Check engine light after throttle body clean

Hey guys, I have a 1997 2wd base with the 3.4L V6. Last night I took my throttle body apart and cleaned it and the IAC valve. I was encouraged to do so in a previous thread because my truck has been struggling with a low idle. The thing was GUNKED up, and in desperate need of a clean so it was a satisfying job.

When I started the truck back up after, it was idling extremely rough. The thing was literally bouncing and almost stalled several times. I tried to take it through an idle relearn sequence by letting it idle up to operating temp then drove it around for awhile. It drove great from the get go, and the idle improved in time. I shut it down for the night figuring things would continue to improve with more driving. When I fired it up this morning the idle was still noticeably improved but my check engine light was on. I don't have a code reader so I ran it by a shop for them to read. They did not give me the exact codes but said it had a misfire code on all 6 cylinders and a code for running lean that related to the O2 sensor. Then they quoted me what felt like a ridiculous amount of money to have all my coil packs replaced ($700).

I inspected my work closely and found the culprit for it running lean: I missed connecting one of the vacuum hoses, yikes! Absolute amateur hour, but I'm the first to admit I'm still learning! So I connected that and it did immediately run all that much smoother, but the check light persists.

My question is, is it likely that the misfires were caused by that vacuum line being unattached or do I have a larger problem on my hands? Or, do I just need to take the truck through several drive cycles before the ECU resets itself and the check engine light goes away? It's certainly not continuing to misfire and is running beautifully.

 

I believe you need to run it through some drive cycles. Or take it back to the place than ran your codes and have the clear it and see if it comes back after a few drive cycles. The later is what I do every time I get a CEL

 

If you'll go to a parts house they'll check it, give you codes and reset it free.

They may want to sell you parts, but don't bother until you see what happens

 

I would suggest that you double check that you didn't connect the vac and coolant lines up incorrectly. Misfire on all 6 cylinders would be pretty rare from a vac leak.

 

take off neg battery terminal....press brake....then hook batt term back up
will clr codes
then see if they return......if running fine.....you might be golden!

 

This right here. Disconnect battery for a few minutes. Let everything discharge.

 

My friend and I accidentally made the CEL come on in my 2010 following replacement of the spark plugs in October 2021 at 140K miles. I forget what the problem was, but mechanic plugged his scanner in and cleared the code for free. It never came back.

 

I appreciate this suggestion because I read prior to doing the job that this is a common mistake. I did go out and double check my work alongside my repair manual and the coolant hoses are definitely where they are supposed to be.

 

The ecu has a learned value that compensated for the dirty throttle body and it doesn't know that you cleaned things off. As others suggested disconnecting the battery will reset its memory in a sense. It's worth a shot for as quick as it is to try. I'm not aware of check engine lights from this but it very well could be the cause of the rough idle.

 

if i actually finished reading I would have seen you fixed the idle DERP

 

this....

 

The vacuum line was for sure the reason and you have no underlying issue if your engine is sounding happy now.