I need help with this 3800 rpm crap!!

[Mr. Griff750]

Dammit!! Ive been working on this damn problem where my cars secondary injectors dont fire at all and it's a bit irritating. Ive reground the battery to the chassis and to the engine block, reground the MAP sensor, and a bunch of other small crap. I really dont want to pull the UIM, but if I was to I dont know what I would do. Check the connections? Isnt there a way I can do that without pulling the UIM? Somebody please guide me in the right path!!

[J-Rat]

Okay...

First thing. When did the problem start occuring? Can you free rev above 3800 in neutral? More information please!!!! When you hit 3800 under load is it a brick wall? Or does it stumble on?

And you regrounded the MAF? What in gods name for?

If you know what the pressure sensor is, try removing the vac line from it, then taking a drive... 3800 wall gone?

[MBTN]

In neutral it won't matter because the 5/6 don't open. They are probably stuck if you've redone all the grounds properly.

[J-Rat]

Stuck 6-ports will NOT prevent your car from revving above 3800 under load.

[Mr. Griff750]

My car has done this since I bought it (for 200 bucks but it needed a tranny which I replaced). I can rev above 4K in neutral, but not as fast as it should rev. When I hit 3800 it slowly goes up. I will try removing the vac line in a little bit.

[Mr. Griff750]

Removing the vac line didnt seem to have an affect on it.

[Mr. Griff750]

When under a load at WOT it very slowly pushes past 4K

[J-Rat]

Hmm... Stupid question, but have you checked the plugs on the secondary injectors?

[FDTT]

1) Locate the boost sensor on the front of the passenger's side strut tower. Note: There is a vacuum line running from the sensor to the side of the engine block.

2) Disconnect the 4*wire 'gang plug' from the sensor.

3) Locate the upper left wire.

4) Take a very small flathead screwdriver and insert it into the back of the plug on top of the wire. You should be able to raise a small flap of plastic allowing the brown wire with it's crimped connector still attached to be removed from the gang plug.

5) Take a 12" piece of thin gauge wire and solder one end to the connector where it is crimped around the brown wire.

6) Insert the crimped connector with the new wire attached back in the gang plug.

7) Loosen one of the bolts that holds the radiator cap housing to the filler neck. Strip ¾" of wire off the end of the ground wire your just soldered and wrap it around the loose bolt. Tighten bolt.

[J-Rat]

He already grounded the MAP sensor.. Read first post..

[J-Rat]

Originally Posted by Mr. Griff750

Check the connections? Isnt there a way I can do that without pulling the UIM? Somebody please guide me in the right path!!

If you have an N/A, the secondary injector plugs are acessible without removing the UIM.

[MBTN]

Stuck 5/6 ports wouldn't prevent it from revving past 3800, but it could make it stumble.

[Mr. Griff750]

I cant seem to get to the plugs on the secondary injectors. Some mechanic told me my problem might be the MAF sensor. Could that actually be a problem?

[J-Rat]

Originally Posted by Mr. Griff750

I cant seem to get to the plugs on the secondary injectors. Some mechanic told me my problem might be the MAF sensor. Could that actually be a problem?

Let me give you some background on what you are seeing.

At 3800 RPM, the 13B transitions from 2 injector operation to 4 injector operation. Basically, the ECU cuts the primary injector duty cycle, and adds duty cycle to the secondaries (You should be able to see these injectors on an N/A motor. The are the ones that are on the outside of the Upper Intake Manifold). Before 3800, the Secondary injectors were just chillin, not bothering anyone, and laughing at the primaries because they were doing all the work.

Now, at 3800, if you have not done the regrounding, you may have a stumble, but eventually the ECU will catch up and you will be able to run to the redline. 6-ports not opening will not cause a magical "wall" or "stumble" at 3800. At partial throttle operation, you will still transition to 4 injector operation and the 6-ports will not be open. So lets put that theory to bed now.

So does the MAF tie into this? Not particularly. If the MAF is causing your stumble, it would be exhibited at other RPM ranges BESIDES just the magical RPM of 3800.

You have 1 of the following, and I will put $20 bucks on this.

1. Faulty ECU
2. Fautly pressure sensor
3. Disconnected secondary/broken wire to secondary
4. Malfunctioning secondary injector
5. Dirty/loose secondary injector connectors

If you get this problem fixed and it isnt one of the above problems, you get 20 bones courtesy of your pal J-Rat.

[Mr. Griff750]

Thanks, J-Rat. I'm going to try getting to my secondaries, but I cant even see them. I know that they are close together under the middle of the UIM. I will try replacing my pressure sensor, though. Thanks everyone for helping me with this so far.