Bogging Problem

[LegionHelium]

First off, thanks for looking, and yes I did do a search.

I've gathered that I need to do a Stomp test and check my plugs. Also there may be a vacuum leak. Let me know if any of that is way off base.

Yes, I realize the lifters tick pretty bad and my airfilter could use a cleaning.

So here is my issue:
I was driving down the highway at ~70, everything was peachy and smooth, then I seem to have lost power so I give it some gas and it bogs. It does not stall out though. After a few seconds it goes back to normal, then a minute or two later and it bogs again, it did this the rest of the way home which was about 5 miles and about 10 minutes of driving. The first video is what the car sounded like when I parked it. Sorry it was dark out. Notice it never stalls but it runs rough.

http://www.youtube.com/watch?v=zg088...ature=youtu.be

So this morning I start the car up and it starts right up like normal. But is running a little rough. That is the second video. It seems to be bogging again but it is kinda hard to tell from the video.

http://www.youtube.com/watch?v=Vh55I...ature=youtu.be

Lastly is a video of the tailpipe you can kinda hear it but not that well. it does not usually sounds like this. It is usually much smoother.

http://www.youtube.com/watch?v=GEGlu...ature=youtu.be

Some info about the car:
1991 318is
HQ Autosport COP kit installed ~6 months ago
New Plugs ~6 months ago
New o2 Sensor ~3 months ago
I recently changed the trans fluid, oil, and oil filter. Oil level is good. I also put in ~3/4 quart ATF in with the engine oil as I had read that can help with the lifter tick I am experiencing. That was 3 days ago. Car has been perfect since then.

I guess since it is was so much worse while the car is warm that has something to do with it. The car is driveable but I'm avoiding that. It is my only car at the moment as well. Any help or advise would be greatly appreciated. Thank you.

Original post over at M42club: http://www.m42club.com/forums/showthread.php?t=16145

[LegionHelium]

Ok, I just completed the stomp test, it gave me 1444 which means no error codes. So thats not very helpful haha.

[Ryann]

Symptom points to a worn AFM, but that should give you a CEL.

Also, check the ground strap that goes from the body to the motor mount on the passenger side for corrosion.

[mr ilia]

Fuel pump or bad fuel filter.

[LegionHelium]

Fuel pump was something I was thinking, it seems to run smooth while engine braking and very very light throttle though, so maybe it is able to supply a little bit of fuel but not much. But then why would idle be so bad?

I'll check the ground, assuming I can see that from the above the car, I'm at work so I can't get under it right now. Also I'm not really sure where that is but I can probably find it.

Would I just need to adjust the AFM like I see people asking about after a 5 second google search or replace it?

Thank guys, its a big help!

[vpilarrt]

I had this also - it was the fuel pump

[LegionHelium]

Thanks, I ordered a new one, I hope that fixes it.

[smyleboyd]

Im having the same exact problem! except stomp test gives me a code for fuel injectors. Please let me know how you fix this!

[LegionHelium]

Will do, the injectors also crossed my mind as something I could try replacing, I believe he mustang injectors part number is 0280150556 and it comes out of a 5.0. They need to be 19lb and 4 pintle. Does anyone know what years the mustangs used these? I guess I can get them from the ford dealer.

[Threehz]

I would replace fuel filter first. If you think the injectors might be gunked add some fuel cleaner and octane boost to your gas, warm the car up, then hit the rev limit a few times. Italian tuneup does wonders for a car.

Pump is a possibility, do you hear it whining when the bogging happens?

Air filter could use cleaning??? Filters are cheap as hell, if it's noticeably dirty just change it although it would need to be pretty dirty to make the car bog.

AFM is easy to check. Pop the top plastic square off and look at the track that the needle runs along, if there are well worn lines where on the track it could use an adjustment, but cleaning it with alcohol should help a little. Seal that square up with silicone when you put it back.

So many factors can cause this, so rule out all the easy ones.

Check:
Fuses, Plugs, Vacuum Leaks, Filters (Air/Fuel), and AFM.

Then move on from there.

[LegionHelium]

thanks, I'll check into the AFM like you said.

I just mentioned the air filter because you can see it is black thats all. A PO put on a cone and got ride of the OEM intake unfortunately.

[u3b3rg33k]

if you suspect the fuel pump, the easiest way to test it is to throw a T in the line and tape a pressure gauge to your windshield, then drive around. pressure should be relatively constant, and follow manifold pressure. if you floor it and the pressure drops or starts jumping - you know you have a fuel problem.

[LegionHelium]

Someone else said they think it might be the throttle position sensor. I don't know much about them so I guess I will look into that. I saw something about someone being able to clean his so hopefully that will be a cheap worth while thing to try.
The fuel pump comes in the mail today, and I just got a filter last night, I'll do them tomorrow.
Funny thing is though, I drove the car around the block yesterday. After it got a little warm I floored it to the rev limiter, the car drove almost fine for like 3 minutes then got worse again, so I did it again, and again.

[Threehz]

Telling you man, pour some fuel injector cleaner and octane boost in your gas tank and fill up. Take a nice long cruise at night then hit the rev limiter a few times. I found if you don't give the M42 some love, rev her high, and throw her in some nice curves she'll get mad at ya.

[LegionHelium]

So I put a new fuel pump in and filter. That did not change a thing, car still ran exactly as it had been, but I was pleasantly surprised by how easy it was to change that fuel pump though.