Engine flatlines/jumps

[dgoodhue]

Re: Engine flatlines/jumps

Nah, it couldn't do that, but it could make one cylinder run extremely lean. What do the sparkplugs look like? Those could give you a clue.

Just think out loud. I would think you might see a rich plug under boost for the leaking intake port (less air than expected)

 

[dgoodhue]

Re: Engine flatlines/jumps

the vacuum is solid at 15in for idle. any my wideband gauge (surprisingly without adding the capacitor) is nice and steady.

I definitely think he might be onto something there with the gasket. Unless something has changed since I last saw it in Pittsburg, your Sy has never lived up to it potential.

 

[Aeroking]

Re: Engine flatlines/jumps

found the screws in my dizzy cap had backed themselves loose. So the cap juggled on the dizzy. Tightened back down. Ohmed the wires and go about 100 on the longest one, 70s and 80s on the rest. They're rated for max 50ohms/ft. so they seem good, no burns. I did have the cap off this winter, and definetly remember it being tight when i took it off. So that might've caused the backfiring, and i might still have the flatline.

did a compression test on a few cylinders, they were in the 140s.

I rebuilt the dizzy last summer with a new pickup coil, ignition coil, cap/rotor and cam gear. I'm not sure if the cap screw holes are blown out or not. it tightens down though. I'm gonna bite the bullet and buy a procomp billet one.

i feel this might fix the backfiring, but no neccessarily the engine flatlining. again, it revs clear to 6k in park.

rainy day, so no road testing today.


edit:
just put 30psi on the intake. heard air out the turbo and the tailpipe, no where else. Definitely not a blown intake gasket.

 

[bezerk]

Re: Engine flatlines/jumps

i forgot......you ruled out the tc lockup, right?

 

[WyoSyclone]

Re: Engine flatlines/jumps

found the screws in my dizzy cap had backed themselves loose. So the cap juggled on the dizzy. Tightened back down. Ohmed the wires and go about 100 on the longest one, 70s and 80s on the rest. They're rated for max 50ohms/ft. so they seem good, no burns. I did have the cap off this winter, and definetly remember it being tight when i took it off. So that might've caused the backfiring, and i might still have the flatline.

did a compression test on a few cylinders, they were in the 140s.

I rebuilt the dizzy last summer with a new pickup coil, ignition coil, cap/rotor and cam gear. I'm not sure if the cap screw holes are blown out or not. it tightens down though. I'm gonna bite the bullet and buy a procomp billet one.

i feel this might fix the backfiring, but no neccessarily the engine flatlining. again, it revs clear to 6k in park.

rainy day, so no road testing today.


edit:
just put 30psi on the intake. heard air out the turbo and the tailpipe, no where else. Definitely not a blown intake gasket.

Did you try having someone put their hand over the exhaust? You don't need to do 30lbs.... 15 will do it. Have someone put their hand over the exhaust then check for air out the breathers.

 

[Aeroking]

Re: Engine flatlines/jumps

i forgot......you ruled out the tc lockup, right?

scanner reads that its locking under the right conditions. I have not road tested it yet, or tested it at the connector. I have an override switch, just the ALDL switch, not a spliced switch.

raining again today, so wont find out until tomorrow. the billet distributor might be in by then.

 

[Aeroking]

Re: Engine flatlines/jumps

was checking connections last night, and noticed the pigtails running to/from the ignition module and to/from the coil, are bent, and kinda kinked. The harnesses are short for the application, so the wires have no slack.

Is there anywhere i can get some of the correct weatherpack connectors for this harnesses. I'd need the one from the main harness to the ignition module. And the one from the ignition module to the coil.

I'm gonna email Caspers and see if they can get me some pigtails/connectors.

 

[WyoSyclone]

Re: Engine flatlines/jumps

was checking connections last night, and noticed the pigtails running to/from the ignition module and to/from the coil, are bent, and kinda kinked. The harnesses are short for the application, so the wires have no slack.

Is there anywhere i can get some of the correct weatherpack connectors for this harnesses. I'd need the one from the main harness to the ignition module. And the one from the ignition module to the coil.

I'm gonna email Caspers and see if they can get me some pigtails/connectors.

I would just pull the dizzy out and rotate it clockwise a few teeth and reset the timing. This will get the ignition module closer to the coil and give you some slack on those wires.

 

[dgoodhue]

Re: Engine flatlines/jumps

I would just pull the dizzy out and rotate it clockwise a few teeth and reset the timing. This will get the ignition module closer to the coil and give you some slack on those wires.

I would loosen up the distributor turn it about 1/6 of the way to alleviate the tension in the wires and then change the spark plug wires by one. You will have to reset the timing as well. You probably have the distributor orientation wrong.

 

[WyoSyclone]

Re: Engine flatlines/jumps

I would loosen up the distributor turn it about 1/6 of the way to alleviate the tension in the wires and then change the spark plug wires by one. You will have to reset the timing as well. You probably have the distributor orientation wrong.

