cityjack

Evening all,

Working through the Helms troubleshooting for the above listed codes. Car is completely stock and is at 134K on the odometer.

From my Actron I am seeing the following data at 725rpm and coosant temp at 183;

STFTM1% -26.6
LTFTM1% -16.4
02S11(V) .075 to .85 and back again (Nice square wave)
STFTM11 -27.2
02S12(V) .8 steady

I see by the fuel trims I am definitely running rich. Not sure what the second ST trim means though.

Anyway according to the Helms and my code flow chart first check fuel pressure. I had to rent an "OEM" fuel pressure tester from Autozone. Their fittings did not allow for me to hook to the fuel rail so I was checking pressure at the top of the filter. The gauge being rented is not absolutely perfect. The needle starts at like 7 or 8 psi not zero. I disconnected the vacuum line from the regulator and pinched it. At idle I had a bouncing 58 psi. Connecting the vacuum line back to the regulator gave me a bouncing 47 or 48 psi. The gauge also was leaking fuel down the drain line constantly so I pinched it off also. The gauge remained the same. I know I am supposed to have 47 disconnected and pinched and 37 connected back. Subtracting 7 or 8 psi for the screwed up gauge start point gives me like 50 psi and 40 psi.
So I figured my fuel psi was too hi so I moved on to either the fuel return line was kinked or clogged or the fuel regulator. According to the Helms. Hooking the gauge backup and at idel still at a bouncing 58 psi. Reconnected to vacuum line back to the regulator and the psi drops to 47 psi. Disconnect the vacuum line again and the pressure jumps back up to the 58 psi. According to the Helms my regulator is working. Assuming the 7 or 8 psi bad starting point on the gauge. Absolutely no fuel present in the regulator vacuum line port, all dry.

I saw where to check the return line I can just hook a fuel line to the return from the regulator and put it in a bucket to see if the psi changes. Checking for a clogged line.

What do you all think? I am thinking my regulator is good, given my borrowed *** not perfect gauge. From my O2 sensor numbers I think they are both good also. That leaves the EVAP purge control solenoid valve. How would this valve cause a rich condition?

Thanks all and have a great night.

Sid

cityjack

Afternoon all,

A little bit more info to hopefully help you all help me.

Went and got a different fuel pressure gauge today. Measured on top of the fuel filter not at the rail, 54 psi with the regulator vacuum disconnected and pinched. 44 psi with it connected back to the regulator. The connecting and disconnecting of the vacuum to the regulator does cause the psi to change up and down. However as you see, its not 47 psi and 37 psi as the Helms suggests.
I then disconnected the return line from the regulator and ran it to a bucket. Started the car and got the same psi readings. 54 and 44 psi. So no clogged or pinched return line. But the Helms test for the regulator says the regulator is good. At this point I am confused. The psi is obviously too high so its either the regulator or the return line. Its not the return line and the Helms says its not the regulator because the psi goes up and down when you give and take vacuum to and from the regulator. Again, still no fuel present in or around the regulator vacuum port or vacuum hose. Completely dry.

Just for the heck of it I moved on to the next step of checking the closed loop O2 sensor at 3K rpm. My voltage did not stay between .3 and .6v. It jumped from .08 to .8 volts. According to the Helms, that sensor is good. Last thing is the EVAP purge control solenoid valve. Have not got there yet to that test. Have to get a vacuum pump.

Any ideas about the regulator or too high psi?

Thanks

Sid

cityjack

Any idea at all anyone?


Have a good holiday

Sid

DCFIVER

Because it purges evap vapors back into the engine(from the evap canister) to burn. It only activates occasionally and should be not be open all the time. Do the fuel trims impove if you raise the rpm?

cityjack

Thanks for the reply DC. Unfortunately I didn't get your reply until just now and the sun has set. Going to Nashville for work for a few days and I'll check your suggestion once I return. I'll get back with you when I return if thats ok.

Have a good week.

Sid

cityjack

Evening DC,

Just got back home from work and decided to check the fuel trims and your suggestion while the car was still hot.

