Contour Enthusiasts Group Archives Forums General Troubleshooting Low RPM Stumbling, Especially on Cold Mornings

I have a 95 V6 Mtx with 158,000 miles. Lately it has been running rough at lower RPM's. Give it heavy throttle and at ~3000 or so RPM its like turning on a switch and it pulls hard and steady. In the cold, it idles rough and acts rough at low RPM's. It gets better when warmed up, but still doesn't feel really smooth until 3000+ rpm.

Have changed all the plugs (Autolite 764 PP) and had a shop fog clean the air intake system in response .

Before I take this in to the stealership, help me zero in on the most likely culprit.

Thanks,

Chris

i would chang the ECT "engine coolant temperature sensor"
and spark plug wires first

I would start with making sure that the cleaning they did didn't just stir up the junk and mess up the IAC (idle air control). There is a good chance that the IAC needs cleaning. Clean the throttle body while you are there.

Would the IAC being gummed up only affect the idle? or the drivability too?

Note that the intake cleaning was in response to my problem, and it should have cut through anything on the throttle body.

It depends on where they introduced the cleaner and how thoroughly they cleaned things. My experience is that the throttle body usually needs at least a light brushing to get clean. I use an old toothbrush.

The IAC will most definitely effect both the idle and light thottle operation.

Pull the air intake hose off and have a look at the throttle body. I'll bet that it didn't get cleaned very well.

I'll I'm saying is review the work that was just done.

what does the engine coolant temperature sensor do? and why would that affect driveability at first startup?

it tells the computer if the car is cold or hot and adds or subtracts fuel as needed

OK, I got the OBD codes using the paper clip jumper. They are in order:

522
522
176
177
542
176
177
542

Any hints here? I don't see much to help based on my 3 digit code guide. O2 sensors have only about 40K on them. Note that my stumbling problems started about two days after I corrected a serious misfire on #2 plug that had been going on for about 2 weeks. I changed out #1 and #2 plugs in finding the misfire. Ran great, then stumbling and poor idling started 2 days later; then I changed out the rest of the plugs with no real difference in the stumbling.

I also yesterday tried gapping the plugs down to .044. No difference in performance.

I'm going to pick up new Motorcraft wires tomorrow. Thinking also about picking up a CTS, IAC, and a TPS, and tearing down the throttle body myself, but I really can't afford all that.

Could I have a vacuum leak?

Thanks for the experienced help.

Chris

I would put money on plug wires, they seem to last a long time untill you strt moving them around, IE changing the plugs.