mods at the bottom

after a dyno run this weekend, my car hasn't been running right. i did a few runs at the first boost setting, nothing bad happened. then i switched to the second boost setting. at approx. 3700 rpm, there was an extremely loud 'frapping' sound. kind of like a thin piece of metal slapping against another piece of metal really really fast. my peak boost since i've had the PFC was 0.91 kg/cm2 on the second boost setting. this was hit on the interstate a few days ago with no problems.

driving on the highway is pretty normal, but getting around town is kind of a pain. i have to rev it to ~1500-2000+ to even accelerate from a light or a stopsign.
I've replaced the plugs with 9's all around. the new plugs helped a little bit, but didn't get rid of the problem.
compression for the front rotor is ~89 psi, and rear is ~100. i'll do another compression check tomorrow morning as i didn't let the car warm up very long.

earlier tonight, i did a few WOT runs in 3rd gear paying very close attention to the PFC commander readings. most of the peak measurements came from a 1st gear WOT run though.

Peak Hold after 1st gear......................Idle

• InjDuty -81.7%.......................4.5-5.4%
• IgnT Ld - 52 deg......................~-5
• IgnT Tr -52 deg......................~-20
• Eng Revs - 8187.........................750
• Air-T - 52 C.........................54 C
• Wtr-T - 95 C.........................94 C
• Boost - 0.64 kg/cm2..............~340mmHg
• Knock - 45.............................---------------

before the dyno pull, the car would consistenly pull 16-18 inches of vacuum at idle. since the dyno, the car is only pulling an 12-16, 17 if lucky. i know of a couple other 3rd gens that pull that have trouble pulling that much vacuum under no kind of load what-so-ever, and their idle isn't 'jerky' like this. the idle is very good, just the motor/car is very shaky. there is a 'kink'-like sound coming from somewhere below the UIM, maybe from the passenger side while the car is idling. It almost sounds a bridgeport, just withought the high idle

my boost guage will quickly fluctuate at idle also. there is a kink in the line that i'm going to fix tommorrow.

the engine severly shakes at idle. the whole car will shake really bad. i've never noticed the engine shaking this bad at idle before.

MODS: full open 3" exhaust, NON-ported wastegate, PFC w/ commander

i've got some video of the car at idle and the car under load that i'll try to get up tomorrow.

plugs? wires? ignition? injectors? blown gasket? loose vacuum line somewhere?

TIA

Jimmy

 

Unfortunately, that sounds like a blown engine. The "paint-shaker" idle is the give-away.

-Max

 

i was dreading that... although i still have a decent chunk of change left over from my tax refund.

 

if you did a compression test already and got 89 all around on one rotor and 100 on the other one all around then it cant be a blown motor. That is a pretty big difference in compression though for the 2 chambers.

If it was an apex seal you would have something like 40 40 89 and then 100 100 100
A sideseal would be 40 89 89 100 100 100

even if your engine was cold you will just get higher readings but they would still be uneven on a couple sides with a blown motor

but otherwise, it really really sounds like a chipped apex seal and that would suck

it's not likely that it came off but did you check the map sensor?

 

Same thing with mine Jimmy. For about 3 weeks or so, then she died completely.

Sometimes she'd idle good, but most of the time it'd be like how you described. Then one night on the freeway, total loss of power. When I made the mistake of letting her actually get down to idle: died and couldn't be started again.

 

Jimmy, after seeing it Saturday and how it was acting, I would still be surprised if it's blown. Your vacuum was only flucuating about 1hg or so, not the typical 12-6 flucuation I was getting with my 5.3 compression. I still think you might have something else causing these problems, as the symptoms just don't quite add up yet. Best of luck though.

Bryan

 

i looked at the compression again today. an apex seal on the front rotor is definitely blown. i didn't notice the quick 2 drops then the jump to ~80.

Thanks for all your input guys. guess it's time for a rebuild w/ a streetport now

jimmy