UMich97

Hey everyone, curious on getting some thoughts on the below....

Today on my way to work, my '99 V6 Stang would sputter when I hit the gas and even had a couple of mis-fires (blinking SES light). It doesn't sound like it will stall out and seems to run fine when I am coasting or giving it light gas. However, if I try to punch it, it sputters and struggles. It seems to sound fine if I rev the engine with the clutch pushed in also. I swapped out the air filter and added some Lucas fuel injector cleaner at lunch, but after my hour drive home, it was still sputtering when I would accelerate. So, I stopped at Autozone and had the codes read, which kicked out the following:

It kicked out the following codes:
P0301 - Cylinder 1 misfire
P0303 - Cylinder 3 misfire
P0135 - HO2S11 heater condition (heated oxygen sensor bank 1)
P1131 - Lack of bank 1 O2 transitions - Lean explanation

So, I'm guessing it's an oxygen sensor causing all the issues, but not sure how to tell which one. I noticed the O2 sensors run about $50, so would hate to replace all of them, if it's only one causing the issue. Anyone have any thoughts or ideas on how to approach repairing this?

Onesickstang01

It's your coil pack. They are notorious problems on ford v6s. 1+3 fire of the same coil linkage which is why it does that. Only one other thing can cause that problem and it is a vaccum leak on the intake, although much less likely on the metal intakes than the plastics. Try to coil pack first or at least listen for vac leak under hood

Onesickstang01

Also 02 sensor codes can pop lean codes like that if there is a vac leak. Best thing to do is smoke the intake if you have a reputable shop near you to find a leak. Bank 1 is side that #1 cylinder is one which is passenger on that motor I believe. Oxygen sensor would be last thing to do first find misfire/ vac leak

UMich97

Thanks Onesickstang01! I'm going to head outside in a couple minutes, start it up and see if I notice anything. Part of me is now wondering if something may have come loose when I cleaned my throttle body last weekend....that might contribute to a vacuum leak??? None the less, swaping out the coil pack sounds a lot easier than changing out the O2 sensors, so that would be great if it's just the coil pack.

UMich97

OK, I think I found the issue. I was letting the car run while looking and listening inside the engine compartment and heard a noise that sounded like an air flutter coming from the passenger side. I then noticed that every time I heard the noise, I saw a small spark/light coming from the below part. I'm not exactly sure what this connection is, but it's definitely causing at least some of the issue.

The arrow points to the connection that looks bad and the red insert in the top left of this image shows the two parts that seem to be interacting with one another when the spark lights up. Anyone know what these two items do? It was hard to follow all of the wires in the dark, but it looked like the cracked tube (on the right) connected from the metal tube (which came off of the exhaust manifold) and then the cracked tube led to an electronic looking device that sits at the top of the engine compartment (DPFE sensor?). The metal tube looked like it led up to the EGR valve. Does this sound correct? Ideas? I'm hoping this might be as simple as replacing that short tube.

UMich97

Update: Well, I replaced the vacuum hose between the EGR tube and the DPFE sensor and it seemed to resolve the issue. However, unfortunately the spark plug wire that was running right next to the vacuum hose had shorted out as well, as the heat from the EGR tube burnt through the protective shield and the rubber, all the way down to the bare wire. So, I have my local mechanic changing out the wires for me today. If only I had noticed this earlier, I could have just changed the tube for all of $10-$15. Oh well.

Thanks again for your insights Onesickstang01, when you mentioned the vacuum leak possibility, that got me thinking and helped me figure out what was causing the issue.

Onesickstang01

Glad you got it figured out.