Truck is running rough and backfiring.. Help!

[imq707s]

I've got a 97 Mountaineer ( just like an explorer) with a 5.0 v8 and 87,000 miles. It's all stock and I have had no other problems since I've owned the truck. It has lost most of it's low end power and if you mash the gas at a stoplight it will burble and pop really loud out the exhaust before it finally starts to rev. If I'm cruising around town at around 40mph and the RPM's are really low (1300) it will somtimes backfire. I'm not getting any check engine light at all. My millage has not went down either. I'm thinking it's either plug wires, plugs, or O2 sensor. It seems like it's loading up one of the cylinders with gas, and then it fires the plug and BAM, it backfires. I put new plugs in it 10,000 miles ago, and I thought that if one of the 4 (yes that's right, 4) O2 sensors was going bad, it would trigger the check engine light. Can some of you guys give me some help. Thanks.

 

[section525]

Check your wires and coil packs. My '96 5.0 has had two coil packs go out on it so far. It acts sort of like what you describe. You should change your wires anyway since you have over 80k on them.

 

[imq707s]

Is there any way for me to test each coil pack?

 

[section525]

What I did was pull the wires off while the motor was running and make sure there was a spark coming out. Just be very careful not to get shocked!

Go like this: pull wire number one, make sure spark is coming from the pack, put it back. pull wire number 2, etc etc.

You can use some sort of non-conductive pliers or something.. but I just used my hands. Just dont get too close to the spark!

 

[Howard]

Ok here is how to test the coil pack:

To check the primary (which must be ok or no spark at all) disconect the plug and probe the connections with an ohm meter (three pins centre +ve both outers -ve) looking for 0.3 - 1.0 ohms.

To check the secondary
Probe the pairs 1-6,3-5,4-7 and 2-8 looking for 6.5k - 11.5k ohms.

In theory you can check the plug wires with the meter looking for about 5k ohms per foot cable.

With the milage you prob need new plugs and leads.

Just my 2c worth anyway hope this helps.

 

[imq707s]

The motor idles great, but only acts up when it get a heavy load on it. Is it possible for a coil pack to act up under heavt loads, but work great under light loads (idleing)? Thats kind of how bad plug wires act, they start to act up under heavy load.

 

[Howard]

I'd start with new plugs and leads not too $$$$ and needed soon anyway.

 

[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