Its almost confusing that after 550 - 600 miles of driving since I reset the P0172 and P0175 codes that they have not returned. I almost would have bet on my long Thanksgiving vacation drive the CEL would have come back on, but no. I figured maybe the colder air and the less dense air might have helped with my rich condition and fuel trims. I was again confused to see that my fuel trims did not change. Almost the same as the last time I posted back on the 21st. the following is what I saw in the data;

@780rpm and coolant temp at 194

STFTRM1% -25.2
LTFTRM1% -17.2
O2S11 .085 - .855
STFTRM11% -25
O2S12 .8

@2500 rpm
STFTRM1% -10 - -12

Both short term and long term trims dropped by like 10 - 12 when going to 2500 - 3K rpm. To answer your question, yes the fuel trims improved.

What do you think sir?

I did get my vacuum tester today in the mail, so I can begin to check the purge solenoid valve this weekend. But I am interested in your ideas and thoughts.

thanks again for your help.
Sid

DCFIVER

Check the valve lash. Too tight valves on a MAP based system will cause a rich condition.



(Unlike this vehicle,which uses a MAF based system. Tight valves will NOT cause a rich condition
https://honda-tech.com/honda-accord-...tment-3263033/
)

cityjack

Evening DC,

Well following the Helms flow chart, the next thing in line was checking the purge solenoid valve for the EVAP canister to see if it held a vacuum. Hooked up the Actron vacuum pump this morning. The solenoid held a vacuum just fine. Did not leak down a bit.

I think you are on to something. The next thing to check is valve clearance according to the Helms. First breakfast in the morning and then the valves.

Thanks for the guidance DC.

I'll let you know how it goes after I'm done.

Have a good night.

Sid

cityjack

Morning DC,

Well I finally got around to do pulling the valve cover and looking at the valves. I was already to get in there and start adjusting until I realized there was no way in H**L one could do this job without the proper tappet adjustment tool. I borrowed my buddies and wrapped it up yesterday afternoon.
Well, you were correct so far. Every single valve, exhaust and intake were tight. Some more than others. The Helms calls for .006 - .007 on the intakes and .007 -.008 on the exhausts. I adjusted all of my valves to .007 and .008, intakes and exhausts respectively. I mean, exactly and double checked and then torqued all the locknuts back down. Reassembled, and started it back up. Idles perfect and runs great. Sounds quiet too. No leaks, all is good. I wonder if my valves being tight would have anything to do with my IACV also. I always was battling a surging idle when cold also. No surging idle this morning, although it was about 38-40F this morning at startup. NOW for the "proof in the pudding". Took it to work today and when I get home tonight and while its still warm, I'll check the trims. Fingers crossed and I'm feeling confident here, all will be good with the trims. I want to go back and check the fuel pressure too to see if the increased vacuum now to the fuel pressure regulator has lowered my fuel pressure to within spec.
If not anything else DC, this has been a great exercise in understanding my car and learning to operate the scanner.

I'll let you know tomorrow how things look.

Thank you again so much for your help.

Sid

cityjack

Evening DC,

Well these results just in after getting back from work;

@rpm 855
coolant 194
ST FTRM1 -10.9 - -14.8
LT FTRM1 -11.7
O2S11 .095 - .8
ST FTRM11 -11.1 - -15.2
O2S12 .8 steady
ST FTRM12 -10.2 - -14.8

I'm thinking the valve adjustment was a fix given the 14.7 stoichiometric spec.

First off DC, thanks a ton man. I appreciate your guidance. Secondly, I have an additional question. I understand short term and long term trims (ST FTRM1 and LT FTRM1), but what is FTRM11 and 12? Any idea?

Have a great holiday man.

Sid

minilogoguy18

Tight valves WILL cause a rich condition because even newer Honda's that use a MAF sensor still use a MAP sensor to detect load for base injection timing and a leaking exhaust valve from being too tight introduces an inert gas to the manifold causing it to go rich. Not just that but the loss of manifold vacuum at idle due to that gas being put into the manifold tricks the PCM into thinking the car is under a slight load.

Your scan tool is weird, it doesn't show fuel trim values like anything I've used, I'm using Honda's equipment and even on my SManager a value of 1 is stoichiometric, less than 1 is rich and greater than 1 is lean. You also shouldn't use the AFR that the scan tool gives to assume the car is OK, if the STFT isn't right then that's what matters. For instance, the STFT could be 0.92 which is rich but the AFR can be 14.79 which is perfectly stoic but it's only stoic because the AF sensor (primary O2) is making a correction to the table, it shouldn't have to constantly correct, especially at idle.

