Rough idle

KLOOG

MEMBER
MAZDA PROTEGE

1991 mazda protege 1.8 DOHC

I have a constant rough idle that I can't fix. I've checked all the obvious things
1. Motor mounts (2 replaced, 2 others checked and seemed fine)
2. Wires/plugs/cap/rotor replaced
3. Throttle body gasket replaced, throttlebody cleaned
4. Changed exhaust manifold gasket checked for leaks
5. Changed o2 sensor
6. The IAC was broken but I replaced it (didn't help)

I am really at a loss about what to do to fix it
the idle is steady and rpms appears to be proper for the car
it's just really bad vibration, it occurs during hot and cold operation

if anyone has any suggestions i'd love to hear them

6 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Find the EGR and open it up and clean it out.

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Friday, April 20th, 2007 AT 12:06 AM

KLOOG

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4 POSTS

This engine doesn't have an EGR valve

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Friday, April 20th, 2007 AT 8:45 PM

RASMATAZ

MECHANIC
75,992 POSTS

I don't get this one, the idle is steady and rpms appears to be proper for the car
it's just really bad vibration. Sounds more like a mechanical problem.

Ignition timing okay -no vacuum leaks?

Bad vibration when your moving from a stop or while idling at stationary.

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Friday, April 20th, 2007 AT 9:39 PM

KLOOG

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The rough idle is when the car isn't moving, I haven't checked timing and there are no vacuum leaks

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Friday, April 20th, 2007 AT 9:43 PM

RASMATAZ

MECHANIC
75,992 POSTS

BTW is it a Carb or and EFI

How about tranny mounts they ok too. Be advised the EGR is been around since 1973, are you positively sure?

Could be the brake booster/check vale/hose, PCV valve to include its hose, intake manifold gasket, throttle body shaft

there are no vacuum leaks: Did you use one of these methods to confirm that theres no leak-Carb cleaner, propane, pressure, smoke, electronic vacuum leak detector, Vacuum gauge, exhaust analyzer w/propane.