Jerking and foul odor issue

[brunocas06]

I'm sure this kind of thread gets started a lot and I did some searching on this forum for my issue but nothing to what I consider exactly like mine.
So here is whats going on....
When Im at around 40 mph and Im just lightly holding the gas to maintain speed I feel like if the truck jerks, sort of like a bad gas situation. I do notice it at higher speeds as well but sometimes its difficult to tell it apart from a rock road here in texas but I do know that it jerks.
The other issue which Im sure can be related...
At idle, at a red light, drive thru, wherever many many times I smell a really bad odor from the exhaust. It smells like a catalytic converter that is failing yet if that was the case wouldn't it be safe to assume that it would have failed already? Its been smelling like this for about 2 months now...just a little after I bought it. And I did notice the exhaust pipe really black inside of which I could swipe it with my finger. I believe thats fuel no?

Other research has led me to believe that the cam position sensor/synchronizer is going out and that may be the issue? I'm not getting any chirping noises at the back of the engine nor anything else so how do I diagnose that?

Oh and I have the dtc p0401 which is egr low flow, I know the dpfe sensor is the main issue with that but could that cause the bad exhaust odor and/or jerking? no check engine light but that code did come up when scanned.


by the way my truck is a 99 mazda b3000 auto, 114k.
new motorcraft plugs, wires, fuel filter, air filter, cleaned fuel injectors, removed egr to clean but was very clean itself, sprayed throttle body cleaner in egr pipes for possible blockage but that was ok, oil changed obviously.

Any help?

 

[jhammel85]

I would bet on the cat being the problem. It sounds a lot like that. Take a look at it in the dark after running on a highway. If its bright red then you know its toast.

If the can sensor is easy to do and cheap enough, I would do that first. I've only had those sensors go out on me when they completely fail and the car won't start.

 

[Beef52751]

Soundd like an 02 sensor or something making it run rich

 

[87 XLT]

I would bet on the cat being the problem. It sounds a lot like that. Take a look at it in the dark after running on a highway. If its bright red then you know its toast.

If the can sensor is easy to do and cheap enough, I would do that first. I've only had those sensors go out on me when they completely fail and the car won't start.

Thats the thing about the 3.0 if the cam sensor craps out it will run just fine but the oil pump stops as it is driven by the cam sensor. Change it ASAP i think ford recommends every 70k miles.

 

[kimcrwbr1]

Have someone give it gas as you hold your hand in front of the tailpipe, the exhaust coming out should increase with engine rpms. If not there is a restriction in the cat or muffeler.

 

[brunocas06]

I would bet on the cat being the problem. It sounds a lot like that. Take a look at it in the dark after running on a highway. If its bright red then you know its toast.

If the can sensor is easy to do and cheap enough, I would do that first. I've only had those sensors go out on me when they completely fail and the car won't start.

I may just change the cam sensor anyway but I do think the cat may be done for anyway, I'll see if I can get it to glow.

Soundd like an 02 sensor or something making it run rich

I dont have any trouble codes or the check engine for them but I'll go ahead and check them manually anyway. The black dust on the exhaust pipe made me think of an O2 sensor going out.

Have someone give it gas as you hold your hand in front of the tailpipe, the exhaust coming out should increase with engine rpms. If not there is a restriction in the cat or muffeler.

I'll go ahead and try that first and then the glow test like jhammel85 said.

 

[Earl43P]

Don't bother.

All the proof you need is in that code.

Replace the DPFE.

If you want "proof", simply disconnect the vacuum line that goes to the EGR valve.
Don't even have to cap that line, just drive it for a day like that. You'll see that it quits bucking.



Welcome to The Ranger Station.

 

[brunocas06]

Don't bother.

All the proof you need is in that code.

Replace the DPFE.

If you want "proof", simply disconnect the vacuum line that goes to the EGR valve.
Don't even have to cap that line, just drive it for a day like that. You'll see that it quits bucking.



Welcome to The Ranger Station.

That whole reply made me laugh so hard because at the end it says "Welcome to The Ranger Station" like a badass or something. Not making fun of you it was just all clever.
Thanks for the insight as I have checked around for that issue and it sort of seems to follow some of my issues. However I used a scan tool to check the o2 sensors and the voltage changes on every single one as normal. It doesnt stick below .5 volts or over indicating rich or lean conditions but i did pull two codes afterwards... one is p1151 and the other p0171 which is lack of ho2s switch sensor lean and lean to bank one but sensors look good so it may be another issue causing that possibly the dpfe.
I did a vacuum test to check for exhaust restrictions but its all good there and holding my hand to the pipe was good to go.