The fuel trim value is interpreted like so, if the fuel trim is 0.92 then that means Yx0.92 is the injector duration where Y=base injector duration so like 3ms could be the base duration so with the fuel trim adjustment it's actually 2.76ms because the AF sensor sees too much fuel so it decreases injector duration. You should see if the settings in your scan tool can be altered to show FT values like this as the 0.7-1.7~ range is like the standard that most scan tools and technicians go by. Seems like yours is just showing actual AFR values and not FT values.

cityjack

Evening sir and thanks for the info and reply. I have an Actron CP9580A scanner. I read that a true reading of stoichiometric AFR is 14.7:1. 14.7 grams of air to 1 fuel. So me seeing the Fuel trim #'s as my scanner shows makes sense to me. No disrespect, still learning here and I have never used any Honda equipment either.

I understand that tight valves would cause a lower manifold vacuum thereby causing the FPR to not be correct and thereby allow more fuel to be presented to the injectors due to the improper regulation. Am I wrong with this assumption? Aren't fuel trim readings air fuel ratio? Especially when fuel trims are read like mine are showing? In my scanners case, I am thinking so. As the stoichiometric ratio stated above.

Trying to digest your last paragraph. Go easy on me man. Still learning here.

Check this out.. SAFR - Standalone Air Fuel Ratio Diagnostic Tool

I understand your formula and whats happening there. So Fuel trim and air fuel ration is not the same? I guess the trim that is being added or subracted is what is happening while trying to achieve stoichio? That right?

I'll check my scanner.

Thank you so much for the reply. Again, non of my questions were meant in a bad way. Just trying to learn. You mind if I toss you a PM?

Thanks

Sid

minilogoguy18

Fuel trim and air/fuel ratio are not the same. Fuel trim is a math formula used to find out how much the injector duration is being altered to achieve a stoichiometric AFR, short term fuel trim is pretty much what's happening at that moment, where long term is a averaged amount which when it gets to a certain threshold triggers the DTC, in your case usually around 0.7~.

A car with an incorrect fuel trim can still have a 14.79 AFR and that is a problem because it shouldn't have to make a correction to compensate. The fact that it's having to make a correction is the problem, that is what the DTC's are telling you.

You've also got it backwards about the valves and the injector duration. The exhaust valves being hung open allows for exhaust gasses to go backwards through the engine. Exhaust gas is inert and cannot be burned twice, the oxygen isn't there. This in turn cools the combustion process which causes the rich running condition. The AF sensor sees this and reduces injector duration to compensate as a rich condition can damage the catalyst which is the main programming of the PCM, protect the catalyst, second is tailpipe emissions, engine performance isn't factored. You can pick up on the valve lash being incorrect without even removing the valve cover, the MAP reading will be higher than normal and fluctuate as exhaust pulses make their way back to the IM. You of course have to block the EGR valve to be sure since a leaking EGR valve will cause the exact conditions as tight exhaust valves.

This brings me to the next thing, have you checked the EGR valve? Valve lift reading is irrelevant with a scan tool as the PCM often adjusts what it sees as closed to compensate for carbon buildup around the seat of the valve over it's life. A hundredth of a volt will be ignored by the PCM when it could be a problem. Block the valve at idle and check the MAP sensor reading to see if it drops in voltage. Also, compare the manifold vacuum before and after blocking the valve, inHg should increase, most engines are around 20-22inHg.

About the Honda scan tool, I mentioned it because it's what I'm most used to, I'm a dealer master tech. For your problems what you're using just isn't sophisticated enough, you need to be able to see MAP sensor data in a line graph live as well as know the ST and LT fuel trim.

cityjack

Thanks again. I really appreciate the tutoring man. I know my scanner is far from a dealership unit. It does graph live data. I just have to choose which data. I'll take a look at it tomorrow to see if I can truly get FT data.

The vehicle has 130K on the odometer. I bought it from the original owner. I have the dealership receipts where he had to have head work done when he lost the timing belt. He replaced all the timing belt set, idler system, water pump and the rest. Head work and all new valves. That was at 121K. Also I see where he had an EGR code and the dealership replaced the EGR. TWICE. They replaced it for him. The CEL came back and then they replaced it again. I could not see where he ever brought it back to the dealer. I have never got a code for the EGR. You can see the EGR is very new by the looks of it too. I did back in the spring get a EVAP code. I replaced the gas cap and that code never came back. As you have read, I just recently got that 172 and 175 rich code.

