Purple Poncho

I will try and make a long story short from my last track outing late last year. Now I am trying to fix the problem but I'm totally stumped. The head gaskets were done a month before this and was running great up until the vacuum line came off the alky system. I really don't want take the heads off again.

So here it is:

The vacuum hose that goes to my 2 bar MAP sensor that runs my alky system had popped off. I made a run through 4 gears at WOT with no alky on a tune that relies on it. Massive lean condition and the IATs didn't move lower at all. 14-1 at the begging of a gear and 12.5-1 by 6K where I shift. Massive knock counts all through the run. Needless to say there was lots of detonation.

The bad:
Mechanical wise the headers tubes 2,3,4,5,6 and 8 get red hot and glow after 4 minutes of running and I have lost 2 HG of vacuum. It idles fine on its own after you open up the throttle blades to get the RPMs up.
It is running SUPER rich, plugs get wet with fuel after a few minutes of running…causing glowing headers.
It idles fine in open loop but goes to **** in closed loop where I have to shut it off as the headers are red-red.

The good:
Idles fine in open loop.
No knocking noises when at idle or blipping the gas.
No ticking from the valve train .
No coolant in the cylinders or the ground. Still in the rad.
Oil and filter were changed and checked out good, no metal on the oilpan magnet.
Oil pressure is solid.
Coolant temp is fine.
No puff puff from the valve cover breather indicating there is no blow by from the rings

Did a compression test.
Results in PSI:

#2 165 #1 175
#4 175 #3 175
#6 170 #5 175
#8 165 #7 170

Keep in mind this is an 8 year old 9:1 blower engine.

A leakdown test was done on the first 4 cylinders. The easy ones were done including one of the 165psi compression holes.
Results were 10 for all holes with no air escaping from the valves and a shade from the rings. To be expected from such an old motor.


From the logger I see:

Before lean ++ After lean
MAP 50-52 ++ 65-67
IAC 55 ++++maxed at 160
MAF air flow grams/sec
10-11+++ 16-17
Base pules widths
1.4-1.5 +++2.4-2.5
INJ DC
1 ++++1.6-1.7
The BLMs looked good from the few secs it went into closed loop. No codes either


Conclusion:

It is running way rich and the plugs were soaked in fuel. The PCM is seeing lots of air come in for some reason. The MAP is high (confirms loss of 2 hg on boost guage) and I *think* it thinks the car is under load and commanding fuel to equal the (wrongly calculated) air. That is one theory anyway but why??
Why this would happen right after it went lean at the track? I don't see how anything mechanical could cause this unless there is a leak somewhere that I am not seeing. It seems the engine is OK though.
With a vacuum leak I've always seen the BLMs go green for a lean condition (uncompensated air) which I am not getting this time around. No codes either and it doesn’t high idle like you have with most intake leaks. The BLMs look good for the few minutes I let it go closed loop. I looked for intake leaks, sprayed contact cleaner on the IAC and TPS connectors, cleaned the throttle body, reconnected the Crane box and a few other things. No dice.

Any ideas?? I am stumped and don’t want to pull the heads anytime soon. I am thinking a huge intake leak or a bunch of bad valves in a bunch of cylinders…bent pushrods??
People are pointing the finger at the old stand-by opti and to replace all the sensors. I think they are reading correctly and detonation wouldn’t kill a bunch of different sensors all at the same time.

jsetzer

One possible thing - exhaust leaks? I haven't tuned an lt1 pcm in a while. If your blm or counts look normal once it goes into closed loop but you know for sure its running very rich then part of the loop is broken. 02 sensors are bad or reading wrong because of something else (extra 02 in the exhaust?)

I have had a bad wire on the knock sensor make one run pig rich.

Small changes in fuel or air will make small changes in map and maf readings, even if the idle stays the same. What rpm do you see open/closed?

Also, most injectors have @ 1ms opening time, so even before lean you had to be a little bit above that.

With the IAC pegged I'm guessing it idles higher? Again that would point to air coming in the intake side - along with the maf and map changes.

2 hg is a very small change. I can change the PW and IAC settings on my motor and get different map readings but keep the same idle speed. (Sounds strange right) - But if there is a ton of extra fuel I'm sure thats related to it.

What do long and short term counts do (sorry, again I haven't done blms in a long time) when it goes from open to closed.

Glowing headers is either etremely rich or too much/little timing. Think you had enough detonation you could have botched the timing set or jumped a tooth?

Sorry, I know this is more of a discussion than answers, but maybe something will help.

Purple Poncho

One possible thing - exhaust leaks? I haven't tuned an lt1 pcm in a while. If your blm or counts look normal once it goes into closed loop but you know for sure its running very rich then part of the loop is broken. 02 sensors are bad or reading wrong because of something else (extra 02 in the exhaust?)

Could be but you would think detonation wouldn't cause a bad exhaust leak. BLMs look good too.

I have had a bad wire on the knock sensor make one run pig rich.

This could be something. The logger showed knock counts jumping huge throughout the run.

Small changes in fuel or air will make small changes in map and maf readings, even if the idle stays the same. What rpm do you see open/closed?

The tune didn't change. But if there is a huge intake leak the IAc would open up to allow more air and cause more fuel to be dumped.

