Ignition problems or something... need advice
Thread Starter
Joined: Dec 2004
Posts: 1,294
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From: Dallas (Richardson), TX, USA
Ignition problems or something... need advice Hey all,
I was cruising in the car on Friday, and at first everything seemed fine. Then, while sitting at a light, I noticed that I could feel a slight thumping in the clutch pedal. I couldn't feel it in any other pedal or through the floor. I didn't think much of it because the car was still cold and I figured it was either running real rough or something was tapping (my exhaust has been getting loose lately, so that was my thought). Anyway, I pressed on.
After a few more miles I started to notice the thumping increasing. It still was only detectable through the pedal, but it was more consistant. Eventually, I could start to tell that the car was breaking up (misfiring) a little when I was accelerating lightly. I punched it once, and it seemed to pull well.
I drove some more and it continued to get worse. I was detecting more and more misfiring to the point of noticable power loss when accelerating at any amount of throttle. This continued until BANG! It backfired. This was not afterburn because it felt like someone hit the bottom of the car with a sledge hammer. I drove straight home at this point. There were several backfires on the way there.
When I got home, I lifted the hood and listened. Everything sounded alright. I walked around to the back of the car, and you could hear it misfiring if you listened carefully. The idle just cut off for a split second every once in a while. I walked back to the front of the car and started giving it a little throttle and listened to the valvetrain. It sounded normal. When I let off the throttle BANG!... another backfire. So, I just backed it into the garage and left in my shitbox DD (constantly thinking about the car while floating through the rest of my day).
Saturday I started the car and pulled it out of the garage. I let it idle for a minute or two, and there was no thumping in the pedals and no other problems. After mowing the lawn, I took the car for a spin. No problems at all. I ran it hard through first, second, third, and fourth. She pulled like a raped ape and gave me no problems.
Today, I drove her to work. I felt that thumping in the clutch pedal before I even got out of my neighborhood. I almost turned around to take her home, but I decided to go for it. I never experienced any problems, and the thumping finally went away when it warmed up. I really have serious doubts that the thumping is anything more than the engine rocking the car as it idles rough when cold (or misfiring when warm). This may be normal and just have escaped my attention until now, because it's pretty faint.
So, all that being said, do you guys have any ideas? I'm going to pull the plugs when I get a chance to see if one of them is fouled. However, since this problem is not consistant, I don't expect to find that. I also don't expect to find anything like oil on a plug because if it were a mechanical issue, it would be consistant. I'm thinking more along the lines of a bad coil pack or wire.
I was wondering, though... is there a way that the PCM could lose track of the cam and/or crank positions and thus screw up the timing? When I think backfiring, I don't think lack of spark. I think wrong timing. However, I don't know if this is even possible or if the PCM would correct the problem without intervention. Anyone?
Thanks in advance, everyone!
I was cruising in the car on Friday, and at first everything seemed fine. Then, while sitting at a light, I noticed that I could feel a slight thumping in the clutch pedal. I couldn't feel it in any other pedal or through the floor. I didn't think much of it because the car was still cold and I figured it was either running real rough or something was tapping (my exhaust has been getting loose lately, so that was my thought). Anyway, I pressed on.
After a few more miles I started to notice the thumping increasing. It still was only detectable through the pedal, but it was more consistant. Eventually, I could start to tell that the car was breaking up (misfiring) a little when I was accelerating lightly. I punched it once, and it seemed to pull well.
I drove some more and it continued to get worse. I was detecting more and more misfiring to the point of noticable power loss when accelerating at any amount of throttle. This continued until BANG! It backfired. This was not afterburn because it felt like someone hit the bottom of the car with a sledge hammer. I drove straight home at this point. There were several backfires on the way there.
When I got home, I lifted the hood and listened. Everything sounded alright. I walked around to the back of the car, and you could hear it misfiring if you listened carefully. The idle just cut off for a split second every once in a while. I walked back to the front of the car and started giving it a little throttle and listened to the valvetrain. It sounded normal. When I let off the throttle BANG!... another backfire. So, I just backed it into the garage and left in my shitbox DD (constantly thinking about the car while floating through the rest of my day).
Saturday I started the car and pulled it out of the garage. I let it idle for a minute or two, and there was no thumping in the pedals and no other problems. After mowing the lawn, I took the car for a spin. No problems at all. I ran it hard through first, second, third, and fourth. She pulled like a raped ape and gave me no problems.
Today, I drove her to work. I felt that thumping in the clutch pedal before I even got out of my neighborhood. I almost turned around to take her home, but I decided to go for it. I never experienced any problems, and the thumping finally went away when it warmed up. I really have serious doubts that the thumping is anything more than the engine rocking the car as it idles rough when cold (or misfiring when warm). This may be normal and just have escaped my attention until now, because it's pretty faint.
So, all that being said, do you guys have any ideas? I'm going to pull the plugs when I get a chance to see if one of them is fouled. However, since this problem is not consistant, I don't expect to find that. I also don't expect to find anything like oil on a plug because if it were a mechanical issue, it would be consistant. I'm thinking more along the lines of a bad coil pack or wire.
I was wondering, though... is there a way that the PCM could lose track of the cam and/or crank positions and thus screw up the timing? When I think backfiring, I don't think lack of spark. I think wrong timing. However, I don't know if this is even possible or if the PCM would correct the problem without intervention. Anyone?
Thanks in advance, everyone!
You're on the right track. The backfire is unburnt fuel in the exhaust. So, unless the PCM is throwing code (SES or CEL lite), then she's either running rich or fouled plug, wire, coil,...etc. as you have stated. If it's a PCM issue, she'll throw a code.
Thread Starter
Joined: Dec 2004
Posts: 1,294
Likes: 0
From: Dallas (Richardson), TX, USA
Thanks for the response.
So, I'll start digging into the ignition if the rpoblem reoccurs (I'll check the plugs regardless), but is there any way for the crank/cam position to get confused? I seem to remember reading a thread about this in the past but the engine wouldn't start at all. I'm just curious and want to be able to rule it out entirely.
And, just FYI, there's no codes. I have the random misfires code tuned out due to the cam, obviously, but there are no codes for a specific cylinder either.
So, I'll start digging into the ignition if the rpoblem reoccurs (I'll check the plugs regardless), but is there any way for the crank/cam position to get confused? I seem to remember reading a thread about this in the past but the engine wouldn't start at all. I'm just curious and want to be able to rule it out entirely.
And, just FYI, there's no codes. I have the random misfires code tuned out due to the cam, obviously, but there are no codes for a specific cylinder either.
