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stephens 09-21-2012 05:28 PM

2003 ZX5 Sudden loss of power, no codes, timing problem?
I was driving along and all of a sudden the car loses power and won't rev over about 3,000 rpm. No warning lights and it wasn't overheating so I babied it home and it would barely make it to at a max speed of about 30mph.

I plugged in my reader and it doesn't return any codes at all! I thought maybe the cat was clogged really bad or something so this morning I took it by a local shop that also does exhaust and he says exhaust tests fine, fuel pressure 44psi, Baro sensor 136hz, and his reader wouldn't bring up any codes either. He suspects the timing is really retarded and/or isn't advancing and this makes sense for the symptoms I guess. Timing belt and tensioner were changed 7,000 miles ago and belt looks fine and tight when I peak under the cover (stupid that you can't remove the inspection cover without removing the motor mount!!)

Another symptom is harder than usual brakes but mechanic said this lack of vacuum could also be because of the timing. (Hmm...)

So...did timing belt jump somehow? Is Ecu faulty? Or some other part that controls ignition timing/advance? And all of this happened without any codes being recorded?

I've got the car back home now and have the battery unplugged now on the off chance that the Ecu will reset itself.

I searched and read some older threads but can't find this exact scenario. Little help? Thanks.

BC_ZX3 09-22-2012 09:23 AM

Zetec engine? (Not sure as you're in CA)

Check the coil connector wiring. Sometimes it takes complete failure (wire(s) break completely) before it throws a P0351/P0352 code and the symptoms you describe - loss of power, inability to rev, no DTC codes, no overheating - were the same for me when mine failed. Also had a very strong gas smell and wet plugs.

Easy to inspect first by yourself - you're looking for cracks in the insulation, green corrosion or a complete wire break in either of the two outer wires of the three wire connector plug. Motorcraft WPT 517 is the part needed to fix it, if it proves faulty.

ECUs rarely go wrong. Hard brakes is the only symptom you've mentioned that seems out of place.

stephens 09-22-2012 11:36 AM

Awesome. I'll check that today. The brakes may be unrelated and I wouldn't have even noticed if the mechanic didn't point it out so maybe he's just used to more boosted brakes. My focus has always had much harder brake pedal than, say, my wife's golf.


And yes, Zetec engine.

FocusGhia 09-23-2012 01:37 AM

Could try unplugging the TPS connector and see if revs will increase. Also wouldnt hurt to disconnect the MAF sensor and see if you get any improvement.

V8Cruiser 09-23-2012 04:15 AM

My focus has been doing the same thing recently.
But only when the tank is 1/3 or less.
Today I found the sender float had come out the the bracket and it was reading 1/4 high.
I also found the fuel pump bucket was full of crap.
I cleaned all this out and took it for a 260 km drive (Went to the next town over and back) and didn't have the issue once.

whynotthinkwhynot 09-23-2012 08:08 AM


Originally Posted by BC_ZX3 (Post 4367605)
ECUs rarely go wrong. Hard brakes is the only symptom you've mentioned that seems out of place.

That could be indicative of multiple problems. The coil is a usual suspect for lack of revving along with the TPS, and the PCV vacuum line is the usual suspect for lack of vacuum. In this case, after inspecting that one I'd also inspect/replace the vacuum check valve which is the hard plastic connector that the vacuum line goes into on the power brake booster. You might be noticing some hissing when you hit the brakes.

stephens 09-23-2012 10:17 AM

Thanks guys. I messed around with it yesterday (coil connector wiring looked good) and basically I just got frustrated with it. Modern cars are full of electronics, but if they don't throw you a code, it's so frustrating to troubleshoot. So I gave up and dropped it off at the shop that had done the timing belt and whatnot a few months back. It's just weird that it'll start right up and doesn't die but has no torque going uphill (20mph max,) and won't go over 3000rpm on the flats either.

I'll update the thread if/when he fixes it so we know what it was for future reference.

stephens 09-25-2012 08:48 PM

Update: mechanic called to say that it was the timing belt tensioner. It broke, belt got loose, slipped...he's covering the repair under warranty since he had done the installation about 5,000 miles ago.

FocusGhia 09-25-2012 09:29 PM

At least your mechanic has admitted the fault and will make good. Very rare.

stephens 10-05-2012 01:20 PM

Just wanted to update that the part that failed was a Gates brand tensioner ("made in Canada"). The mechanic replaced with official Ford part and put the car back together and I went on a long road trip over the last week and all has been perfect.

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