Getting closer - '99 454 P0171 code

You are probaby on the right track. How many miles are on this vehicle? If you are over the 60K range it probably wouldn't be a bad idea to pull all injectors and have them cleaned and flow checked. Not at all expensive and will put your injectors to like new condition. If you live in a area that specializes in injector service your best bet is to go to them. Have new screens put in, this is normally part of the cleaning service. There are on rail systems but for the cost and trouble its just as easy to pull the rails and injectors. You can test for shorted or open windings with a ohm meter. Not sure what injectors you have but they all should be close to each other and obvious opens or shorts mean bad injector. If you find all windings are good bad pintles and seats will show in the flow test. If you have high mileage on these injectors and have them cleaned and your problem still exists you are not at a total loss. You will still benefit from the cleaning in fuel savings. A good cleaning at about 75K intervals is a good thing to put on your PM list. Probably should have started here first but a injector test light is cheap. Make sure your injector driver and wires are good.. There are other things that may be the culprit but just my opinions.

Thanks for the info, David. I am over 60K, less than 65K, so that fits with what you're saying. I've been avoiding tearing the injector system apart since it resides beneath the plenum. There is no access to any of the injectors without removing it. Sounds like that may be in order, though.

I will be getting new rotor/distributor cap/wires on Thursday. I've been getting advice from several different sources and they all say "change the wires". Easily and cheaply done, so that's what I'm gonna' do.

Auto-lite brand wires have been recommended to me. Yea or nay?

Thanks again.

My opinions on the wires/plugs... go with delco, I've used plenty of diff kinds in my chevys/gmcs over the years and always end up going back to delco, even advance auto carries em now. a little more expensive but worth it. The plugs run the same as any other brand. Just my .02 here.

JLarss>

I replaced the plugs (with Bosch platinum, even!) rotor and distributor cap when I bought the truck. It had around 40,000 + on it at that time. I did NOT change the wires then.

Sounds like a good deal on your Moroso kit. I'll have to look into that.

Thanks again. I'll try to post an update when I get them installed.

JLarsson

So if I offer you a penny for your thoughts, what happens to the other penny? ;)

Thanks for the advice re:delco. I will check into those.

JLarsson

The other penny goes to fuel costs for my big block ;-)

JLarss> > My opinions on the wires/plugs... go with delco, I've used plenty of

Okay - a brief update.

New rotor, cap, and wires. MUCH more power and acceleration. Computer shows approximately equal fuel trims for both banks. I reset the code and will monitor performance for awhile.

Think I need to disconnect the battery so the computer can start from scratch or just go ahead and drive it?

Thanks again.

JLarsson

========= ========= If you're dealing with the fuel trims, disconnect the battery. The ECM will reset to factory pids and give you a "known" starting reference pid for future tinkering.

You can just go ahead and drive it. The footprint left over on the fuel trims will adjust over driving time. (as i'm sure you know)

~:~ MarshMonster ~:~

Well, I suspected as much, but I didn't really know that....until now.

Thanks very much for the input. I tell ya', the way this thing runs now it's like having a whole new vehicle.

One question - what's "pid" stand for?

JLarsson

Parameter IDentification

IOWs, a line of data on a scan tool, B1S1 O2 voltage for example.

Excellent. Thanks very much.

JLarsson