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Contaminated gas, the gift that keeps on giving

I bought a half tank of gas nearly 2 weeks ago and have been having problems ever since.

The first 3 days, my minivan bucked and stalled and hesitated. I replaced the fuel filter after 2 days and after one more day of running poorly it seemed to get better.

The next 2 days it ran well, only stalling once per each time I ran the engine. For example if I went out to do some shopping, it would stall once on the way to the first store, restart and run fine then when I left to go somewhere else it would stall once on the way to that location, etc.

Last Friday morning I was trying to run it down and finish off the remains of that half tank of gas when the van stalled at the end of my driveway coming home and wouldn’t restart. Figured I ran out and got 5 gallons in a can. Van was hard to start and didn’t want to stay running. Filled it up thinking maybe it was still low to the pump in the tank. The next 3 days it would stop about every stop to every 3rd or 4th stop and would sometimes take a few tries and pressing the gas pedal to get it going.

I dropped the tank to drain the last bits of gas and make sure there wasn’t any dirt leftover from before the filter changes, which did catch a bit.

Put the tank back in and put in 5 gallons fresh fuel. Van was hard to start and wouldn’t idle. Pulled the spark plugs and all 6 were fouled: black sooty residue indicating running rich. Replaced them and it started and ran. Shut it down until this morning and went to drive for work.

Didn’t even get out of the garage before it stalled again. Knew I needed to fill the tank and figured it was just after effects of all the other symptoms. But the van won’t run easily unless I keep very slight pressure on the gas pedal. Stalls at stops and sometimes at low speeds if not using the pedal.

I would think it might be the O2 sensor, but the symptoms started before that should have kicked in. It could be the pressure regulator, have to check that later.

Any other ideas it could be? There are no codes showing so whatever it is isn’t tripping the computer to signal me.

The vehicle is a 1991 Plymouth Grand Voyager SE, 3.3 V6, automatic FWD.

I would check for water in the tank.  Even if you did not notice any, a can or two of a gas-water treatment will not hurt. 

When you say you checked the filter, you likely have two or even three “filters” One screen type in the tank and a changeable one somewhere and maybe a third.

The problem may not have been the gas at all. You’ve got fresh gas, a clean tank, and a new filter and the problem is still there.

Running rich can be caused by bad fuel injectors, bad engine temperature sensor, perhaps a bad fuel pressure regulator, and maybe a few other things.

I don’t think “contaminated gas” all by itself, would make the engine run rich.

If you had bad gas…there’s a good chance the dirt made it’s way past the filter and to the injectors. You’ll either have to replace the injectors (about $150 each)…or hopefully chemically clean them with something like seafoam or Chevron gas-line cleaner.

I really doubt it’s water at this point. I took the tank completely out and emptied it. I then cleaned it out and reinstalled it and filled it with fresh gas.

As for the filter, the best I can tell there are 2 screens in the tank, both of which I cleaned out, and the big inline filter under the van itself, which I replaced twice in the last week. Since I have seen no evidence of another filter, either on the van itself or referenced as a part number in any other search.

Thank you for actually reading my post before replying.

The reason I ruled out injectors is that it’s unlikely all 6 would fail at the same time, but nothing is impossible. Your other suggestions also make sense, but I’m not going to just throw parts at it and hope something works. If you could point me at some testing procedures, I would greatly appreciate it.

I have to agree that the gas in and of itself wouldn’t do this, but it could have caused something else to fail and start the problem.

Mike, you must work in a shop since you more than doubled the price I would have to pay for the injectors at my local parts stores. I’m going to try some more fuel injector cleaner, I’m also going to take the throttle body off and clean that out. Since the newest issue is at idle, it’s possible the air passages have gotten blocked or at least restricted and cause it to stall.

Since it won’t run properly at low speeds and that’s where I run it primarily, I have to get it running there long enough to be able to drive it.

You don’t have to take the throttle body off. The Throttle Body Cleaner will go to all the surfaces that air goes over on its way to the cylinders. While you have the large, black, intake tube off, you can use MAF Sensor Cleaner on the MAF (Mass Air Flow) sensor, also. This action can cause leaning of the air/fuel mixture.

Mike, you must work in a shop since you more than doubled the price I would have to pay for the injectors at my local parts stores

I haven’t worked as a mechanic for over 30 years to help put my self through college…The price was a WAG…My sister-in-law had to replace the injectors on her Taurus…and they were around that price. If you can get them cheaper…great…but I’d try cleaning them first.

