I'd like to chime in here. You've tossed a couple of hundred dollars at this problem by replacing parts that it didn't need and failed to fix the problem. Did you ever think that maybe it needs a trip to the dealer to fix it once and for all? What you've spent already would have likely covered the cost of the repair originally.
It's already cost me over $1500 at the shop, and they were just doing the same as me, replacing things blindly and costing me money. At least when I do it the parts are a lot cheaper and the labor is "free".
But yes, if I could find a mechanic that could diagnose the problem with
100% reliability before it started costing me money, then I'd be there like a shot.
Unfortunately it seems that most mechanics go the easy route because it's not their money that they're burning through, and as a bonus they get to charge labor for fitting unnecessary parts.
Yes, but was this "shop" a Ford Dealer? If so, I stand corrected. If not, well.... Until 2001, I was a Ford Master Tech. If I had your vehicle in front of me I could very likely find the problem fairly quickly. To this day, I tend to choke on GM vehicles, even with the factory documentation. Given that, is it entirely fair to expect a "General Mechanic" at an Independent shop to completely understand your Ford vehicle, especially with an intermittant concern such as yours? If you are being charged for repairs that don't solve the problem, it's not the shops fault. Why are you paying the bill?
No, he's not a Ford Dealer, but he *was* someone I trusted to be able to understand how a car works and provide a reasonably accurate diagnosis. There's an element of trust needed in these situations since I'd expect a mechanic to be an "expert" in matching symptoms to problems. This however, was not the case.
As for being charged for repairs that didn't change anything. He'd inform me that "the MAF tested bad and needs replacing" and so on, so I'd pay for a new one then collect the van. Because the problem is intermittent, it wouldn't show up for a day or so before I'd call in and take it back. Of course, he never kept any of the original parts, so I got kind of screwed over. That's why he's not touching it again.
I value your advice, so I'm going to give my local ford dealer a call today, and see if I can get a diagnosis estimate. If it's just a hour's labor I'll go ahead and do it to see what I'm up against.
Intermittant drivability concerns are probably THE toughest problems to properly diagnose on any vehicle. Even for Techs specifically trained in one manufacturers products. The particulars of the engine management systems, although similar in concept, vary widely between car makers. It's an impossible task for a Tech at an independent shop to be an "expert" in diagnosis of all the different systems. Most driveability symptoms are easily diagnosed, but there are always a few that will lead to head scratching even by a competent Dealership Tech. I wouldn't hold not being able to find the problem against the fellow that worked on your car. What I would hold against him is the fact that he didn't stand behind the "repair" and kept charging you for parts that you didn't need. That's just bad practice. He should have informed you that the problem was beyond his scope and offered an adjustment to the original repair price. Good luck, and let us know how it turns out.
I agree. It was the fact he never communicated to me that he was just "guessing", and he also never experienced the problem himself but never told me that either. I'd been assuming that he'd test it, see that something was wrong, fix something, test again and it would be okay. But no, he was replacing things blindly.
I still haven't had chance to contact the dealership about it, but there are a couple more bits of information that may be important.
I had the fuel filter replaced, and the fuel pouring out of the old filter was black! I'm guessing it hadn't been replaced for a LONG time. New filter made no difference to the problem though.
I tested the voltage to the fuel pump while the problem was happening, and it remains constant, so no electrical problem form that side.
I found that I can get it to happen fairly regularly on a particular hill. If I'm on this freeway hill doing a steady 70mph, I will get 2 rapid stumbles (within 1 second) almost exactly every 4 seconds.
Dunno if any of that info sheds light on anything else, but the regular stumble might point to the CKP sensor. I don't know for sure, but it might be worth trying having come this far with it.
Still no closer to fixing this yet. I don't have the money right now to let the dealer diagnose it.
Ruled out the power to the fuel pump (and therefore the impact switch thing), by monitoring the voltage to the pump. I was getting a pretty steady 13.8v and it didn't fluctuate at all when hesitating.
I have also ruled out the IAC, since I tried it with the IAC unplugged and still had the intermittent hesitation.
It's not easy to drive without the IAC, so I ended up letting the revs drop too far and stalling it which threw a code. Gonna have to go to autozone and borrow their reader again to erase it.
I haven't tried a pressure gauge yet, since I have no way of reading it when the problem happens (only when driving), so I didn't see much point unless the pressure is consistently low (which doesn't make sense because when it's not bucking, it can be driven hard without problems).
I DID have the filter replaced. I went to jiffy lube because I couldn't get enough clearance to do it myself. I supplied my own filter and had it fitted for $35. The mech showed me the old one, and poured out BLACK gasoline, it was really horrible looking so certainly needed replacing.
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