Also, most injectors have @ 1ms opening time, so even before lean you had to be a little bit above that.

With the IAC pegged I'm guessing it idles higher? Again that would point to air coming in the intake side - along with the maf and map changes.

It doesn't idle higher then before in open loop and stumbles when it goes closed but I have to shut it down at that point as the headers start to burn stuff. I have to crack the trottle a bit for the RPMs to come up then it idles fine.

2 hg is a very small change. I can change the PW and IAC settings on my motor and get different map readings but keep the same idle speed. (Sounds strange right) - But if there is a ton of extra fuel I'm sure thats related to it.

What do long and short term counts do (sorry, again I haven't done blms in a long time) when it goes from open to closed.

They don't change and look good at 124 which is my target.

Glowing headers is either etremely rich or too much/little timing. Think you had enough detonation you could have botched the timing set or jumped a tooth?

Possibly and I hope not.
Sorry, I know this is more of a discussion than answers, but maybe something will help.

boosted-lt1

10% is a good amount of leak down. If I can paraphrase Smokey...'You don't have a motor' Maybe get the other 4 cylinders? If you busted something, a leak down should show it...Like you said, so far it doesn't look like something mechanical. I wouldn't think a bent valve unless you over-revved.

Cranking compression is within ~6% which would be ok.

jsetzer

I did run on a bit, I'll try to keep them short.
If the pulse width changed, theres a different amount of fuel. Which would affect air, and map readings.
Check the knock sensor just to rule it out. Mine was counting like crazy when the wire broke.
Last thing - is 160 closed or open on the IAC? (With my MS setup that would be closed so its trying to lower idle - points to air getting in)

Purple Poncho

I can hardly get my fingers on those 4 plugs let alone the fitting for the leakdown. Damn headers.

Purple Poncho

IAC is wide open letting air in. I think it is seeing more air, then dumping the fuel in, tries to stall out the motor so the IAC opens to get more air in.

As far as I can tell it is more air causing more fuel to dump and not more fuel causing more air to be let in.

dookie454

Whatever caused your 2bar MAP hose to pop off might have caused somethign else to pop off, aside from that check your plugs you should see evidence of knock if you say the PCM detected it... if not maybe no knock occured and it's a false knock thing.

Check your datamaster realtime screen for "knock retard" and "knock counts", retard with no knock counts means something entirely different like safe mode or bad gas mode if your not getting any actual knock counts, knock counts is the one to worry about if your get it. It's possible the PCM has soo much knock count history that it's pulling serious retard from what it saw, but it should go away.

When in open loop does it still feel just as responsive/torquey as it usually does? If so then I would suspect something external to the motor like a sensor, if not then I would suspect something in the motor, though I dont know what unless something is waiting to unleash it's uglyness.

mn_vette

If you have to crack the throttle blades open to keep the idle at a decent rpm then it would lead me to believe either your timing is off or you are dumping too much fuel into the cylinders.

Can you scan what the O2 sensor is saying? Or atleast put a voltmeter on it and get the voltage? If its reading very lean then it will dump in the extra fuel in closed loop mode to compensate. You might have an exhaust leak somewhere, or the sensor might have gone bad.

If its the timing then you might want to try resetting the ECM. Pull the battery cables, let them sit for 10 minutes or so, then touch them together and then hook them back up to the battery. I had a loose opti disk once and this was the only way to get the thing reset.

Purple Poncho

I've changed the plugs twice and other they came out in one piece. The first set lean for obvious reasons and the second set wet with fuel. I've checked all the vacuum lines including underneath at the opti and nothing.

The datamaster shows big knock counts so it was detonating big time. The start at 2696 in first go to 61 286 by the start of 4rth gear , reset to 484 and go up to 27 484 by the end of 4rth. Majot knock om te run but nothing when idling as I have tuned it out.

I don't even drive it. The glowing headers starts to burn stuff and I shut it down about a min. after it goes open loop.

The question is other then an intake leak, what can cause you to loose vacuum?? 2hg on the boost confirmed by an increase in my MAP sensor readings??

Purple Poncho

110% there is too much fuel in the cylinders. I tried a hail mary and got new O2s but no luck. They are acting like the old ones.
I did reset the PCM and threw in an old tune with no luck. I am convinced it is mechanical at this point and not all my sensors reading wrong. I am going to fire it up this weekend after sitting for winter storage. Maybe Santa will have brought the magic fix to the old LT1.

Purple Poncho

I think I might have found the problem, I hope anyway.

While under the car I found one of the vacuum lines that goes to the opti was wiggling loose. As I tried to get the clip off the whole tab/bracket came off.
It is a shame. That opti has been great for 8 years. Fingers crossed.

Purple Poncho

Holy old thread update batman. For the sake of others researching the problem was the #8 injector wire grounding out and causing the injector to go full flow when key was on the on position. 72# injectors flow a ton wide open.

David94TA

Thanks for following up and sharing the info. How did you go about diagnosing that? That is certainly an off the wall situation.

Purple Poncho

Using the spray bottle method I found a cold/dead cylinder. The ton of fuel was killing the spark. Pulled the plug (new) and it was wet and non fired. Then started on the wiring and fixed it.