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Discussion Starter #1
Hi everyone. I need help with a 96 Windstar 3.8 that is not running right. I replaced the lower intake manifold gaskets because they leaked (common split-port problem). I also replaced the plugs, plug wires, thermostat, coolant, and the fuel, air and oil filters. I tested the ECT and ACT sensors, and they seemed ok. Today I replaced the rear O2 sensor in response to a code (more on that later).

Major symptoms:

1. Runs rough ... lumpy idle, chugs slightly while driving.

2. It makes a rapid popping noise when under load, as in going up a hill. It sounds like popcorn is being popped in my exhaust. I can even make it do it in my driveway if I give it some gas in gear. It pops more when I floor it quickly.

It even pops slightly at idle. I got out and looked at the tailpipe, and when it popped, it made dust fly from the ground around the tailpipe. Also, the exhaust gas seemed like it might be unusually hot.

3. Last week, I finished a test drive around sunset, and I could see at least one cat. converter glowing dull red.

It was running really badly last week, and it threw codes 151 (O2 lean), 174 (bank 2 lean), and 302, 305, and 306 (misfires in cylinders 2, 5, 6). I figured at least one of the O2 sensors had been damaged by coolant, so I replaced the rear O2. I actually think that's Bank 1, but that is the side that had a coolant leak, so I figured it was most likely gone. It did look funky when I removed it.

So, the car runs somewhat better since I replaced the rear O2, but it's still got the same problems, just less of them. I drove it a few miles today, and the CEL has not illuminated for even a moment.

Has anyone corrected a similar problem? I would love to hear suggestions!
 

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Try temporarily disconnecting the exhaust system in front of the offending catalytic converter or both converters. The one that's glowing red *could* be blocked up. See if you can back it out of your driveway and drive it back in. Don't go nuts revving the engine with the exhaust disconnected, just drive it out and back into your driveway as if your kids were in it. If it acts ok, replace the cat(s).
 

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I would recomend cleaning the MAF to eliminate it as a problem. Is the sound coming from the engine compartment or further down on the exhaust?
 

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Jer2g said:
I would recomend cleaning the MAF to eliminate it as a problem. Is the sound coming from the engine compartment or further down on the exhaust?

Agree to MAF sensor problem, it is running lean because the MAF sensor is telling the computer incorrect amount of air, so the computer is not giving it enough fuel. This is why you here "popcorn", the engine is pinging. I had the same problem with my tbird and it had the same exact symptoms you described. I ended up getting a new MAF and all was good.
 

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Discussion Starter #6
Thank you all for your responses.

Jer2g, the noise seems to come from underneath the car. It's hard to pinpoint, so I think it's more from the exhaust than the the engine compartment.

You guys have given me some good ideas. I think I will look in my tech info and see if there is any way to test the MAF, then try cleaning it. I think disconnecting the exhaust is also a good idea, but I am reluctant to do that because I live in the rust belt. I want to try everything else before I touch the exhaust. I might test the TPS sensor too.

I want to get this fixed before this engine is toast!

Warped: I don't have any kids yet ... check back in a few years. :tongue: But I get the idea ... no hijinks without the exhaust.
 

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I'm going to agree with clogged cat. The only other reason exhaust would glow red is because it's running very rich and leftover fuel burns in the exhaust. So if the codes say it's lean and the cat is glowing, chances are it's plugged and messing up the o2 readings.
-Thomas
 

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Discussion Starter #8
Hi again, fellas. I worked on the car for a while today.

1. I tested the MAF. My Haynes manual says it should read 0.5 to 0.7 volts at idle. My MAF read 1.01 volts or so. When the engine was revved, the voltage did increase.

I then cleaned the MAF with electronic parts cleaner. When I reinstalled it, the idle voltage read a consistent 0.95 volts. It increased when the engine revved.

So, the MAF idle voltage seems a little too high. I don't know if the problem is with the sensor, or if the engine is really sucking that much air.

I unplugged the MAF and it ran worse, but it ran.

