Hi, I just bought an 02 Tribute LX. v6, 2wd, auto, 165k miles. There were a lot of issues when I bought it, the main problem was that it was barely running. My mechanic found the wiring harness that goes to the coils on the front bank to be "backwards", so only the middle cylinder was firing. After switching it around and getting it running on all cylinders, an intermittent drivability problem has surfaced.

The problem is that it sometimes drives fine and sometimes it's extremely underpowered. The problem is there whether or not it's warmed up, at every speed, etc. Let's say you are driving it and giving it steady throttle, and it's clearly not running at full power... keep giving it gas and all of the sudden you can feel it running at full power. Sometimes you have to floor it in order to get it running at max power. This seems like a classic ignition problem to me... So, I replaced all 6 coil packs and plugs, as well as intake gaskets, and the problem is still there. My mechanic has gone over the entire truck and cannot find anything else wrong with it. He suspects a computer issue, but in my experience computer issues are pretty rare, so I am hesitant to shell out the money for a ecu or a reflash (even less likely to work IMO).

Any suggestions?

 

ANY CODES?

That's a lot of miles. I would check catalytic converters. Raw Fuel was being sent to them when ignition is not occuring as you said. This raw fuel will melt and at least partially clog catalytic. Pressure test of exhaust before and after cats should be done: All Catalytic Converters - How do I know if my catalytic converter is defective?

Although if cats were clogged, you would not get full power.

Vacuum leak would be another route. It's possible to have a vac leak without you knowing. I had an internal leak on my brake booster, and the only way we found it was to monitor the computer when we pinched off the line going to it.

Leaky fuel injectors would make it run rough at lower idle but it would be OK at higher revs.

EGR, DPFE problems could be a cause. If EGR remains open @ idle, it would run rough and probably stall. Won't be as noticeable on higher revs.

 

Thanks for the reply.

I don't think it's throwing any codes anymore. I believe it was throwing a cylinder misfire code before I change the coils. I also forgot to mention that the cats are all gutted... surprisingly, this doesn't throw a CE light.

My mechanic has gone through and looked for (and fixed) several vacuum leaks already, and there should not be any leaks at this point.

It doesn't really run rough, just runs with reduced power until something "catches" and all of the sudden it runs at full power. At idle, the rpms jump a little, but only 100-200 rpm. It doesn't stall or sound like it wants to stall. And revving it high doesn't always make it run fine either, sometimes you can floor it and it won't go anywhere.

The previous owner had changed a few sensors, from memory I think it was the TPS, IAC, and EGR. I'm not sure if the mechanic has checked out the DPFE, but none of the above feel like they are related to this problem though, as it definitely feels ignition related, or at least some type of electrical issue related to the ignition system.

Anyone who has ever washed their engine at the spray bay and got their coils wet, causing stumbling or intermittent power issues, would know exactly what I am talking about... this i what it feels like is happening, except that I have already changed the coils, and even tried another set of used coils to verify the new ones were good.

 

It's no wonder they were gutted, due to that misfiring!

Hollowing out a catalytic converter will cause resonance problems. The symptom is most often seen as a hesitation, popping, or backfire at or about 3,200-3,500 RPM. Upon hard acceleration, the engine will appear to cut out for a split second as RPMs drop and a split second later recover and continue past 3,200-3,500 RPM. Additional symptoms are a loud and continual popping sound when the vehicle is allowed to decelerate under load and a whooshing sound that is delayed from or following the engine speed. This is due to the open chamber within the hollowed out catalytic converter case. It loads up and releases pressure in the exhaust system that acts almost as a capacitor. The open chamber allows the formation of standing waves within the chamber which reflects back toward the engine and causes the hesitation and miss in the RPM range.
Above from: ISUPAGE; Performance Exhaust System Basics

It may be better to replace cat with a straight pipe! And put O2 simulators for the secondary after ones.

 

These are newer cars, not like the old days of no cats. I bet thats your problem, they are gutted. The trucks sensors are confused half the time. You need to get some cats on that thing and make it like the factory had it.

Sounds like fuel to me too instead of ignition. Ignition usually doesnt turn on and shut off with half power here and there, fuel does that. Make sure your fuel filter is new too.

 

I am pretty sure the previous owner gutted the cats because they were clogged, which is REALLY common on the Escape and I am assuming the same would be true for the Tribute. These cats are part of the exhaust manifolds which makes them very expensive. I think somewhere around $600 each, plus labor. What does it cost to get both cats replaced... $1500ish? I'd gut mine before shelling out that kind of dough too if I were in his shoes. That's crazy.

I've never heard of gutted cats causing any type of problem on a vehicle of any year, other than throwing some codes, which mine isn't even doing. I don't understand how it isn't throwing codes being an OBDII vehicle and all, but it isn't. I picked it up from my mechanic today and was about to take it to the stealership for a $95 diagnosis, and it was running fine when I picked it up. Like I said, the problem is intermittent. Maybe I'll take it up there if it starts acting up again. I just hate overpaying for anything, and things are far from cheap at the stealership.

 

Dealerships cost that much because they have so much overhead to pay for ( car lot ). I take mine to Goodyear repair center. It's basicly Napa. They are HALF the price of a dealer with any job and the work is top notch ( the one I go to anyway ). I can't tell you over the years with any car I took in there how many $1000's i've saved. You can go to the dealer if you want to see whats wrong with it, then take it to Goodyear to get the work done. I just had an oil leak, valve covers gaskets, front engine cover gaskets, oil pan gasket, intake gaskets ( have to change all that to get to the front cover where it was leaking ) dealer wanted $1200 plus parts. Goodyear did it all with parts for $720. Took them 2 days, it was that much of a job since you have to tear half the engine/truck apart. When they were done, looks brand new now. Excellent work.

Also, the place is PACKED with customers 24/7. This is the reason. Police station across the street from them even take their cars over there. Half the price + good work = business.

 

exactly, that's why i don't take my car to the dealer. i work out discount prices with my mechanics for bringing them cars in bulk as i am a used car dealer myself. i pay $40-$45/hr for labor on my cars at established shops with qualified mechanics.