Bad Gas? Or something else...

[DL4567]

Hi guys,

TL;DR version: Engine hesitates when revved above idle. Sounds like it will stall. Bad gas? Or look for other things? (video link below)


Long version:
I went to drive my car today to give it some exercise, and for the first time in 16 years of ownership, it had a problem that kept me from leaving the driveway. After 10 minutes or so of letting it idle and messing with it, I ended up putting it back in the garage. I'm *hoping* it's as simple as bad/old gas, but wanted to ask on here and get some opinions.

Admittedly I'm getting worse these past few years of not driving it enough, and only get it out about every 1-2 months. But it has always been reliable, and if it's a longer interval, it might stall after the first starting try (automatic transmission), but it always runs great after the 2nd try on those occasions. Today it had been 7 weeks since I drove it last, and anticipating a stall on the first turnover I gave it a bit of gas to keep it running. There was a bit of a "pop/ping" noise from the engine as it turned over, which was unusual. It wasn't super loud or anything, but it bothered me because I haven't heard it before on startup. After that, it just settled in to 750 rpms and stayed there. It did NOT do the normal rpm-hunting that it typically does on every cold start in my ownership. But ok, I shrugged it off, and backed out of the garage. All seemed fine just letting off the brake and letting the idle speed move the car.

When I wanted to actually drive out of the driveway and put some load on the engine, is when I realized that when you press on the gas pedal, it stumbles and gets very hesitant, and sounds like it will stall. No matter how many times I tried, even after warming up for 10 min, raising it just above idle stumbled pretty bad. In neutral, it seems to be smoother if you get it up to 2,000 rpm or so, but no dice between 750 and 2,000.

The gas tank was last filled 4 months ago in August, and has been on 1/2-5/8 of a tank for maybe 2 months or so. I googled and see that gas can go bad in 3-6 months, but this interval is nothing I haven't done many times before for years and years with no problems. Also, not sure if it's of any significance, but this was the first "cold weather" startup this season on it. 7 weeks ago, it was much warmer weather.

Here's a short video. It really doesn't sound that bad on camera, but under load when trying to drive, the engine sounds like it will stall.

https://youtu.be/1WxIcD_eVcs

Am I on the right track to siphon out the gas, put in fresh and see what happens? Thanks all, for your help.

[artisticent]

Hi, I know with my car if i start it cold like that and let it idle, it takes a long time to get up to regular operating condition. Right now I have the center console so I can see the light from the bulbs. When I start the car those bulbs turn on but only when I rev the car to over 3k ish, the bulbs all get brighter and stay that way and the car runs normal. I noticed on your youtube video you only applied a little acceleration, but if you apply a higher rev like I do, does it settle back to a more normal idle?



Hi guys,

TL;DR version: Engine hesitates when revved above idle. Sounds like it will stall. Bad gas? Or look for other things? (video link below)


Long version:
I went to drive my car today to give it some exercise, and for the first time in 16 years of ownership, it had a problem that kept me from leaving the driveway. After 10 minutes or so of letting it idle and messing with it, I ended up putting it back in the garage. I'm *hoping* it's as simple as bad/old gas, but wanted to ask on here and get some opinions.

Admittedly I'm getting worse these past few years of not driving it enough, and only get it out about every 1-2 months. But it has always been reliable, and if it's a longer interval, it might stall after the first starting try (automatic transmission), but it always runs great after the 2nd try on those occasions. Today it had been 7 weeks since I drove it last, and anticipating a stall on the first turnover I gave it a bit of gas to keep it running. There was a bit of a "pop/ping" noise from the engine as it turned over, which was unusual. It wasn't super loud or anything, but it bothered me because I haven't heard it before on startup. After that, it just settled in to 750 rpms and stayed there. It did NOT do the normal rpm-hunting that it typically does on every cold start in my ownership. But ok, I shrugged it off, and backed out of the garage. All seemed fine just letting off the brake and letting the idle speed move the car.

When I wanted to actually drive out of the driveway and put some load on the engine, is when I realized that when you press on the gas pedal, it stumbles and gets very hesitant, and sounds like it will stall. No matter how many times I tried, even after warming up for 10 min, raising it just above idle stumbled pretty bad. In neutral, it seems to be smoother if you get it up to 2,000 rpm or so, but no dice between 750 and 2,000.

The gas tank was last filled 4 months ago in August, and has been on 1/2-5/8 of a tank for maybe 2 months or so. I googled and see that gas can go bad in 3-6 months, but this interval is nothing I haven't done many times before for years and years with no problems. Also, not sure if it's of any significance, but this was the first "cold weather" startup this season on it. 7 weeks ago, it was much warmer weather.

Here's a short video. It really doesn't sound that bad on camera, but under load when trying to drive, the engine sounds like it will stall.

https://youtu.be/1WxIcD_eVcs

Am I on the right track to siphon out the gas, put in fresh and see what happens? Thanks all, for your help.

[Michael]

What you are experiencing could be contaminated gas but it could be many other things as well. I would not immediately suspect contaminated/water in the gas as it is rare. I would look for vacuum leaks first. Checking(not setting or adjusting) the dwell might zero you in on the problem.

