Rough idle and no acceleration
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Rough idle and no acceleration
A friend of mine has asked me to help fix his 2001 Mazda Tribute with 150K miles. I don't think it has ever been serviced, except oil changes.
Day 1 - Running poorly.
Replaced fuel filter.
Replaced all six plugs.
Day 2 - Gets OBD codes P0304 and P0305.
Replaced all six COPs
Replaced air filter.
Removed 1 quart extra transmission fluid
Day 3 - Now has rough idle.
Replaced PVC value.
Cleaned injectors.
Replaced upper and lower intake gaskets.
Replaced IAC valve and gasket.
Cleaned throttle body with carb cleaner and replaced gasket.
Cleaned MAF with MAF cleaner.
Checked vacuum. Good solid 20 inches of vac.
Still had rough idle.
Drove it for about 10 miles and it progressively started to slow down to 10mph.
Now, it will not idle long before dying and will not drive over 10 mph.
Today, unplugged MAF and started engine. No change.
What could it be?
What should I check next? and How do I do it?
Seems to get worse the more we change out parts.
Please help!
Day 1 - Running poorly.
Replaced fuel filter.
Replaced all six plugs.
Day 2 - Gets OBD codes P0304 and P0305.
Replaced all six COPs
Replaced air filter.
Removed 1 quart extra transmission fluid
Day 3 - Now has rough idle.
Replaced PVC value.
Cleaned injectors.
Replaced upper and lower intake gaskets.
Replaced IAC valve and gasket.
Cleaned throttle body with carb cleaner and replaced gasket.
Cleaned MAF with MAF cleaner.
Checked vacuum. Good solid 20 inches of vac.
Still had rough idle.
Drove it for about 10 miles and it progressively started to slow down to 10mph.
Now, it will not idle long before dying and will not drive over 10 mph.
Today, unplugged MAF and started engine. No change.
What could it be?
What should I check next? and How do I do it?
Seems to get worse the more we change out parts.
Please help!
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Joined: Jun 2011
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Fordman400,
Thanks for answering.
No CEL lights, no OBD codes. Just barely runs.
I was thinking about blocked CATs; because I don't know what to check next.
How can I test for that? Remove exhaust and run it without exhausts?
What could have clogged the CATs.??
Thanks !
Thanks for answering.
No CEL lights, no OBD codes. Just barely runs.
I was thinking about blocked CATs; because I don't know what to check next.
How can I test for that? Remove exhaust and run it without exhausts?
What could have clogged the CATs.??
Thanks !
Posting Guru
Joined: Apr 2002
Posts: 1,471
Likes: 3
From: Greenwood In. USA
Front Cat has probably fallen apart blocking the common cat. (Had it happen on an 04 with less miles) I would start at the front and work back you may need to change all three.
Good luck
Good luck
Senior User
Joined: Oct 2003
Posts: 161
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From: wisconsin
Cats could have clogged or fell apart do to running rich or lean. Burning too much oil. Or just bad luck. I would start by checking the common cat. See if its plugged then go to the front bank and work back. Good luck cats are not cheap.
Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
Before dropping the cats, I'd check fuel pressure and volume. A lot easier, and fits the symptoms. If you have minimal delivery, the engine will slowly lose power, and run slower, likely dying if you open the throttle and try to rev the engine.
The cats would have to be very blocked to cause an engine to run slowly that quickly. If the engine was running without dying before replacing all the parts, the new parts would have made things better, not increased cat blockage.
IF the cats are plugged severely, you will get no exhaust gas out the tailpipe. Look there too before condemning the cats. I don't have any reason to disagree, but am lazy and would check that stuff before crawling underneath and trying to unfasten bolts that have had 150,000 plus miles of rusting together. {I ALWAYS break stuff whenever I try to undo muffler/manifold/cat fasteners, so avoid that until last...}
Start it, and at idle feel the exhaust coming out the tailpipe, if any. I'd also do the fuel delivery test...
tom
The cats would have to be very blocked to cause an engine to run slowly that quickly. If the engine was running without dying before replacing all the parts, the new parts would have made things better, not increased cat blockage.
IF the cats are plugged severely, you will get no exhaust gas out the tailpipe. Look there too before condemning the cats. I don't have any reason to disagree, but am lazy and would check that stuff before crawling underneath and trying to unfasten bolts that have had 150,000 plus miles of rusting together. {I ALWAYS break stuff whenever I try to undo muffler/manifold/cat fasteners, so avoid that until last...}
Start it, and at idle feel the exhaust coming out the tailpipe, if any. I'd also do the fuel delivery test...
tom
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Thanks to all for your help !