Sometimes, it’s hard to see the forest for the trees. It’s easy to get distracted after all that work ridding yourself of the “bad gas”. Have you checked the fuel pressure?

As far as I can tell, this van doesn’t have a MAF sensor. And the throttle body is a bit awkwardly located to clean in-car. I can easily spray the bottom half but can’t easily get the cleaner to the top half, this also restricts my ability to clean the back of the butterfly valve. The gasket is only about $3 with sales tax and the job is much less involved than dropping the fuel tank.

It’s not likely bad gas at all. If bad gas is suspected then why haven’t you dumped the fuel filter contents and made sure?

Cleaners won’t work on solid particulates and water contamination won’t hurt fuel injectors.
Dump the filter contents. If it’s clean then you problem is elsewhere; fuel pump, fuel press. regulator, etc.

Your van has a MAP sensor (manifold absolute pressure) not a MAF sensor.

This determines the load point of the engine, so it could cause a rich condition. They rarely fail though.

Right. No MAF Sensor. It has a MAP (Manifold Absolute Pressure) Sensor.
How does the van stall? Suddenly, or does it stumble and stall? If it stalls suddenly, I’d suspect a sudden loss of electrical power (like, to the ignition from the ignition switch); or sudden loss of spark caused by a loss of the primary ignition signal to the ignition coil.

I don’t suggest throwing parts at a problem, and I agree it’s unlikely all 6 injectors would fail at the same time. More likely is the computer telling the injectors to spray too much fuel due to a bad signal from one or more sensors.

I like to have service manuals for my vehicles, and highly recommend them. Factory manuals are best, but expensive. I’ve found Haynes to be pretty good (and not expensive) for most do-it-yourself maintenance, and they usually have test procedures and step-by-step diagnostic diagrams.

Don’t guess, get a manual, then follow the testing procedures to find the problem. If you can’t find a manual locally for your van, try

If you read everything I did in the original post, I did change out the filters.

I didn’t state that I blew out the first filter and got a bit of dirt/rust come out.

I have since replaced the filter again, but the second time it was clean (as in nothing came out that I could see).

Since I have taken the tank out and completely emptied it, taking any dirt and/or water with it. I then bought fresh gas to put in the tank. The same brand from the same pump I put in a relative’s Dodge Dakota, even bought at the same time by filling the gas can and then the pickup. Since I am having no issues with the pickup and the gas, I am assuming the new gas is clean.

Thank you for a good diagnostic question.

It doesn’t just stop, it’s more of a slight change in the rpm and then it dies. I guess you could call it a stumble but it is very slight. Again, if I’m able to apply slight pressure to the pedal(not so easy to do with it in gear and keep it from moving), it won’t stall, as though the throttle plate is sticking or maybe the TPS is slightly off. The TPS is non-adjustable and I did set a code for it the other day by turning the key on with it unbolted. The code went away when I disconnected the battery to work on the tank.

I have the Haynes manual but I have found it lacking for the 91 and up models. I have a friend with a Bentley for his van, but it might be an older model and he’s out of town for the day.

I wasn’t saying you were saying to throw parts at it, and I apologize if it sounded that way. I just like to know what’s wrong so that I know the repair is done right, which is part of why this has me pulling my hair out.

Update: I cleaned the throttle body and got the same problems.

Then I dug out my fuel pressure gauge and got 40 psi cranking, about 50 running with the vacuum line disconnected. My Haynes manual says 1991 and later should be about 48.

I put in some Lucas Fuel Injector Cleaner but it won’t be much help if I can’t get the van running to get it through them.

Have you checked for any fault codes? Here is my copy and paste special on how to.

You may try to get the code by turning the ignition key on, off, on, off, and on. Note, on is run position not start position. The check engine light should go on as a bulb test then go off, the following flash that follow are codes, so if you had four quick flashes a short pause two more quick flashes followed by a long pause then five quick flashes a short pause, five more quick flashes. This would indicate two codes. The first code would be 42. Open or shorted fuel pump or ASD relay coil. Second code is 55. Which is end if diagnostic codes. You should always get that at the end.
If you can get the code number, and post back someone should be able to tell you what it is.

                                    Good luck and post back