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Last week at a track day I had to pack up and go home early. Car would go down on power and throw a P0328 knock sensor on bank 1 codes. I'm thinking the sensor is a symptom of the problem, not the problem. The very short videos capture the problem.
Took it into dealer today but they won't be able to get to it until tomorrow or Monday. As is usually the case when I have a problem the dealer and I are facing the "failure to replicate" dilemma as it only happens under track conditions. Hard to get it to track operational parameters on the street...
- The issue only occurs when car is “track” hot. Oil/water are still well within allowable temps but as stated, track temp hot. Runs great when below “that” temp. Most people wouldn't even know there is a problem as it runs fine unless pushed as on track. Ran fine all the way home but problem occurs every time it gets to track hot.
- The issue is reduction in power when moving as well as running a bit rough and missing. When stationary as in videos the car bucks, shakes, stumbles and nearly stalls when going to full throttle.
- Temps in videos are 275 F oil and 230 F water. Well below the thresholds for limp mode which are 320 F oil and 262 F water. Car NEVER got "hot".
- Coolant reservoir is empty.
- The same “smoke/steam” you see coming out of the engine compartment also comes out the exhaust.
- It seems as if car is consuming noticeably more fuel since the problem began.
- Fuel is fresh. To rule out bad fuel I drove it till it went dry and refilled with fresh fuel from a different location.
- Again, car runs fine once it drops below the temp which triggers the problem. I say this assuming a specific temp is triggering the issue.
I sure do seem to have really bad luck with these cars. Can't catch a break...
that doesn't sound good...IMO, sell it/trade it as soon as its fixed. G-L.
Your opinion is comical at best.
For clarification, I take your opinion on mechanical issues to be if a machine breaks you get rid of the machine even though the manufacturer stands by it and fixes it. Just illogical.
Curious what you'd do if one of the A/C units goes out on your house. Your logic dictates you'd sell the house.
Christ, it's a lousy stinkin' car/machine. I use my car as it was intended by utilizing the performance offered on track and elsewhere. I'm surprised something hasn't given out prior to this incident. Cars/machines break on a somewhat regular basis, more so when they are actually used as intended.
I'm really lucky from the stand point that I'm getting an assortment of new metal pieces to replace "old" pieces that have been subjected to 17k miles of upper design parameter usage (i.e., no car shows or cruise-ins). I was hoping I'd get "lucky" and have the entire engine needing replacement, however, I'm never lucky.
Is the car completely stock? I would say since it is very warm it is for sure pulling tons of timing. Plus the stock M7 has off idle bog which could made worse from the very low timing. Almost so low it is back firing the steam. My A8 has no issue but the M7 had the off idle bog which the Mamo fixed 95 percent of it.
I never had any Corvette near 275* oil but I enjoy a nice climate than has a smaller temp swing. I would expect the poor running too hot for me to play with like your doing. What are the outside temps?
Is the car completely stock? I would say since it is very warm it is for sure pulling tons of timing. Plus the stock M7 has off idle bog which could made worse from the very low timing. Almost so low it is back firing the steam. My A8 has no issue but the M7 had the off idle bog which the Mamo fixed 95 percent of it.
I never had any Corvette near 275* oil but I enjoy a nice climate than has a smaller temp swing. I would expect the poor running too hot for me to play with like your doing. What are the outside temps?
Thanks for responding but your suggestions have NOTHING to do with the issue. Neither oil or water are "very warm" and it's surely not an off idle bog. Ambient was around 90 F. I know C7Z's VERY well with LOTS of track time in multiple C7Z's and I guarantee you there is a very real issue apart from your suggestions. Something is broken.
Car is a stock M7 and 275 is by no means high in the context of this discussion.
Comparing the off idle bog as delivered from the factory to what my car is doing is like comparing a small exhaust leak to running open headers.
Your coolant loss would be the concern. Pull the plugs on that bank to see which one may have coolant on it. Possible bad head gasket, and since water can’t compress, that cylinder would detonate and the knock sensor would see it...
Thanks for responding but your suggestions have NOTHING to do with the issue. Neither oil or water are "very warm" and it's surely not an off idle bog. Ambient was around 90 F. I know C7Z's VERY well with LOTS of track time in multiple C7Z's and I guarantee you there is a very real issue apart from your suggestions. Something is broken.
Car is a stock M7 and 275 is by no means high in the context of this discussion.
Comparing the off idle bog as delivered from the factory to what my car is doing is like comparing a small exhaust leak to running open headers.
Thanks for your thoughts.
Rick
Hot for even the fuel what octane are you running? My M7 did a similar thing till I swapped it out to the PTB. I'm not seeing any valve at hammering the throttle at 650 rpm's while the thing is hot according to the timing tables your not getting 650 hp by any means nor would I expecting a fast response. Watching again it is running pretty sick off idle you have an issue. Did you have the stock paper filter in the stock intake? Not sure of the fix beyond some cooling mods.
Your coolant loss would be the concern. Pull the plugs on that bank to see which one may have coolant on it. Possible bad head gasket, and since water can’t compress, that cylinder would detonate and the knock sensor would see it...
John
This would a good guess! The steam is coming from some where?
The knock retard is there explaining the rough response.
Your coolant loss would be the concern. Pull the plugs on that bank to see which one may have coolant on it. Possible bad head gasket, and since water can’t compress, that cylinder would detonate and the knock sensor would see it...
John
I've given a lot of thought to the head gasket. Only flaw in the head gasket scenario is I would think it would leak all the time. Also unusual to leak into both the cylinder and external to the head resulting in the visible smoke/steam escaping from a "closed system".
