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Fuel Injector code P0172 'Too Rich'

31K views 11 replies 6 participants last post by  Aaron Cake 
#1 ·
Our VIN #148 (2000) has had four O2 sensors replaced under warranty.
In 2004 we footed the bill for yet another O2 sensor out of warranty.

Now this month we have a similar idle surging issue (200 - 2500 RPM with stalling, battery drained, engine light on), and took it to the shop. Shop says code # is P0172, which means 'fuel mixture too rich'. They want to replace the fuel injectors (three of them I presume) for $850.

We purchased this car to a) save the environment and b) save money. If we have $1,000 repair bills every year we cannot meet objective #2.

Service man says the fuel injectors need to be replaced -- so I ask this forum:

Why so many bad O2 sensors, and why now the fuel injectors?

Cannot the fuel injectors be flushed or somehow cleaned, rather than replaced?

Thanks.

Geoffrey Smith
#148
Red
Stick
Cal Lic 'CLEANER'
858.442.1425
 
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#2 ·
injectors

Which dealer do you use? Same one all the time?
Suggest a second opinion.Injectors can be cleaned.
Going thru that many sensors is un heard of. Need info on recalls performed, (not recals).
 
#3 ·
Wow sorry to hear that. Have you had the ECM recall done? Part of this "emissions recall" also fixed a known bug that caused O2 sensor codes to be set (at least I think). That's a very very early vin number.

Fuel injectors can be cleaned, but it's not necessarily the best fix. You should have shops near you that specialize in injector cleaning. Also, it is best if you do have all the injectors done at once because imbalance between injectors can cause problems down the road. Also, if it really is running too rich that will foul your 02 sensors fairly rapidly.
 
#4 ·
Sorry to hear about your problems. I would be grateful if you could answer a couple of questions -
what symptoms were shown when an O2 sensor went bad? do you ever stall in auto-stop (myself and a couple of other forum users have this problem) and does your engine run rough during cold idle?
 
#6 ·
Wow, 4 O2 sensors. Where there reasons given for the replacement?

Obviously, something is seriously wrong. You need to check/do the following:

1. Have the injectors cleaned. Many communities have shops that specialize in this. Check the Yellow Pages for "injection service" or "diesel service". Many diesel injection places have gas injector rigs as well. Cost is usually around $20 per injector. Generally, this is done ultrasonically and you get a nice printout with spray pattern, flow rates, etc. You will need to remove the injectors and drop them off.

2. Check fuel pressure. Proper pressures and proceedures are located in the service manual.

3. As mentioned, make sure the ECM recall is done. The recall addresses an issue that causes the car to throw LAF/O2 related codes.

If the car really is running rich, then you run the risk of damaging the cats, a very expensive problem. So this should be taken care of as soon as possible.

As an aside, the "technicians" in your service department CLEARLY don't have much in the way of troubleshooting skills past "replace the part indicated by the code". This seems to be a common trait among Honda dealers.
 
#7 ·
Another thought, after you have some stuff done like Aaron suggested, I'd take it to a shop that specializes in emission repairs and have them run it on their gas analyzer. This could tell you if it is still running rich or not after having it fixed. Like Aaron said, you don't want to foul your catylitic converters, they're almost two grand to have replaced.

Oxygen sensors do wear out over time, but 4 in that period of time is way too many.
 
#8 ·
Awesome tips! Thank you.

VIN 148 was purchased used at 16,000 miles in Fullerton, CA. Engine light was already on, and O2 sensor (#1) was not avail at shop. We had local San Diego dealer install.

Three O2 sensors replaced under warranty, and also the ECM was recalled/replaced. I don't have the codes handy, but they were 'bad O2' codes. This was all done at Cush Honda in San Diego/Mission Valley, under warranty.

In 2004 O2 was replaced by Poway Honda, out of warranty. They said the previous 'bad O2' codes were mis-reported due to faulty ECM. This report (sorry don't have the code handy) is 'for sure'.

May 2005, idle surging, drained batt, engine light on, took to Cush Honda in Escondido (all three shops have been dealers). He wants to replace injectors for $850. (Also replace a rat-chewed a/c wire for $350.)

Prior to this latest malady, have had no idle problems, no auto-stop stalls, no cold running problems. Clutch seems to be going -- it lurches at cruising speeds, sort of like 'slack' gear, just between coast and acceleration it often lurches.

Haven't had injectors cleaned. Haven't tested fuel mix. Praying to God that the catalytic converters are ok.

Next stop: The Dealer, where I will discuss this with him.

Geoffrey
 
#9 ·
injectors

I recommend Tipton Honda in El Cajon.
Talk to "Ray", he is the Hybrid gru, also the lead man in the service department.
They have been great to me, even beyond the warranty.
 
#10 ·
geoffreyhawk said:
In 2004 O2 was replaced by Poway Honda, out of warranty. They said the previous 'bad O2' codes were mis-reported due to faulty ECM. This report (sorry don't have the code handy) is 'for sure'.
That's actually correct. The code in the ECM used to be too strict about the values it expects from the LAF sensor. The result was that the ECM would decide the LAF sensor output was "out of range" way too early.

May 2005, idle surging, drained batt, engine light on, took to Cush Honda in Escondido (all three shops have been dealers). He wants to replace injectors for $850. (Also replace a rat-chewed a/c wire for $350.)
DO NOT REPLACE injectors. :) Have them cleaned first. If that doesn't do it, then DON'T buy "Honda" injectors. Almost all injectors are made by only a few companies. I believe that ours are Nippondenso. Buying them from a Denso dealer will result in a SIGNIFICANT savings (like over $500).

Which battery was drained?

Prior to this latest malady, have had no idle problems, no auto-stop stalls, no cold running problems. Clutch seems to be going -- it lurches at cruising speeds, sort of like 'slack' gear, just between coast and acceleration it often lurches.
That sounds like the classis EGR problem.
 
#11 ·
Yesterday I went ahead and authorized the injector replacement at the dealer. Cost of the injectors (and 'rail'?) is about $388 from Honda. The rest is time. Time is money, and they spent the time, not me.

Looks like I'll be learning how to repair my own Honda very shortly!

I will certainly check out the El Cajon shop you mentioned.

What is the 'That sounds like the classic EGR problem."? Is that another discussion thread? 'Exhaust Gas Recirculation', right? You think that would explain the lurching problem we often have while cruising (not related to his current idle surging)?

Geoffrey
 
#12 ·
Yes, EGR = Exhaust Gas Recirculation. It has been determined that a dirty/sticking EGR valve can cause the symptoms you describe (rough cruising, lurching, etc.). Unequal/unpredictable EGR flow causes combustion problems. Usually, cleaning the valve solves the problem. Sometimes, the entire passage must be cleaned, which means pulling the intake manifold to get at the EGR plate.
 
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