How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Mazda Ed Your Own Question

Mazda Ed
Mazda Ed, Auto Service Technician
Category: Chevy
Satisfied Customers: 2223
Experience:  ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience.
5624692
Type Your Chevy Question Here...
Mazda Ed is online now
A new question is answered every 9 seconds

2007 chevy vin u 6.0 has misfire on #7 & 2 at idle only above

Customer Question

2007 chevy vin u 6.0 has misfire on #7 & 2 at idle only above 1000 rpm goes away. Have traded plugs/ciol/injectors also had valves done on motor 105,ooo on motor. Have lab scope injector coil ckeck ok I do known in the fire order 7&2 are next too each other Any help would be nice thank you dale I have over 40 yrs in this feild of diagnostic
Submitted: 1 year ago.
Category: Chevy
Expert:  Gary replied 1 year ago.
can you feel those 2 cylinders dead at idle?or just the misfire is showing those 2 cylinders ?
Customer: replied 1 year ago.
you can feel like dead cylinders runs ruff at idle smooth above 1000 rpm going down the road runs good fuel trims are very good all the time 3 to -5
Customer: replied 1 year ago.
also did compresson test ok
Expert:  Gary replied 1 year ago.
can you connect a vacuum gauge to manifold vacuum line and when its skipping at idle tell me what its reading and tell me if the needle is bouncing a lot on the gauge ?
Customer: replied 1 year ago.
a steady 18.5 vaccum at ilde in gear dr it skips 16 to 14
Expert:  Gary replied 1 year ago.
no needle jumping at all ?
if not the next step will be to do a fuel pressure drop on the fuel injectors and see when fired if they all drop the same PSI
OR you can swap # ***** with # ***** injector and see if the skip moves to cylinder # *****
Customer: replied 1 year ago.
fuel test done 60psi also runnig at 60psi did a injector test on all they drop the same to 38psi on all 8
Customer: replied 1 year ago.
also swap injectors and coils tested power at coils/inj ck ok
Expert:  Gary replied 1 year ago.
well you eliminated spark ,fuel and compression. Now we are down to 2 things. Possibly the crank sensor or cam sensor is sending a wrong pattern to the PCM
we can also do a running compression test on each cylinder one at a time with the little valve removed in the bottom of the compression gauge so you can see the psi going up and down and see if all 8 testing them one at a time are the same
Customer: replied 1 year ago.
also did this test showed running at 70psi all 8
Customer: replied 1 year ago.
did at lab scope only on crank showed good pattern If the cam had a bad signal why only at idle
Expert:  Gary replied 1 year ago.
well I have never seen this before. Lets see if any other experts have seen this. Hang on let me open this question back up to the other experts.no need to reply back to me another expert will reply to you hang on
Expert:  Mazda Ed replied 1 year ago.
Hi Dale! Let me see if I can help.
First things first I want to make sure we are shooting for the right cylinders. Please don't get insulted, I just don't want to miss something easy. Cylinder 2 is passenger side front and cylinder 7 is driver side rear. Is that what cylinders you are troubleshooting?
Also when you swapped coils, injectors and plugs... what cylinders did you swap with or did you swap in new parts?
Customer: replied 1 year ago.
hi #7 and 2 are misfiring at idle Yes i swap injector on the motor THE SWAP WAS form 4 to 2 3 to 7 also coils where swap. At this piont ask anything I will not get insulted I have also lab scope crank sensor good pattern did not scope cam because it runs way to good off idle I am at my wits end my boss and cust: Are not happy we me because i said a valve job would take of problem
Customer: replied 1 year ago.
valve job done new plugs and still #2 #7 misfire I do not know what I miss I smoke at 5psi in #2 #7 the intake valves show smoke on intake side exhaust ok
Expert:  Mazda Ed replied 1 year ago.
Are any other cylinders showing a misfire but not setting a code yet?
Are you saying those cylinders show smoke through the intake?
Are they the only ones?
Customer: replied 1 year ago.
no other or cyl. 2;& 7 are showing codes the only code come and goes is p0300.The other cyl are okay. to clear a statement 2 & 7 never gave a code only showed a misfire at idle on the scanner But off idle runs great./ at idle runs ruff but not setting a code but every now & then p0300 pops up and goes away fuel trims are good 02 are reading good But in gear at idle runs really ruff like 2 cyl are dropping out
Customer: replied 1 year ago.
the only thing i just thought was pull #5 plug wire see how it effect # ***** the reason why is fire order 18436572 what do you think
Customer: replied 1 year ago.
because 7 / 2 are next to each other in the fire order
Expert:  Mazda Ed replied 1 year ago.
Ok, I did have a problem once that was similar to this but I can't remember the exact year of the truck. Even though all test passed I removed the fuel rail and all injectors. I found that because of the way the fuel rail was designed all the crap would accumulate at the end of the rail by #7 and by #2. I was able to shake some of it loose by spraying carb cleaner in but ultimately I ended up replacing the fuel rail. I don't know for sure if this is going to help you, but when you swapped the injectors did you do a through examination of the fuel rail?
Customer: replied 1 year ago.
okay I see that at the end of the fuel rail is 2 7 but I had injector out with a glass jar one at a time I energ: the fuel pump and draw aline on it so I could see exat amount on 2 match same amount 4 amount of fuel in glass jar If you think another fuel rail would help I"ll change it Can you think of test at idle to see whats happen in 2 7 misfire please advice open to anything
Expert:  Mazda Ed replied 1 year ago.
It was a weird occurrence for me... Everything seemed normal during testing. Injector flow, fuel pressure, etc.. My thoughts were the debris was causing some kind of cavitation effect and disrupting the steady flow while the truck was running.
When you mentioned the smoke test before... was that before or after the valve job?
Customer: replied 1 year ago.
before and after heads install 2 7 still misfire I did a running compression test 70 on both cyl a couple other cyl the same 70 psi to see if okay they where at 70 also
Expert:  Mazda Ed replied 1 year ago.
You said you did a smoke test... Are you still getting smoke through the intake valves of those 2 cylinders?
Customer: replied 1 year ago.
no test good
Customer: replied 1 year ago.
also pass on cyl leak down test
Expert:  Mazda Ed replied 1 year ago.
Is this truck equipped with the AFM (Active Fuel Management)? If so, some of those trucks were having lifter problems. One of the fuel management cylinders is #7. I'm wondering if this could be part of your problem...
Customer: replied 1 year ago.
as I know when the intake was off i did see any fuel management or in the scanner pids
Customer: replied 1 year ago.
if it where how would i know or find out looks like no elec: on lifter
Expert:  Mazda Ed replied 1 year ago.
I would think that this would show up on a compression test, but it could be possible that right now it is a minute difference that you are recognizing on the gauge. If you open the glove box there are RPO codes listed. Look for one of the following codes on the sticker.
RPO Codes L76, LC9, LFA, LH6, LMG, LS4 and LYS
Customer: replied 1 year ago.
thank you I will look at this monday morning to see If it is are thier any tbs to prove this problem I have I dentfix did look for tbs saw nothing If you have tbs on this problem I would like to know
Expert:  Mazda Ed replied 1 year ago.
Also, have you done a Crankshaft Position Relearn and verified that it was successful?
Customer: replied 1 year ago.
yes and it verified
Expert:  Mazda Ed replied 1 year ago.
Check GM bulletin 08-06-01-018C also engineering information EI08245.
It wouldn't hurt to do the CKP relearn again.
Customer: replied 1 year ago.
have done 4 relearn no diff in misfire thank you on tbs Dale
Customer: replied 1 year ago.
I will get back to you on monday Have a nice day
Expert:  Mazda Ed replied 1 year ago.
Did you install new intake gaskets when you did the job?
Customer: replied 1 year ago.
yes all gasket new fel pro also smoke intake both before and after okay the fuel trins are good also 3to -5 o2 switch plus pull o2 out no diff in misfire
Customer: replied 1 year ago.
i try looking up tbs 08-06-01-018c found no tbs on i dent fix advice on it
Expert:  Mazda Ed replied 1 year ago.
Basically it says you could have a lifter tick noise, an engine misfire or a check engine light on. It would be on cylinder 1, 4, 6 or 7. It is caused by a collapsed active fuel management lifter. They want you to replace them in pairs.
I was thinking maybe the lifter is weak and won't pump up at idle causing this misfire.
Customer: replied 1 year ago.
found the problem let the motor run at idle loosen rocker on # ***** and the miss when away So been said gm has a lifter and cam problem thank you for all the help Let me know what you think about this I will on next one how to prove the problem fast have nice new year Dale
Expert:  Mazda Ed replied 1 year ago.
Well I'm glad this mystery is solved. Please don't forget to rate me! Have a Safe and Happy New Year!

