ok the truck is a 1989 ford f250 standard cab 5 speed 4.9l the truck will run but always acting like its running outta gas always bucking and hesitating violently i have replaced the following parts both fuel pumps in the tanks fuel pump on the rail and filter all the fuel lines even new injectors new plugs wires caps and distributor theres no vacum leaks and i have good even compression on all cylinders and when the truck runs its extremely rich smelling and idles horribly like it wants to stall imguessing maybe fuel pressure regulator is done cus theres no difference when i remove the vacum line from the regulator with the truck running please someone help

 

Check your IAC, there known to cause those symptoms and restricts air causing the motor to run rich on fuel

 

already checked that it was replaced awhile back and is still working fine ty for the reply though

 

Sputtering
1. The first sign of a faulty fuel pressure regulator is when the engine sputters or stumbles as it runs. This often manifests itself as a heavy vibration as the engine accelerates.
Trouble Starting
2. Often times, cars with bad fuel pressure regulators will have trouble starting when they have not been running for a while. This is most noticeable if it persists for multiple mornings over a long period of time.
Noisy Pump
3. Faulty pressure regulation can lead to a noisy fuel pump. This is the common result of the fuel line attempting to inject too much gasoline into the engine, making the pump louder than normal.
Spark Plug
4. Spark plugs used with engines with bad fuel pressure regulation will often become fouled. Fouled spark plugs will show thick deposits on the contact surface.
Mileage
5. The biggest indicator of a bad fuel pressure regulator is a noticeable drop in gas mileage. This results as more and more fuel than is necessary is forced into the engine and burned up at an increasing rate.

 

so most likely i need a regulator ? if i install a new iac and regulator and problem is still there what should i do

 

They call around $25-$30 for a FPR. Either way your not out alot of money if that doesnt do the trick. Youl never know unless u try

 

what is the fuel pressure? what is the vacuum readings? did you check for codes? i would tackle these 3 and then it might shed some more light

 

anyone else have any suggestions? should i be able to pull the vacum line off the regulator and there be no difference at any rpm or load condition? i have driven the truck with the vacum lined crimped off and open and noticed no difference

 

vacum says normal on my gauge fuel pressure is 58 leaks down within minutes of shutdown o2 sensor code

 

ok replaced regulator and aic same issue

 

If you don't want to truck. Atleast try to sell it. You'll get more than the scrap price anyways. Someone would fix it.

 

What is the exact O2 sensor code?

A fouled O2 sensor can also trigger a lean or rich condition. Have you pulled it out to inspect?

Have you pulled the plugs and check them for signs of fouling?

 

it could be a valve not opening all the way, like a bent push rod, loose or broken rocker arm, bad valve springs. while running, pull spark plug wires individually and see if you can located which cylinder is causing the problem.

 

My 95 exhibited the same symptoms when the MAP sensor failed. Try disconnecting the connector or the vac line and see if it makes a difference.
regards
rikard

 

Does the speedometer jump arround when it sputters?