Large amounts of steam out the exhaust as well as the engine/engine compartment is strange. I'd think it would take path of least resistance instead of two distinctly different paths.
Your coolant loss would be the concern. Pull the plugs on that bank to see which one may have coolant on it. Possible bad head gasket, and since water can’t compress, that cylinder would detonate and the knock sensor would see it...
John
Originally Posted by lordofwar
possible hairline crack in block causing coolant to leak into cylinders.or cracked head.
Agree with both here. She is for sure drinking your koolaid in one of the cylinders. Whats happening is you get the car “track hot” and the aluminum heads and block are expanding more than normal driving would see due to the increased heat.
The metal streeeeetches until a pinhole leak in either the block or heads presents itself allowing coolant to enter the combustion chamber. The car is still trying to combust fuel in there and with the small amount of coolant it is knocking and “steam cleaning” the chamber which is why you are getting steam out the back.
When the cars heat is reduced below “track temp” the metal cools and contracts and seals up the leak.
A head gasket could also still be to blame, as the heads could be warping at that temp (even though they arent supposed to) causing coolant to get by into the chamber.
Either scenario is bad news I'm afraid.
Best next step - pull all four plugs on bank 1 and see if any cylinders look cleaner than usual.
Rick old school says loss of coolant is usually a cracked head or blown head or intake gasket. Crack may expand under track heat more than street temps and suck more coolant. Sorry but i think your right about the sensor.
My thoughts prior to posting are consistent with yours. Specifically, thermal expansion of an unknown failure point occurring at "track temp" is allowing communication of coolant both internal to a combustion chamber and externally as well.
The internal combustion chamber communication point is being expelled via the exhaust. The external point of failure is exhausting exhaust/steam/smoke to the engine compartment.
The failure point(s)need to be identified. First step is to pull plugs and if inconclusive a compression test on Bank 1. From there pull heads, etc.
Times like these helps justify buying new with a warranty. Also lessens the depreciation hit you suffer buying new.
You might also consider doing a leak down test on bank one and look for bubbles in the coolant reservoir. Good luck.
Yeah, I would expect a leak down as well as the compression check. I'm confident in the capabilities of the techs at the dealership who will be doing the work. They care and will fix it properly. I'm always nervous until they positively identify not only the failure point but what caused the failure.
Car has right at 17,000 miles with 30 hours of track time or 2,400 track miles.
Hhmm. I think your concerns on coolant loss are sound. It's going somewhere, and apparently is in communion with at least one chamber on that bank.
There really are only a few paths it can take. Cracked cylinder sleeve.
Warped head. Head gasket. Fatigued/stretched head bolts (with accompanying gasket breach). Intake manifold.
At stock power level, I don't think cylinder sleeves would be a prime suspect (although possible, just doesn't seem as most likely). Track hours don't seem at the extreme end, so head bolt fatigue/stretch would be second from the bottom. That leaves warped head - or head gasket - or intake manifold leak. If the head were warped, you'd think that would manifest under cooler temps, and not just under thermal expansion (although if minor/on the cusp, thermal expansion I suppose could manifest that). Here's hoping it's either head or manifold gasket - as those are far less dire.
I'm sure your tech will do so, but if he pulls a head(s), make sure he uses new head bolts going back on.
Good luck, Rik. No fun having your rig down. Sounds like you've got a competent tech, though, so that helps a lot (and the warranty).
If the knock sensor is detected bad by the PCM it will not advance timing during acceleration and this causes a stumble like you show here.
The knock sensor may not be bad itself. There could be a short to ground (more likely a melted wire touching the block somewhere).
I wont speculate on the coolant and steam issue until the knock sensor issue is resolved.
It could be caused by elevated engine temps caused by an incorrect timing solution for long periods of time. (Being driven by the faulty knock sensor).
Fix the knock sensor issue and you may find all is well.
Last edited by dar02081961; 06-01-2018 at 10:47 AM.
Last week at a track day I had to pack up and go home early. Car would go down on power and throw a P0328 knock sensor on bank 1 codes. I'm thinking the sensor is a symptom of the problem, not the problem. The very short videos capture the problem.
Took it into dealer today but they won't be able to get to it until tomorrow or Monday. As is usually the case when I have a problem the dealer and I are facing the "failure to replicate" dilemma as it only happens under track conditions. Hard to get it to track operational parameters on the street...
- The issue only occurs when car is “track” hot. Oil/water are still well within allowable temps but as stated, track temp hot. Runs great when below “that” temp. Most people wouldn't even know there is a problem as it runs fine unless pushed as on track. Ran fine all the way home but problem occurs every time it gets to track hot.
- The issue is reduction in power when moving as well as running a bit rough and missing. When stationary as in videos the car bucks, shakes, stumbles and nearly stalls when going to full throttle.
- Temps in videos are 275 F oil and 230 F water. Well below the thresholds for limp mode which are 320 F oil and 262 F water. Car NEVER got "hot".
- Coolant reservoir is empty.
- The same “smoke/steam” you see coming out of the engine compartment also comes out the exhaust.
- It seems as if car is consuming noticeably more fuel since the problem began.
- Fuel is fresh. To rule out bad fuel I drove it till it went dry and refilled with fresh fuel from a different location.
- Again, car runs fine once it drops below the temp which triggers the problem. I say this assuming a specific temp is triggering the issue.
I sure do seem to have really bad luck with these cars. Can't catch a break...
05-31-2018, 06:33 PM
Engine Problem - I Fear the Worse