If it runs and idles decently but gets worse under a load or acceleration I would suspect in order:

Low battery voltage (check battery and alternator output)
Vacuum leak (especially in the back on the distributor advance or the cpr)
Fuel filter dirty
Ignition problem (possibly bad coil or broke /cracked dist. cap or burnt rotor)

[dn010]

You can typically smell that old stale gas smell in the exhaust if the gas is bad. If it sat for two months with gas containing ethanol then it is bad, I find it starts turning in a matter of weeks.

[Jonty]

As others have said could be a number of things including bad gas but you need to run through all the test. Test your fuel pressures and also flow patterns and rates from the Injectors because uneven flow rates and patterns can cause this.

[David T]

The two most likely causes are;
Stale gas
Stuck plunger in fuel mixture unit

Other possibilities include;
Low battery
Vacuum leak
CPR out of calibration
Fuel injectors dirty

[artisticent]

Could the fuel accumulator be in that list of possible issues?

Sent from my SM-N976U using Tapatalk

[DMCMW Dave]

Could the fuel accumulator be in that list of possible issues?

Sent from my SM-N976U using Tapatalk

Not likely.

[DL4567]

Thanks for the responses everyone, it is much appreciated! It's gonna be a busy next few days with Christmas, but I will try and swap out the gas for fresh, check that the plunger isn't stuck, and report back. If that doesn't help, I'll start exploring the other possibilities mentioned. FWIW, the battery should be good as it's a fairly new Optima yellow top, and I keep it disconnected with a kill switch when the car's not in use.

[David T]

Just because you have a "fairly" new battery and you disconnect it doesn't mean it can't be low on charge. A battery loses it's charge over time even if you don't use it. You should get it fully charged. Get a Battery Tender or something like it and keep the battery fully charged when the car is not in use.

[Michael]

Not to change the subject but Optima batteries suck ever since they moved their facilities out of the country(just like the old Bosch oe fuel pumps when they stopped making them in Germany).

I went through 3 yellow tops in 4 years. Apparently you also need one of their proprietary $200.00 charger/maintainers with their batteries as well. I'm team Interstate now and I doubt I will ever use another brand.

[DL4567]

I'll double check it, but I do periodically put a multimeter on it and it has always read strong since I put it in.
Interesting about them moving out of the country. My previous battery was another yellow top, from approximately 2005. It lasted me 12 years before I replaced it with this one.

[Michael]

I'll double check it, but I do periodically put a multimeter on it and it has always read strong since I put it in.
Interesting about them moving out of the country. My previous battery was another yellow top, from approximately 2005. It lasted me 12 years before I replaced it with this one.

A multi meter will only read the surface voltage. A load test is the only way to test a battery. That said, if the battery is showing +/- 14v, at idle, I doubt it's causing the engine problems whether the battery is good or bad.

[DMC-Ron]

Not to change the subject but Optima batteries suck ever since they moved their facilities out of the country(just like the old Bosch oe fuel pumps when they stopped making them in Germany).

I went through 3 yellow tops in 4 years. Apparently you also need one of their proprietary $200.00 charger/maintainers with their batteries as well. I'm team Interstate now and I doubt I will ever use another brand.

+1 on the Interstate batteries.
Ron

[Ron]

$.02

I don't see it being the battery.
If it's strong enough to start the engine, there would be enough power left to run the engine past the time it takes to get to operating temperature; Even with a dead alternator.

[David T]

I have seen where, even with a good alternator, a low battery causes a low system voltage and the ignition ECU doesn't like it and the car ran badly. Easy enough to check and rule out as a cause so it is worth taking a voltage reading. Anything under 12 volts is a problem. Remember, at idle an alternator can't put out much so if the battery is really low, the alternator is dumping everything it can into charging the battery and that can cause a system undervoltage. Add in a few bad connections, maybe a loose belt, and that's enough to make it run bad.

[DL4567]

After all the holiday parties and dust settled, yesterday evening I was able to work on the car. I think replacing the gas has solved the issue. Below are pics of what it looked like. Pretty ambery in color, and while the scent was rather weak, it smelled more like a paintbooth than gasoline (still not awful though). In the cups, new gas is on the left, both have only about 3/4" of liquid in them.

I knew there would be some lag time for the new gas to circulate around from the tank to the engine, but it still took longer than I expected. It ran horribly again for several minutes, sometimes shaking to the point where I almost turned it off. But I kept revving it to smooth it out some, and after about 8 minutes, it finally ran like normal. Revving it from that point on, was nothing but smooth. Woulda been nice if it didn't take 8 minutes of rough running, but I didn't feel like this situation warranted a total fuel system cleanout as if the car sat for years.

On the subject of the battery, I agree with the statement "if it was strong enough to start the car, it's probably not the issue for the rough running." But FWIW, a few months ago I did install new AC and alternator belts, as well as a new adjustable alternator tensioner bracket. So a battery issue wasn't out of the realm of possibility. But happy to report that with the engine running, the battery reads 13.98 at the terminals.

I let the car run for about 15-20 min, and will take it for a drive tonight, but (fingers crossed) I think it's good now. Definitely a wake-up call that I need to drive the car more!
My best theory is that the gas at the station in August when I last filled it, was already older than normal due to decreased Covid summer traffic. It's hard to imagine now, but not too many people were on the road still at that point.


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[Michael]

Glad it was a simple issue. Be sure to replace that fuel filter and it wouldn't be a bad idea to add a can of Seafoam with your next fill up.