Hey guys, yesterday i was at the parts store(worthless autozone) and went to leave i started my truck and it fird but was real choppy and rough. i gave it some gas and it smothed right out. Hadnt done it since then. No check engine light or anything. Also it was nice out and i had the window down, i could hear what i can only describe as a cop siren sound that came and went with the throttle. Not as loud or defined as but its what the noise reminded me of. She been running great all summer long with out a hicup. Anyone got any ideas or clues as to what might be going on? Thanks.

Oh almost forgot, 2003 F-150 4.2v-6 auto trans.

 

No one?

 

Serpentine belts have been known to make squealing noises when you first start the engine. Could it maybe have been that?

 

I dont think so, the noise was coming and going when you pressed on the pedal and if i didnt say before i heard the noise drving down the road. On more than one occasion. Quite a few really, hasnt done anything the past couple of days, and the truck had already been drving 2 hours(long way just for a brake part for a different car) so it was fully warmed up. Could this maybe be a percuser to something thats gona happen. Im baffled.

 

Tough to say, I would still investigate the belt unless you are absolutely sure that is not the culprit. It wouldn't just squeal when you first start the car. If you had the AC\defroster running, it would put more load on the belt and cause the squealing noise along with pressing the go pedal.

Maybe grab some belt conditioner from that auto store the next time you're there, apply it and see if the noise comes back. Good luck in narrowing it down.

 

Yeah i thought about the ac/defrost and it did it with it on and off. The belt looks ok(no cracks yet) but thats not to say its bad. And i really dont hear the belt squeal at all.

 

Well its still making the noise. I am able to get on to Mitchel ondmeand at work and i guess maybe the IMRCs will sometime make the noise that i have been hearing. (Spark Knock they call it) If i am right i have to pull the upper and lower intake off to get a peek at the IMRCs to see if the plastic bushings are gone or a rod its sticking. Need some advice on whats the next step here. Thanks Dave

 

What what RPM range does it sound like a "cop siren"?

 

I couldnt really tell you, no rpm gauge. But it is on moderate acceration. If i would have to guess i would say round 2800-3000 rpms. I also notice sometimes at idle, it just sounds dufferent.

 

I would take the accessory belt off the truck and run it for about a minute without a belt. See if it still makes noise. But don't drive around with no belt... just start it up, give it some gas and listen.

Hmm... It sounds like the exact thing happen to me this year and it was my alternators shaft and the two idler pulleys and the tensioner pulley that got that noise to stop. It sounded like a cop siren...

To check your alternator, I would take it out, and rotate the pulley on it, and watch it carefully. Does it wobble? If so, then it is bad. You need to look at it carefully. Another trick is to use a screwdriver as a guide, and keep it close to the pulley, rotate it, and if at any point it touches, it would be bad. But watching how it rotates is key. If that is the case, then the shaft is bad in the alternator. IF not, then the bearings are likely shot.

I highly suggest going with a NAPA NEW alternator. I bought one for my truck, and the voltage regulator is precise -- it keeps the voltage at a perfect 14.3 volts!

If you are going to replace the alternator, I highly suggest replacing the pulleys as well because they could've gotten messed up to. They run on needle bearings too and with the alternator hopping around like that, it more than likely screwed the bearings up.

Now why did it all of a sudden do this? I don't know. I have no clue how the shaft on my alternator got bent at only 30,000 miles. But it threw my Ford dealer through the loop. Until I got the right people involved, did I figure out what was wrong.

 

Ok, i guess I might go with that instead of comdeming myself to an intake job. Sure is cold right now, and i dont have alot of extra dough. I know my belt needs to be replaced, not horrible bad but bad enough. So I think i take a look see tonight and go from there.