Advice please. '87 FB Formula, 5L, injected, 5-speed; About a month ago it started cutting out and bucking as I was accelerating though the gears; usually between 1000 and 2000 rpm. I was not accelerating hard - just pulling away from the lights with the traffic. By increasing the rpm above 2000, it smoothed out. AC running. Voltage meter (dash) around 13. Temp gauge is around 170 deg. 73,000 miles on odometer. What should I check first... plugs and wires, fuel filter? I ran fuel injector cleaner though the system twice in the last two months. Seems worse when outside temp is hot. It ran fine this morning going to work with the outside temp around 72.

thanks, Jimmy

 

I am having a similar issue with my '86 2.8l. I have recently replaced the fuel filter and had the fuel pump operation checked.

 

Always fuel filter first.

 

Replaced the fuel filter… no change. I think I'll try SeaFoam next. I always like to try to cheap and easy fixes first. Wish me luck.

 

I added the SeaFoam today and drove it home (22 miles). The problem seems to be getting worse but I'll need more miles to see if the SeaFoam is working. I also noticed that the Temp gauge was on 160 degrees all the way to work and back. Normally, it registers between 190 and 200 degrees. (It has a 195 deg thermostat). I figure the thermostat is stuck open; could that be the cause of the lack of power and the engine stumbling? I will plan to replace the thermostat this weekend.
Any other ideas?

 

You need to watch your fuel pressure.

 

update… shortly after the last post, the problem went away. I stopped using the AC as the weather cooled down. It ran fine all winter and just today as I drove it and turned on the AC is started acting up again. I suspect a vacuum leak in the HVAC control head. It seems that under a load, it sputters and cuts out. I will drive it to work again tomorrow and see if I can isolate it to a particular setting. It doesn't cut out on Vent or Heater. I had it on Max and Normal today and it cut-out while trying to accelerate. Also, there is a vacuum actuated valve that redirects the coolant and doesn't send it through the heater core. Has anybody had any issues with this valve?
- Jimmy

 

To finish this thread... The vacuum lines that run under the fuel vapor canister had basically dissolved. It was a simple fix once I found it. Runs much better without that big vacuum leak.
- Jimmy

 

Okay... the saga continues... help. The vacuum line fix helped the idle to smooth out and now it doesn't stall when stopped for a red light. But now under moderate acceleration it is sputtering. This is in all gears. If I am gentle with the gas pedal, it does okay... but that's not why I bought the car. I have replaced the TPS, fuel filter, plugs, wires and MAF. Do you think it is ignition or fuel or maybe the cat is plugged? Car has about 78,000 miles and the gas mileage is consistently around 23 mpg.

What is the best way to check the fuel pressure? I have an old vacuum gauge that has a reading for fuel pressure, but the scale only goes to 15psi (which I think is not high enough).
Is there a test to check the cat without removing it?

Thanks.