Fuel-Related Issue?

[kenworth2500]

After some pretty decent driving, the S4 started to run like crap - as if it was running out of fuel, but it has 1/2 tank - and highway speed was limited to about 40-45. So I drove it the final 10 miles to the house. I changed both coil packs, but that didn't solve the issue. Next on my list: check fuel injectors; depressurize the fuel system and change the filter. What else do you guys think I should check?
Bob

[amanda11270]

I have an 88 esprit that has a diff. FI system however I believe the s4 has a more modern system that may have a schrader port on the FI that you can attach a fuel press. Gauge to, that should rule out whether you have a fuel pob or not.

[CarSalesman]

Unfortunately, a fuel pump or pumps are a good possibility. Pumps aren't bad to replace, but if one fails due to rust in the tank, you've got a big job ahead.

[lotusespritse]

Is there a way to inspect for rust on the inside without blowing yourself up?


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[CarSalesman]

With the pump and fuel removed, you can inspect inside the tank with a borescope. I don't want to say they are absolutely bad, but if you are replacing a fuel pump its a good possibility.

Ralph in NJ is doing the timing belt on my S4s right now. He scoped the tanks, they are ok, so I'm lucky! While its apart I am getting the a/c belt, alternator belt, water pump rebuild, water pump hose, chargecooler pump rebuild, cooling system flush, and 104 degree green dot cam wheels. I only had to buy one green dot wheel because the ex-distributor pulley on GM-EFI cars already has the green dot, so that can be moved to a cam position.

During the job Ralph called, said that the crank pulley got buggered coming off, not unusual for the age. He got one from England, not too expensive, but mentioned the supplier only has a few left, and won't be any more unless someone steps up to manufacture them. If you want to keep a spare pulley on hand, now's the time to order.

[QuadCam]

kenworth,

I had a similar issue with my 93.5. After about 1/2 an hour of driving, my esprit would stumble and fall on its face when going WOT. I also noticed a howling sound coming from the right side of the car.

ON an educated guess, I narrowed it down to a possible fuel pump issue. I had already changed the fuel filter and checked fuel pressure and couldn't find an issue. So, I went for it and changedf the fuel pump one evening in my garage......Bingo! Problem solved. I think my pump was just old and was failing when it got hot enough. not sure exactly though, but the pump was the problem.

the good thing is the pump is cheap.... about $75 from amazing for the appropriate bosch pump with all the necessary o-ring, pulsator eliminator, etc. You should also buy a new sock for the bottom of the filter, too. It is only a few bucks more.

Pump:

Amazon

Amazon

Sock Strainer:

Amazon

Amazon

[Vulcan Grey]

Did you check the spark plug wires or the plugs?

It definitely could be the pump at the age of the car, but check the easy stuff first.

I've had to replace plugs every 10k, and the wires several times in 12 years.

[MeisterS4]

Originally Posted by kenworth2500

After some pretty decent driving, the S4 started to run like crap - as if it was running out of fuel, but it has 1/2 tank - and highway speed was limited to about 40-45. So I drove it the final 10 miles to the house. I changed both coil packs, but that didn't solve the issue. Next on my list: check fuel injectors; depressurize the fuel system and change the filter. What else do you guys think I should check?
Bob

Basically had the same thing happen 2 springs ago. Was one bad fuel injector. I had a local place make me up a set and haven't looked back. Good luck.

[ChrisH]

Water in the gas tank can give similar behavior (occurs due to condensation over a long period of time). A cheap experiment to try is adding water remover. Don't use the cheaper methyl alcohol type. Pay 50 cents more for the isopropyl alcohol type, such as ISO HEET (not regular HEET). You can get it at an auto parts store. Pour it in, let it mix for awhile (e.g., overnight), and drive around some to mix it more. The experiment will cost about $3.

[jtrealty]

I would be very careful before adding anything to the gas. With all of the Ethanol they put in nowadays adding more can cause problems all by itself. Assuming the fuel is fresh you could try a can of Techron. Only add to a full tank, use it as far down as you dare and then refill with a fresh tank. As previously posted we are only guessing it is a fuel problem anyway. From your description of the symptoms it is possible it could be an electrical or vacuum problem. Guessing and then throwing parts at the problem is not the most efficient way to fix this. A little logic and some testing should help to narrow this down to at least the system causing this. Check fuel pressure, pull the spark plugs and examine them. How long has it been since any parts were changed? Maybe it is time for a tune-up?
David Teitelbaum

[mieczkow]

Here's the path I would take - the simple things first:

1. Verify that the fuel pump is pumping - just turn on the ignition and listen for the hum. If it's running then
2. Inspect the plugs and check the spark at all four cylinders. If that is good then
3. Verify that the fuel rail is being properly pressurized by the pump (that will require a simple pressure gauge). If so then
4. Using a set of noid lights verify that the injectors are getting the appropriate signals from the ECU. If all that checks out OK then
5. You very likely have a bad injector. If you have a spare set of injectors you can swap them in pretty quickly (30-40 minutes) and see if that cures the problem If you don't have a spare set:

Safest way to check injectors is take then to a professional - you can get injectors checked, cleaned, and serviced for about $15 each. If your injectors are OK and your spark is OK, and your ECU is delivering the appropriate signal via the injector harness I would say you likely have a fuel problem (water contamination, e.g.).

It can, of course, still be "something else" - but in my experience it is more likely to be a simple and identifiable problem (like a bad injector or bad fuel pressure) than something very exotic and rare.