Hi guys, I have my 3.5 swap done 2 weeks ago and have been driving it 3 days a week. All seems fine but I have 3 issues. 1) When i start it up, i need to press on the gas and keep the idle at 1000 to 1500 rpm manually and then after a minute, i can let go of the gas without it stalling. 2) sometimes, my idle will drop below 500 rpm and if i go to a stop then my engine will cut off even if i have my foot on the clutch pedal. 3) my engine backfires alot...could i be running too rich?

Thx for all the feedback guys


B.

 

no insight?

 

Your timing might be off. See if you can borrow a timing light from someone.

 

What are you using for idle control?

Backfiring is possibly due to valve overlap. Depending on how your intake cams were drilled, you probably have considerably more valve overlap than the VQ30 you replaced. If it is just some burbling and popping out through the exhaust when backing off the throttle I wouldn't worry too much about it.

 

Yeah, is the IACV hooked up? Are there any vaccum leaks?

 

Just to clarify i was referring to cam timing. This would subsequently throw the ignition timing out of whack and would be made apparent by using a timing light.

Edit: You're right stephen max. The timing could be on point as far as the ECU and crank postion relative to cam sprocket postion is concerned and still be off if the drilling job was botched.

 

Having more valve overlap than the oem VQ30 is not necessarily botched. When drilling the intake cams you have to make a decision about intake cam timing. Advancing the intake cam (which will also increase valve overlap) results in efficient high rpm breathing at the expense of torque and idling smoothness. It could also result in some backfiring when backing off the throttle. Retarding the intake cam will give good idling stability and good torque, but at the expense of power. A compromise has to be made.

 

I understand the theory of cam timing. But i'd be pretty upset if i had to keep my foot on the gas to keep it from stalling at start-up.

 

I think that is probably due to IACV issues.

 

I apologize if I sounded condescending. I wasn't trying to be.

 

So when you re-drill my cams for me they will not be in the original position?

 

that is because of the iacv

 

Thanks guys, That really helps. Indeed, the backfire is heard when i let go of the throttle. I'm glad i don't have to worry about that. As for the drilling, i sent them to Tilley so i guess that it is good. You guys are right on the money with the IACV. It is off right now. Still trying to figure out how to add it to my setup. Doesn't seem to have a place where i can put it on the 3.5 IM. If i find a way to add the IACV, do you guys think it will fix my stalling problem when i slow down or go to brake? This problem only seems to appear after an hour of drive or so in the city.

 

oops sorry as for leaks in the vacuum, there is none, i brought it to my mechanic for him to check it with the Leak master.

 

Not unless you want the intake cam timing to be in the fully retarded position. Otherwise I will use the same amount of advance that Tilley uses.

 

I think adding the IACV will fix your problems.

 

I know of at least one 3.5 swapper that is running sans IACV and doesn't have to hold his pedal down during cold start-up.

 

To those who did the swap, where and how did you install the IACV??? thx

 

This is how I did it:

http://forums.maxima.org/showthread.php?t=408291

Look at the last picture in the first post of the thread. The IACV is mounted to a plate that you can see on the backside of the intake manifold towards the passenger side.

 

If you have the throttle butterfly plate opened far enough you won't need to, but idle speed increases a couple hundred rpm as the engine warms up, depending on how cold the weather is. How high is his idle with a warm engine?

 

1300-1400 RPM, when it's really cold, I just have to tap it once so it won't stall. And it idles at about 1200 until its warm and then it rises a few hundred RPM. When it's about 35 degrees and up it starts on its own just fine.

BTW I am using a modded 2k2 TB, and no IACV. (no fast cam idle etc)

 

nismo3112, how about when the car is warmed up?

 

Starts fine every single time when warm.

 

no whats the idle?

 

1300-1400 Rpm

 

That's a about twice the normal speed. I don't doubt at all you don't have any cold engine idle problems.

 

my idle when warm is 650. 1300-1400 rpm is very high especially when warm

 

Thanks Stephen max...ur pics sure helps me out alot. i'll talk to my mecanic and see if we can make an adapter like yours.