Easier yet!

 

[Aeroking]

Re: Engine flatlines/jumps

dist is facing right, they're just kinked.

since the red/yellow are signals, i doubt they would work at low RPMs and not at high RPMs. But i noticed they didnt look too healthy, and thought that might cause a problem.

 

[dgoodhue]

Re: Engine flatlines/jumps

It's suposed to be toward the right with a ~45 degree angle towards the firewall

 

[Aeroking]

Re: Engine flatlines/jumps

It's suposed to be toward the right with a ~45 degree angle towards the firewall

it is, if you look #1 is closest to the plenum

 

[turbodig]

Re: Engine flatlines/jumps

Any later 4.3 (bravadas, astros) have those connectors.... lop them off a junkyard harness.

 

[Aeroking]

Re: Engine flatlines/jumps

took it out today and tested it. It flatlines in every gear, regardless of boost. I never noticed it before, cause it shifted out of 1st at 4800, and by the time i got to 4800 in 2nd gear, i was well into boost.

could it be valve float?


edit: had a couple engine builders come by today, and both agreed its ignition. If it isnt, then possibly in the valvetrain. The only ignition piece that isnt aftermarket is the distributor. But i'll have a billet one on Monday. I've gone though and isolated the different parts of the ignition. I took the Blaster coil off, and put the stock back on. I unplugged the MSd 6AL. I ohmed the wires, and replaced the plugs. The ignition module seems functional. The 160A alternator puts out 13.8v. I replaced the harness i pictured above with a perfect one. I'll report back on Monday.

 

[Aeroking]

Re: Engine flatlines/jumps

new billet distributor, new ignition coil, new cap/rotor. same results.

http://www.youtube.com/watch?v=ku3HEUwby3o

it does that with a steady pedal.

 

[Aeroking]

Re: Engine flatlines/jumps

bump for more ideas.

the surging in park/neutral was traced to the fuelcutoff being set wrong on the last BIN. It is fixed now and revs fine again in Park/Neutral

But the flatline under load still remains. If i stay WOT it'll stick at 4500 for a few seconds then continue to rise again. Why does it freeze?

http://www.youtube.com/watch?v=Tb8n_sfwuwQ

 

[sy#2716]

Re: Engine flatlines/jumps

what kind of converter is in it? could it be that the converter is balloning and then releasing at that RPM under load and not aloowing it to rev any higher? Just throwing some thought out there. What did Datamaster look like when it happends any logs.

 

[UR50SLO]

Re: Engine flatlines/jumps

bump for more ideas.

the surging in park/neutral was traced to the fuelcutoff being set wrong on the last BIN. It is fixed now and revs fine again in Park/Neutral

But the flatline under load still remains. If i stay WOT it'll stick at 4500 for a few seconds then continue to rise again. Why does it freeze?

Exactly where it's pausing your at or over 5deg of knock retard. What fuel are you using?

You could have a over-sensitive knock sensor or be picking up false knock from somewhere.

I'd try and limit the boost to maby 13psi and disconnect it for one time and see if the problem go's

away. There's a couple tricks to make it less sensitive. But that's what's making it fall on it's face.
~Scott

 

[Aeroking]

Re: Engine flatlines/jumps

Exactly where it's pausing your at or over 5deg of knock retard. What fuel are you using?

You could have a over-sensitive knock sensor or be picking up false knock from somewhere.

I'd try and limit the boost to maby 13psi and disconnect it for one time and see if the problem go's

away. There's a couple tricks to make it less sensitive. But that's what's making it fall on it's face.
~Scott

running 93 with methanol. i know i ahve false knock occasionally, Crusiing down the highway under vacuum and light throttle, it'll knock a couple degrees. Its never long and steady enough to draw my attention, it just quick blips. Sometimes i'll get it revving it in park. I cant hear anything at all. Looking back at old logs i'll get a 10deg blip here and there and within a fraction of a second its gone. I'll try disconnecting it, turning the boost back, and see what happens. If memory serves me right, i believe i set the Knock threshold for 4deg, but i'll have to check on that.

The first knock attack on the datalog i actually hit a little pothole, and i saw it spike into the 12s. Felt like someone pulled the e-brake on it.

I dont think the knock sensor is the problem. But its not really helping the cause at this point. I've had 3rd gear flatlined at the track with no knock, so i dont think thats it.

what kind of converter is in it? could it be that the converter is balloning and then releasing at that RPM under load and not aloowing it to rev any higher? Just throwing some thought out there. What did Datamaster look like when it happends any logs.

its a brand new billet 9/11 about 200 miles on it. It acted the same with the older 9/11 converter.





also, it took a lonnnng time to get it started last night. i held the throttle down to get it to fireup, then had to give it gas to keep it running. and after a minute it found the idle again. kinda strange.