Could an improper seal on my fuel suction assembly be causing these issues?

[ThrowingChicken]

Long story short[ish], my fuel sender gauge went bad on my 2007 Yaris and on Monday I ended up having a mechanic go into my tank to replace what everyone assumed was a bad fuel pump only to discover that it was actually just out of gas. After getting everything back together and pouring in 5 gallons, I was able to drive it about 15 miles over the course of two days before I noticed it was getting a little sluggish the check engine light came on.

On Wednesday, I run into a store, and when I come back out the car starts very roughly, engine is shaking a bit. I'm thinking maybe it will work itself out once I get going, but as soon as I pull out of the parking spot the engine dies on me and I coast into another space. I can't get it to start. I have about 25 miles on it since Monday, so there is no way I am out again. I hit up the mechanic and he asks me to add more gas to see what happens. I come back about 3 hours later and dump in another 5 gallons, and it starts on the second try. It's rough, but I am able to get it home.

It sits until Friday when the Mechanic comes back over. He puts his scanner on it and reads out a few codes and starts going through them to figure it out. He starts by cleaning the MAF sensor, and the car starts up wonderfully. We go for a ride through the neighborhood and everything seems peachy, better than ever. We hop on the free way so we can test it at higher speeds, everything seems good, though when I hit around 70mph, which is about 10 miles into our drive, I feel the acceleration cut out on me for a moment. The mechanic can't really feel it like I do so he assumes it's just the gears shifting or me hauling it or something. Anyway, we exit and I am going around 45mph and the acceleration cuts out again, only this time it is very obvious since I have the pedal to the floor and nothing is happening. He thinks maybe I am low on transmission fluid, so we get it home and check that out. Levels are fine (though it is probably due for a change). While he is checking it, the car is in idle and the engine starts developing a shake and the exhaust is popping a little. His scanner is reading misfires. He unhooks the fuel line to check the pressure and he says it is flowing but he expects it to shoot out like a super soaker (I guess he doesn't have a gauge?), so his next assumption is that maybe he kicked up some gunk on Monday when he was messing with the fuel pump, and that gunk has clogged up the filters and the fuel pump, so I might as well order a new filter, fuel pump, and while I am at it, fuel sending gauge.

So here is where I get to the question about the improper seal. While researching the parts I need, I ended up watching a video about the fuel sending gauge and how you can test it, so I decided to do that myself, but after removing the retainer I found the rubber gasket is sitting on top of the pump assembly, when it is supposed to be between the pump assembly and the fuel tank. Now, I could be wrong, and the gasket could have simply become dislodged and ended up in the wrong spot when I was taking the retainer off, but my question is... *if* this mechanic put the gasket on in the wrong spot, thereby eliminating an airtight seal, could that cause the problems I have been having since Monday?

[ex-x-fire]

The top seal is there to prevent fuel from evaporating & leaking (among other things). You need to verify the fuel pressure.

[dogsridewith]

Something fouled or connected wrong in the Evap system causing excessive fuel tank vacuum?

[ThrowingChicken]

Rats, I was hoping it was something that simple. I got everything back together and started her up, she runs okay for a little bit but then starts losing acceleration.

[CoryM]

Since it's easy to do, try driving with the gascap off so that air can enter. Don't corner hard while cap is off. If this fixes it, replace the EVAP vent valve
Do you know what DTCs it had? P0420?

[ThrowingChicken]

Actually I am getting a P0171 code.

While I wait for a replacement pump and filter to arrive, yesterday I decided to go back into the fuel pump assembly to see if I could clean the filter and inspect for other possible issues. When I popped the tabs off the filter housing the fuel pump slid out and I noticed right away that the o-ring was practically shredded.

https://i.imgur.com/m8CgWeHh.jpg

It stood to reason that a bad seal there could be causing low fuel pressure, so I replaced the o-ring and took a shop vac to the filter and the accessible tubes just in case that would do anything. I got everything back together and fired it up (which took a number of tries compared to the last time I pulled the fuel suction assembly, but it got there). I drove around the neighborhood a bit and tried to force the slippage I was experiencing earlier by gunning it at a low speed, but everything seemed to be working fine for quite a while, but eventually I thought I felt some hesitation on acceleration, so I headed home and had a look under the hood and realized the ventilation hose #2 was disconnected. No idea if that affects performance any but I hooked it back up, and a couple hours later after traffic died down I went on a longer test.

I put about 30-40 miles on it last night without issue, highway speeds, everything seemed resolved. The check engine light even turned off. Then today I put on another ten or so, go get a couple tires replaced and rotated, then after leaving the tire shop, I find I was having trouble accelerating past 60mph while going on a slight incline. A little while later I am getting some fairly consistent slippage/hesitation again. It seemed to happen more often when I had the AC on, but I can't be sure that actually has anything to do with it.

The guy at AutoZone who read the codes thinks it's probably a couple of bad spark plugs, which in turn are dirtying up the MAF sensor.

[B.B._07]

The guy at AutoZone who read the codes thinks it's probably a couple of bad spark plugs, which in turn are dirtying up the MAF sensor.

How in the world a bad spark plug is dirtying up your MAF sensor is something that the Autozone guy can only know. Autozone is good at recommending you parts that you don't really need. The iridium plugs have a service interval of 120,000 miles I believe so unless your have a ton of mileage on your car they're most likely fine. I'd suggest renting a fuel pressure gauge from Autozone or another of the car part places. You should see 44.1 to 49.7 psi with the system pressurized or with the car at idle.

