Hey there! The car is a 1986 Bronco II.

Here's the problem. The car starts just fine (even if it’s been standing still for a while), idles normally at about 800-900 rpm, but dies at around 1000-1500 rpm when on light throttle. If I floor it, it works beautifully and revs quickly. I had my fuel pressure checked and that turned out to be very strange. At that exact moment when the car dies, the fuel pressure is at around 3.0 bar (43 psi), which is far too much.

As a result of that it is impossible to drive in slow moving traffic, since it constantly dies at that sort of speed.

Most of the sensors (map, iac etc.) are new and seem to be working. No error messages on the dash.
So, where to look at?

 

Published spec is 35 to 45 psi, so 43 doesn't seem way out there. Is it jumping up to that pressure? What pressure do you read at idle? What pressure do you read with no vacuum to the regulator?

If it is, as you suspect, that the fuel pressure is jumping too high when it stalls, then there are basically two possible causes for high pressure. 1)fuel pressure regulator sticking closed or 2) some kind of kink or blockage in the return line to the fuel tank.

 

Thank you for your reply!
It does seem to stay at around 26-29 psi and then when on light throttle (just like I described) it shoots to around 43-45 and the car stalls.
If it's the clogged up return line or a faulty fuel pressure regulator, why doesn't the car stall when on full throttle? (sorry, just trying to figure it out)
Also, how do I clean the return line?

 

At full throttle, there's more air, and the engine doesn't flood out. At part throttle, the engine would be flooding out.

Any way you can. You might try compressed air to see if you can blow it out. Or stick a long wire/pipe cleaner through it. Personally, if I determined that I had a clogged return line, I'd consider replacing it rather than trying to clean it.

 

You need to pull the trouble codes. When i had the very same trouble with my 87 it took me 2 minutes to pull the codes and find that the throttle position sensor was shot.

Connected my CP9087 to the TPS & sure enough the voltage was way to high at the low speed end of the sweep.

Your 86 is not equipped with a check engine light so "No error messages on the dash" is normal. 88 was the first year to have a CEL.

Pull the codes & ask the scanner gods to give you a nice easy fix with a code 53 "TPS voltage too high"