Im stumped. I have a freshly built Ls block with a gsr head. It starts great and idles but when I hit the throttle its falls on its face hard. If i very slowly get it past that point it revs quick and sounds great. As long as I hold it above that point it comes up and down like it should but from idle it will bog all the way if not die. I have chacked all sensors, checked for vacuum leaks, checked timing multiple times and it is all as it should be. Fuel pressure is steady at 38-40 throughout. And there are no check engine codes except vtec solenoid which I dont have wired yet. Any suggestions?

 

A couple more details in case it helps. Stock bottom end and top end just rebuilt, header, stock throttle body and injectors, skunk 2 intake manifold, and a p30 obd1 ecu.

 

Do you have that fuel damper on the end of the rail?
The one that uses a special washer? If you use a regular washer on it, it will not supply enough fuel.

Just a thought. I've seen that before.

The plug for the tps and map sensor are the exact same plug I believe so make sure those arent backwards.

 

Yeah fuel rail is good and I've traced all plugs so they're good. I went ahead and reset the tps so the voltage is right on.

 

I dont know why the video sounds like it does. The motor just falls off when I hit the throttle not whatever it sounds like in that video but it might give you an idea. Its hard to tell but the last part of the video I slowly get past the dead spot and then you can see how nice it revs after that.

http://youtu.be/7pImlEmHAbU

 

Almost like; not enough spark to ignite the fuel. The cylinder is being over loaded. hmm........I'm just trying to help so my next step would be. Pull the spark plugs and see if they are covered in fuel or dry/normal. Do that and get back with me.

once again, this is just what i would do

 

Do you have a wide band o2 sensor on it? You should and it would tell you if it's getting enough fuel.

 

All suggestions are appreciated man. I messed with it for a while tonight to no avail and went ahead and pulled the plugs. They look great, nice light burn and no wetness.
Oem O2

 

As previously stated, do you have a wideband o2? And is the car tuned on anything?

 

Is there just a dead spot in the TPS? Maybe you need to replace your TPS or your throttle body.

 

Additionally, the two plugs on the back side of the engine are the same. Make sure you didn't swap them by mistake.

 

I have another tps I can try so Ill try that tomorrow and Ill try to get my hands on another throttle body. The harness is plugged up right, I have checked that multiple times. As I stated in the earlier post it is an Oem O2 sensor and no the car isnt tuned on anything. Its running on a p30 which came off of the same build which was running great. The P30 map is fine for a stock internal ls vtec. I also tried the chipped p28 out of my daily and it did the same thing.

 

make sure you dont have your tps and map sensors pluged in wrong , happened to me before. i had the tps engine harness pluged in my map sensor

 

I exPerienced similar problem with my Gsr swapped ek

I had used y8 internals on my Gsr dizzy and one of the plugs within was just resting on its contact. It would run fine till I ripped it and it would come apart and fall on its face

Assuming you didn't tamper with your dizzy may not be the case but just ideas

 

Sounds good to me, Ill check it tomorrow. I didnt mess with the dizzy plugs but you never know. I wish I had another one to try.
Again I appreciate the suggestions but I assure you all of the harness is plugged into the right spots.

 

You got me stumped bruh lol

 

For those trying to help I have couple updates with no good news. I tried a new throttle body and removed the spacer first but it didnt help. I rechecked the plugs but they are all good and I tried the distributor off my b17 but again same problem. I went ahead and checked compression but all four cylinders had good numbers within 3 pounds of each other. So basically Im still stumped.

 

Map sensor?

 

Nope, already changed it once plus the throttle body I tried had its own.

 

You may have to swap one of the wires around on your MAP, or TPMS. I had a crx with a 96 ITR motor obd1 converted, doing exactly what your describing. It would cruise just fine but would fall on its face at wide open throttle. Id double check the 3 wires on both plugs and make sure they're in the right places.

 

are you sure the ecu is good? try swapping it with a friend and see if that works

 

Yeah I have a chipped p06 and a chipped p28 also. Tried them both and no change.

 

detonation!

 

Have you checked your timing?

 

Seriously, you need to verify your statements with pictures or detailed information.

For example:

Post pictures that allow members to verify that the wire colors in connectors match to the sensors.

Have you checked the ignition timing with a timing gun? If so, what did you align the pointer to?

Does the problem happen only when the engine is warmed up? If so, unplug the O2 sensor to see if the problem is eliminated.