficiency.”
You have to remember, there are a lot of shops that don’t have this equipment and can not afford to purchase it for limited use. This is an alternative method to accomplish the same result. This is a technique used my techs for many years and has proven to be successful. As long as the timing is set to zero there will be no issues.
Mark Hicks
Wells Vehicle Electronics
I have to agree it does appear a little lean. This shot was taken right after the job, there was no road test. Just start and take the readings. After the road test and the PCM learned the new values it came into a normal range.
Mark Hicks
Wells Vehicle Electronics
It is 498.1, the font they use is funny when a 3 appears it kind of covers the decimal point.
Mark Hicks
Wells Vehicle Electronics
This was one of the issues with early computer vehicles. If the O2 saw lots of oxygen the algorithm was to add fuel. A mistake when a misfire occurs especially a rich condition misfire. this is the main reason air/fuel ( or oxygen/fuel as you like to call them ) ratio came into being, in my opinion.
Mark Hicks
Wells Vehicle Electronics
Ahh Haa very good!
Mark Hicks
Wells Vehicle Electronics
Not true. CO is a reading of incomplete combustion, which you can and probably will have with a very lean mixture.
Mark Hicks
Wells Vehicle Electronics
6:37 “Elongate the distributor mounting holes.” Is that a good idea? I looked up this vehicle (97 GMC Jimmy) on ALLDATA, and ALLDATA says “NOTE: The Distributor is located in a fixed, non-adjustable position. No attempt should be made to adjust the engine base timing by rotating the distributor. Attempting to do so may result in engine cross-fire and misfire conditions. Timing is not adjustable. Ignition timing can be changed by reprogramming the PCM using TIS2000 PC, and the Tech 2 scan tool.”
8:25 The “after” 5-gas readings look a bit lean to me. O2 is 5.73% and A/F is 18.3. I was expecting 1.5% for O2 and 14.7 for A/F.
At 1:33, the HC reading has 4 digits. Just to clarify, is that a decimal point between the third and fourth digits? Or is that just a blemish on the display screen or camera lens? It looks like 498.1 parts per million, but then again it could be 4981 parts per million.
Opps. I figured out the answer. Misfires cause the O2 sensors to read lean due to unburnt O2. As you can see on the 5-gas analyzer, the O2 reading is 6.43%. The “false” lean signal from the O2 sensor is the reason the PCM is commanding + fuel trim. I guess in the case of a misfire, it’s better for the PCM to err on the side of rich than on the side of lean because lean can cause knocking and engine damage, whereas rich would risk damage to the cat.Cats are cheaper then engines.
My understanding is that “command corrects condition”. The condition is that the poppet fuel injector is sticking and holding open longer than commanded. If that is the case, then you will have a rich condition and the command should be negative fuel trim — not positive. This video shows positive fuel trims. The smoke test indicated no vacuum leaks, so what is up with the POSITIVE fuel trims?
1:40 According to the 5-gas analyzer, the CO reading is 4.54% while the air/fuel ratio reading is 15.1%. It seems to me that the value displayed for air/fuel ratio can not be trusted. CO is indicating rich. But the A/F ratio displayed says lean.
Thank you for the update! This is excellent news and a great lesson for everyone. Always always always, did I say always, check and verify the basics first!
Keep up the great work!
Mark Hicks
Wells Vehicle Electronics
Thankfully all I needed to do was replace the spark plugs. 32$ and 1hour of skinning knuckles was much easier to take than what I was fearing would be necessary!
Thank you for the kind words. It makes all the effort worth while knowing we helped. Remember, you can help someone find this information by pressing the like button or sharing the connection.
Take Care,
Mark Hicks
Wells Vehicle Electronics
Awesome video, thanks for posting.
Clean all components while disassembeled.