I had the LIM gasket changed this past Sunday along with the upper intake and gasket, thermostat, PCV valve and valve cover gaskets. While my guy was in there I had him change the plugs/wires and O2 sensors. After reading around for help today I have seen on multiple occasions not to use Bosch plugs and O2 sensors. Of course, that's what I used. Bosch Iridium plugs. Just my luck.

Car drove fine Sunday evening through Thursday morning. Then the CEL came on halfway through my commute to work. After work I swung by my local Autozone and had them read the code. P0171 system too lean, needless to say it was sucking gas too. After utilizing the search feature here I decided to clean the MAF sensor. As I was on my way home to clean it the car started to sputter a little and RPMs were bouncing back and forth. Felt like the car wanted to die out. The MAF didn't appear to be dirty whatsoever. Cleaned it anyways. I let it dry out completely, reattached everything, and started it up. CEL was off, presumably due to the battery being disconnected for almost an hour. The car struggled to start and is now idling pretty rough. I did some more searching and decided to change the IAC valve(filthy) and the MAP sensor, just in case. Still rough idle. I decided to take it for a drive. As soon as I put it in reverse to back out of my apartment it stopped sputtering and seemed to operate normal. It operated normal for the whole ride, only about 10 minutes. Ran smooth while accelerating, decelerating and coasting. Put it park at a stop sign and ran smooth still. Got home happy thinking maybe everything just needed to learn the system. I turned off the car and restarted and it idles just as rough as earlier.

I'm stumped. I can't seem to find any vacuum leaks, plug wires are correctly installed, clean MAF, new IAC and MAP. Why would it run perfect once I start driving then idle rough when I start it up again? Are Bosch plugs so bad they could do that?

 

I would dump the bosch plugs...1st
Use ... OEM plugs...
That should eliminate any running/driveability issues...

Should it act up afterwards....(Just in case)

I would unplug the MAF...(do it with the motor off)

Start it up and drive it...If the driveability improves....
Then you need to replace the MAF with a new one...

But I believe changeing out the bosch plugs should cure your problem.

Hope this helps.
Maybe someone else will chime in with other ideas/answers.

 

Agree on replacing plugs.

 

X2 Do not to use Bosch plugs ..

 

Thanks for such a quick response STUMPMI, I wish I noticed the negative view on Bosch plugs before changing them. I'll be swapping them out ASAP, I got so frustrated tonight I had to get away from the car.

Is it not strange how it runs great once Im moving but after the start up it idles really rough? Why would it run fine for a few days then all of a sudden run like ****?

 

YW Dylan...
Were here to help!

 

Maaaan, I was afraid yall were gonna say that

Hopefully that's all it is. I can live with that. Frustrating but an easy fix

 

U can use acdelco plug or I'm running ngk plats in 2 diff 3400 cars. Some acdelco plus r rebadged ngk plugs.
Get rid of the bosch plugs, start there. When u do, see how they look. If u find one or two that look different u may also find prob cylinders. Also check the plug wires.

I had a 3100 that would run rough for the first couple of minutes and then fine (in that case it was a bad head gasket, coolant getting into a couple cylinders). But if this issue did not exist prior to the work done last week, focus on what was done b4 looking for something deeper.

 

I changed the plugs today over to ACDelco Iridium plugs. Kept the Bosch wires since my Autozone didnt have any ACDelco in stock. The car ran perfect once I started it. However, backing out of the driveway it sputtered for a second before getting on the gas. After that it ran fine as well.

I guess I should try and swap the MAF sensor too


UPDATE: I ran it up to the store which is about a half mile away, running rough again, not as bad as before but noticeable. Also noticed the fuel gauge fluctuating a bit(approximately an 1/8th of a tank in both directions)

Think it could it be fuel related? Filter? Pressure regulator?

 

First, BOSCH wires are 100% fine, no issues (just the plugs).

Next, did this rough idle condition exist before or after all the work you had done a week ago? If this is a brand new symptom after having all that work done, I think everything that was done needs checked. It's lending it self to a possible vac leak IMO.

Get a can of starting fluid, with the car idling, mist the starting fluid around. If you have a vac leak and the mist is near it, you will hear the engine idle change. If you find a spot where this happens, repeat the process in that spot until you get a good idea of what region this issue is coming from.

If can boil down to a damaged vac hose, loose connection, missing bolt not holding something in, a poorly seated fuel injector.... These are all things to check and consider.

NOW, if this was happening before you took the car for all the work that was recently done, then we need to look at other possible causes.