I thought I had a bad fuel pump, but now I have no idea what is wrong.

Scottwax · 05-21-04, 10:52

Since Tuesday night, occaisionally when driving, my car would feel real sluggish, sometimes when lightly accelerating or at a steady speed and I would have to step harder on the gas to maintain my speed, step hard enough and it would downshift and accelerate again.

Took it into my Honda mechanic this morning, figuring the fuel pump was getting weak. Nope, passed all testing, idle, cruise speed and it didn't lose pressure when you turn off the car. EGR valve passed, TPS passed, MAP Sensor passed, distributer (coil, ignitor, wires, etc) passed, PA (atmospheric sensor) passed. Even changed the ECU (I had a spare one at home) and still it was not running right or throwing a CEL code. Vacuum gauge needle was rock steady at idle and accelerating, so no apparent valve problems and at 2500 rpm, the vacuum didn't drop off, so we could rule out an exhaust blockage.

On the test drive after changing the ECU, I finally had to get gas, since I had let it get low in case the fuel pump had to be changed (tank has to come out), and after putting in about 5 gallons, I was driving back to the shop and after driving maybe 1/2 a mile, my car wouldn't accelerate past about 45 mph, either in 4th or 3rd, finally after about a mile, the CEL came on and the engine problem cleared up. Ran fine all the way to the shop and then at 15 mph in the parking lot, same thing.

Pulled the code, 43 which is fuel delivery. Pulled the (2 month old) fuel filter, dumped it out, couldn't see any debris, could blow through it. Put it back on, ran decarbonizer and fuel injector cleaner through the engine. Still felt sluggish at times on the test drive. My mechanic took it out and noted a few times acceleration seemed sluggish. Checked timing and it was right on.

I went with him on a long test drive and a few times it was sluggish, but at least now it would accelerate instead of just maintaining speed, and it was only sluggish for a few seconds, same on my drive home....so the problem doesn't seem as bad.

I filled up on gas last Thursday and the problem began on Tuesday, so I figure if it was bad gas, the problem would have shown up sooner, right?

Now, today, the car runs fine on the freeway, drove all the way to my brother's in Rockwall (about 42 miles freeway) averaging 70-75 mph. The problem occurs under light acceleration, I can hit the gas harder, the car will downshift and accelerate normally. Seems to mostly occur when accelerating lightly between about 1500-3000 rpm. Comes and goes too. I added a bottle of fuel injector cleaner and more gas today.

I think extended freeway use, including a full throttle burst from 70-85 mph with no problems, bogging, etc rule out the fuel pump.

BTW, 1990 Accord, automatic.

MattZ28 · 05-21-04, 11:41

Did you check the O2 sensor? If it's contaminated, or getting lazy, the A/F ratio will be out of whack. This happened to me.....I installed ceramic coated long tube headers, and when I first started it after the install with brand new AC Delco O2 sensors, the coating smoked for a few minutes. I didn't think anything of it, then starting 2 weeks later, whenever the car would go into closed loop (using the O2 sensors for the A/F ratio instead of just the Mass Airflow Sensor), it would stumble and give the same symptoms you described, barely accelerating. It finally got to the point where the car was running so rich when it went into closed loop that it would nearly die at idle, then when the service engine soon like came on, it would run perfectly smooth......this is because the PCM detected both O2 sensors getting slow response and put it into open loop, ignoring them, and using pre-programmed fuel maps (14.7:1 A/F ratio). It's definitely worth a try....shouldn't be hard at all to change either since the manifold is right in front of you once you open the hood.

Hope you get it worked out...keep us posted!

-Matt

zzyyzx · 05-21-04, 11:46

Hey Scott... had a similar problem on a Saturn I just sold. I had replaced the fuel filter as I thought that was most obvious. Then I did the air filter also just to be safe. No improvement to speak of.

Then, all at once, I replaced the PVC valve, spark plugs and wires. Something in that combination did the trick. It ran like a charm for the week we drove it before we sold it.