Not sure if this is related, but before these codes showed themselves, back when I first bought the vehicle and up until I adjusted the valves, I had the surging idle at startup and would sometimes stall at lights and stop signs until it was warmed up. I checked and cleaned the IACV and the thermal valve as well. They seemed ok. I was going to just buy another IACV. But since the valve adjustment last week, the surge or bouncing idle is gone and no more stalling. It goes right to fast idle at startup and does not stall anymore at lights. I know the IACV and thermal valve are coolant controlled. Maybe just a coincidence. The car runs strong and idles great.

I was ready to wave the victory flag after adjusting the valves since the AFR came to where I thought it needed to be. Not sure if I still have a problem by seeing now what my tool is telling me. The 172 1nd 175 codes have not come back. Maybe the duty cycle has not elapsed yet. Less than 250 miles since adjustment.

Reading back at your first post, you mention constantly correcting. By my AFR at idle going from -10 to -14. Is that what you mean by constantly correcting? If that were steady or steadier, would that mean the trim is steady and the PCM is not constantly adjusting?

Not sure where to go from here. I have followed the Helms on pages 11-81 for the certain codes I have. I did stop though after adjusting the valves when I assumed I solved it with the lower AFR. Even though the previous owner replaced the EGR twice, not sure if they cleaned anything under it or if there is anything EGR wise you can do other than R&R. Other than that, theres the EVAP purge control solenoid which I checked and it does hold a vacuum. So I assumed it was good. I will look at the EGR as you suggested. I am definitely up for learning. Although it'll have to wait till Friday. Suppose to rain all day here and my wife is dragging me around on my vacation. Tomorrow is a rainy day shopping day. Hurray.

Sir, I cannot thank you enough for listening to my silly questions and listening to me babble. Trying to learn and I want the car perfect.

Have a great night and I'll check back to see what you say. Thanks for the quick replies too.

Sid

DCFIVER

Riiiiight. I had not thought of that. I completely disregarded the fact that Hondas utilize MAP sensors in conjunction with MAF sensors.(I knew this too,but for some reason dismissed it)

Good correction.

Thats easy.Its standard OBD2 protocol. Required generic data. Honda(much like Nissan) displays fuel trims in terms of Lambda=1(I have HDS software as well)
But OBD2 displays fuel trims in terms of percentage. 0% is stoich and anything to the right of 0(+) is lean and anything to the left(-) is rich.The STFT will oscillate between -5 to +5 and this is considered normal. LTFT will ideally remain at 0 and go no higher than 10% as the vehicle ages.

His short term trims are still showing a rich condition.

cityjack

Thanks for the explanation. Going to try to see what the EGR tells me today. Still working thru the HELMS flow chart for troubleshooting these codes.

I'll report back and thanks.

Sid

DCFIVER

Try disconnecting the battery for a couple of minutes first.


This will reset the trims to 0, then the PCM will start to make corrections from there.

cityjack

just got back to the house. Had to order a decent vacuum gauge/tester from NAPA. The one I had was like 35 - 40 yearsold, my dads. Hooked it to the vacuum line going to the PCV and the needle didn't even move. I'll have to check vacuum in the morning. But before the sun went down, I did manage to mess with the EGR for a few. I did not get to disconnect the battery as I just seen your message.

At 780rpm idle and coolant at 185

STFTRM -10 -14
LTFTRM -10
MAP (not a voltage reading) inches of Hg 7.7 - 8. it goes back and forth from 7.7 to 8 and back just sitting at idle. When I pinch the vacuum line going to the EGR I see no real change in Hg at the MAP. Still 7.7 - 8. What am I doing by pinching the vacuum line going to the EGR? Is that preventing the EGR port from opening? What is that doing to the system?

Disconnecting the battery and pulling the radio fuse, is that the same thing or no? Just curious.

