RPMS drop low after i rev the engine

[boosted954g63]

Every time i rev my engine my RPMs drop down to around 0 then my dash lights come on and then it bounces back up to normal idle at 900. I checked the battery and alternator to see if that works and it did not. I also unpluged the ISC to see if i changed the idle and it did not change any thing. I am going to do a boost leak test after i get done with posting this. I am totally lost on what could be causeing this. Any help would be great.
Thanks Nick

 

[andymoraitis]

When you pull the ISC, it's a good idea to disconnect the battery to re-set the ECU. Also, are your vacuum readings normal? If not, you may have a nasty vacuum leak that's causing the RPM falloff. To check for these, run the car at idle and spray carb and choke cleaner around your individual vacuum lines. If the idle changes, you have a leak.

Try than and let us know if it works,

Andy

 

[weaver]

I had a similar problem and once I replaced the biss o ring and adjusted the biss it took care of the problem. A boost leak test is probably the best thing to do right now.

 

[bluetlr2001]

Is your bov vented or recurculated. And has your adjustment screw backed off the bov some you may want to check that.

 

[boosted954g63]

Wow great idea!! I will do that in a few minutes and post the results. My boost guage is reading a little under -20 at about -17 or -16. Keep on coming with the great ideas!
Thanks Nick

 

[boosted954g63]

Yes my BOV is recurculated i know better . I will check the o-ring on the biss screw and adjust my BOV too.
Thanks Nick

 

[andymoraitis]

Your vacuum is a little low for your altitude, but nothing that I would consider alarming. Definitely check the vacuum lines and also spray around the biss as well. The posters who brought that up have a very valid point. If the idle is OK and you lost the O-ring, you can either replace it or fill it with RTV black to seal it temporarily.

 

[boosted954g63]

Ok i found one boost leak it was the BISS screw so i fixed that and no other ones i could find and it also held the pressure for like 15 sec. I noticed the PVC valve hose was pintching when any vaccum was present so i replaced it with a thicker hose. Now whats going on. If i rev the engine when it is not in gear it will go back to the correct idle but when i get done accelerating in gear and press on the clutch it dips down and bounces back up again to normal idle. Also i have had a previous problem of sputtering and stalling under boost at like 3 grand, but now it is doing it at 4 grand. O ya my boost gauge is reading -20 at idle now so that is normal again. Thanks for all the help so far!! Hope to keep seeing all this great help even more to solve this problem!!
Thanks Nick

 

[andymoraitis]

Nick,

Now that the idle issue is sorted out, we can go after the misfire. I would replace the plugs and wires if they haven't been done recently. If you have replaced them recently, I'd make sure the gap is correct at .028-.030. A bad gap can cause the spark to blow out. Another thing to look into is fuel starvation. If the fuel filter wasn't replaced in the last year or so or if you're not sure how old it is, change it out as that can cause the same symptoms.

About the bouncing idle when pressing in the clutch, I have cams and my motor will dip and sometimes catch itself. I consider it normal and not a big deal unless it drops very low (200-300 RPMS)

Keep us posted...

 

[boosted954g63]

Ok i will try to replace the fuel filter tommarrow. I did another boost leak test and i found that my boost gauge is leaking! i am hooking it up with out the boost guage now to see what happends. Thanks for your all your help!
Thanks Nick

 

[boosted954g63]

Ok nothing has changed so far i have tried all that i could have tonight. I did a OBD-II reading and it came up with 4 codes(listed below).

P0136 O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0335 Crankshaft Position Sensor A Circuit Malfunction
P0325 Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)
P1400 Map Sensor

Those could be easily causeing the sputtering and bucking when it hits 4000 rpm but will any of those help with the idle?
Thanks Nick

 

[boosted954g63]

Just a update. I am going to order the crankshaft sensor and the knock sensor tommarrow i belive. Hopefully that will that care of my sputtering but i am still lost on what do do with the idle surge. Any help is greatly apreachated.
Thanks Nick

 

[boosted954g63]

Another update. I replaced the knock sensor but it did not solve any problems. It still bucks and stutters when it is boosting. The idle did not dip as low as it used to. It hits about 500 rpms and then bounces back up to normal after i accelerate in gear. I am lost on what to do next and i really need some help on what to do. I notice also that my oil pressure gauge does not move at all, even when the car is off. Is that normal?
Thanks Nick

 

[Tobuk]

My car does the same thing. If I press in the clutch after getting the engine above 3500 or so, my idle dips down to 200-300 before it bounces up. It has stalled once from this problem, but it's normally not a big issue.

For now I just blip the gas a little when the RPMs get close to idle and it doesn't dip at all.

Now I'm wondering what it is too...

 

[boosted954g63]

Thats what i have been doing when it starts to dip. But i just hate having my car not running at its best and its kind of annoying to do that.
Thanks Nick

 

[boosted954g63]

Car still does the same thing with the idle dip. I cant figure out whats doing it. Any more ideas of what could be causing this?
Thanks Nick

 

[Newlogics]

Car still does the same thing with the idle dip. I cant figure out whats doing it. Any more ideas of what could be causing this?
Thanks Nick

Are you running stock or alum. flywheel?

 

[boosted954g63]

Yup just a stock one. Have not messed with the tranny at all.
Thanks Nick

 

[Newlogics]

Yup just a stock one. Have not messed with the tranny at all.
Thanks Nick

If you can source a good used ISC, I suggest go ahead and put it in to know for sure if it's your ISC or something else that's messing with the idle.

 

[redeclipse7782]

If you can source a good used ISC, I suggest go ahead and put it in to know for sure if it's your ISC or something else that's messing with the idle.

I agree, ISC's have been known to cause these issues, to the point were a lot of people have completely eliminated them on the 1g throttle bodies, I'm not sure if they can be eliminated on the 2g throttle bodies though.

 

[Laysher91]

In addition to fixing your CEL...I would properly set the curb idle speed: 1. make sure your TPS is set correctly 2. Make sure your throttle cables are within adjustment 3. Set your BISS screw. If one of these is out of adjustment and you try to fix the problem by over-adjusting the other two...you're in for a big headache. Good luck

 

[boosted954g63]

Well i have to order a new one to see if it is it. Thinking about it i unplugged the isc and it did not change anything at all and stayed the same. I will have to order it tommarrow or find one real fast.
Thanks Nick

 

[boosted954g63]

Well i have been looking up prices for them and i cant afford a new ISC right now. So does any one have one in the kansas city area that i could borrow or buy from them cheap? If not i will just have to wait till i save some money for it.
Thanks Nick

 

[jongreene]

Hey Ive been having the same problems. Seafoam fixes it for about 2 days but then it goes back to sputtering and when I rev, its not smooth at all until around 4k. NO CEL's either ,what could it be?

 

[dr1ftx3]

I get the same exact thing, but it only started happening after my big turbo upgrade, fmic/injectors/evo3/ etc etc. I've just been giving it some gas at about 1k to stop the dip down. It doesn't seem like a huge problem, more of a slight inconvenience. Oh well.