Scottwax · 05-21-04, 11:48

Thanks, Matt. My mechanic says normally a bad O2 sensor on my car won't affect how the car runs too much, but I do know mine is pretty old, I changed it when I got a header and that was about 160,000 miles ago.

Usually though, it throws a code pretty regularly and other than that one time, the CEL hasn't been on. Mileage has been good also, but maybe the O2 sensor got contaminated by bad gas?

Scottwax · 05-21-04, 11:52

Quote:

Originally posted by zzyyzx
Hey Scott... had a similar problem on a Saturn I just sold. I had replaced the fuel filter as I thought that was most obvious. Then I did the air filter also just to be safe. No improvement to speak of.

Then, all at once, I replaced the PVC valve, spark plugs and wires. Something in that combination did the trick. It ran like a charm for the week we drove it before we sold it.

I know the plugs are good, they are only about 6 months old (NGKs), the plug wires are a few years old (ACCELs) but seem fine and I replaced the PCV valve about a year ago. It just seems if I had bad plugs or wires, the problem would be worse at full throttle or at freeway speeds. The PCV is cheap though, I can just replace that and see what happens.

MattZ28 · 05-21-04, 11:56

It's possible, I've seen it happen to some people who fill up at gas stations that use certain additives in the gas.

Also, check the ECU grounds......I've also seen stuff like this happen on the Camaro/Firebird forums from something as simple as corroded battery terminals

Scottwax · 05-22-04, 12:03

Okay, I can check engine grounds. About 6 months ago, I cleaned every single ground connection and the spot each ground was attached too. Maybe one of them worked itself slightly loose. Battery terminals look real good though.

I swapped out ECUs with no change, seemed properly grounded.

Anyway, I really won't be doing anything to my car for a week or so. My parents told me I could take my Dad's car to get my kids next week in Kentucky (my parents are on a cruise to Rome), so I just picked up his car a few days early. I don't think my Accord is going to strand me, but I have 4 fully scheduled days between now and when I leave Wednesday for a 930 mile drive and I don't want to take a chance.

BlueRanger · 05-22-04, 01:59

Im having the same issue on my ranger, it happens so sporatically, I really am at a loss of what it could be. I still need to change my fuel filter, not sure it that will do anything, keep us updated, I want to know what to look for!

prowler · 05-22-04, 01:09

Sure sounds like a fuel filter. Question: when you changed it 2 months ago, what did the old one look like? If it was REAL bad, you could have a clog elsewhere - is there another filter ahead of your fuel pump, perhaps? (I know nothing of Hondas, but some cars have as many as 3 fuel filters, some only replaceable with major units like the fuel pump). Sounds like Honda did a pressure test, did they do a flow test as well? Just some ideas.

Scottwax · 05-22-04, 09:30

Quote:

Originally posted by prowler
Sure sounds like a fuel filter. Question: when you changed it 2 months ago, what did the old one look like? If it was REAL bad, you could have a clog elsewhere - is there another filter ahead of your fuel pump, perhaps? (I know nothing of Hondas, but some cars have as many as 3 fuel filters, some only replaceable with major units like the fuel pump). Sounds like Honda did a pressure test, did they do a flow test as well? Just some ideas.

The only other filter is the sock on the fuel pump...and the gas tank has to be removed to get to it. With 277,900 miles on the car, if I pull the tank, a new pump is going in even if the current one (which is the original) tests fine.

It was flow tested too. Passed. Problem is only under light load, and yes, the fuel pump/filter were the first things I thought of and he checked.

MattZ28 · 05-22-04, 09:37

Hey Scott, I just realized we have the same birthday! June 7th....except mine's 26 years after yours

Scottwax · 05-22-04, 10:19

Quote:

Originally posted by MattZ28
Hey Scott, I just realized we have the same birthday! June 7th....except mine's 26 years after yours

Which would make you 16, almost 17? I have a bowling ball older than you. Seriously!