Hello, I am new to this forum and vehicle repair in general. My daughter owns a 97 Ranger XLT 4.0 with about 150k miles (automatic). She dearly loves this vehicle and it has been fun to tackle some of the old truck issues that have popped up with her. The vehicle is currently experiencing some rough idle issues once the truck has warmed up. It seems to idle just fine for about 5 minutes and then it just stutters while stopped at a light. We have recently changed spark plugs (at mechanic). Then we have personally changed the fuel pump and fuel filter, as well as the IAC, ourselves. MAF and O2 sensor have been checked by mechanic as well. We do have the ERG valve and pipe in which we plan to replace. We have also attempted to look for any other vacuum leaks and have not found any. Other than replacing the EGR does anyone have recommendations?

Thanks in advance!

 

Welcome to the forum

Put a can of Seafoam or similar injector cleaner in the gas tank, once a year
Helps my 1994 4.0l idle smoother, get slowly worse over the year
Dirty injector tips

Assuming an automatic since you don't tend to "feel" a rough idle in a manual trans when stopped, with an automatic in gear the engine is under load even when stopped so any misfires are felt

EGR valve leaking exhaust into the intake can certainly cause a rough idle, exhaust should only be added to intake when accelerating or cruising at speed, it reduces Toxic gas emissions, and pinging/knocking

Also on the 4.0l clean the MAF sensor every year or so, easy to do
And make sure to keep cooling system working well, and tell her to PULL OVER at the first sign of overheating, DO NOT try to "make it home", as overheating will cause a cracked head(or 2), no do overs on these engines, lol

 

New to the forum you say? Did you replace the IAC with OE? That'll be a Motorcraft or Hitachi part only.

 

Thanks for all the tips. We have put injector cleaner in with no change, but plan to continue that yearly.

If the EGR is bad will it idle low or high? Mechanic said he didn't believe that was the problem since the idle is low.

We will keep an eye on the MAF and thank you for the overheating tip. She would love to see this vehicle to 300k+.

 

We did replace with Motorcraft.

 

Just a quick update. We found someone to switch out the EGR valve and pipe. That fixed the rough idle issue. Thanks again for the above advice. Glad to have the issue repaired.

 

Be sure to check the wires really well by the eve. We taught a cel for months and I just happened to find a bear wire cel went away so did the rough idol