I have been having trouble with my 99 ranger. I just replaced the heads a year ago. Now I'm having trouble with it running rough. At the a idle it runs rough. I have know acceleration, then when I get up to cruzing speed it it really runs rough. I thought it was from the catylitic converter being cloged changed that but still running rough it helped a little. I can't figure it out. Any ideas what this could be?

 

Spark plugs and wires?

 

changed them changed the egr valve. pcv valve. still scratching my head

 

Hey Chris.

St. Clair Shores, eh? Nice place. I hung out there a few times on trips to Selfridge; was a guest of the Mueller's (prior to their untimely disappearance at sea). Trying to remember the name of their restaurant right there along the water.....good people anyway.

It sounds like you have way more than just an rough idle problem. First, I would verify you are getting spark at each plug. Use the installed (new) wires and any old spark plug. If that checks good, it COULD still be a bad plug, but doubtful since you replaced them. Begs the question, what did the OLD plugs look like? That can tell you a LOT.

Unplug your MAF and see if it runs any better disconnected. If it does, bad MAF.

Then I would suggest a compression check of each cylinder, first dry, then wet. That'll tell you if it's bad rings or valves (if you even HAVE a compression problem).

It doesn't sound like a fuel filter, but you oughtta check the fuel pump pressure at idle and higher rpm. You can actually use a dial tire pressure gage for this, but it needs to read over 60 psi. It will also probably ruin that gage if it has rubber seals inside as most do, but it's cheaper than the ones the parts store sell (and will work). $5 well spent for your quick test, then chuck it.

I assume your air filter is clean and intake tubing is all intact, tight, with no leaks.

Other than that, I'm about out of suggestions unless you've got more info. Good luck.

Somebody WAY smart is gonna jump in and help you.