LudeBehavi0r

Anyone in the san diego area have a fuel pressure tester and/or a valve adjustment tool/feeler gauges I can borrow? I just moved here a few weeks ago and have been trying to figure out whats causing my fuel trim DTC codes (p0172 -- system too rich).

I've tried pep boys and autozone and none of them have a fuel pressure tester to sell or loan me. I believe the part # for the tester I need is :07406-004000A.

Any help or suggestions would be appreciated. I really need to get to the bottom of this so I can get my vehicle inspected.

Thanks in advance.

Enzo15

Do you have a misfire in any of the cylinders? Check your air filter, and your fuel pressure regulator. If you have a way of watching your STFT and LTFT then look at them and get back to me.

vinuneuro

Find someone that will lend you their working O2 sensor.

LudeBehavi0r

I am not getting any misfire codes. My air fliter is old I know for a fact, but following the trouble shooting guides in the pdf manual I have says I need the fuel pressure tester to check the FPR (which is one of the tools im trying to borrow). I have a scan tool that i've been using to post data on honda-tech in this thread... https://honda-tech.com/forums/honda-prelude-4/dtc-p0441-p0170-already-searched-2829941/. Any help would be appreciated.


Vinuneuro -- The primary is brand new. I ordered from Sparkplugs.com (ordered a Denso OEM replaecment) and I was using the scan tool to check voltage from the secondary.

If you guys care to check out my other thread (link posted above) and can help I'd love to hear what you have to say.

So far i have put in a new EVAp purge solenoid (denso from Honda stealership) & new primary O2 sensor (Denso). Its really hard to find a fuel pressure tester for a HOnda around here so when I get that, next is checking the FPR and if that is ok then I need to check my valve clearences/do a valve job.

The engine has less than 50,000 miles on it so i assumed they should be ok ........which might have been a mistake.

Enzo15

Well if your air filter is old try to remove it and have the car idle. DO NOT DRIVE IT! Check with your scanner while looking at your Long Term Fuel Trim(LTFT) and Short Term Fuel Trim(STFT). Do a before removal and after removal test. Have each one last maybe 6 min. When the filter is out keep the area clean to make sure nothing gets sucked in. Those numbers will help me figure it out more. If the filter is really in that bad of a shape you should see the numbers change. Also check your TB to see if it needs to be cleaned.

DCFIVER

A drity or resrticted filter will not cause the vehicle to run rich. The PCM will compensate.

Enzo15

Theres only so much a PCM can compensate. If the air filter is dirty how is the engine supposed to get the air it needs?

DCFIVER

The PCM will easily modifiy the injetors PWM to compensate for the amount of air coming in. It will ensure the vehicle remains in stoich. So less air entering=less fuel being distributed. It does so by way of the MAF on most cars, in non MAF cars it will use O2 feed back. Power and performance will suffer. What the PCM cannot account for is unmetered air (vaccum leaks) and mechanical failures (fuel system leaks) and biased O2 readings. This will cause the LTFT to swing wide in one direction or the other and set a code on an OBD2 car.
(This is why a feedback system is ideal boys and girls)

Enzo15

Dude Im a tech. Ive already learned all this. Ya the PCM will compensate.... to a point. and it has reached that point other wise he wouldnt have had the code in the first place. Most cars use both the MAF and O2 as a redundancy to check itself. There are logic circuits built in these new ECU's. The Preludes use a MAP sensor, which checks PRESSURE in the intake manifold and not the FLOW through the intake tract. Its not that hard to take the filter out and do my simple tests. 6 min and you will see if the filter is truely clogged or not. Its better than buying a ton of parts and wasting money when it would have simpler to actually DIAGNOSE his car, instead of taking guesses

DCFIVER

Great youre a tech...with a lot to learn. I've been a tech diagnosing and troubleshooting every thing from CAN communicaiton failure to Class 2 serial data faults for around 10 years. Ive also been a smog tech for 5 years now, and have diag'ed various forms of rich and lean conditions So save your "im a tech" spiel and listen and learn. Every modern car uses a feedback control system, including the Prelude. Reread my previous post. i said if the car does not use a MAF it will use the O2 for feedback. Taking the air filter out is wasting his time. A feedback controled vehicle WILL NOT run rich if the air filter is clogged. Plain and simple.

92civlude

Maybe to a point where its so clogged the car wont run. But then the car wont run.

Enzo15

Fine dude. What ever. Im done trying to help. Just because Im younger doesnt mean that I dont have an idea of what Im talking about. Since you havent said ANYTHING to even try to help him. All youve done is bash me. So you figure it out for him if your so smart and experienced.

Enzo15

http://www.obd-codes.com/p0172

DCFIVER

Im not tryingto bash you Im trying to teach you. Ive helped him as much as i could in his other thread. but you will have him chasing his tail with your "advice"
Read and learn grasshoppa:
http://www.motor.com/article.asp?article_ID=1629
Cliffs:the author covered the air filter until only a 1/4in sq. area was left for the car to breathe through. More clogged up that ANY air filter will EVER be. Drove the car and datalogged it. The car ran at stoich and only suffered top end power. Different car but same principle.

Enzo15

Which ECU are you currently running? Also have you checked the vacuum line to the Fuel pressure regulator? Ive had a car once where it was reading rich on both banks and had a misfire in one cylinder. On that car the diaphragm on the pressure regulator ruptured, which I figured out after removing the vacuum line and having gas squirt onto my hand, so fuel was being drawn into the intake manifold through the vacuum line causing the car to go super rich, and the leaky injector also didnt help the misfire. Once both problems were fixed the car was running fine.

mgags7

Noooooo

that car's like a black hole leave my o2 alone