[ThrowingChicken]

I can't say, he made it sound like a misfire could contribute to dirtying up the sensor faster.

I actually have 127,000 miles, so I'm there.

https://i.imgur.com/jLXw601l.jpg

I reset the computer tonight using the terminal discharge method, and drove it around for about 90 minutes, covering 75 miles. The check engine light hasn't come on yet, though I felt some hesitation a few times, mostly when at high speeds. I feel like I have it 95% restored from how it was a week ago, but that last 5% is just killing me.

I'll look into getting the fuel pressure reading.

[dogsridewith]

Now we have to remove covers and coils to do it, but the reasons to inspect plugs first or early in troubleshooting remain. (Less, I suppose, if we know that Hal will notify and provide a trouble code for misfires.)
One plug looking different from the others is really informative. A head gasket starting to go or a cylinder burning oil will show. A leaking valve can cause lower compression (compression check is another early thing to do) which can cause a misfire. If something is causing an intermittent lean misfire, the effects of unburned fuel may be on the plug. Of course, check the gaps and condition of the plugs. If porcelain around the center electrode shows a crack starting, you might save an engine.

[ThrowingChicken]

I pulled the plugs and they were in pretty bad shape, so they all got replaced, unfortunately that didn't really solve the hesitation and I'm still getting an lean error code. Haven't been able to measure the fuel pressure yet.

[dogsridewith]

bad shape in what way(s). Did they all look just the same? Still might be useful to read them again for some cylinder showing different. (When a headgasket leaks between cylinders, both of their plugs may show effects.)

(Lean code reading more suggests something affecting all cylinders though?)

[B.B._07]

I can't say, he made it sound like a misfire could contribute to dirtying up the sensor faster.

I actually have 127,000 miles, so I'm there.



I should have been more clear with my comment, there is no way a misfire is somehow making the MAF sensor dirty. The MAF sensor is located behind the air filter and whatever is happening is the combustion camber and cylinder can't make it any more dirty or clean.

Reading the plugs won't be very useful unless one looks drastically different from the the others. Like the Autozone printout for a P0171 lean code is suggesting verify you have good fuel pressure first. Then you'll know for sure whether a new fuel pump will solve your problem or will be a waste of money. Renting specialty tools from Autozone is free (there is a refundable deposit) so there's no reason not do it.

[tmontague]

You may have already done this but a P0171 lean code is often triggered by a vacuum leak. If you can read your fuel trims at idle and at 3k rpm it will help you diagnose this. Easy fix once you identify it

[castles]

Just about a month ago I bought an '08 Hatchback. Within a couple weeks I was getting a flickering check engine light and no acceleration intermittently. AutoZone codes indicated a misfire, forgot the exact wording, but it turned out to be an ignition coil pack. Replaced the bad one and haven't had any problems since (knock wood).

[ThrowingChicken]

bad shape in what way(s). Did they all look just the same?

They all looked pretty close to the same to me, but they were discolored and ashy. I think I tossed them already or I'd take a photo, but pretty similar to the one on the left here except the white ash was further up the ground electrode. http://automotivebros.com/wp-content/uploads/2017/02/bad-spark-plug-vs-good.jpg

Like the Autozone printout for a P0171 lean code is suggesting verify you have good fuel pressure first.

I picked up a fuel pressure gauge and sure enough it was reading 25-30PSI at idle, so I replaced the fuel pump and took another reading and it came in at slightly above 45PSI. This seems to have resolved the hesitation I was feeling at higher speeds, however the car still does not have as much punch as it did just a few weeks ago. So far the check engine light hasn't come back on, so it not having the same pep seems to be the only issue now. The only thing I really had planned to do was replace the injector insulators but I'm not sure the ones I have on there are causing any problems.

You may have already done this but a P0171 lean code is often triggered by a vacuum leak. If you can read your fuel trims at idle and at 3k rpm it will help you diagnose this. Easy fix once you identify it

I feel like this is a stupid question, but how do you read RPMs on this thing? It doesn't have an RPM gauge on the dash, just the speedometer and mileage/fuel/clock.

[ThrowingChicken]

Alright, replaced the injector insulators and replaced half of the transmission fluid. Didn't really notice much of a change in the pep. Poured some engine treatment into the gas tank and the take off starting to feel a lot closer to how it felt a few weeks ago.

[B.B._07]

I'd suggest a Bluetooth OBDII scanner to read the engine rpm's. They're really affordable and can do a lot more than just read rpm's.

This is a good one, but there's many others;
https://www.amazon.com/Veepeak-Bluetooth-Automotive-Diagnostic-Vehicles/dp/B011NSX27A/ref=sr_1_8?s=automotive&ie=UTF8&qid=1523726819&sr=1-8&keywords=bluetooth+obd2

[tmontague]

^ this, or buy an ultragauge online which you can configure to show rpm

[dogsridewith]

An end pin on OBDII connector and anyfer ground to multimeter set on "frequency." Stand multimeter in pull-out driver's side dashboard cup holder and you've got a tach. (How I found mine idles close to 600 when warm.)
(probably more info by advanced search--type dogsridewith on right side of page and multimeter on left.)
(I found which end pin, of the 4 on the two rows, by a search here.)