Air Intake Question 2.9

[1SG OX]

I have a question, not critical ATM not driving the Bronco, waiting to upgrade to a 3G alt. Anyway, when I first start the vehicle:

1. It does not stay running on the first try, about the 3rd time I start it, it will stay running at idle.

2. Once I get it running it sounds like it is sucking alot of air into the intake, almost like hearing a vacuum cleaner draw air in. Has an aftermarket air intake. Just sounds odd, because I am not used to the air sucking sound on an engine, not to this extreme anyway.

3. If you get the vehicle under a load it wants to stall out, does not matter if it is hot or cold, once you get up to speed it seems ok, but if you stomp on the throttle it wants to stall and it does backfire at times.



86 Bronco II, 2.9l, 5 Speed manual.

I have checked and cleaned a few items, throttle body, MAP, TPS to name a few. I have not however, pulled codes or checked the timing. Plan to dig into this issue down the road, but just curious if anyone has had an issue with too much air into the system.

Thanks

OX

 

[90B2Loud]

If you have the stock intake put it back on and see if it still has the issue almost sounds like the engine is leaning out

Sent from my LGMS330 using Tapatalk

 

[1SG OX]

I thought about adding a stock air box back to the system just to see if there is any change. May do that down the road, have the parts from a ranger. Bronco came with the aftermarket air filter on it. Just seems odd to me is all. Not sure it is a real issue, just more curiosity at this point. Thanks for the feedback.

 

[ab_slack]

It is probably making that noise because the throttle body plate is closed restricting air flow. So you are essentially hearing it move fast thru the limited opening.

If you ever watch manifold pressure you will note the highest vacuum when it isn't being given gas and throttle body plates are closed. When you give it gas and the throttle body opens the pressure drops as it can more easily get air and then as RPM goes up generally the vacuum increases.

The engine doesn't just suck more air. It only pulls air by the normal operation of the pistons pulling intake air when moving down while the intake valve is open. Mechanically speaking the engine can't take any more air unless the pressure is higher. A higher pressure would involve things like throttle body plate being open but or air leaks in the throttle body or mounting allowing air in ways it shouldn't.

The fact it is making lots of noise at the air intake sounds normal air flow restrictions (louder when more restricted). But if the air rushing sound isn't from the intake but from other places like the base of the throttle body it could mean there is a leak someplace and that can cause problems. Much of this can easily be diagnosed by hooking up a vacuum gauge.

By all means though, pull the codes and also run the KOEO and KOER tests which will be part of the getting the codes process. Those tests will identify sensors that are grossly out of range and a number of things that may not be functional.