Saga for today...
Picked up a loaner from Autozone to measure fuel pressure. Actron fuel pressure tester kit.... Nice.
Measured zero. I tested guage and it works; so my guess is that the schrader valve doesn't work. I'll have to cut into the line tomorrow.
Car starts so it has to have SOME pressure.
Measured the vacuum again today (after yesterday's 10 mi drive) and now it is holding steady at about 16in. Yesterday it was 20in before we drove it.
Read on the forums that I can test the CATs by removing the pre-cat O2 sensor and measure the pressure at the O2 hole. Recommended pressure would be 1 to 5 psi. Should measure the same pressure on the after CAT hole too. Does that should right to you???
I thought I would try this trick before I try and pull the CATs completely off.
Thanks again for all you help.
Saga for today...
Picked up a loaner from Autozone to measure fuel pressure. Actron fuel pressure tester kit.... Nice.
Measured zero. I tested guage and it works; so my guess is that the schrader valve doesn't work. I'll have to cut into the line tomorrow.
Car starts so it has to have SOME pressure.
Measured the vacuum again today (after yesterday's 10 mi drive) and now it is holding steady at about 16in. Yesterday it was 20in before we drove it.
Read on the forums that I can test the CATs by removing the pre-cat O2 sensor and measure the pressure at the O2 hole. Recommended pressure would be 1 to 5 psi. Should measure the same pressure on the after CAT hole too. Does that should right to you???
I thought I would try this trick before I try and pull the CATs completely off.
Thanks again for all you help.
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Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
The pressure developed before the catalytic converter would be due to the converter, any developed after the converter would be due to the muffler, resonator and tailpipe.
I would expect the 'after' pressure to be lower.
If you depress the core of the schrader, you should see fuel flow. I don't see how they can be defective unless the fitting you used did not depress the core of the valve enough to allow the pressure to register.
tom
I would expect the 'after' pressure to be lower.
If you depress the core of the schrader, you should see fuel flow. I don't see how they can be defective unless the fitting you used did not depress the core of the valve enough to allow the pressure to register.
tom
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I agree with tom, sounds like a fuel issue. Sounds like the fuel pump is going or the pressure regulator is clogged. You might want to also take another look at the fuel filter to make sure you didn't put it on backwards.
Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
I just remembered the 1st time I checked fuel pressure, I had to remove a bit of whitish-semi-transparent plastic from the schrader valve. It was inside, next to the pin that gets depressed to open the valve. Once that was removed, the pressure gauge worked.
tom
tom
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Well.. I finally got the pressure tester to work correctly.
Fuel pressure is 68psi and rock steady. Drops to 66 when throttle is opened and closed. Recovers back to 68 almost instantly.
Shut off engine and after 15 minutes, holding still 62 psi.
Idle vacuum is 16in.
Starts at the click of the key. Rough idle and no acceleration.
Labors to get up to 20mph.
I really don't want to take the CATs off.
It is a V6, one for each side and welded to the exhaust manifold.
Any other ideas? What else should I check?
Thanks to everyone for helping so far ! ! !
Fuel pressure is 68psi and rock steady. Drops to 66 when throttle is opened and closed. Recovers back to 68 almost instantly.
Shut off engine and after 15 minutes, holding still 62 psi.
Idle vacuum is 16in.
Starts at the click of the key. Rough idle and no acceleration.
Labors to get up to 20mph.
I really don't want to take the CATs off.
It is a V6, one for each side and welded to the exhaust manifold.
Any other ideas? What else should I check?
Thanks to everyone for helping so far ! ! !
Tuned
Joined: Apr 2008
Posts: 406
Likes: 1
From: Cleveland,OH
If you have a muffler shop nearby take it to them and have them cut the bolts off with a torch,shouldnt be more than $10-$20.
Then see how it runs,if all is good install some stainless bolts and nuts.
Then see how it runs,if all is good install some stainless bolts and nuts.
Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
The fuel pressure is not supposed to drop when you open the throttle. It is supposed to go up. The demand for fuel rises with a drop in manifold vacuum, as that means the throttle is opened to allow more flow. I do not know of one regulator that drops pressure when the throttle is opened by design. I am guessing the pump is not producing the pressure it should. Go read the specs in the manual... replace as necessary.
tom
tom
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The few items I have not replaced are the fuel rail damper and the throttle position sensor along with the fuel pump/regulator.
Could it be one of these items?
I guess I'll replace the damper first and then dig into the fuel pump.
Thanks again..
Could it be one of these items?
I guess I'll replace the damper first and then dig into the fuel pump.
Thanks again..