The Money Mustache Community
Learning, Sharing, and Teaching => Ask a Mustachian => Topic started by: CatamaranSailor on January 23, 2017, 07:21:47 AM
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So I was driving my wife's 2003 Acura MDX when the engine suddenly lost all power and would not rev past 1000rpm even with the peddle to the floor. We towed it home and now it will not start at all. It's got the Honda 3.5 VTec.
So far I have verified:
It's getting spark
It's getting fuel
It's getting air
The timing belt is not broken
No engine codes (probably due to the fact the battery went flat while it was sitting on the side of the road with the flashers going and wiped any codes that were in there from memory)
My wife had complained a week earlier it was idling rough and lagging on acceleration.
At this point, I'm suspecting the camshaft position sensor but I don't want to have to tear the front of the engine off if I don't have too.
Any ideas, suggestions would be greatly appreciated. My wife is already hinting about a nice new Mini Cooper.....
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Cam position sensors can make it very hard to start when they fail, so this is possible. Did you check to make sure it is getting spark in all cylinders? I would check that. Sometimes the misfire codes aren't thrown right away. Then ohm out the coil packs. Check for vacuum leaks. You could always get a compression gauge and verify all cylinders are getting good compression. Most auto parts stores should let you borrow or rent one.
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Wild guess: Mass airflow sensor bad or dirty? It will fall back to "limp home mode" if it goes out... and that sort of sounds like what you are describing.
I've also had similar issues with an idle control valve.
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You may have 2 issues
1)failure to start - is it trying to crank? if not, the interlocks may not be happy. Steering wheel, brake pedal, gear selector interlocks ok?
2) power loss. Baring a major mechanical malfunction (not likely, you'd probably notice something so major...) it sounds like a sensor to me. Sorry but you may have to get at that cam sensor. Different car, but a co-worker had the exact same thing happen on his PT Cruiser, would start and kinda run, no codes. Cam sensor.
imho, Avoid Mini Cooper unless you are in the market for a depreciating, poorly made, problem ridden pile of $hit. FWIW we are really enjoying our 2013 Fiat Abarth.
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Was it running hot before? Does it crank or do nothing?
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I would jump start it, let it idle and see what check engine light codes come up. Go from there.
A rough idle and sluggish acceleration are typical in misfire situations. I would start by changing all of your spark plugs and coil packs; it's a 2003 so the coil packs probably should be changed anyway if you haven't done that yet. I would definitely start there if you are going to diagnose/fix the issue yourself since it's cheap and easy.
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Losing power with the pedal to the floor could be a faulty accelerator cable or some other break between pedal and throttle.
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Does the engine run at 1000 rpm and do nothing when you press the gas? if so broken throttle cable is almost certainly it.
does it bog down when you press on the gas? if so almost certainly the throttle position sensor. (the little black rheostat on the outside of the throttle body opposite the throttle cable. you can check it for voltage by backprobing it or remove it and check for resistance, it should change as you twist it. It also could be a broken wire going to the throttle position sensor.
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If it has a hot wire mass air flow sensor - look for tears between the MAF and the throttle body. You might have a big lean problem. That said I would expect it to start but not do anything above idle.
I'd run the codes - most car computers will save codes. Unplugging the battery will reset the light but not wipe saved codes.
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Thanks for all the suggestions but I think I've figured out the problem.
Did a compression check and cylinders 1-3 all have low compression which to me suggest blown head gasket. Checked with two different gauges just to make sure. Haven't done a leak down test, but with compression in the 40's I think I'm on the right track.
Haven't torn into the engine yet, but I guess that's the next step. The car has 205,000 miles and is probably worth around 3-4k in working condition (probably less than 1k as a parts car) so I figure one more day getting into the mechanicals to find out for sure what's going on and then decide from there is it's worth fixing.
Any other thoughts would be welcome.....
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Is that the DOHC 1.8L? if so I did a head gasket on one once. It was not hard, just make sure you mark the belt and cam and crank sprockets when you pull the cam drive belt. And replace the water pump while you got the head off.