3.2 Surging/Bucking :( Fuel tank filter?

[2cam]

Greetings all.

I have a 1986 3.2 that was running fine until yesterday. It was running great until I stopped at a stop sign on a somewhat steep street. The car had about an 1/8 of a tank (or maybe even a bit less) in it at the time. As I pulled away from the stop sign it began to surge and buck (hasn't done that before) and has continued to do it since then. Thinking that I may have starved the fuel pump due to the steep incline, I went straight to the gas station and filled the car up.

The issue has continued and is getting worse. The car was idling fine but would surge and buck off of idle. After surging and bucking, the car would die. It would then restart and idle fine but again would surge and buck off of idle. The fuel pump can't be heard when starting the car but can be while it is running or immediately after the car dies.

Any suggestions? I've read through the different threads regarding surging and bucking and all of the potential causes. It may just be coincidence, but given when the issues started, I'm wondering if the fuel system could have picked up some trash. Perhaps the fuel tank filter?

Anyone encounter a similar issue in the past?

Thanks!

2cam

[DRACO A5OG]

You do have a back DME relay, right? first try that.

[scarceller]

If you suspect fuel starvation DO NOT apply any heavy load on that engine till you resolve the issue. These motors do not like running lean and can be permanently destroyed from lean mixture resulting in detonation.

You should do fuel pressure test and fuel pump delivery rate testing.

[TheSt|G]

Do you often run it low or was this a rare occurance?

[2cam]

Originally Posted by DRACO A5OG

You do have a back DME relay, right? first try that.

I don't have a back-up relay (just recently purchased the car) but will pick one up. Thanks for the suggestion. Although I was leaning more toward a fuel issue due to the circumstances that immediately proceeded the surging (low fuel/steeply inclined street).

Originally Posted by scarceller

If you suspect fuel starvation DO NOT apply any heavy load on that engine till you resolve the issue. These motors do not like running lean and can be permanently destroyed from lean mixture resulting in detonation.

You should do fuel pressure test and fuel pump delivery rate testing.

Thanks for the guidance. Fortunately the car was being driven in a low(er) speed environment at the time without significant loads.

Originally Posted by TheSt|G

Do you often run it low or was this a rare occurance?

First time, but to be honest, I've only had the car about a month.

Could a blocked tank filter impact the fuel flow significantly enough to cause the surging and bucking?

Thanks!

2cam

[scarceller]

These cars are old and who knows what's in these tanks. So I'd say it's very possible something from the tank could have caused some sort of blockage. Fuel Pressure test and fuel delivery rate test may help point you in the right direction.

[TheSt|G]

It could, and when you run it low you increase the chance of picking up things from the bottom that have accumulated over the last few decades.

Since fuel pumps tend to fail all at once in my expierence, I would suspect you are ok there. That said, they cool themselves via gas so running out of fuel is very wearing on them.

[kidrock]

the fuel filter in the engine compartment can give you the same symptoms. What do you know about its history?

[dentist90]

Try this thread

My problem was exactly like yours. Idled fine, but bucked and hesitated at throttle tip in. Smoothed out and drove normally after I got past 2000rpm or so. Sound familiar?

[twistoffat]

On a low tank an a steep incline my money would be on dirt in the fuel line. IŽd certainly change out the fuel filter. I had slight bucking myself after getting dirty fuel. Drained the tank and changed the filter and it seemed to do the job.

[2cam]

Originally Posted by kidrock

the fuel filter in the engine compartment can give you the same symptoms. What do you know about its history?

Looking back at the records, I don't see any mention of a fuel filter replacement. I was planning on replacing it anyway as part of my baseline service on the car. I may as well start there as it's probably the easiest to do.

Originally Posted by twistoffat

On a low tank an a steep incline my money would be on dirt in the fuel line. IŽd certainly change out the fuel filter. I had slight bucking myself after getting dirty fuel. Drained the tank and changed the filter and it seemed to do the job.

Thanks. I'm going to give this the 1st shot.

Originally Posted by dentist90

Try this thread

My problem was exactly like yours. Idled fine, but bucked and hesitated at throttle tip in. Smoothed out and drove normally after I got past 2000rpm or so. Sound familiar?

Great thread! Thanks for the link and the info. I haven't had any issues with low end drivability until now and it happened suddenly. I'll move to this after ensuring that the fuel filters are in good shape.

Thanks to everyone for their input.

2cam

[Quicksilver]

Test the fuel pressure while running.