schultzsj

iTrader: (1)

Within the last couple weeks my car started occasionally having a severe stumble or loss of power. It feels like it has dropped at least a couple cylinders or the traction control has come on for no reason (TCA is and has been unplugged). It seems to happen more when the car is hot and especially shortly after it has been turned off hot and re-started. It happens more at low RPM but has happened for a few seconds on the highway as well (at maybe 2500 RPM). It will bog for several seconds, then catch and run normally, and then bog again for several more seconds, and might repeat that cycle several times.

Sometimes it throws a code and sometimes it doesn't. I didn't get the DTC number but it was something to do with the right O2 sensor. However, we looked at the sensor output and it seemed to be reading normally so it clearly was not completely disfunctional (although it could be intermittent). Also, I have had O2 sensors go out in the past and the car doesn't run anywhere near this bad when they do.

I tried cleaning the MAF wires but, otherwise, I have not changed anything on the car in quite some time.

Any ideas? Mods are in the sig.

Thanks,

Steve

schultzsj

iTrader: (1)

Top

69lemansguy

iTrader: (12)

Maybe a damaged spark plug wire? when its connecting your car is running fine, but then it loses connection, and you drop that cylinder... also maybe a fowled plug. Might be worth taking a look at, and could be a cheap and semi easy fix as well.

schultzsj

iTrader: (1)

I will take a look at the wires but I am sure it is more than one cylinder dropping out - it looses most of it's power and won't hardly hold speed. It feels like an electrical problem but it could be an electrical problem causing several injectors to drop out. I don't notice any significant fuel smell when it happens (like the injectors are working but the plugs aren't) but I don't know that I would be able to smell it from the driver's seat anyway.

I have a couple old O2 sensors, at least one of which is probably good, that I will try tomorrow but, like I said, it is running worse than bad O2 sensors usually cause.

Any other thoughts?

Steve

Slvr00Bird

iTrader: (2)

If it's not plugs/wires i'd check the cam sensor.. and if it's not that.. maybe the crank..

Does it ever do it from startup (cold)? Just hard to start and won't, but then might and will go a couple feet and die.. then when you get it up and going everything is alright for a bit?? Describe it a little more..

69lemansguy

iTrader: (12)

Didnt realize it was that heavy of a power loss. Yea, it probably isnt a plug/wire problem... fuel pump problem?

Slvr00Bird

iTrader: (2)

Forgot if it's mentioned above or not, but if it only happens when there's a load on the car (ie it's in overdrive and trying to pull up a hill or something similar) then it very well could be a coil pack..

schultzsj

iTrader: (1)

It is more noticeable under load because it looses so much power but it happens during steady state driving also and I pretty sure it is more than just one cylinder.

I installed an old O2 sensor on the right side that throws a code and it made no difference. The sensor I removed was completely black on the tip so the right side at least is running very rich at least some of the time. Looks like maybe the injectors are working so perhaps a lack of spark is causing the bogging.

Any other ideas?

Steve

streetassasin

iTrader: (30)

clogged cat or maybe fuel filter

Slvr00Bird

iTrader: (2)

I wouldn't think it's either one of those.. Clogged cat usually has symptoms of slow slow slow (did i say slow) acceleration when it's to the floor and it won't ever pull its self all the time... Not like dropping a cylinder out.

And fuel filter.. Don't think that explains the stutter or roughness and just doesn't sound like it'd be it (but could)..

My money is on a coil. Is there anyway you can log it while you drive? Or maybe borrow a coil off of a buddy (or hell a set if you could) and either swap them all out and see if you still have it, or swap them out one at a time and see if this remedys it.. Usually under load is when the coils break down and give out and it feels like you dropped a cylinder or two. And the hot thing that you said makes sense too because when they get warm they're more prone to do it as well.

I have experienced a bad coil (when I had the V6 in the car.. yea it was a real turn only running on 5 and was very noticeable), as well as a bad cam sensor. So as stated above, if it was my guess, I'd say coil, and if not then maybe cam sensor.. At any rate, there are some good spots to start at.

PittHammer

Shultz dude get your knuckles bloody and check your plugs. The most simplest things cause you pain but saves you money.

schultzsj

iTrader: (1)

I had a mechanic look at the car and he could not get the power loss to happen when he drove it (figures, but it has been cooler here the last few days). He did say it had low fuel pressure (starts at 20 and goes up to 40ish within a few minutes of starting) so he thinks it might be the fuel pump on the way out. I have had a gage on it for the last few days and I have not seen any low pressure so I am not convinced.

However, the car still has the original pump (10 years and 150k plus miles) and I was going to upgrade it anyway when I do heads, intake, and hotter cam next spring so I went ahead and ordered the Racetronics/Walbro kit with hot wire. Hopefully it will fix the problem but, like I said, I am not convinced.

I believe it might still be something electrical but not a single plug or coil because it is much worse than that when it acts up.

Thanks all,

Steve