1998 3.1 lumina has a misfire at 2000 rpm and above.
Recently did
lower and unpper intake gaskets
middle ignition coil pack
cam sensor
champion double plainum plugs
motorcraft wire set
Cleaned throttle body
a set of used injectors from salvage yard
thermostat

Started car after above work was completed. Car ran rough at idle
check engine light came started flashing for 30 seconds then went solid. Continued let car run and purge of air in coolant loop.
Turned off after it reached OT
Pulled negative battery cable. Codes came back.
Pulled neg cable again and checked all sensor connections.
Codes came back
Pulled neg cable and undid two large pin connectors near altenator and re connected
Car ran great at idle and no codes
Ran down 25 mph street ran great
35 mph street started to stumble a bit
50 mph road chugging type misfire, lack of power when pedal mashed
When you let up on the pedal during a misfire or chugging episode the car smooths out with some power but when you accelerate especially up a hill this load makes the misfire show up more.
There are no cades at this time
When I had codes they were P0101 MAF and P0300 random misfire
I rechecked spark at each wire at the coils and a good hot spark is present

Any ideas? Thanks

What was the initial reason you did all this stuff?

MFamaly mechanic gave 1600 dollar estimate of the above work. All except he missed the bad coil pack. He stated to junk the car so I did it myself off his estimate. Car barely would make it up the driveway befor. I am almost thier. Missing somethig.

Didn't leave anything in the airbox did you?

I know...long shot, but I had a Nissan Sentra in the shop once acting exactly the same after another shop did some work to it.

They left a shop rag in the airbox. It could pull enough air to idle and run at low rpm, started choking up at higher speeds/loads...it went up the pipe and was stuck on the MAF sensor grid. Can't explain how it got left there.

Anyway...does it ever intake backfire when you pounce on it and it sags?

Anyway a fuel pressure reading while the problem occurs would be helpful. I think AZ will loan you a FP gauge if you don't have one...

Didn't leave anything in the airbox did you?

I know...long shot, but I had a Nissan Sentra in the shop once acting exactly the same after another shop did some work to it.

They left a shop rag in the airbox. It could pull enough air to idle and run at low rpm, started choking up at higher speeds/loads...it went up the pipe and was stuck on the MAF sensor grid. Can't explain how it got left there.

Anyway...does it ever intake backfire when you pounce on it and it sags?

Anyway a fuel pressure reading while the problem occurs would be helpful. I think AZ will loan you a FP gauge if you don't have one...

Funny you mention that. I was pondering and did just that. Found nothing..... but was something I had to check off. A rag would have been cool. Everyone makes mistakes now and then. I will check fuel friday and report back. Thanks

Have catalytic converter (exhaust system) checked for being plugged. Seen many lack-of-power problems caused by this.

Have catalytic converter (exhaust system) checked for being plugged. Seen many lack-of-power problems caused by this.

Bullseye Bearwulf.
:worshippy
Thats what it was. I removed the egr valve and stuck a shop rag into the intake port and down the road I went. Car showed increase in hp. Went to local muffler shop and got it taken care of the morning of your post.

I got my swagger back. Hell I put new tires on her also I was feelin so good that morning.:lol2:

Thank you, glad to share.