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2005 scion tc 5 speed. 106xxx

Yesterday driving home car stalls out on the highway and power steering goes with it. Battery and oil light come on and won't restart immediately. Dash lights still work, headlights etc all work. Cranks over like it wants to start, but just won't fire.

After disconnecting the battery terminals and cleaning them, which were pretty dirty, fires right up and I drive it home. Today the same thing happens except this time when I try to restart the car rev's itself up to ~5000 rpm and dies. Again disconnecting the negative terminal of the battery intermittently fixes it.

The car runs strong through all gears up to redline even at WOT. I'm going to have the codes pulled this afternoon.

  • Out of total curiousity, did you try popping the clutch while still doing highway speeds to see if you could bring it back? – Lynn Crumbling Apr 15 '16 at 13:41
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    Unfortunately, unhooking the battery clears the codes. Guess it hard to determine if the CEL came on, since it will always be on when the key is on and the engine is stopped. You would need to read the codes after it is stalled, but before disconnecting the battery. After your disconnect the battery, does it fire right up, or take a little bit of cranking? Thinking either fuel pump or crank/cam sensor. – rpmerf Apr 15 '16 at 13:43
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    My guess is that disconnecting the battery is resetting trim levels to defaults, and that's why the battery "fixes" it. – Lynn Crumbling Apr 15 '16 at 13:43
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    While this is an arbitrary thing, when you get faults like this, I wonder if it's a grounding issue to the PCM. It sounds like it isn't getting proper power, so is causing wanky things to happen. Pulling the codes the next time it happens would be a great diagnostic tool. – Pᴀᴜʟsᴛᴇʀ2 Apr 15 '16 at 14:40
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    Were you able to pull the codes? Without them, this question is ripe for closure – Zaid Jul 28 '16 at 21:08
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It sounds like you have an intermitant failing sensor. On most of the systems I have worked with the crank sensor isn't required and wouldn't inhibit the engine from starting. The cam sensor or possibly the maf sensor could cause this behavior. Really what you need to do is pull the code. One thing to add, is that crank and cam position sensors are Hall effect sensors. There isn't much to fail. Maf sensors are notorious for intermitant failure.

  • Welcome to the site. Not so sure about the intermittency diagnosis. OP is able to repeat the fix (disconnecting battery). While a MAF could cause this, what information are you basing this diagnosis based on? It could be that there are other sensors at play here, more information is needed to make sense of what's going on here (OP needs to pull the codes). – Zaid Jul 28 '16 at 21:07
  • Ziad's, I'm not telling him to do anything until he pulls the code. However, here is my rationale. There are a million things that can cause a car to stall out. For an engine to crank and not start: it could be a starter solenoid, or maybe a crank or cam position sensor. None of these are likely to improve their state by resetting the Ecm. Maf sensors work off of stored tables in the ecm's vram. By flushing these tables, you might put a band-aid on a maf. Finally, he said that his engine autonomously reved to 5000 rpm. This means the engine autonomously raised the throttle. – mreff555 Jul 28 '16 at 21:24
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    Based on your comment you have my upvote. Hope you stick around and enjoy the site! – Zaid Jul 28 '16 at 21:35
  • Thanks Ziad. It looks like stack exchange truncated my post. Oh well. Mark, let us know what the result is when you pull the code. – mreff555 Jul 28 '16 at 22:36
  • You can edit your answer to include the comment – Zaid Jul 28 '16 at 22:37
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Could be camshaft position sensor or crankshaft position sensor, or another sensor (or the connection to that sensor), something that tells the controls what RPM the engine is running at. I'm not familiar with this engine to advise any further, but pulling codes might point you in the right direction.

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The ISC valve/sensor (Idle speed control valve) and/or Throttle Position Sensor/actuatur (TPS) sensor has the problem. Disconnect the connectors and inspect the rated voltage values and ground connectivity across the sensors/actuators and the respective terminals.

The cleaning of ISC valve is easy DIY job, but TPS sensors are advised not to be removed as they are very re-installation sensitive.

Sometimes, spraying of the electric terminal cleaner or the wd40 also mitigates the contact/continuity errors, if any, due to time-bond/climatic corrosions.

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