So my car is an automatic 193211 miles and when you try to gain speed fast like entering freeway the RPMs go higher then normal before it shifts. It kinda sputters when you're driving (a lot of freeway speeds so that's when I notice it). Maybe that's what is a called a misfire or missing idk. I had a check engine like few weeks ago and advance auto said it was random misfire. Light hasn't been back on since. Fuel pump was last replaced at 92,000 miles along with the filter but I just had a new fuel filter put on this week hoping it would fix the issue but it didn't although it runs a little better. Idles a little rough, doesn't overheat. Plugs and wires done last year. Dealership tried to find problem but nothing came up on the tests they did so they asked me to come back when another tech was there and he could run further tests. All I know is they had a computer at my car and something they plugged in under the steering wheel. Taking it to another mechanic Saturday to see if he can find anything. I've read could be MAF sensor, O2, clogged cat...any thoughts would really be appreciated!
Ok thanks! I'm gonna try another shop tomorrow just to stop and ask some questions. They close before I get off work so maybe I can get it there Saturday.
A random misfire can be so many things. The technicians are going about it the right way by pulling the diagnostic trouble codes (when they plugged something in under the steering wheel).
They will need to start with some basic tests. Chilton has great testing and diagnostics for your 2003 Malibu at ChiltonPRO.com or ChiltonDIY.com.
Can they get info without having the check engine light on?
Yes! They can run diagnostic tests on each system: Fuel, Ignition, and Engine Mechanical.
The tests and diagnostic procedures, specifications, etc. are in the Chilton subscription for the 2003 Chevy Malibu at ChiltonDIY.com and ChiltonPRO.com.
Well still no answers...said I have multiple misfires, misfire on 1&3 (different coil packs), running lean, O2, MAF, TPS all were showing having some issues so I do t even know. No check engine light still! Could be MAF sensor, EGR, cat converter, fuel pump, vac leak...pretty much same stuff I got from googling it...now what? We cleaned EGR and got the MAF cleaner and did that...nothing changed. Gonna replace PCV tomorrow and I guess just start throwing money into the first thing on the list since it can't be narrowed down. I really don't understand having to pay for a diagnosis when they can't even tell you exactly what the problem is...oh well, I'll find the problem myself.
Did you have the fuel system tested? Lean conditions and light misfires may be caused by low fuel pressure or a dirty fuel system. Check your Chilton subscription for fuel system testing procedures for lean misfire conditions.
Find it by following this PATH: Fuel Systems > Fuel Controls - 3.1L > Diagnostic Information And Procedures > Fuel System > Fuel System Diagnosis in ChiltonDIY.com or ChiltonPRO.com.
No fuel system wasn't tested. When they tapped the MAF sensor the readings changed so they said it was MAF sensor then they said if it still acts up after replacing it then here's a leak in the intake somewhere. Every time they said it was one thing then they would turn around and say could be this or that so idk. I think I'll start with MAF AND cat converter. Better to throw money at a fix rather then more tests that don't give me a definitive answer.
That's a shame.
If the tests are performed in the correct manner the problem often presents itself.
After scanning your vehicle the shop should have asked you to agree on the first hour of diagnostics. This should have been to check all the input and output readings with a scan tool. And then to check for vacuum leaks, engine compression, and at the very least check the fuel pressure before even advising you!
If not find a different auto repair shop.