spcjenn

Hi, I noticed while I was driving one night at highway speeds of 70 75 my Accord would stumble from time to time. The following morning my check engine light came on. It was a code 45 rich/lean. I reset the ecu and the light never came back on. However, mostly during highway driving, and sometimes while getting up to highway speeds it will stumble. I did notice when it would stumble it wouldn't accelerate anymore. It was like the car wouldn't allow me to go any faster... even with the throttle pedal mashed to the floor. The engine idles normal, and I have in the last year or so cleaned the EGR pathways, and I did change the fuel filter the other day. My question is what should I trouble to resolve this issue I'm having. Can someone give me some ideas?

Thanks!

MAD_MIKE

Check your fuel pressure/ fuel pressure regulator. You will need to attach a fuel pressure gauge to the test port on the fuel rail.

IIRC it should be 40-47PSI. You can artificially raise the fuel pressure at idle by disconnecting the FPR vacuum hose, or by pinching off the return line slightly after the FPR. If the fuel pressure is low and increases with pinching off the line, then the pump is able to create the pressure, and most likely the FPR is not functioning correctly.

spcjenn

Would you know of a place where I can buy a pressure gauge that will fit a Honda.... I have having troubles finding one that has a Honda fitting.

holmesnmanny

Harbor Freight has a $20 fuel pressure tester kit that fits our cars.

I would also check for an exhaust leak. Also, it would be better since that's a generic code for you to pull the obd2 code.

If you haven't replaced the oxygen sensor in a while I would pick up a new Denso upstream sensor.

spcjenn

Just making an update I checked the codes and there was second code P0301,so I have two codes P0301 and P0171/P0172. I have bought a fuel pressure tester gauge from Harbor freight just waiting for the rain to go away. If the fuel pressure checks out what else should I look at? Could the o2 sensor be the issue even though that code is not showing up?

holmesnmanny

bad oxygen sensors dont often throw.a code

MAD_MIKE

If you have a P0301 code then you have a misfire issue on #1. Check you plugs/wires/cap/rotor. Pull off your EGR manifold again and check that the #1 port has not clogged up again.
P0171 is for too lean
P0172 is for too rich

Recheck your EGR system, after checking the ignition. Check that the EGR valve is able to open smoothly.

spcjenn

Well the results are in for the fuel pump pressure test. At idle the pressure was 32 psi if i revved the engine it would top out at 40 psi if I snap the throttle it would go to 40 psi. When I turn off the engine and let it sit for a minute the psi was 20. BTW the FPR checked out good. Sooo... it looks like I need a new fuel pump?

MAD_MIKE

How did you test the FPR? Did you disconnect the FPR vacuum hose while pressure testing?
Did you clamp down on the return fuel hose AFTER the FPR to see if the fuel pressure increased?
More details on what and how you tested components would be helpful in aiding your diagnosis.

If you have no records of the fuel filter being replaced, start there first. It is cheaper/easier than dropping the tank and replacing the fuel pump. If the pump did fail/begin to fail the filter may have caught some debris.

spcjenn

I redid the pressure test. At key turn on the pressure was 42 psi while the engine was running it was 32 psi. If i revved the engine to 3k the pressure went up about 35 psi. If I snap the throttle it go up to 42 psi. When I removed the vacuum hose fpr the psi was 42. When I pinched the return line I was getting 80 psi. Thank you for your help... I hope this was detailed enough?

holmesnmanny

those numbers are fine ... when was last time the oxygen sensor replaced ?

spcjenn

I have not changed the o2 sensor since I have owned the car. So, your telling me that which makes sense is that the o2 sensor is toast, and because it's toast the computer is not getting the right feed back so the computer is throttling me back?

holmesnmanny

Yes, you can test by unplugging the oxygen sensor and it will throw a code for it but that's fine cause you just want to test if it will run better since with the connector unplugged it will use predetermined air fuel values. If it runs better the issue is likely the oxygen sensor.

Obviously you will warm the car up completely before testing.

Make sure to only buy a Denso oxygen sensor.

holmesnmanny

One more thing, I would really suggest checking for an exhaust leak first using seafoam. If you don't know how to use it properly I would suggest having someone help you or having a mechanic do it.

What you would basically do is start the car on a cold start up, remove the brake booster hose from the intake manifold and pour in just a tiny bit of seafoam into the hose or the intake manifold. Then check the exhaust manifold and the exhaust downpipe for any white smoke leaking out. There should be none obviously. The reason to do it on a cold start is that the car will idle higher which will help keep the car running as you gently pour in a little bit of it.

spcjenn

Well I went ahead and did the smoke test. I had a standby bottle of seafoam . I pulled the exhaust shield off and did the smoke test. I noticed that smoke was raising what looks like from where the exhaust manifold meets the down pipe. I went ahead and pulled the plug on the o2 sensor.The drivability on the highway is the same... no change. The engine idles fine and drivability in town is fine or shall I say normal. Can this exhaust leak be the problem? Does the leak get worse as pick up speed?

holmesnmanny

exhaust leaks kill oxygen sensors so replace the downpipe gasket first .. make sure to torque it in several stages so the gasket sets properly and doesnt leak ... then get a new denso oxygen sensor however with the car still not running correctly with the connector pulled possibly points to something else ... have you replaced the plugs, cap, and rotor lately ?

spcjenn

I have about a year and half ago. I shall order up those items to include cap, rotor, plugs etc.

holmesnmanny

they should still be good then for the most part ... how noticeable is this miss ur feeling ?

i would say fix the exhaust and sensor and see what happens ... make sure to clear the code

94 accord typeR

i would try a bottle of fuel system cleaner along with using 93 gas from time to time also get a new pcv valve and grommet

spcjenn

Holmesnmanny it's real hard to explain... when I jump on the Interstate and I try to rev the engine up to get to speed in my state 75 is the speed limit. The car will jump a couple of times around 3k but main thing is that the car will not speed up. It will very painfully slowly get up to 70 or 75. If I set the cruise it will maintain that speed. If there is a decline on the highway I can pick more speed and the cruise will maintain that speed. But, if I step on the gas I might get nothing or I might jump... no speed. So, if i do manage to get 70 or 75 I can not pass I can not do nothing. So, i'm thinking ignition system. I will pull the plug wires and test them with a ohm meter if they are over 25k ohms I will replace them. What are your thoughts? If I could post a video on here I will. I will look in to replacement gasket for the exhaust and sensor.

holmesnmanny

im wondering if maybe your catalytic converter is a lil clogged

if it was me i would disconnect the cat and see if it runs better

the exhaust leak causes the oxygen sensor to dump fuel which can cause the cat to go bad

spcjenn

I was thinking it could be the cat... i'm holding my breath but is it possible to unclog it?

holmesnmanny

you can either disconnect it or remove the oxygen sensor ... it will be hot and louder so be prepared but it will run better if it is ... obviously disconnect the oxygen sensor connector if u remove it

spcjenn

I'm going to do a vacuum check sometime today. The vacuum check will determine if there is a restricted exhaust. If its restrictive then it's the cat. If it's not I need to have the car scanned to see if the map sensor is acting up. What do you think?

spcjenn

Well I have completed the vacuum test. The engine pulls 20 inches in the green, and when I rev the engine 2.5K its drops a bit but gains inches. In this test I believe there is not a restrictive exhaust. So, it makes me think that the early code of P0171 may have been a rich not lean.