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Rumbling Engine in Idle an in Drive


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ttdragon23
New User

Sep 17, 2012, 6:52 AM

Post #1 of 5 (2878 views)
post icon Rumbling Engine in Idle an in Drive Sign In

2001, Chevy Blazer V6, 152000 mileage

When in park and idling, the engine usually runs at right at or just below 1000 RPM... But now, in park and idling, it runs at almost half that... between 500 and 750 RPM. It sounds as if the engine is rumbling and once every 10 seconds it sounds as if the engine 'clears its throat' and the RPMs jump back to normal... but only for a second... then it goes back to the abnormal rumbling and RPM level.

When put into drive, the rumbling still continues and the RPMs increase, but it is not constant... it takes longer than normal to get up to highway speed.

The temperature of the engine has not changed even when driven for a long period of time. The battery guage is normal. The belt is not messed up.

Also, when I drive for a while and then park... when I get out I smell a dirty, smoky odor... I've popped the hood to smell... but the odor does not seem to come from under the hood.

The 'Check Engine' light is on... but it has always been on for the 7 years that I've had the vehicle.

Any ideas?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 17, 2012, 7:15 AM

Post #2 of 5 (2866 views)
Re: Rumbling Engine in Idle an in Drive Sign In

Ignoring that CEL for a couple days is long enough. 7 years! Gonna cost you now as that wasn't just an amusement warning. Get the codes and you should have the idea of how much trouble it's going to be,

T



ttdragon23
New User

Sep 17, 2012, 7:29 AM

Post #3 of 5 (2859 views)
Re: Rumbling Engine in Idle an in Drive Sign In

The check engine light hasn't been ignored. In 7 years, I've had plenty of issues from torn belt, alternator, battery, radiator... The mechanic checks why the 'check engine' light is on every time I've ever brought it in. Most of the time the code given is completely wrong because what is says is wrong is working correctly. I've learned that simply having your gas cap loose can cause the CEL to come on. The mechanic I use told me what it said the previous time, when the water pump was being replaced, was that it was the O2 sensor. I researched that in my Chilton manual, online, and discussed it with the mechanic and the 02 sensor really isn't a problem worth my money. The rumbling engine is... could it be a spark plug not firing? Would that cause the rumbling engine and the RPM's to be low in idle and in drive?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 17, 2012, 7:42 AM

Post #4 of 5 (2853 views)
Re: Rumbling Engine in Idle an in Drive Sign In

The CEL is never wrong, however your mechanic can be very wrong.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 17, 2012, 7:53 AM

Post #5 of 5 (2848 views)
Re: Rumbling Engine in Idle an in Drive Sign In

O2 sensor may be the result not the cause. When an upstream one fails to provide credible info the computer controls for the engine can't make the correct adjustments of several possible, then the problem will compound to damaging other items with too much or too little fuel burned properly. Now other sensors subject to perhaps raw fuel to excess are likely wrecked. No power could be several things but a clogged converter would be possible.

I don't know and you don't seem to know the exact code or reason and may be an assortment of new codes now. Codes are great info but tell of area or circuit sensing a problem not the exact reason why. Ignoring them was a bad suggestion IMO back when and might have been just an non damaging issue but same light may have developed other issues and you wouldn't know it.

It isn't running properly now so some real diagnostics are in order NOW to stop the bleeding and any more problems,

T







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