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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I have a 2003 Trailblazer LT w 4.2l six. Dealer I bought

Customer Question

I have a 2003 Trailblazer LT w 4.2l six. Dealer I bought from had replaced fuel tank and pump assembly. Now it's developed an intermittent miss at idle and while driving. Computer code shows a miss fire, but no specific cylinder. Mechanic friend suggests replacing ignition coil and / or the throttle position sensor. I also noticed that sometime the cruise control will work, sometimes it doesn't engage. The car has 112,800 ***** ***** on it. Any idea?
JA: Thanks. Can you give me any more details about your issue?
Customer: It's annoying at idle, but worrisome that while driving 55 @ 1600 rpm there will be a miss (or hiccup as I'd like to say) and notice the tach jumps about 100 rams. that should be rpms
JA: OK got it. Last thing — Chevy Mechanics generally expect a deposit of about $18 to help with your type of question (you only pay if satisfied). Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 1 year ago.
Category: Chevy
Expert:  Gary replied 1 year ago.

did you replace anything yet ?

are there any codes set at all in the computer ?

Customer: replied 1 year ago.
Nothing replaced yet. Codes just indicate misfire, no specific cylinder. Just now the Service Engine Soon lite came on. Any thoughts? I'm not confident on driving this here in rural PA (don't want to get stuck).
Expert:  Gary replied 1 year ago.

any access to a scan tool to view live computer data ?

we need to know if it is a specific cylinder or if all are showing a misfire to know which direction to go next

Customer: replied 1 year ago.
My friend checked it this morning. No code showing as to which cylinder, just 'miss fire' occurred. He suggested buying one coil and try replacing #1 cyl first, then go to 2 and so on to see if it settles down to smooth idle.
Expert:  Gary replied 1 year ago.

that will be very time consuming you need to plug in a high end scan tool and see which cylinder is misfiring on the current and history misfires in the data list

Customer: replied 1 year ago.
He used a big Snap-on hand held box this morning... It only showed a generic misfire code.... Again, no specific cylinder was showing. I'll pass by his shop again in about an hour.
Expert:  Gary replied 1 year ago.

ok you need to view the live data list and view the current and history misfires on the data list