M20 revs down then a little up when gassing it

[Eydreeyun]

After I warm up the car, I try to blip the gas a little and it goes down first then up. It sounds like its not getting fuel, like it wont rev like a regular car. I'll post vid if hard to understand. Car is running fine since I bought it.

[jlevie]

And intake leak can cause that. Have a smoke test run on the intake and check vane in the AFM to make sure it isn't sticking.

[Eydreeyun]

I had suspicion on the intake, haven't check the filter yet. I'll let you know when I get off work. Appreciate the fast response.

[Eydreeyun]

I checked the air filter and look what I found, Ima clean the TB too


And heres the video of me blipping the gas and you can see the rpm goes down first then up.

http://s302.photobucket.com/albums/nn116/Heydriyan/Delphin%20e30%20only/?action=view&current=VIDEO0005.mp4

[Young Gun]

^I think you should also have a look at the 90 degree plastic intake tube, for leaks.

Did the changing of the air filter help your issue?

[Eydreeyun]

Changing the air filter didn't help and its still there. I cleaned the whole arm and the throttle opening. I rev the car with out the whole arm, when I blip the gas it still do the same.

[Eydreeyun]

still havin problem

[kamotors]

a bad AFM did that to me, every time i would try to rev it the RPMs would first drop about 300-500 and then rise.

[Eydreeyun]

How do you check if its bad? When I was cleaning the intake arm, I took the afm out and revved it with just the 90' degree intake boot/arm and it still does it. Second, I took the 90' degree boot to clean the TB, I revved the car with just the TB on(cleaned by the way) and it does same thing.

[kamotors]

How do you check if its bad? When I was cleaning the intake arm, I took the afm out and revved it with just the 90' degree intake boot/arm and it still does it. Second, I took the 90' degree boot to clean the TB, I revved the car with just the TB on(cleaned by the way) and it does same thing.

I didn't check I just got a different AFM and the problem stopped;)

[Eydreeyun]

Alrighty, I guess gotta find one at the junk. Will update when I change em.

[Eydreeyun]

UPDATE: Got the new AFM in, runs a little bit better now, but rev still goes down first on idle when I blip the gas. I ran the car without the filter box. Anymore ideas? I'm not feeling the torqueness of M20. The car had history of overheating. PO had the head rebuilt, new exhaust valves, cleaned the head, new HG, Hoses.

[Sagaris]

Mine did that and it was fixed by eliminating the vac. leak that was due to a slightly cracked PCV tube and a bad oil cap.

[Eydreeyun]

If I had a leak, would that change my idle? I'm not getting a crazy idle from cold to warm. Its stays in 800 til it warms up. It's just when I blip it, the engine chokes and is about to die on idle. but when I step on the gas halfway down. it revs to 1800rpm. Healthy engines revs about 2-3k just blipping the gas.

[lonestar22]

mine does that, kinda stops for like half a second before it goes up. doesnt really go down in rpms though just kind of pauses before the upswing. ive never had an issue though. its only when its just started though