DanMan35

So my engine light came on yesterday and the error code is P0174 and P0171 "system too lean". I found out this usually means there is a vacuum leak somewhere. I took some brake cleaner, started the car and let it idle and sprayed brake cleaner and every time I sprayed right where the throttle body and intake meet the RPMs would increase slightly. So the leak seems to be right there but I can't seem to find it. Both clamps connecting the intake and TB appear to be tight. I can't find any loose connections or hoses or anything like that.

When I spray brake cleaner right on these two clamps is when the RPMs raise slightly.


This connector seems to be pretty loose when I move it by hand. Seems looser than what would be normal. But there is no way of tightening it. It's simply a connector that snaps into place.




This piece is what the connector connects to and this piece seems to be very loose inside of the rubber grommet in the intake. But once again there doesn't appear to be any way of tightening this.


This is a gap between the intake and the clamps connecting it to the throttle body. Is this gap normal? Is this what could be causing the leak?

sillycon

Have you taken the coupler off to check if it's cracked?

MTPZ06

^Agreed...I'd be pulling it apart for a closer look.

atljar

But to answer your question, correct way to diagnose is with a smoke machine. It will inject a fog into the engine and show you where vacuum leaks are

stefuel

Any place that spray blends with air for combustion will cause the rpm's to change. If you are looking for a vacuum leak that is changing rpm's it would be on the engine side of the throttle body blade. Try getting that spray on where the throttle body bolts to the intake manifold. What was the most recent thing done to the engine? Look there. I think in your other thread you just picked it up from the shop. Bring it back.

Michael_D

They sure do come in handy when these pesky leaks come up...... He'd need to wrap the filter pretty good, or remove it and tape up the connector.

I made one. About $25 in parts and maybe two hours tops. Only downside is it uses baby oil, and couldn't find any that was unscented...... I get funny looks by people walking by when I'm using it......

JaredW

Which vacuum line do you use when you do yours?

Michael_D

Depends on the vehicle. I was looking for one on this car, and I just taped up the throttle body opening, and inserted the hose through a small hole in the tape. Seeing how most of the vac lines are routed to the intake manifold, you should be able to check all of them.

dp201

Check the connections on the opposite side where the MAF enters the cone. I had the same codes and the smoke machine showed it coming out of that connection. The screw to the rear of the MAF sensor had backed out and allowed air to enter behind the sensor. This caused a lean mix and threw the codes. I replaced the screw and the small spacer which solved the problem.

DanMan35

I ended up taking it to a local shop. The guy looked for about an hour before finding it. He said it was a hose that was routed wrong. He corrected it, cleared the codes and it drives great now. Idle is nice and steady at 700 RPMs.