Do I Have Vacuum Leak?

[svarog]

Hello I was changing my spark plugs.

Took of upper intake manifold to get to rear ones. Replaced plugs with NGK.

Everything ran great for a day.

Then I had p0170 and P0305, fuel trim malfunction and cylinder 5 misfire. Car would drive great but in park and idle it would shake felt like vacuum leak.

Then it would do a bunch of random misfires, P1300.

Now I put in new pcv valve and some new vacuum hoses and the only code I get is p0170.

Now in just D idle car idles at 700 rpm and feels great, in Park it idles at 700 and goes whoom whoom.

So what is causing my p0170? I checked hoses 100 times, intake is good, I had same error code few years ago, and fixed it by replacing cracked intake.

Is it vacuum leak that I can't find? if so, is there some simple way to figure it out, without some smoke blowing devices or infrasound or something similar which I googled.

Thanks in advance!! I want car to have no Check engine Light before I do more stuff

[92Lex]

Carb cleaner or propane would work to find intake vacuum leaks. Did you replace the manifold gasket? Spray some carb cleaner around the suspected parts and if the RPM suddenly increases then you have found the vacuum leak. Carb cleaner is extremely flammable, so I'd use it with caution.

[Toysrme]

Vacuum gauge for the win. :)

The biggest, "should own, but never used" car tool ever. Even professional mechanics have quit with the vacuum gauges.

[svarog]

Thanks, I am scared, but will try with carb cleaner tomorrow!

[tckcumming]

Thanks, I am scared, but will try with carb cleaner tomorrow!

Don't be frightened, everything will be OK....

I agree w/ 92lex, carb cleaner could do the trick. Warm up the engine, make sure the A/C is OFF. Use the little red tube on the nozzle and just squirt a little shot at each spot you think a vacuum leak could be. Don't forget to spray a bit around your intake too, even though you've replaced it. And around the brake booster hose. Any change in idle when you spray, you've probably found your leak.

I've used this method many times on some of the old beaters I've owned over the years, it usually works.

Good luck, and be brave!

tck...

[1995_ES300]

I still have the same problem. No issues until i took my manifold off. I beleive it may be related to the oxygen sensor...but i am not sure. Ive had the cel for about a year and I have just learned to deal with it since I still get about the same mileage and the car drives fine. It just idles rocky in neutral or in park....give it a tad of gas and it does away...almost like the idle is a bit too low.

[1995_ES300]

Hey guys...I think I found the source of this mysterious vaccum leak. Right under the throttle body next to or on the IACV. When I cleaned out my throttle body and shot the carb cleaner in the IACV hole inside the throttle body, the cleaner started to drain out a little bit from the bottom.

I put my finger under there when I started my car, and I heard I high pitched whistle noise when I had my finger on the suspected area. There is air being sucked in at that point. Next weekend I will dismantle and see what I find.

Svarog, see if this is where your problem area is...

[1995_ES300]

It is the gasket that meets with the manifold and the throttle body