Does this mean I need new plug wires???

[imq707s]

I've got a 97 Mountaineer with a 5.0 V8 (same as an X-plorer). It's got 87,000 miles on it, and until now I have not had any problems with it at all. It started off with a "check engine" light about a month ago. I took the truck to Auto Zone and they scanned it and said it was the pas. side 2nd O2 sensor. Well, a day after I had it scanned the check engine light went off and has not came back since so I just thought that maybe the O2 sensor had some crude on it and it burned off. Well today when I was getting on the highway I noticed that the motor would start to backfire slightly if I put a big load on the motor, but when I let off the gas it ran fine. After I got off the highway and came to a light I powerbraked (1 foot on brake, 1 foot on gas) the motor just to see what would happen. The motor ran really rough and shook the entire truck. So tell me if I'm on the right track.

1. It feel like one of the spark plug wires may be going bad, they are original. I put new plugs in it after 70,000 miles.

What do you guys think?

2. Maybe the O2 sensor still needs to be replaced.

 

[Alec]

regardless of what's going on with the truck, the recommended service interval for plugs and wires on these motors is 60k.

 

[Robert]

Who's recommendation is it to change the plug wires at 60K? It is not in my '97 Owner's manual. The spark plugs have a change interval of 60K under severe duty, but the spark plug wires are never mentioned.

A dirty MAF can cause his symptoms. As a matter of fact last weekend when I decided to spray the Sea Foam Deep Creep into my throttle body, I left my intake tube disconnected since part of the procedure is to spray the Deep Creep into the throttle body with the engine running. Well my engine would idle without the air going through my MAF, but as soon as I attempted to give it gas, it would bog. I kept spraying the Deep Creep into my throttle body while trying to rev. it up. Eventually my engine shot a 12" flame out my throttle body and made a loud "bang". I decided to put the intake hose back on and sprayed the Deep Creep past the MAF.

 

[imq707s]

I've tried cleaning the Mass Airflow Sensor, but that didn't seem to make a difference. If one of the plug wires is bad, will it show up when you scan the ECU? Also, why did my check engine light turn off even if I never replaced the bad O2 sensor? It it possible that it just threw a freaky signal and set of the check engine light, and now it's fine? How many miles should I be able to get out of the o2 sensors? Thanks for all the help guys.

 

[Robert]

The way most CEL codes work is the first time your computer detects a fault it will put the code into "Pending". It will not set your CEL. If the very next time (with at least 8 hours in between) your computer detects the same fault it will move the code to "Trouble" and turn on the CEL. If your vehicle can be ran 40 times (with 8 hours in between to cool off) without detecting the fault it will clear the code and turn off the CEL. My Service CD isn't specific as to which codes would not follow this procedure, but it does say most codes do. It's possible that what the shop attributed to an O2 fault was wrong. It could have been something else that cleared up that was just affecting how your O2 sensor was operating. It is also possible that it was your O2 sensor and it was just barely at the limits of its operating range. If you get the same code again, I would go ahead and replace the O2 sensor.

Every time you start your engine it goes though some readiness checks. One of the checks is a cylinder mis-fire test on each cylinder. If you have a bad wire, it should show up there. Get it twice in a row and you'll set a code. Also you can get a mis-fire fault (P0301-P0308) when driving. If you get more than one, you will also get a P0300 which is a "multiple mis-fire detected". I had that when my intake hose was about to fall off my MAF.

As far as the life expectancy of an O2 sensor. Some people recommend every 60K. NAPA and Autozone both recommend changing them every 100K. I just replaced mine a couple of weeks ago at 95K since twice in the last month my engine lost all power and would bog down when I stepped on the gas. The first time was when I was pulling my tent trailer up a steep mountain grade. The second time was when I was cruising down a flat road at about 45 MPH. That time I pulled over and scanned my computer. I found a code in my pending location for an O2 sensor heater that didn't turn on. With the miles on mine, I felt it best to go ahead and get all four. I haven't had any episodes since I replaced them two weeks ago.

 

[imq707s]

Well, I finally went out and bought some new spark plug wires. I got the good Borg-Warner wires for around $60. After I put the new wires on the motor ran great. Started much easier, idles smoother, and didn't backfire when I would power brake it like before. I thought my problem was fixed. But now two weeks later, it's starting to run rough and backfire again. What the hell is going on? I'm still not getting any check engine light. I checked all the wires again and they look ok. Any suggestions?

 

[Alec]

You have 4 of the same thread going. All are going to be locked except this one:

Dead Link Removed