rough idle......

[DJ4180]

Hey everyone. I could use some help here. I started up my 5.7l 99 tahoe after work today for what I thought was going to be a nice ride home after a 12 hour shift. Made it to the red light and I started to idle a little rough. Once green I accelerated onto the highway and it seemed as if the engine was hesitating. So rather than risk anything like getting stuck I drove to my local parts store and had them run the codes on it the guy told me I had a cyclinder #2 misfire, mass airflow sensor. Emissions sensor. And a downstream o2 sensor code. Obviously the big ones here was the misfire and mass airflow sensor. I'm just curious as to weather they are related or two separate issues. And what's the best way to go about fixing it. I didn't wanna just throw parts at it hoping to fix a misfire which could be a number of things. Also the MAF sensor I was wondering could it just need to be cleaned? I should note that the check engine light did not come on but that was only because it doesn't work. And also once I actually got the thing moving it seemed to run smoother at higher speeds on the highway. But thay initial jump from stop to 30mph was rough and took forever for fear of blowing something up. Any help here would be greatly appreciated. I hate throwing parts at a car for no reason. Thanks in advance guys

 

[MO Viet Vet]

The misfire can be covered a little at higher speeds. Likely a plug either burned bad or fouled. May be wires or cap/rotor. How old are those components. The MAF can be cleaned with cleaner from the parts store and follow directions. May still need replaced but try cleaning first. It would help if you gave us the exact code numbers instead of the crap the parts guy told you. What the heck is an emissions sensor? The misfire fix and MAF cleaning may fix all concerns and keep all codes away.

 

[DJ4180]

Sorry about the codes. only one I know the number for was p0302? I believe. Which was the misfire code. I pulled the number 2 plug and while it had some buildup on it it didn't look any ddifferent than the rest. And the wire looked ok. Will buy new ones just to know when they were put on. I've only owned this for about 6 months. I will hopefully have an update for you soon as to weather it is fixed or not. I also pulled the MAF off and all the little wires look intact. The screen was dirty but not blocked Like I thought it would be. but I will clean it anyway to be sure. Any recommendations on plugs?

 

[DJ4180]

Also will have the codes run again once I change plugs and wires and get any Numbers that show u. Thanks again raider

 

[MO Viet Vet]

If you don't know the age of any of the ignition components then change all plugs, AC Delco, all wires, AC Delco, cap and rotor, AC Delco. By the way, plug wire can "look" good but be bad. They either have too much resistance or get melted or nicked or spark jumps out. Clean the MAF as per instructions on can. The dirty screen needs cleaned. Careful with reinstall and make sure all connections go back clean and tight.

 

[DJ4180]

Ok update guys. I already had the MAF sensor and all the tubing out. So it made no sense to put it back on to go run for parts. So I took the soccer mom van (made me feel so manly. Lol) to grab new plugs wires cap and rotor. Picked up a can of crc mass airflow sensor cleaner. Awesome stuff. Sprayed it up good and let it sit while I swapped the plugs and wires out. than proceeded to clean off the MAF and put it all back together. Started it up and took it for a drive..WOW what a difference. It had all its power back. Drove it back to the parts store while out and had no codes. brought it home and replaced the cap and rotor on raiders advice fired it up and it even seemed to start a little smoother. Thank you raider. Also should note that I called 3 different stores before I found one that had 8 AC Delco plugs (again on raiders advice). Again thank you sir and hope this can help someone out somewhere

 

[MO Viet Vet]

And that is exactly why we always ask for a final update when fixed. We all want to know and learn. Glad I could help. Thanks for the thanks.


You are :welcome:

 

[lesterl]

Thanks for the final status, Ron is right on the nose with GM parts for ignition for shure, alot of grief has been had over aftermarket stuff, best to go with the OEM.....

Glad you are back up and running.....

 

[acfd813]

I have a 96 with a 350 vortec that's doin the exact same thing. What is the correct plug to use? I can ac Delco copper, platinum, platinum professional, and iridium. Which one is right?

 

[lesterl]

platinum