car surges/rocking at idle whether at idle or in park but runs fine. have new plugs and wires new 02 sensor and mas air flow but still the same problem
I can’t figure out what the “rocking” at idle means. But the first thing to look for with a surging idle is a vacuum leak. There’s probably a schematic of the vacuum system under the hood that may help. Don’t forget the brake booster itself and also check the intake manifold/all things connected to the intake.
Another thing you can do is give the idle air control valve a good whack with the handle of a screwdriver or something. If that affects the idle at then you may need to clean or replace it.
Is it rocking like there might be a bad motor mount? Is there a check engine light on?
surging is also a correct word, no vacum leaks and nothing lose from intake manifold. pulled following codes:p0171 p0174 p0300
Well, the codes surely do help. I’d ignore the P0300 for now since it very possibly may be a secondary symptom of the P0171/P0174. I’m sure there’s a factory service manual that would give “official” diagnostic steps, but in general there are certain things I’d set aside for now. I’d not assume intake gasket problems or false O2 sensor reading problems - its possible but that would be too much like an odd coincidence for both banks to have a problem at the same time.
The first thing I would do is clean the MAF sensor, reset the codes and see what happens. If that doesn’t work check the power supply to the MAF with a voltmeter (even better if you have access to a scan tool.
If none of that did anything I’d pull the intake tract off and inspect everything carefully all the way from the air cleaner box to the throttle body. I don’t know how you know there are no vacuum leaks - these can be really hard to find even when you’re looking. A vacuum gauge would come in handy.
I would also check the fuel pressure. Lean is too much air but one of the reasons you get a reading of too much air is that there is actually not enough fuel.
Anyway, I’m betting on either a fuel pressure problem or a vacuum leak problem that you haven’t found yet.
most common cause of p0171/174 is upper intake leaking at lower intake. It will leak mostly when cold. After the engine warms up it will probably mostly seal. I diagnose this with a scanner and a can of brake clean. Watch the O2 voltages and fuel trims while spraying. Fuel trims are most likely positive now but will take a negative dive when spraying if there is a leak.
we have tried so much already now we hear to try fuel pressure regulator and maybe even the filter, maybe even the fuel pressure sensor,tired of sinking money into it already. we just took it back to the shop/carlot to see if they can figure it out. but please keep the advice coming, thank you guys.
Did you actually get a fuel pressure gauge on it yet? I’m not sure what you’re spending the money on unless you’re paying someone else to check these things out. You don’t “try” a new fuel pressure regulator, if by that you mean install a new one to see if it works. You find out if it has a problem. To see if its leaking you can just pull the vacuum line & look for gasoline - there shouldn’t be any. But you can also tell with a fuel pressure gauge on there. Unlike a pressure regulator, a fuel filter is something you just change b/c that is a matter of basic maintenance, not repair.
Also don’t miss pete perters note below about the intake.
for all you guys who gave free advich, thank you. but the whole problem was a crack in the pcv elbow so the car runs good now. yesterday, i put a new ac pump on what a fun job that was .thank all of you again