Thread: Rough Idle/ Misfire(?) NO CODES!

I'm in desperate need of someone more knowledgeable than I. I am a parts changer, no mechanic. I am tech savvy and do know my way around an engine. That being said I'm stumped. I have a buddy that went to schooling for auto work but never pursued the career take a look and he is also stumped. I will attempt to explain as best I can.

**05 grand prix 3800 3.8L standard**

First and foremost, I do have one code that pops up. P0107 , MAP sensor circuit, low input. The code has been on for about a year now. I have replaced the sensor and even tested the connector. Everything checks out, code won't go away. No noticeable change so "f**k it". That being said, 3 days before Christmas 2016 I go to leave work, having no issues on the drive in or at lunch, started my GP and to my surprise it feels as though my engine is misfiring. I changed plugs and wires last year around the same time and when they went I got CEL codes. This time, no codes. So I change plugs and wires anyways and nothing changes. Here are my issues:

* Rough idle, worsens when I change the gear from park to drive/reverse. Also noticeable change when A/C or heat is on.
* Sluggish when accelerating, but evens out once up to speed.
* 1500 rpm to 2500 rpm range causes a kind of squeal combined with a slapping sound to come from serpentine area. Cant recreate in idle.
* Sputtering or "putt putt" sound from exhaust.
* Burnt plastic smell coming from engine bay with no traceable signs of actual burning. Checked wiring harness, fuse box, alternator.... if it has wires or looks electrical I gave it a good eyeing and sniff. Cant trace the location of the smell. Maybe belt?
* Slight ticking from engine. Oil levels are fine.
* Just noticed a small oil leak from bottom of engine.
* flakes of metal around serpentine area.

What I have tried:

* Lucas fuel treatment.
* Removed MAP and MAF sensor one at a time while engine running. MAP creates no noticeable change. MAF dips when removed and plugged back in.
* Pulled serpentine and checked pulleys. All pulleys spin freely except for a slight hang up on power steering pump pulley and crankshaft doesn't spin at all, not sure if it's supposed to when off though. Crankshaft does spin when running. The idler pulley does move more than i figured it should, worth noting anyways. Slight movement up and down on the pivot.
* Pulled plug wires from coil packs one at a time with engine running to check for spark. One pack did show signs of maybe less spark than the others but all nodes are firing off. And no codes.
* Cleaned the throttle body with cleaner and a new tooth brush, it was a bit gunked up but no noticeable change occurred as result.

My issue is that being so close to the holidays, and of course after money is all blown on gifts, I am a bit limited on funds at the moment so my next steps need to be in the right direction. I have googled and read everything and anything even remotely related, several posts from this forum as well. With no new codes to go off of I'm stumped. Everything I think of should(?) throw a code. That being Misfires, fuel pump, cat converter etc... Worse case scenario I can bring my car to the dealership and they'll work with me on the bill, they just take so god damned long and this is my only means of transportation at the moment. With limited funds I need to work, and unfortunately have to do a lot of local traveling. So putting the car in the shop for 2 weeks to have them do something I can handle in a day or weekend is the last resort. I'm newly registered to the forum but have used the forum several times previously to diagnose issues so I figured this would be a good place to start. I can post pics and vids if need be, though would have to educate myself on the procedure. Thanks for taking the time to read. Hope the information provided yields at least a nudge or maybe something I'm not considering or overlooking.

I have disconnected the MAF. I have not driven it disconnected. I did notice a dip in rpms when unplugging and then replugging the MAF. The MAP sensor is the trouble code though and the socket has been tested and has the 5 volts required. I have checked fuses and relays. In the electrical box in the engine bay there are a few relays that have light brownish marks on the sides that looks to be maybe due to excessive heat Is this normal or should i start checking around that area? Note burning plastic smell does not iminate from this area.

****UPDATE****

Pulled MAF sensor out today while car was running. Car immediately shut off. So I started with the plug removed. Ran for about 10 seconds and then died. CEL p0068 as well as message center error message reading engine power lose. At this point I couldn't get my GP to even turn over. So retracing my steps I cleared error codes and car fired up and ran, still rough mind you. Then the faithful p0107 code returned. I was also wondering how to check the tension on the idler pulley. I can grab my serpentine belt and pull up and watch the tension arm move in that direction. May explain squeal coming from serpentine area as well. The actual pulley has no issues, free spins like it oughta. Removed the serpentine yesterday and pulley arm was tight in the removal direction. Just so many things going on not sure exactly where to even start. Im down to either the idler pulley assembly, something in the between MAF to MAP, or something electrical. Electrical being the least likely in my ignorant a$$ opinion. Given the fact that there is so much play in the idler pulley arm Im almost thinking that may be the majority of my problems. Thoughts welcomed and greatly appreciated.

Don't forget about mechanical/internal issue. If it is an actual mechanical/internal part failing like a lifter, spring, valve, etc... It would cause a slight miss and run rough. It may not ever set a code.

Originally Posted by waupachino

Don't forget about mechanical/internal issue. If it is an actual mechanical/internal part failing like a lifter, spring, valve, etc... It would cause a slight miss and run rough. It may not ever set a code.

I did consider this but im going off what i can visually see is amiss and to me I dont think the tensioner pulley should be so easily moved just by slightly pulling up on the belt. Thanks for the info, I will definitely keep this in mind.

I realize this videos are of a series 2 and yours is a 2005 series 3, but I thought it would help.

I would guess your MAP sensor took a sh!t. This video has a guy with the same issue (running like crap). He tests in MAP sensor connector and moved on to the MAP sensor itself. https://www.youtube.com/watch?v=a_5IYjnbNqQ and the continuation video https://www.youtube.com/watch?v=pnCglmiY8yc

Looks like Autozone stocks them where I live, OReilly's and AdvA look to be online order.