weird bogging down issue

[3100 MPFI]

My STE just started doing this a few days ago, but because of the weather I have not had a chance to look into this.

I was on my way home from my parents house. I was going about 45-50 MPH in 4th gear when the engine started bogging down, missing, hesitating, and backfiring. I was holding the pedal steady and it was almost bucking.

It finally stalled, so I pulled over to restart it (PNP switch is not adjusted properly, so I have to put it in park to restart it). It started up fine, and I took off, and it was normal, but once it hit 4th gear, it started doing it again. When I turned onto my road, it stalled again, so I restarted it, and once again, it took off normal.

As I went around the curve, I was doing like 30 MPH in 3rd gear, and it started doing it again. It lasted about a half mile ot the house and died as I was pulling into the driveway.

Today, I finally did some checking. Obvious stuff seems fine. The car started up fine, and nothing arcing, and no funny noises.

Once the car warmed up, the exhaust note changed, and when I went to the engine, it started doing the hesitation, misfire, backfire when I would mess with the throttle.

This is something TOTALLY NEW. It has never done this before, and I have not made any changes to anything in the car within the past MONTH.

Here is a vid of the EXHAUST SIDE. 27 seconds into it, you hear the exhaust note change. It almost sounds like it is just going into closed loop, but once it did that, it didn't go back to normal, and that is when the engine started doing weird stuff. The engine was fine until the exhaust note changed.

http://s174.photobucket.com/albums/w86/riven2129/video/?action=view&current=exhaust.flv

This is the engine vid. When I play with the throttle, you can hear it start doing weird things. It even backfires. In the end, I go to goose it, and it just stalls out.

http://s174.photobucket.com/albums/w86/riven2129/video/?action=view&current=engine.flv

If I let the car cool down, it starts up again fine, but once it starts warming up, and goes into closed loop, it starts doing this.

On top of all of this, the engine still has that minor SURGING when coming to a stop. I am sure they are related, but I can't find the connection.

Any ideas?

[TDIXON]

maybe your o2sensor. freinds car sounded like that except the stalling. put new o2s in and was fine. just a thought.

[3100 MPFI]

has new O2 sensor.

I guess I should put in that almost all the sensors are new, including O2, MAP, DIS, TPS, IAC, and crank position sensor.

[TDIXON]

maybe yur cat is starting to plug up then. but one time i had a potiac 6000 that started doing that and replaced all sensors and still did it. was very confused on it. so went to another mechanic and he told me to replace the tstat i thought he was crazy but i did it and the problem dissapeared. i said wtf and was completely confused. but to my surprise it worked and i have no clew why.

[davida1_hiwaay_net]

Have you checked fuel pressure (under load) or changed the filter? Low FP can cause a lean condition with the same symptoms shown. Don't know your FP spec but whatever you see at idle, it should jump UP when you blip the throttle as you were in the video. If it does not, or if it drops down when you open the throttle, fuel supply is weak.
Another possibility is a collapsed hose to the MAP sensor. If the sensor doesn't immediately see the air pressure rushing into the manifold as you open the throttle, ECM will not immediately send the fuel to it.
Hope this helps!
David

[3100 MPFI]

fuel pump, strainer, pulsator, and regulator are all less than a year old.

i guess i need to check more things out.

[davida1_hiwaay_net]

Have you tested the fuel pressure at the rail? What about the inline filter? (outside the gas tank in the fuel supply line) What you describe sure sounds like a LEAN condition. Low fuel pressure or a faulty MAP reading are 2 main causes of a severely lean condition.

If the MAP signal is wrong but "beleivable" the ECM will calculate based on the faulty data and may not trip a code.

Please let up know what you find!

[TazMan]

That was happening to me awhile back and it turned out to be a bad ICM. I didn't get a code until it completely crapped out.

[torq455]

it sounds like it running too lean. need a data log of the 02 and MAP readings. the ecm adds gas when it looses vacuum. maybe it's not reading right.

[3100 MPFI]

i cant datalog.

My laptop does not have a port for my cable like my old one did. Money is too tight to get a new one right now.

[davida1_hiwaay_net]

FWIW Radio Shack sells an inexpensive USB to RS232 adapter cable that will connect your scan tool to the computer witn no built-in COM port. I use one for my ECM tuning program and it works wonderful.

Just my $0.02 worth

David

[3100 MPFI]

I will have to look into that.

On a side note, I think it might be my DIS after all.

A couple nights ago, I was stuck in bed with a fever, and in the middle of that, I remembered that my 3100 had done some weird things right before I pulled it off the road, so I now think the DIS was on it's way out.

I am going to swap the control module from my spare twin cam in there (It should be good). I just need a temp fix for now. I just need a car to get me back and forth to my mothers house from mine so I can get my gold car running.

[Hell_raiser]

lol take you pc tower out side like i do lol

[davida1_hiwaay_net]

A couple nights ago, I was stuck in bed with a fever.....

So maybe whatever's wrong with your motor is CONTAGIOUS.......

Sorry couldn't resist.... Hope you are feeling better - Most of my friends have had some sort of nasty stomach virus lately hope I don't get it....

David

[3100 MPFI]

Okay. Today I did the engine grounds and other than the fact I can now do a nice WRITEUP with pictures, it didn't fix it, so once it cools down some (ran the engine for almost 10 minutes before it started bogging down and stalling) I am going to put my twin cam coils, and DIS in it.

I thought of one other thing that it might be. I remember when I did the heads, I accidentally cut the CRANK POSITION SENSOR wires, so I resoldered them, but I am starting to think that might be part of the problem. It has been fine for a year now, but with everything else checking out GOOD, then I guess I need to look into other things.

I will do another update after I get the twin cam coils and ICM in there. For now, I will start the writeup for the ground cleaning.