4.0 Rebuilt engine - Rough Ide

[Steve Campbell]

Hello,

I had my 96 Explorer 4.0 liter engine rebuilt a few months ago with 240K miles. Since the rebuilt, it ihas always idled very rough. The engines seems smooth while driving and over about 1200 RPM's. I replaced the fuel filter, had the vacuum check lines checked out - no leaks. I ran fuel injector cleaner and then took it a shop and had the fuel injectors cleaned, this was appro $100. The compression is at 155-160 accross all cylinders. I have taken it back to the engine rebuilder a few times and they are telling me that the possible issue might still be that the fuel injectors need a better cleaning. The check engine light is not on and there an not any trouble codes in the computer.

Is the fuel injectors the issue here? If the compression is good...is there anything that the rebuilder did wrong rebiuliding the engine? I would appreciate any and all comments. Thanks!

 

[gonenuke]

Could be the IAC. Try cleaning it and see if that helps. Might want to clean the MAF also.

 

[joe doe]

could be so many things ....maybe they bent the flywheel removing or installing the engine .this would add vibration .

 

[Steve Campbell]

Could be the IAC. Try cleaning it and see if that helps. Might want to clean the MAF also.

Okay... thanks for the suggestion. I might just buy a new IAC, looks like I can buy a motorcraft around $75.00 from Rock Auto

 

[Steve Campbell]

could be so many things ....maybe they bent the flywheel removing or installing the engine .this would add vibration .

Thanks .... I might just take it to the dealer. I think they have more sophisticated dianogics equipment then my local mechanic.

 

[Steve Campbell]

Could be the IAC. Try cleaning it and see if that helps. Might want to clean the MAF also.

I cleaned the MAF sensor and IAC today. The MAF looked brand new ! I bought MAF cleaner and also used it on the IAC. The IAC was very dirty - oily and I look in the intake manifold with a flashlight and it looked the same - dirty oil was covering the inside walls of the intake manifold. The truck also sometimes starts hard.

Any ideas ?? Should I buy buy a new IAC, MAF or EGV valve, or take the intake manifold off and clean.

 

[ralasa41]

hey there I rebuilt mine and hand the same problem rough idle and running rough, when you floored it it was ok ,, turned out I had the oxygen sensors plugged in the wrong sides ei ( left one plugged into the right side ) changed them around all sweet, worth a look

 

[wood1]

Did you install new plugs and wires with the rebuild? If wires are suspect, idle the engine in the dark, spray a saltwater mixture on the wires. If they are grounding out it will be obvious. Check the plug wires to make sure they are correct as well. If it idled this way from the beginning (of the rebuild) it could be something simple like that. Check the basics first.