88 CRX HF, bad fuel mileage - Page 2 - Fuelly Forums

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Old 06-11-2007, 05:59 PM   #11
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Another thing that could be causing your car to run so bad is a clogged catalytic converter. If you can stand listening to it for a test, you might remove the cat and drive it around the block.
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Old 06-11-2007, 06:15 PM   #12
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Another thing that could be causing your car to run so bad is a clogged catalytic converter. If you can stand listening to it for a test, you might remove the cat and drive it around the block.
Have you done this before? There would be exhaust venting under the hood seems a little dangerous. I was/am thinking about changing the cat though.
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Old 06-11-2007, 06:48 PM   #13
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Have you done this before? There would be exhaust venting under the hood seems a little dangerous. I was/am thinking about changing the cat though.

Sorry, I forgot a stock HF has 2 cats, one on the manifold and one after the downtube. (Mine has a header that eliminates the 1st cat) You definetly would not want to try this with the 1st cat, you would have an open manifold that could burn exhaust valves. You could try it with the second one, but I wouldn't drive it like that for more then a trip around the block.
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Old 06-11-2007, 06:55 PM   #14
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hose crushed

It appears this hose off the intake manifold may be crushed... I have pictures from both cars so you can tell the one that looks kinda crushed... but I couldn't get it off... I tried on both cars and they appear to be maybe melted on a little bit or something. I thought there was only one cat but two mufflers. So there are two cats huh... that sucks. I need to replace my mid-pipe anyway (one of the bolts broke off in the flange when replacing the muffler). If you put anything other than OEM back on the front cat wouldn't that hurt gas mileage if it even moved the O2 sensor a little?
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Old 06-11-2007, 07:15 PM   #15
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Is that the hose for the PCV valve? When hoses get that old they harden that sometimes you have to cut them off and then replace them.

The manual says to inspect the interior of the cat and if 50% of the element is clogged, to replace it.
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Old 06-11-2007, 07:43 PM   #16
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If that doesn't work I'll be attempting to move the timing belt, but I'm not sure which way to move it a notch. Am I correct in saying that the 3 and 9 o'clock marks are supposed to line up with the head?
Correct. You want to set the engine so no.1 cylinder (the one closest to the timing belt) is at top dead center (TDC) of it's compression stroke. If you line those notches up with the valve cover mating surface, the cam will be properly aligned.

If you look at the crank pulley (the pulley that drives the alternator and A/C belts), you should see 4 notches cut into it's rim. The cluster of 3 is for ignition timing, the 4th mark is TDC - the mark you need.

The with the cam marks where they should be, the TDC mark should be lined up with the pointer/sight thing molded into the lower timing belt cover. If not, your cam timing is off.
Loosen the timing belt tensioner - it's behind the black plug in the lower timing belt cover. Just carefully pry the plug out with a small flathead screwdriver. Break the tensioner bolt loose and then keep going two or three turns to free up some slack on the belt. Be careful not to unscrew the tensioner bolt all the way... You would likely have to remove the crank pulley and lower belt cover if you did.
Slip the belt off the side of the cam gear. The belt's not designed to bend the way you're trying to bend it, so don't be surprised if it's a little difficult.
Turn the crank until the TDC mark lines up with the pointer/sight thing on the timing belt cover.
Slip the belt back on the cam gear. Obviously you want to avoid moving either the crank or cam out of alignment while working the belt back on, but try to keep the front, long run of the timing belt tight if you can... It's the run that counts timing wise.
Once the belt is on, thread the tensioner bolt back in until you've picked up the slack (the point where you would go from simply threading it in to tightening), then back it off a half turn so the tensioner can move. Turn the crank counter-clockwise a quarter turn to put tension on that long run of the belt, and all the slack on the tensioner/water pump side. Tighten down the tensioner bolt... The torque spec is 33 ft/lbs if you have a torque wrench.
Keep turning the crank counter-clockwise until the cam is back at #1 TDC. Check that the crank is also at TDC.
Replace the tensioner bolt plug and upper timing belt cover.


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Another thing that could be causing your car to run so bad is a clogged catalytic converter. If you can stand listening to it for a test, you might remove the cat and drive it around the block.
Yeah, if you don't mind flames shooting out of the manifold at the back of your radiator.
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Old 06-11-2007, 08:18 PM   #17
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It appears this hose off the intake manifold may be crushed... I have pictures from both cars so you can tell the one that looks kinda crushed... but I couldn't get it off... I tried on both cars and they appear to be maybe melted on a little bit or something.
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Is that the hose for the PCV valve? When hoses get that old they harden that sometimes you have to cut them off and then replace them.
Yeah, that's definately the PCV hose. Though if it were leaking, it shouldn't affect power at all. Hondas use a speed/density system to measure air flow, so there's no mass airflow sensor to bypass. If air leaks into the manifold, the pressure rises, the increase shows up on the MAP sensor and the ECU injects more fuel to compensate. If anything, you should see an increase in idle speed.
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I thought there was only one cat but two mufflers. [...] If you put anything other than OEM back on the front cat wouldn't that hurt gas mileage if it even moved the O2 sensor a little?
There is only one cat on a stock CRX. The HF cat is bolted to the exhaust manifold on the front of the engine, the DX and Si cat is under the car, just to the rear of the firewall. Oxygen sensor placement isn't critical beyond making sure it gets hot enough to operate. The CRX engine management system just isn't sophisticated enough for it to make a difference. Newer generations of Civic (most '92+ models) use a heated sensor, so placement is even less critical. I suppose putting the sensor close to the exhaust ports allows for quicker fuel mixture responses in closed loop operation. Putting it further from the ports would allow more time for the exhaust from individual cylinders to mix... If that makes a difference.
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Old 06-11-2007, 08:28 PM   #18
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There is only one cat on a stock CRX.

I stand corrected. This misinformation was from the original owner of my CRX. My car has a header and a cat in the DX position. I asked the former owner for the original exhaust manifold if I need to put the car back to stock and when I saw it had a cat on it, the former owner said the stock car had 2 cats.
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Old 06-11-2007, 08:45 PM   #19
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timing

I'm not sure what those instructions were for. Was that to set to TDC and properly align the belt? The engine is in the car... should I take out the driver's wheel and plastic housing to be able to see the crank pulley? Maybe tomorrow I can take a picture with the top belt cover off so someone can explain what i'm looking at.
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Old 06-11-2007, 09:08 PM   #20
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should I take out the driver's wheel and plastic housing to be able to see the crank pulley?
Yeah. Since you described the cam gear earlier, I assumed you had gotten that far before.
You should take off the splash shield in the driver's wheel well so you can reach the pulley, and the upper timing belt cover. You'll need to remove the spark plug wires (they can stay attached to the distributor) and valve cover in order to remove the upper belt cover. The remaining chunk of belt cover is the lower timing belt cover. Most of the timing belt, the water pump, and the timing belt tensioner are all covered by the lower timing belt cover. You have to either remove the crank pulley or cut the cover to remove it. Removing the pulley is a PITA without either something to hold the crank still and lots of leverage, or a big mofo impact gun... So, the above instructions work around the cover instead of removing it.
Removing the upper cover will expose only the cam gear (the first pic I posted) and the section of belt running over it.
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