Sid

minilogoguy18

Sorry, should have clarified, block the valve completely, loosen it and slide a business card under it and bolt it back down. See if the STFT changes when blocked and see if manifold vacuum increases. If so then the valve is leaking causing the rich condition. Don't disconnect anything and keep it at idle while blocked.

cityjack

Morning sir,

Just got back from NAPA with my new vacuum gauge. Unplugged the battery for like 5 minutes to reset PCM also while in NAPA parking, lot drove home 10 miles and plugged the scanner in and checked vacuum.

@878rpm and coolant at 193

MAP goes back and forth between 7.7 and 8.0. Scanner says " of Hg for this MAP reading. This AGAIN is NOT a voltage reading. Not sure how much this "of Hg is helping you when you want volts. But I'll state it as it reads. At least it will be relative anyway.
STFTRM -10.1 - -13.2
LTFTRM -11.7 and steady
Vacuum at the pcv valve hose 21"Hg steady.
O2S11 .095 - .835 back and forth
O2S12 .800 steady

Funny thing, after plugging the scanner in I got a P0133 code. Main O2 sensor slow to respond. Never saw that and no CEL came with it. Not sure if that was because I just reset the PCM or not. Also while at NAPA I decided to loosen the vacuum line #16 going to the EGR so when I got to the house I could slide it off easier. I noticed then that there was two small tears in the hose where it slips onto the EGR hard line. Replaced that hose already.
Let me go out and do the business card trick and I'll report back.

Thanks for your help.

Sid

minilogoguy18

Well the thing with the MAP is that I don't know exactly where it should be voltage wise for this car, every car is different by about a hundredth of a volt or so and each PCM is programmed to see a different value as proper manifold vacuum under no load at idle. We'd pretty much need a known good 5th gen prelude that is all stock for comparison as far as MAP goes which I MAY be able to provide on Monday since someone I work with has one that hes selling. The one he has though is an automatic but if yours is a manual I should be able to put the auto in neutral to get a similar reading since in Park there's a **** hair of load from the transmission.

cityjack

Well mini, some different things to report. AND the baseline data of your buddies car would be awesome. Since everyone around here rides around in hatchbacks. Not many 5th gens around and if you do see one, its all ragged out. Mine is a 5 spd by the way. Thanks again man for all of your help. I am tired of getting advice to just remove this and try that. I don't like to roll like that you know. Any baseline data you can get me off your buddies would be money in the bank for me. I know you see voltages but an AFR reading off his might help too for the future, as well as his MAP. But your the Dealership mechanic, I do not need to tell you. Hope your Xmas is going good by the way.

Anyway, here it is.

WITHOUT business card under EGR again for easy reading;

855rpm coolant at 183
MAP 7.7 - 8.0, back and forth between the two
STFTRM % -10.1 - -13.2
LTFTRM% -11.7 steady
O2S11 .095 - .835
Vacuum at idle is 21"Hg

WITH business card under EGR and tightened

@rpm 960rpm and coolant 194 car was getting warmer as I had it running at idle
MAP 7.4 - 7.7
STFTRM% -7.8 - -10.2
LTFTRM% -9.4 steady
O2S11 .095 - .800
Vacuum at this idle 21"Hg

FTRMS were starting to inch up as the coolant got up close to 200-205 or so

Heres the funny thing also. I removed the business card. Tightened the EGR back down. Started it back up.

MAP 7.4 - 7.7
STFTRM -7.0 - -10.9
LTFTRM -3.1 steady
Vacuum still at 21"Hg

Coolant got back down to about 187 in the amount of time it took me to remove the card and put it back together.

What do you think?

Sid

DCFIVER

Looks like the trims are correcting somewhat.




Heres the thing,you have a HUGE improvement in trims after the valve adjustment. At this point with the trims at where they are now, you will NOT set a code and your MPG should be decent. It is possible the EGR valve may be leaking,but at this point the fault is minor. Id drive it around for a few hundred miles and see what occurs.....

cityjack

Sounds like a plan DC.

Appreciate your help man.

Have a good Xmas. I'll keep you all posted.

Sid

minilogoguy18

I don't think the valve is leaking, the vacuum would from what I've seen on a car with a EGR valve leak was around 17 inHg, 21 inHg is actually pretty good. With those vacuum numbers I don't think that your issue is something mechanical but probably electronic. You also mentioned getting a slow to respond HO2 sensor DTC, that could have something to do with it but there are so many other sensors that can richen up the mixture.