Looking for a little expert guidance here;
Basil has developed a couple of problems, which I believe to be 2 seperate issues:
1: vibration. At idle, the engine stutters and shakes. Feels like a "miss", but no CEL. At ~3500RPM, a very definite vibration is felt through the pedals. This lasts from ~3500 all the way through redline.
2: Fuel related. There is a very definite "bog" in aceleration. Takes a second or 2 to get going. Also, on 1st cold startup (when the ambient is below 20F) the car coughs, sputters and shakes like it is going to die. Exhaust fumes are enough to make your eyes water. I believe this has to do with the ECU's cold startup program, making the engine run pig-rich until up to op-temp. The dealer had no clue as to what this might be (big surprise there, eh? They can't do anything unless their computer reader tells them exactly what is wrong).

So; any ideas? Think outside the box. The independent shop I took Basil to today suggested that the motor and trans mounts might be the source of the vibration. Plausible, but not definitive.


Could any of this be due to a clutch/ throw-out bearing issue? My "ooort" has gotten louder recently.

Many thanks and blessings upon your offspring for replies.

 

That may be the "cold start stumble"

 

It may well be, but I've had the dealer reflash the ECU with the most current version, and I've still got it.

 

Oh yeah; this is what I love about NAM...Chows and I have had our differences on a couple of issues, yet when I post a problem, there he is with advice. Man, I love this place!

 

I know these suggestions may or may not help but I beleave you commute long distances, 160 miles plus. I'll assume the mechanic checked the obvious: Fouled plugs; Conductivity of spark plug wires; Condition of coils etc.. Now my ideas: Get the fuel from the same place? I beleave you recently had a fuel problem? Get that cleared up? Tryed a different source of fuel? Tryed to get rid of water in the fuel? All the above have been issues w/ my MCS.
The stumble around 3500 RPM could be a bad BP valve or vacume source to it. Final question, after the the ECU reflash did it change the afformentioned stumble in any way? If not, I suspect the this problem has a mechanicl nature reither then an electronic one, ie back to the BP valve. Might be stuck slightly open or have a failing spring thus dumping blower pressure. I don't know if this would cause a lean out or over rich condition but either way it would cause the missing as the Revs rise. I hope this helps, just my 2 cents

 

Thanks for the input. The plugs/wires were recently switched to newer OEM (from a member who upgraded his 06). Doesn't mean they're not the problem, but less likely. Coil? Dunno, can you have them tested?
Fuel-wise, I switched from Chevron to Exxon several months ago (before this started), but sometimes have to stop elsewhere. The problem seems consistent, so I am disinclined to blame the fuel source.
I am inclined to think the BPV may have something to do with this, as it now has 53k miles on it, and they weren't that great to begin with. May have to get a DT version and see what happens.
Could any of this be related to a fuel pressure regulator going bad? Sometimes (not always) when I get on the throttle hard, I get a faint whiff of raw fuel in the cabin.

 

It's a bit early for them, but you could consider swapping out the O2 sensors...

 

In the end, we are all enthusiasts

BTW, it might just be gas. My issue was I changed to Shell (cheaper gas at the time). After going through the tank and switching back to Exxon (or Mobil) ... cold start stumble went away ... it could be the brand of gas or a bad tank of gas.

 

Chows, thanks for the good thoughts, but I go through 3 tanks a week. 1 bad tank would affect me for....2.5 days? And I switch gas dealers regularly. Some of my local stations have started trying to pass off 90 octane as Premium, at the same price as 91 at other stations. Rat bastiches! If I drive into a station and see 90 on the premium pump, I drive right back out.

 

I'm more from the carburated age, but doesn't moisture + injectors = probs. I know diesels don't like that combo. Since you had bad gas in the past......

 

Well, I think I found part of the problem (or at least a problem). Did a WOT run yesterday and I'm only hitting 7.5lbs boost at red line. I have seen 10lbs on several prior ocassions. Got a leak somewhere! Found that the IC boot clamps weren't real tight, so I cranked them down. Will need another test run to see if that helped. Hope so, but I'm guessing that the BPV is at fault. Need to get this sorted out before putting a pulley on.

 

OK, next question: what could cause a gasoline smell in the passanger compartment? FPR? Leaking injector o-rings?
Oh yeah, still got the boost loss. Boo-hiss.

 

Rat b*st*srd's exactly!!! paying premium for 90 Octane!!! KMA!!!

 

On Saturday, a fellow club member used a portable tester thingy (I have no idea what to call it) which measured something in the plug wires (conductivity? resistivity?). Wires 1 & 2 were in the 8-9 range, which he said was good, wire 3 read 18 and wire 4 read 22. These he said were "bad". Replaced the plugs (Bosch +4) and the 3/4 wires (kept my old set just in case). Seemed to smooth things out, for a while. Now it's back with a vengeance! Oh, the plugs were all uniformly sooty black. no wet ones.
Have a replacement coil and some new wires on order. Unsure if this will help, but I am at a loss to figure this out. Still no SES or codes.
Could an O2 sensor on it's way out cause any of this? I know this was mentioned earlier.
Would a faulty O2 sensor be covered by the 8yr/80k mile emissions warranty?