Grinding sound when I put the key in position 1

[og asesino]

First off, hello gmtnation.

This is my first post on this site and you guys have helped me out alot on repairs, but this problem im having...i havent seen anything around here about it. Im fairly new to my 05 trailblazer, ive only had it about since december and it had 130k on it.

Whenever i put the key in and turn it to the first position, theres this nasty grinding sound that last from 2 to 6 seconds. I just replaced my ignition starter switch thinking it was engaging the starter before it should (if that makes sense). My next plan of action is to change out the starter relay...im really hoping its not the starter going bad.

Any ideas or insight would be appreciated.

Thank you guys.

 

[SAR85]

Where does the sound seem to come from?

 

[freddyboy61]

Do you have the air suspension in the rear? If you do, it could be the air compressor coming on.

 

[The_Roadie]

If it happens BEFORE you start the engine: From the fuel tank area - it's the fuel pump. No trailblazer except the SS had air suspension as an option.

More likely if it happens AFTER you start the engine: From under the driver's seat area - it's the SAIS turbine air pump. They die a lot. Should sound like a shop vac for 30 seconds on a cold start. Pull front fuse #56 to confirm.

 

[og asesino]

Someone mentioned the fuel pump to me, but its before i start the engine, like in the ACC position on the key. The sound seems likes its coming from the motor on the drivers side. I changed the relay and of course its still doing it.

What else would kick on while the key is set in the ACC position?

Actually it sounds like its coming more from throttle body area. Still having trouble with it starting.

 

[The_Roadie]

1) The fuel pump *does* come on for a few seconds when the key is in the RUN position, before you start it. It provides fuel pressure needed when you do start. But you say it happens in ACC, not RUN?

2) The throttle body may do some initialization at the same time - I don't remember any discussion of it in the shop manual, though.

3) How many miles do you have, and have you ever cleaned the throttle body. If it's sticky, a cleaning should help it.

4) You can easily disconnect the harness from the throttle body to see if the noise goes away. Is there nobody near you to let you listen closer to find the source of the noise?

 

[og asesino]

Thanks for the responses.

1. Yes, in ACC not in run. Thats why i changed the ignition switch thinking the internal contacts were messed up but they actually looked good.

2 & 3. No, throttle body cleaning has been on my radar, just havent had a change. I know it was gummy when i changed plugs a couple weeks back. Car has 133k miles on it. I bought it back in Dec. and it had 124k. It has had motor work done to it...i dont know what all happened but i noticed wrench marks on alot of the bolts.

4. Will try unplugging the harness and see what happens. Its hard to pin point by myself because it stops when it get to the engine. I have about 30 minutes from when the wife gets home from work and when i go in. Ill see if she will give me a hand.

In the meantime, ill clean the throttle body and try with it unplugged. Thanks for the help and suggestions.

 

[og asesino]

Cleaned throttle body...it was nasty as hell, but now i got REP light. I had the battery disconnected for over an hour. Before i did all that, i disconnected the plug on the throttle body and the noise went away. So no matter what, i guess i need a new throttle body.

Thanks for all your help, guys.

 

[The_Roadie]

Could be a bent pin in the connector.

 

[og asesino]

Luckily i found a throttle body at a salvage yard for 100. Put it on and took care of everything. The trailblazer feels much better and sounds better...got more power.

Got to looking at the old one and the throttle plate (i guess thats what its called) was catching and sticking on the body. Should have seen it when i cleaned it but oh well.

Thanks for the help, buddy...i was stuck on starter issues until i posted on here. I really appreciate it. Thanks.