Car

Ask a Car Question, Get an Answer ASAP!

Have your own Car question?

29 Auto Mechanics are Online Now

characters left:

Not a Car Question?

Question

I have a 1991 ford F150 4.9L straight 6. The engine misses while idling if accelerated and during drive. Most noticed during lower gears. It is sometimes hard to start. The miss is not real bad and seems like it is one cylinder. I replaced the distributor cap, rotor, spark plugs and wires, EGR valve and sensor, fuel filter, and fuel pump relay. I tested the fuel presure and it was good key off and on. The diagnostic check initially showed code 542 fuel pump circuit failure then when ran again did not show any codes. I have duel fuel tanks and the problem is the same when using both. Do you think it is a bad fuel injector, ignition control module, or fuel pump? What do you recommend?

Submitted: 23 days and 1 hours ago.

Category: Car

Value: $13

Status: CLOSED

Year: 1991
Make: Ford
Make (other): F150
Model: 2wd
Engine: 4.9L 300

Posted by scottyz 23 days and 1 hours ago.

Answer

Hi XXXXXXXX. Thank you for asking your question on JustAnswer.

The problem that is causing your slight miss is likely a dirty fuel injector.I recommend running injector cleaner through a tank of gas.If the problem still is present, pinpoint the suspect cylinder and replace that injector.

23 days and 1 hours ago.

Reply

I forgot to tell you that I ran a bottle of cleaner in the tank and it got worse. Do you recommend testing the injectors with an Ohm tester? What ohm reading (2k scale) should I get for a good injector?

Accepted Answer

Ok, the injector problem is not an electrical malfunction ,the passage where the fuel flows through can become obstructed with dirt and grime.
You would be best off pinpointing the cylinder that is dropping off by pulling one plug wire off at a time while running(BE CAREFUL) .Then check your engines compression to rule out a valve or piston issue.You may also swap the injector with a good running cylinder to verifiy if the injector is fauty.

Accepts:
Expert:	scottyz
Pos. Feedback:	100.0 %
Answered:	10/29/2009

ASE Certified Technician

Master ASE tech, Ford senior master tech

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Car

Have your own Car question?

Related Car Topics:

Question

Optional Information

Year: 1991
Make: Ford
Make (other): F150
Model: 2wd
Engine: 4.9L 300

Answer

Hi XXXXXXXX. Thank you for asking your question on JustAnswer.

The problem that is causing your slight miss is likely a dirty fuel injector.I recommend running injector cleaner through a tank of gas.If the problem still is present, pinpoint the suspect cylinder and replace that injector.

Reply

I forgot to tell you that I ran a bottle of cleaner in the tank and it got worse. Do you recommend testing the injectors with an Ohm tester? What ohm reading (2k scale) should I get for a good injector?

Accepted Answer

Car

Have your own Car question?

Related Car Topics:

Question

Optional Information

Year: 1991Make: FordMake (other): F150Model: 2wdEngine: 4.9L 300

Answer

Hi XXXXXXXX. Thank you for asking your question on JustAnswer. The problem that is causing your slight miss is likely a dirty fuel injector.I recommend running injector cleaner through a tank of gas.If the problem still is present, pinpoint the suspect cylinder and replace that injector.

Reply

I forgot to tell you that I ran a bottle of cleaner in the tank and it got worse. Do you recommend testing the injectors with an Ohm tester? What ohm reading (2k scale) should I get for a good injector?

Accepted Answer

Related Car Questions

Year: 1991
Make: Ford
Make (other): F150
Model: 2wd
Engine: 4.9L 300

Hi XXXXXXXX. Thank you for asking your question on JustAnswer.

The problem that is causing your slight miss is likely a dirty fuel injector.I recommend running injector cleaner through a tank of gas.If the problem still is present, pinpoint the suspect cylinder and replace that injector.