Fuel Injector O-rings

[GPFred]

I have 2000 GP 3.1 with 93K on it. The on going problem I had been having was a low voltage code being thrown for the bank 1 oxygen sensor. I have had the sensor replaced 4 times, a new cat, and the gaskets replaced for the upper intake manifold, and a tune-up. Now the dealer tells me that the reason for the bogging down on hard exceleration is the fuel injector o-rings are leaking air into the cylinders and that this is causing the low-voltage code being sent. Somehow I doubt this and I'm starting to get pissed with this money-pit. I bought a new set of o-rings for about $7 and am wondering if this is a pretty easy job and what things I should watch for while doing the job. I appreciate the help.

[maxwedge]

So they are saying the lean condition is being caused by air being drawn past the injectors and thereby leaning down the engine, fuel pressure good under load when this happens, what is the code?

[troy1]

Ah you got a PO134 I had one of those the other day. New O2 sensor and I have not seen it again. But I did just do the upper intake gaskets but not the injector O-rings but I am in the process of the O-rings now. My car was a 99 GT 3800 Series II

[BNaylor]

Unlike the SII 3800 on the 3.1L I believe you have to remove the upper intake manifold to even get to the fuel injectors whereas we don't need to remove the UIM or supercharger to do fuel injector service or replacement. But the job looks easy enough DIY if it is anything like the 3.4L.

Before I'd replace the injector o-rings I'd spray carb cleaner or throttle body spray around each injector that can be accessed and see if there is any change like to the idle, etc.

See link below for fuel injector service on 3.1/3.4:

http://www.autozone.com/servlet/UiBr...3d800ed52f.jsp

[richtazz]

You say you've replaced the upper intake gaskets, but did you do the lower intake as well? The lower intakes on the 3.1 liter are the ones that fail and cause a vacuum leak, coolant loss, pudding looking sludge in the oil (under oil cap, in PCV valve, etc...). It is VERY rare to have injector o-rings cause this condition, unless the injector rail was removed and they weren't replaced then. Look for evidence of coolant loss around the ends of the lower intake manifold where it bolts to the heads. The most common places are passenger side front, right above the water pump area, and the drivers side rear, just behind the throttle body. Do like Bob suggested and spray carb/inj cleaner around the base of the intake manifold too, if the idle changes, you found your vacuum leak.

[GPFred]

Yeah, the dealer did both upper and lower intake gaskets. When I had it on Saturday, they said they confirmed leakage around the injector seals by squirting a little water around them and the water got sucked into the engine. They are saying that because of the air leak, it is causing the engine to run lean and seem to bog down under heavy acceleration. From looking at my Haynes manual it shows that I have to take off the plenum and throttle body and then I'll have access to the injectors. I will not be a happy camper if the dealer should have done the seals on the injectors when they did the manifold gaskets.

[BNaylor]

Originally Posted by GPFred

Yeah, the dealer did both upper and lower intake gaskets. When I had it on Saturday, they said they confirmed leakage around the injector seals by squirting a little water around them and the water got sucked into the engine. They are saying that because of the air leak, it is causing the engine to run lean and seem to bog down under heavy acceleration. From looking at my Haynes manual it shows that I have to take off the plenum and throttle body and then I'll have access to the injectors. I will not be a happy camper if the dealer should have done the seals on the injectors when they did the manifold gaskets.

If the dealer did both the upper and lower intake gaskets it doesn't make sense for them not to put in at least the lower injector seals since that appears to be your problem. I can see them not doing the upper injector seal because unless an injector is suspected bad they will leave them attached to the fuel rail when doing a UIM/LIM job. If the upper injector seal was leaking you'd have a fuel leak. Every reference manual I have recommends replacing the injector seals. Be sure to coat the o-rings with clean motor oil after installing on each injector and before installing into LIM. Good luck!

[maxwedge]

In my opinion this smacks of poor workmanship and a shop comeback, I would sit down with the SM and discuss this with him!

[BNaylor]

Originally Posted by maxwedge

In my opinion this smacks of poor workmanship and a shop comeback, I would sit down with the SM and discuss this with him!

Hey Max, did you say smack the service manager...lol.

[richtazz]

I agree that the injector o-rings leaking are the fault of the shop, as they should have been replaced while doing the lower intake. It is "possible" on a 3.1 to get the manifold out without disturbing the injector rail, but it requires a thin walled socket to get to two of the lower intake bolts. If they loosened the injector rail, it's shame on them, as you should never re-use injector o-rings. I'd have that talk like Max said and get them to fix it right this time.