what size are the stock injectors......

[jimmyv-21]

am replacing the stock injectors on an 01 gt 3.8 na--

zzperformance has 25#, 33/36#, etc.

which ones are stock?

thanks

[BNaylor]

Neither one at ZZP is a stock fuel injector for the na SII 3800. The 33/36# are stock injectors for a L67 GTP. The 25# injectors are rated at 10% more flow than stock fuel injectors for your model Grand Prix. Therefore, stock injectors are rated around 22-23#.

[eippermx]

Is there any added value with using the higher flowing injectors in a stock application? I'm wondering about the effects on the emissions system and any gain in hp.

[BNaylor]

Originally Posted by eippermx

Is there any added value with using the higher flowing injectors in a stock application? I'm wondering about the effects on the emissions system and any gain in hp.

Probably not. But modded with a target of around 300+ hp and type mods like a hot cam and high ratio rockers I would say yes. The problem with unnecessary deviation from the stock injectors is most likely loss of fuel economy and the fuel injection system would be forced into a fuel trim lean/rich mode having to compensate for emissions purposes. Working overtime to keep the air/fuel mixture ratio at that ideal 14.7:1. Plus in most cases the PCM module fuel injection tables would have to be modified for the bigger injectors. I guess the bottom line is the engine would run like crap.

[jimmyv-21]

Originally Posted by BNaylor

Neither one at ZZP is a stock fuel injector for the na SII 3800. The 33/36# are stock injectors for a L67 GTP. The 25# injectors are rated at 10% more flow than stock fuel injectors for your model Grand Prix. Therefore, stock injectors are rated around 22-23#.

thanks!

not really looking to do any performance gains just because it would use more fuel. i was checking the ones at zzp because they seem to be one heck of a lot cheaper than anywhere else i can find. where can i buy the stock injectors for a decent price? or should i just go with the zzp 25#?

thanks again

[GTP Dad]

Try rock-auto.com they have decent prices on everything. I haven't researched the price on injectors but you should do better than the local parts stores.

[BNaylor]

The problem is the injectors will be expensive at any auto parts places locally or on-line. The GM ones go for around $90 each even at Rockauto. Aftermarket $60 and up. Reman injectors around $30-$40 each. Too bad ZZP doesn't have the stock injectors for a na SII 3800 but the prices are outstanding because they buy in bulk quantities. Plus they are flow matched in any given set.

Therefore, I would make darn sure the injectors are bad or actually need replacing.

Here is another alternative on EBay even though you would have to win the bid. Low mileage complete rail with all 6 injectors.

Click here

[jimmyv-21]

Originally Posted by BNaylor

The problem is the injectors will be expensive at any auto parts places locally or on-line. The GM ones go for around $90 each even at Rockauto. Aftermarket $60 and up. Reman injectors around $30-$40 each. Too bad ZZP doesn't have the stock injectors for a na SII 3800 but the prices are outstanding because they buy in bulk quantities. Plus they are flow matched in any given set.

Therefore, I would make darn sure the injectors are bad or actually need replacing.

Here is another alternative on EBay even though you would have to win the bid. Low mileage complete rail with all 6 injectors.

Click here

i am pretty sure it is injector #5( keep getting a misfire on that cylinder). i have replaced the plugs and wires twice- first time with AZ crap, then with the delco parts. next i replaced the coil packs also with delco parts. i have also tried fuel injector cleaner with premium fuel for over a month, and am still getting a random misfire on cylinder 5. i would try to swap injectors to see if the problem changes cylinders, but i am worried that the o-rings will leak. i know there is a process to ohm out the injector, but i do not know what it is. any idea on that process?

[BNaylor]

Remove the electrical connector to the injector. Just a single clip holding it on. With DMM in ohms go across the two contacts injector side not connector plug side. Reading should be around 12.5 ohms. All this will prove is the injector coil is good and that the injector should fire when it is pulsed but won't help if the injector spray pattern is bad or if it is clogged.

[jimmyv-21]

Originally Posted by BNaylor

Remove the electrical connector to the injector. Just a single clip holding it on. With DMM in ohms go across the two contacts injector side not connector plug side. Reading should be around 12.5 ohms. All this will prove is the injector coil is good and that the injector should fire when it is pulsed but won't help if the injector spray pattern is bad or if it is clogged.

ok i am glad i checked before i just went and bought! it ohmed out perfectly to 12.5- what should i try next? the injector cleaner process outlined in the maintenance subformum?

[BNaylor]

Cleaning wouldn't hurt or just to be sure swap out the injector with a known good one and see if the misfire moves. You can get the upper and lower o-rings at Autozone for around $2.99 per pack which contains enough for two injectors. Felpro, PN: ES70599. You'll need 3 packs to do all injectors.

Good luck and let us know how it turns out.

[jimmyv-21]

Originally Posted by BNaylor

Cleaning wouldn't hurt or just to be sure swap out the injector with a known good one and see if the misfire moves. You can get the upper and lower o-rings at Autozone for around $2.99 per pack which contains enough for two injectors. Felpro, PN: ES70599. You'll need 3 packs to do all injectors.

Good luck and let us know how it turns out.

its getting dark outside so i will have to try tomorrow. the injector should just pull right out correct? i was looking at the maf and throttle body and wondering if cleaning all of the above would help i dont know if that would make a difference since it was only on cylinder 5????

[BNaylor]

On a na SII 3800 all you have to do is undo the nuts (at least 4) holding the fuel rail to the lower intake manifold. You'll have to move/set aside the wiring harnesses blocking them. Leave the fuel pressure and return lines connected. Remove injector electrical connectors. But before starting the work relieve fuel pressure first. You can pull the fuel pump fuse while engine is running and let the engine die out on its own. And then remove battery negative cable for safety.

Get a good grip on the fuel rail and carefully pull up until the injector(s) pop off the intake manifold boss. To get injector off the rail remove the upper clip thats holds it on to the rail. Be sure to use a light coating of clean motor oil on the injector o-rings during re-install to help the seal.

[eippermx]

I wonder if he should check the harness side with a noid light.

[jimmyv-21]

just wanted to update here in case anyone else has this problem.

the injector cleaning went ok - used the procedure outlined in this forum. it did not seem to help one way or the other as i still felt a slight miss every now and then. it is weird to me that the injector would go bad as the car never gets less than mid grade gasoline and fuel injector cleaner once a month. i have since then ran 2 cans of seafoam through the tank with super unleaded. today i pulled the throttle body and found the iac valve was caked with soft carbon deposits. i cleaned the entire tb with throttle body cleaner and also the maf sensor with maf cleaner. right now the car is idling the smoothest it has since i owned it. if this does not solve the problem, i will look at replacing the injectors and maybe checking into the egr valve.