lumpy idle and studder under boost and lean

[mattmann]

Ok so I can't get my car to run quit right. Here are the symptoms.... 1st Lumpy idle and almost sounds like an inconsistent miss, when this happens the afr jump to 16-17 lean( otherwise it idols with a 14.5-15.5 afr). 2nd at idle I have only 14 lbs of vacuum on the boost gauge. 3rd under boost the wants to go lean towards 13.5afr and rarely gets to 10.5 or 11 unless it's the first pull on the engine once it's warm then it progressively gets leaner and leaner each time under boost. Side note also while under boost the engine seems to break up and stutter then slams back into boost.

As of now I have pressure tested the system with no leaks up to 10lbs ( I'm only at 8lbs) and I also did a smoke test with no leaks at all. So for now I'm ruling out a vacuum leak. I'm working on rigging up a fuel pressure gauge to see if my fuel pump is going bad.

Here are my current mods... Rebuilt motor with eagle hbeam rods, probeforged pistons .02 over, balanced rotating assembly, ct-26 57trim, front mount intercooler kit with factory recirculation valve, BC 264 cams with titan adjustible cam gears, and I believe it's Arizona speed upgraded oilpump, oh and full 3angle valve job with BC valvesprings and retainers. Everything else is stock.

I also tester thi iac and set the tps. Car seems to drive fine other wise. I had to advance the exhaust cam and retard the intake to get ride of some overlap to get it to idle at all but it starts up fine and drives fine without boost but I don't like to drive around like I sit down when I pee so this is really bothering me lol😂😂 If anyone has any input it would be great!

 

[KKZ SupraMan]

First thing that comes to mind is timing is off you need to figure out why the car won't idle at all with cams a tdc it may be a little lumpy because of the cam change but that shouldn't stop it from running. Also test pump and run 12volt mod.P.S I would also like to say first :biglaugh:

 

[hvyman]

cams need to be degreed. without properly adjusting the cams you wont get any sort of decent idle. and the factory ecu doesnt like big cams.

have you done the 12v mod for the fuel pump?

i would also look into some sort of engine management,

 

[mattmann]

KKZ and hvyman thanks for the help and they would idle at tdc but it's was horrible, soundind like it was fighting just to run lol. Also how do I test the pump. I just ran the 12v mod and it does not studded now under boost and the afr's were in the 10's on the last test drive. It does seem a little under powered and I don't know what would cause the -12 vacuum at idle. Shouldn't it be around -17 to -20 at idle? I do need to degree them but I don't have the tools yet and I'm still reading up on how to do it be for I attempt. Btw hvyman what type of engine managment would you recommend? As of now I'm kinda hooked on a aem standolone since I can use me wideband and boost gauge with it. And of course thanks again for the help!!!

 

[KKZ SupraMan]

KKZ and hvyman thanks for the help and they would idle at tdc but it's was horrible, soundind like it was fighting just to run lol. Also how do I test the pump. I just ran the 12v mod and it does not studded now under boost and the afr's were in the 10's on the last test drive. It does seem a little under sporadicd I don't know what would cause the -12 vacuum at idle. Shouldn't it be around -17 to -20 at idle? I do need to degree them but I don't have the tools yet and I'm still reading up on how to do it be for I attempt. Btw hvyman what type of engine managment would you recommend? As of now I'm kinda hooked on a aem standolone since I can use me wideband and boost gauge with it. And of course thanks again for the help!!!

I have always preferred aem or some type of full standalone one thing that I am anxiously waiting to play with is the infinity ecu but i have seen some good things done with maft pro and map ecu its all what you on what you choose. Make sure you are getting proper fuel psi from the pump check fpr guage to make sure you are not getting sporatic readings.to test for boost leak i have a compressor set to 15psi an adaptor to fit pressure hose to turbo inlet not afm inlet afm must be removed then soap and water away where you have bubbles you have boost leak and or vac leak. I would also try a second boost/vac guage if you have a friend or an extra I have ran into guage being wrong also cams will effect vac to what rpm are you set to at idle.

 

[hvyman]

You won't get as much vaccum at idle with cams.

You also have a lumpy idle and the the stock Ecu fights it.

 

[KKZ SupraMan]

You won't get as much vaccum at idle with cams.

You also have a lumpy idle and the the stock Ecu fights it.

100% correct

 

[DeMoN2318]

All these engine mods and still stock fuel system?? interesting...


If you are going to go standalone, go ProEFI 128.

 

[mattmann]

KKZ Supraman i have a boost leak tester that sounds about what you have, and a snap on smoke machine for vacuum leak testing. The smoke machine is amazing!!! As for the testing the fuel pressure im tapping a spare banjo bolt today to fit a fuel pressure gauge. I do need a full time fp gauge and bigger fuel pump, i have a fuel pressure regulator but i need to get the install kit. The shop i go to by where i live likes aem so ill probably go with that for tuning purposes and like i said before it would also work with all my gauges. just rad up int new infinity system and that sounds like a BAMF:: angry ::. Does anyone know of a good write up on how to degree cams? I have found a couple but their not 7m specific... not sure if that matters i imagine most dohc engines are the same until you get into variable valve timing engines. I thing i read somewhere you have to pull the crank pulley to mount the degree wheel since the crank bolt i recessed. I've tried to get a couple people locally to help me out but it seems like either no one knows what a 7mgte is or runs when the hear about it lol. Thanks again for the info hvyman, KKZ Supraman and DeMoN2318

Oh and one more thing with these mods at only 8 psi could i really out of the factory pumps duty cycle? Thanks again:biglaugh:

 

[mattmann]

p.s. what seems to be the best choice for a fuel pump just curious???

 

[KKZ SupraMan]

p.s. what seems to be the best choice for a fuel pump just curious???

If you want to stick with the in tank design wal bro 400 works if you go with the out of tank I prefer aeromotive 1000 I would also get some adjustable cam gears to help with the timing. As for the fuel rail I have used a tap to accept A/N fittings just make sure you clean fuel rail inside and out before reinstall. infinity ecu you run all your own wires and what sensors you want to use no plug and play harness options yet to my knowledge.