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
< Last | Next >
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland
 
 
 

Meet The Experts:

 
 
 
  • Tim's Auto Repair

    mechanic

    Satisfied Customers:

    7641
    Have owned a repair shop for 25 yrs.
< Last | Next >
  • http://ww2.justanswer.com/uploads/TI/tim37857/2011-10-28_23053_S6301814.64x64.JPG Tim's Auto Repair's Avatar

    Tim's Auto Repair

    mechanic

    Satisfied Customers:

    7641
    Have owned a repair shop for 25 yrs.
  • http://ww2.justanswer.com/uploads/DT/dt69nova/2012-6-15_234154_pic1.64x64.jpg Dave Nova's Avatar

    Dave Nova

    Chevrolet Technician

    Satisfied Customers:

    6870
    ASE Master Certification. GM World Class Certification
  • http://ww2.justanswer.com/uploads/ggrote1/2009-06-27_031011_me.jpg Gary's Avatar

    Gary

    Chevy Technician

    Satisfied Customers:

    5404
    15 years GM master tech
  • http://ww2.justanswer.com/uploads/testedtuff/2009-09-26_170108_pictures.jpg John's Avatar

    John

    Master A.S.E Automotive technician

    Satisfied Customers:

    4071
    A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
  • http://ww2.justanswer.com/uploads/RO/rodcuda/2011-7-25_224114_Donhoff1.64x64.JPG Neal's Avatar

    Neal

    Chevy Mechanic

    Satisfied Customers:

    2306
    Shop Owner and Mechanic on multiple makes.
  • http://ww2.justanswer.com/uploads/goodwrench9124/2008-11-09_220838_dscf0007.jpg goodwrench9124's Avatar

    goodwrench9124

    ASE Certified Technician

    Satisfied Customers:

    2041
    Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
  • http://ww2.justanswer.com/uploads/DR/drivefast1971/2012-1-12_172422_0009051tQKh.64x64.jpg Ron Z.'s Avatar

    Ron Z.

    - Chevy Tech -

    Satisfied Customers:

    1912
    18+yrs experience. State Inspector and Chevy Diagnostics