What can cause the engine to stumble between 1/3-3/4 throttle?

[PiLOTLiTE]

Bad EGR?

Computer problems?

Fuel delivery?

This problem also goes away shortly after starting the car. I only seems to occur right after its been started and the first few times I hit the gas. Any ideas?

[zlightning]

TPS, fuel pump.

[rockotman]

Bad wires can also cause this - check for arcing - are you getting any SES codes?

[MikeB33]

It could be the coolant temperature sensor. If it reads warm when actually cool, when you first start up, it won't give the rich mixture you need. Without the rich(choke) mode, it will stumble on accelleration while cold. Full throttle isn't too bad, because a lot of fuel is added at WOT(wide open throttle).
You need a scan tool or similar to check it after sitting overnight when it is truly cold.

Hope this helps,

MIKE

[FirebirdGT]

<blockquote>quote:</font><hr>Originally posted by PiLOTLiTE:
This problem also goes away shortly after starting the car. I only seems to occur right after its been started and the first few times I hit the gas. Any ideas?<hr></blockquote>

Yes, your removal of the MAF screen. When you first start the engine it uses the input from the MAF. Put it back in.

[strobhen]

actually it uses the maf all the time, esp at idle.

It cuts it out when you are at WOT.

FirebirdGT could be right, and its a simple thing to give a shot to (In your situation I would at least try).

But I also wouldn't be surprised if the behavior continued. If it was the lack of a maf screen, it should happen more than just when you first start the car if the MAF sensor was having trouble taking readings.

A scan tool would definitely be handy to diagnose a problem like this.

[FirebirdGT]

<blockquote>quote:</font><hr>Originally posted by strobhen:
actually it uses the maf all the time, esp at idle. It cuts it out when you are at WOT.<hr></blockquote>

Sorry, no. The MAF and IAT sensors provide input to engine control ONLY until the heated O2 sensors heat up, and at WOT. All other times the heated O2 sensors provide engine control. This is all explained in the Technical Database.

[PiLOTLiTE]

<blockquote>quote:</font><hr>Originally posted by FirebirdGT:


Sorry, no. The MAF and IAT sensors provide input to engine control ONLY until the heated O2 sensors heat up, and at WOT. All other times the heated O2 sensors provide engine control. This is all explained in the Technical Database.<hr></blockquote>

Your MAF screen idea is a great one. I can't believe I didn't think of that. I'm going to put the screen back in and drive for a few hundred miles to see if it goes away.

My question would then be, since many have removed the screen, both the 96-98 angled TB and the 99+ straight one, is there anyone else who has experienced a similar problem?

[FirebirdGT]

<blockquote>quote:</font><hr>Originally posted by PiLOTLiTE:
My question would then be, since many have removed the screen, both the 96-98 angled TB and the 99+ straight one, is there anyone else who has experienced a similar problem?<hr></blockquote>

YES! Do a Search, there's lots of discussion about this. Basically the 99+ seem to deal with the screen removal, but they also have a different TB with electronic throttle and a different MAF.