Gators2kt

Hey everyone,
I searched and found people with similar problems but not exactly the same. I also tried some of the fixes that worked for other people. My car recently started sputtering and running lean. I left my apartment and drove about a mile and it was fine, then I was stopped at a light and started accelerating and the car felt like it was misfiring and my air fuels were reading 15-16 under normal acceleration. So I limped over to my brother's house and started trying to figure out what was wrong. The engine is built with forged internals and it's turboed as well. I just recently replaced the turbo manifold because of an exhaust leak and it ran fine for a couple of days then started acting up.

I checked all the vacuum lines and they looked fine but I replaced them anyway. I ran fuel system cleaner. I also had half a tank and filled it up again just in case I got some bad gas. I checked the valves and all the clearances were within spec. The spark plugs looked fine as well. I actually can't take out my MAP sensor because the screw heads are sheared off completely so I sprayed electrical cleaner into the ducts and let it dry. I checked the fuel injectors and my fuel pressure is still the same as before. There's probably a couple of other things that I checked too but can't think of.

The car "usually" runs fine for a while then it warms up and starts running like "crap." Something might be expanding and causing it to sputter but I can't figure out what. Sometimes the car is fine and others it starts right away. Any help is appreciated.

Gators2kt

Oh, and I'm running an AEM EMS, and I haven't gotten any CEL.

T-Smac

Could be Engine Coolant Temperature sensor. If it thinks it is warmer than it really is (low resistance), it will deliver less fuel.

s2klariat

You may have better luck in the "Forced Induction" section. But you say these issues started after changing the turbo manifold? Check for pre-turbo exhaust leaks and also all inter cooler piping. It sounds like you have a large boost leak somewhere.

Gators2kt

s2klariat, I'll repost in the FI section too.

T-S.M.A.C, I did a little research on the coolant sensor and I'll have to check it out. For the most part though, people said that it would run rich when the sensor goes bad because it would read cold all the time. Maybe mine is doing the opposite?

I just drove the car around for a bit and it ran perfect. Then I let it sit for like 15-20 mins and as soon as it fired up the car was idling horribly and running lean (in the 16-16.5 range at idle). Very frustrating to trouble shoot this issue.

I already started prepping to replace the fuel pump; it's a Walbro 255hp with less than 15,000 miles on it so I don't think it is the issue because the fuel pressure is reading fine. I was gonna change the spark plugs anyway just for peace of mind but I feel like if the plugs or coil packs were faulty it would run rich?

egprelude

If the fuel pressure is fine, don't change the Walbro. It could be possible it's loosing pressure as your drive but probably not as likely.

Take a video of the problem. Does it sound like a bad misfire at idle? If you rev it higher, ~3k, does it feel the same?

Gators2kt

I'll try and take a video, basically, the car runs fine when it starts up cold...usually I can only think of one time since this is been happening when it started missing when it was a cold start. When it warms up it starts giving me problems. Earlier it ran fine at all rpms up to about 6k I hit boost under 75% throttle and the car didn't hesitate or misfire. If I drive it til it's warm and then let it sit and try and start it when it's still hot/warm the car runs like crap. It misfires at idle and has a "rumbling" sound, almost like a Boxer engine, whenever I drive it. If I barely give it gas I can keep the A/F under 14 but it still runs like crap and misfires a bit. If I give it anymore than 20% or so it bucks pretty hard and runs lean. Overall, after the sputtering starts, it doesn't matter what rpm the car just runs horrible.

I just tightened up all the downpipe bolts and manifold bolts because it looked like there was a small bit of carbon build up. I unplugged the ecu as well to see if it needed to "relearn" anything. I did notice that after I swapped out the manifold, the downpipe/exhaust is basically touching the transmission and the dumptupe for the wastegate is touching the downpipe. I'll probably cut the dumptube some so that it isn't touching anymore but the downpipe isn't going anywhere. I also noticed that the clutch pedal has a lot more "play" before it engages. It literally starts catching about 3/4 of an inch off the floor the rest of the way it just feels dead.

I just can't figure out why it starts off okay then something obviously gets warm and starts messing things up.

T-Smac

It would be reading cooler, but not necessarily "cold" (could be though). I would check the MAP sensor. If you have a voltmeter you can check the sensor and you don't have to remove it.

Here's what to do:
Back probe the connector going into the map sensor. (slide t-pins or sewing pins into the back of the connector, where the wires enter)
Make sure the pins don't touch each other.
Check voltage between the left wire on the connector (if you are standing at the front of the car), should be a yellow wire with a red stripe, and the negative battery post. Voltage should be around 5.0 volts.

With the car on and warmed up, at idle (800-1k) check voltage drop between the middle wire (green with white stripe?) and the right wire (green with red stripe?). Voltage should be around .8-1.0 volts

raymo19

And you won't - that's the downside to the AEM. As to the rest I'm SC'd so I haven't a clue.

Gators2kt

So I went out again to try and shoot the video, (it's really bad because all I had was my cell phone and nothing to hold it for me). There's a lot of rattling and background noise because I took off the top tray thing to get to the fuel pump and you can hear every noise from the trunk. Anyway, I forgot to turn the lights on so the gauges would light up but at the end of the video I turn them on and you can see that the vacuum is bouncing a little and the idle is all messed up. Also, something I forgot to mention is that I usually turn the air on because it richens the A/F, with it off, it normally runs in the high 14s and low 15s. With it on the car runs in the mid to high 13s. That's why I turn it on in the video, car runs the same with it on or off.

Again, all I had was my phone, but if you turn it to 720 and full screen it, it's a little better. Top a pillar is fuel pressure, bottom is boost, and A/F is lowest.

http://www.youtube.com/watch?v=aeXgzmJ-6pw