What code are you getting? If it's an injector o-ring. It will typically run lean on the bank/side that is bad.

 

I have a friend who had persistent lean codes but we could not find a vac leak with a cigar smoke test. He's now sold the truck, but I suspect it was just like what Andy2Rover is saying, injector O-rings. If that is what is suspected how, pray tell, are you supposed to spray carb cleaner or propane near the injector rings with the engine running given that they are buried under the upper intake?

 

Pour water over the area of the injectors. It will create a seal and should start running smoothly.

I've never done it but Markd on here had a mechanic do it to diagnose his rings. He called it a baptism...

 

Never mind, I thought you had misfires. I don't think you will have time to drive around after clearing the code with the water staying there!

 

The infamous 0171 and 0174.....I believe that indicates both banks.

 

The o-rings on the fuel rail (top) side continue to seal for a long time while the ones inserted in the intake get dirty, dry, brittle and shrink. Easy job to replace these and many also opt to replace injectors with rebuilt, or at least change the screens. I would recommend using petroleum jelly (Vaseline) on the o-rings because some of it will surely get into the injector ends where the fuel spray comes out. Rather introduce a small bit of petroleum product into the engine instead of silicone grease or some other lubricant- just my preference.

 

Did you try cleaning you MAF? I find it hard to believe that you had an injector in each bank start leaking at the same time. Your MAF is dirty or you have a vac leak somewhere from the MAF to lower intake.

Try tightening the intake tube clamps with a ratchet rather than a flat head screwdriver. If you know someone with a DII try swapping the MAF.

Some additional reading: Mass Air Flow Sensor Testing,P0171-P0174 System Lean | MDH MOTORS

 

Good stuff acamato! Thanks. I've tightened up the intake tube already without effect. I will try cleaning the MAF before I do injector seals. The guy in your article mentions using brake cleaner to clean the MAF. I have a case of that at home, but no MAF cleaner. Think its OK to use the brake cleaner?

 

Andy considering the age of your D2 I would say change the injector seals in any case. I had those dreaded codes too on my 1999 D2 and spent time and money tracking them down. Finally dawned on me that the only place I was over looking was the injector seals. New seal cured everything.

Remove plenum, disconnect the fuel rail and clean area around injectors before removing them. Follow RAVE and remove injectors and their seals.

I found, after breaking one and having to buy a second hand replacement injector, that the heat shields on the end of them is brittle and care is needed in removing the old seals. I decided that it was less risky if I used a sharp craft Knife to cut the old seals off.

With the new seals being a little more pliable it is easier to fit them, but do take care and lubricate them. If you break a heat shield you can't use the injector as the seal will just burn away.

 

I don't know. I would go to an autoparts store / Walmart and get MAF cleaner
Mass Air Flow Sensor Cleaner, 11 Wt Oz - Product Information