2. I tested the TPS. It seems to be fine. It swept smoothly from 0.985 to almost 5 volts.

One note on this: My Haynes manual (printed in 1998) has the signal and ground pins reversed in the diagram of the TPS connector. Signal should be center and ground should be top. This confused me to no end, until I checked my EEC test book.

3. When I unplugged the IAC, the car died quickly.

4. I unplugged the EGR vacuum hose and it made no noticeable difference in the idle.

After all this, the car seems a slight bit better, but not yet right. The cats don't seem to be glowing anymore. It doesn't pop at idle anymore, but it will pop with heavy throttle or going up steep hills. And it sounds a little "diesel-like" when I give it light throttle - that is, a chugging sound. I'm a little worried I might have an exhaust leak, but the exhaust system looks fine from the outside.

Thomas, I guess it could be a plugged cat, but I think the unburned fuel explanation seems more likely at this point. Those symptoms, however, seem to have disappeared for now.

During my latest drive, the "Check Engine" lit up again. Tomorrow, I will take it to Advance Auto and see what the code is.
 

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How did the sensor look, did it look white like it should. When I cleaned mine I used Windex it took off some of the junk, but I had to use a CueTip to properly clean it. I had a similar problem with pinging and throwing a lean code, but after I cleaned the MAF haven't had a code since and I feel the difference.
 

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Discussion Starter #10
The MAF sensor looked ok. The wires were mostly white/silver. They seemed to have a little bit of brown or gray deposits on them, but not much. I sprayed them a few times with the electronics cleaner and wiped gently with a Q-tip. I was very careful ... hopefully not so careful that I didn't really clean it.

I am very interested to see what codes the car throws. I may have a slight vacuum leak. Even so, it seems like the car is just running too badly for that to be the only cause.
 

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Discussion Starter #11 (Edited)
Update on the Windstar:

Monday, I got the codes scanned at Advance. The code was p1151 - a Ford specific code that means, "Lack of HO2S Bank 2 Sensor 1 Switches - Sensor at Lean Limit". This code had showed at the start of this debacle, before I replaced the rear bank O2.

Now, this seemed a little odd, because the car seemed more rich than lean. But I went ahead and replaced the front bank O2 because it was 100,000 miles old. Well, immediately after putting it in, the car ran MUCH worse. When I took it on the road, it popped like crazy and misfired. I thought maybe the sensor was bad, so I tested it. It seemed to switch fine at idle. I didn't try creating rich or lean conditions. I put the old sensor back in and the test results seemed roughly equal.

So, now I am thoroughly confused. I'm not sure what to check next. I may retest the MAF and TPS.

Further update:
I tried disconnecting injectors while the car was running. Disconnecting #1 (left injector, rear bank) slowed the idle down a little, and it ran a little rougher. But the front bank is really interesting. Disconnecting #4 (left front) made the idle terrible, and it made the loud popping noise every second or so. Disconnecting #5 had no effect, and neither did #6. In fact, disconnecting both together made no effect. So I think those cylinders must be dead. When all injectors are plugged in, they all click, so they are probably ok. I will try to measure injector current draw. Then I will look at spark problems (I thought I had that ruled out, but oh well).
 

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Discussion Starter #12
Problem Solved!!!

Okay, it looks like I win the Much Ado About Nothing Award. I had the #5 and #6 spark plug wires plugged into the wrong locations on the coil pack. What a dumb problem! I actually checked on this two weeks ago, but I guess the wires got mixed up where they pass under the EGR and I never noticed it.

Since I saw that two cylinders were dead, I took the plug boots off to see if it made any difference. None noted. The one hung close enough to the exhaust manifold that I could see sparks arcing, so I knew I was getting spark. So, I undid the wire looms and reversed the boots. Viola, smooth idle. So then I removed the intake elbow so I could swap the wires at the coil pack, like I should have done originally.

I think all the unburned air from the dead cylinders must have set the lean code. Then the engine tried to compensate by dumping fuel into the engine. Then all that stuff just lit off when it got to the hot converters.

Thanks to everyone for their suggestions!
 
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