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Discussion Starter · #1 ·
Car is '03 SVT EAP. 106k miles. All scheduled maintenance performed. Problem occurs both with standard PROM and with Tom's Tune.

The car will be cruising along at a constant speed and suddenly it decelerates. If I hold the throttle at the same position it will continue to decelerate for some random period and then come back up to speed. This could go on for 3 seconds or just a blip. If I step on the throttle it immediately speeds up. This never happens when accelerating.

It acts like the TPS has a bad spot in it but it comes and goes. It can happen at any speed from 55 to 75 (I don't spend much time below 55 so it might be happening there too). I'd like to monitor the TPS with the Predator but I can't find anything that looks like the signal from the TPS. Anyone have any ideas? Could this be anything other than the TPS? Bad ground? It happens whether it is cold or warm outside but only after the engine heats up.

Thanks guys!
 

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My 03 ZX3 with 104,000 mile recently started surging Almost felt like I was hitting head winds as the car felt like it would be pushed against momentarily at highway speeds. What I discovered was that my DPFE was going bad this is a common problem on the Focus. Here is the article that helped me solve the problem with mine. good luck http://www.focushacks.com/index.php?modid=80&ht=DPFE Sensor and EGR Information
 

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You don't have a DPFE, it's an EGR component.

I'm not sure what the Predator can log or what they might call the PID for the TPS, generally though it'd be something like TP_Volts.
 

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Discussion Starter · #5 ·
Thanks iminhell. Monday I had a quick look at the exhaust manifold and couldn't find the EGR. Now I know why.

I'll monitor the TPS for a while and see if that's the problem. Any other ideas?
 

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Same issue

My 2004 Focus SVT EAP has done the same thing once before and I am curious as to what it is too. Any solution let me know please.
 

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Discussion Starter · #7 ·
It was the throttle position sensor. I put my DiabloSport on the car and monitored the TPS. There was a lot of noise on the signal. Whenever the noise caused the signal to drop below a certain minimum point the computer sensed an idle condition and retarded the spark. A new TPS cost about $25 at AutoZone and solved the problem completely. So there's at least one original TPS that has failed.
 
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