:::RHMT::: Real Home Made Turbo
General Category => Engine Management => Topic started by: enikolayev on October 24, 2011, 06:36:14 PM
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The setup:
'92 Vx Chassis
D16Y8 block/head
eagle rods
srp pistons
supertech valvesprings/retainers
crower 2 n/a cam
hx35
Walbro 255 Inline
DSM 450's
Engine ran perfectly until i decided to track the car at Thunderhill. Overheated, blew a HG, cracked a piston skirt.
Tore apart the engine and rebuilt it, now i'm plagued with a misfire. At high rpm (6,500-7,000) it takes a little over atmospheric pressure to cause misfire. At low rpm (4,000) it will misfire around 3-4psi. In vacuum car drives perfectly.
O2 sensor reads 21 afr during misfire. I have also attached a video of the misfire while standing still.
Things I've tried:
Replaced Dizzy
Plug wires
new plugs, even tried gapping down to 0.020"
quadruple checked mechanical and ignition timing
adjusted valve lash
threw in the stock cam for shits and giggles
Hot wired the blk/yel wire on the dizzy in case it wasn't getting enough juice
I'm almost ready to put a 12Ga slug through the block.
Engine misfire (http://www.youtube.com/watch?v=qCKM4jkUJ4w#)
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Have you done any logging? I would check that first.
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I'm not sure what insight logging could give, the car won't accelerate during misfire.
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That's a pretty sweet rev limiter you have there.
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Do a leakdown, suspect a slightly bent valve or other leak (headgasket/cracked head/block).
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I'm not sure what insight logging could give, the car won't accelerate during misfire.
well, it sure as hell isnt going to hurt.
it can rule out a lot of things which would do a lot more than typing on a forum will
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Do a leakdown, suspect a slightly bent valve or other leak (headgasket/cracked head/block).
is it using using coolant? smokes? need some more info. what did the sleeves look like when you tore it down?
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I'll do a leak down and report back. Cylinder walls had some scoring from overheating, the stone hone took most of the smaller scratches out, there's still a couple bigger ones left. I believe cyl 2 and 3 have scratches at the top two inches of the bore. Engine smokes a little bit, almost negligible and coolant level is constant.
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Is the dist a vatozone special or oem unit?
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Is the dist a vatozone special or oem unit?
Its an oem one from a buddies car.
HF leak down tester says 70%, 73%, 72%, and 75% Don't know how much I can trust HF tools.
Couldn't do a compression test b/c the tester broke, but after break-in the compression was around 175psi in all cylinders. Problem persisted ever since break-in.
Didn't hear any leaks through the exhaust, intake, and no bubbles in the radiator.
attached pic of spark plugs, this is from normal driving
(https://realhomemadeturbo.com/forum/proxy.php?request=http%3A%2F%2Fi225.photobucket.com%2Falbums%2Fdd84%2Fenikolayev%2FIMG01081-20111025-1740.jpg&hash=051cf8093c52b48512f53b3b89d9d7db68e00605)
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Have you done any logging? I would check that first.
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so you have 70+% leak down in all holes? sounds like you did more than just pop a head gasket. Start it up and take the oil cap off and see if you get sprayed in the face with oil. I am thinking under boost you are only hitting on 3 holes and the one that is hurt is the one that blacker plug came out of. Your putting pressure in the crank case and forcing it past your now scored to hell bores/busted ringlands
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with 70% leakdown you won't have 175 psi cranking.
15-20% leakage = 150-160 psi cranking.
You need 120 psi cranking for the engine to even run.
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Leakdown tests are done at 80psi, I have a feeling he meant 70psi and not %.
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Leakdown tests are done at 80psi, I have a feeling he meant 70psi and not %.
with 70% leakdown you won't have 175 psi cranking.
15-20% leakage = 150-160 psi cranking.
You need 120 psi cranking for the engine to even run.
I think the high reading can be attributed to both the large p-w clearance since this was done on a cold engine, and maybe to some degree the HF tester.
I'll do another compression test to confirm once i get another tester, but the car runs perfectly in vacuum. Even averaged 48mpg from Sac to Reno and back.
Have you done any logging? I would check that first.
You've convinced me.
Also, I'll check all the grounds on the ecu later this week.
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cel?
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cel?
No cel codes.
Just did the compression test. Pretty surprised by the results.
Dry: 205, 210, 210, 210
Wet: 210, 210, 210, 214
Sounds like a healthy engine internally.
Car was tuned with vitara pistons previously and had 150-155psi compression, could this contribute anything to the misfire problem?
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what map sensor is on there
Maybe try a stock and burn a new potato chip for a stock oem sensor
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Headgasket.
I dont care what the leaky tyest or compression says.
My pile has done it.
Leakdown was spot on, HG was just compromised enough to were it wouldnt happen till the car started to warm up and it did EXACTLY what youre talking about.
FUCK YOU
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what map sensor is on there
Maybe try a stock and burn a new potato chip for a stock oem sensor
Tried this. Same story.
Headgasket.
I dont care what the leaky tyest or compression says.
My pile has done it.
Leakdown was spot on, HG was just compromised enough to were it wouldnt happen till the car started to warm up and it did EXACTLY what youre talking about.
FUCK YOU
I have just replaced the HG. Sprayed a shitload of copper gasket spray on both sides, and torqued that bitch to 85ft-lbs. Can't be the HG.
Car refused to start shortly after being turned off today though. Opened the hood and wiggled shit around, then it fired right up. Weird.
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Opened the hood and wiggled shit around, then it fired right up. Weird.
Think about that.
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Opened the hood and wiggled shit around, then it fired right up. Weird.
Think about that.
And if the obvious conclusion doesn't fix it, replace the headgasket.
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Opened the hood and wiggled shit around, then it fired right up. Weird.
Think about that.
Have you done any logging? I would check that first.
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check your map sensor wiring sir. dont mix up the map sensor with the tps and the iacv with with iat