Headgasket going? or valve problem?

[DKneble]

Problems started a couple weeks ago. This is a follow up to a previous thread and I have narrowed the problem down to these options, looking for someone's expert opinion before I start tearing the block apart.

Car is way down on power (was 450 on pump and now it feels like 200)
White smoke under boost (but it is intermittant)
Still hits full boost (23psi) and no boost leaks
No exhaust leaks
Not pulling timing (no knock)
Some oil around exhaust manifold (I don't believe its from the passages behind the studs b/c I just resealed them with loctite)
Turbo is healthy
No coolant on oil cap but havent checked coolant for oil or drained oil to check for coolant yet
Hot compression 160psi accross the board
Cold compression 158-155-160-120

Cold Compression worries me. I did not add some oil to the cylinder to see if it would help so I don't know if it is rings. I'm thinking I have a HG on the way out thats intermittantly opening up under boost or a valve that is not sealing properly.

Any ideas?

Dave

 

[turboglenn]

Try a leakdown test. It's much more usefull for determening a blown head gasket or leaking valves.. the valves can be tapped on with a rubber mallet to open and re-seat them a few times to see if they are giving up anything by sticking open partially or having too much deposits on the seats preventing a seal, or even jsut seeing if it really is a HG or rings starting to go out.

I had similar reading on a compression test once, but it didn't go away when warm and it was a blown head gasket.. from your hot readings i'm almost guessing a stuck valve or a broken ring land

 

[DKneble]

ok now compression is 155 across the board cold and 160 across the board warm....I'm stumped. I have not had a chance to do a leak down yet since finding a tester seems to be difficult.

fyi I did a boost leak test warm and cold to 45psi with no leaks. Ground timing is at 5 degrees. I'm stumped.

Spark is good, fuel flow is good, airflow is good, afr ratio is dead on, timing is correct and compression is perfect now...what else could cause such a huge drop in power and still have all of these vitals in their appropriate ranges?

Dave

 

[DKneble]

Just an update...and this officially has me and all of my fellow dsmers stumped (20+ yrs experience between us all)

Spark is good on all cylinders (yanked wires one at a time)
Fuel flow is good on all cylinders (yanked injector wires one at a time)
Plugs are good (BPR7es gapped at .026 and all appear to have normal wear)
NO (I repeat NOOO) boost leaks up to 40 psi
Compression hot and WOT is 160-159-160-157
Ground timing is 5 degrees
Fuel filter replaced
Fuel pressure good when cold but when the pump gets hot it seems to have trouble keeping pressure when just put in the on position (not started)
-Keep in mind I have a walbro in tank with 044 inline, I'm guessing when it gets hot it has trouble trying to suck fuel through the walbro
Doesn't appear to be any knock
When MAF is unplugged the car idles better but sputters and spits if you try to rev it
NO exhaust leaks
Does not build boost when just cruising so I don't believe its the transfer case being put under load

Car has poor acceleration, some bucking when you try to pull out nice and easy and seems like it has no bottom end torque. At WOT it feels like your pressing the brake at the same time, ie engine is trying really hard but car isn't going much of anywhere.

Please somebody HELP!!!

Dave

 

[super97gst]

Just an update...and this officially has me and all of my fellow dsmers stumped (20+ yrs experience between us all)

Spark is good on all cylinders (yanked wires one at a time)
Fuel flow is good on all cylinders (yanked injector wires one at a time)
Plugs are good (BPR7es gapped at .026 and all appear to have normal wear)
NO (I repeat NOOO) boost leaks up to 40 psi
Compression hot and WOT is 160-159-160-157
Ground timing is 5 degrees
Fuel filter replaced
Fuel pressure good when cold but when the pump gets hot it seems to have trouble keeping pressure when just put in the on position (not started)
-Keep in mind I have a walbro in tank with 044 inline, I'm guessing when it gets hot it has trouble trying to suck fuel through the walbro
Doesn't appear to be any knock
When MAF is unplugged the car idles better but sputters and spits if you try to rev it
NO exhaust leaks
Does not build boost when just cruising so I don't believe its the transfer case being put under load

Car has poor acceleration, some bucking when you try to pull out nice and easy and seems like it has no bottom end torque. At WOT it feels like your pressing the brake at the same time, ie engine is trying really hard but car isn't going much of anywhere.

Please somebody HELP!!!

Dave

If you're driving and it starts losing power, if you let off and press the gas again real quick does it pick right back up?? Also, are you getting an abnormal amount of lifter tick?? This sounds like classic symtoms of phantom knock. When phantom knock occurs you are not really getting knock. The ecu is however picking up lifter tick and diagnosing it as real knock. This in turn pulls timing, but only at certain times. That is why it's impossible to see that the timing is being retarded. Phantom knock is a very common occurence on 2G's. The only solution for phantom knock is a set of 3G lifters. You may also change your oil and use full synthetic motor oil with a quart of Lucas heavy duty oil stabilizer. I was having problems with this when i first bought my car, and the full synthetic oil and lucas stabilizer did help to deter the phantom knock significantly. That however is not a fix all, a set of 3G lifters is the only true solution.

Kenamond did an excellent write up on this install in the tech article's forum.

 

[DKneble]

At first I thought this was the most plausible solution as well, however, I have my boost guage set to display knock (through dsmlink) and it does not show any signs of it at all. Will the ECU register knock and retard timing without showing it to me? I was under the impression it did not but I could be wrong on that. And yes lifter tick sucks

I did talk to a few more people today in town and we are all pretty sure this is electrical in nature. There is something going on with either the timing (via the CAS, knock sensor, ecu or combo of these) or the ECU is on its death bed. One thing to note, I unhooked the battery today and rehooked it up and reloaded my tune. At first when I was driving it for the first few minutes it seemed like it was back to normal again. Then the second time I started it up it was back to being a sloth.

Dave

 

[super97gst]

At first I thought this was the most plausible solution as well, however, I have my boost guage set to display knock (through dsmlink) and it does not show any signs of it at all. Will the ECU register knock and retard timing without showing it to me? I was under the impression it did not but I could be wrong on that. And yes lifter tick sucks

I did talk to a few more people today in town and we are all pretty sure this is electrical in nature. There is something going on with either the timing (via the CAS, knock sensor, ecu or combo of these) or the ECU is on its death bed. One thing to note, I unhooked the battery today and rehooked it up and reloaded my tune. At first when I was driving it for the first few minutes it seemed like it was back to normal again. Then the second time I started it up it was back to being a sloth.

Dave

The ecu will register it as knock, but it's something that is not entirely knock. I don't know how to explain it really. The ecu will retard timing and for some reason it is entirely undetectable. I still think that's your problem, if you run through all the electrical stuff and can't find it, install a set of 3G lifters and see if that doesn't fix the problem. At the very least it will get rid of your lifter tick.

 

[DKneble]

Let me just make sure I know what you are saying here then. It is possible for the ECU to register "knock," which I realize is simply a "noise" at an appropriate frequency that the ECU determines to be pre-detonation (whether it really is pre-detonation or lifter tick etc is an entirely different question), and retards timing accordingly. However it will not show this "knock" on the logger?

The ECU cannot determine phantom knock from real knock, which is a huge problem with the 4g63, so I have been under the impression that if the ECU is going to retard timing due to any kind of "knock" then that "knock" will be apparent on the logs.

Please correct me if I'm wrong here. Thanks

Dave