High speed surge?
10-27-2002, 06:59 PM
#1
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Join Date: Sep 2002
Posts: 46
Greetings,
I just had a productive weekend with the car. I managed to change the oil (Valvoline 10W-30), trans (RP), and Diff (RP) fluids. I also changed the fuel filter (oh joy), plugs, and plug wires. Unfortunately, it didn't fix the current problem.
When I got the car a couple months ago, it didn't have more than 5 psi of boost above 4500 RPM. This was fixed with a hose job. Now that I have 10 psi of boost (trailing to 7 at redline), I have a light to moderate surge that starts around 5500 rpm and lasts till redline. This was NOT there before I picked up full boost, and I hoped that the plugs, wires, or fuel filter would take care of it, but no joy.
The car is completely stock, with 84k miles (only 9K on the engine). I'm trying to get everything working corectly before I start modding it. Here are the things I've read, or thought of myself.
Grounding- The car had a horrible light throttle bucking when I first got it. Once I cleaned up all the engine bay grounds, the problem was gone, and hasn't returned. I do know that the exhaust grounds are in place, but I have not attempted to clean them. I have also not added any additional grounds.
Injectors- I ran a bottle of injector cleaner through the system to see if that would make any difference, but it didn't . Is there any way to confirm that an injector is misbehaving, without removing it to have it tested? Will you get a check engine light if one gets too screwed up? This is the most worrisome possibility, since I assume the surges would be the motor going lean. As we know, lean = $$$$ Would a wideband A/F meter show an injector problem like this?
Boost leaks- I don't see the boost gauge fluctuating along with the surges, but I haven't completely ruled this out.
Plugged pre-cat, or main cat- I'm not quite sure what the symptom of a plugged cat is. Could this be my problem?
Thanks for reading though this, and giving it some thought. If you have any suggestions or comments, I'll be most happy to hear them.
Thanks,
I just had a productive weekend with the car. I managed to change the oil (Valvoline 10W-30), trans (RP), and Diff (RP) fluids. I also changed the fuel filter (oh joy), plugs, and plug wires. Unfortunately, it didn't fix the current problem.
When I got the car a couple months ago, it didn't have more than 5 psi of boost above 4500 RPM. This was fixed with a hose job. Now that I have 10 psi of boost (trailing to 7 at redline), I have a light to moderate surge that starts around 5500 rpm and lasts till redline. This was NOT there before I picked up full boost, and I hoped that the plugs, wires, or fuel filter would take care of it, but no joy.
The car is completely stock, with 84k miles (only 9K on the engine). I'm trying to get everything working corectly before I start modding it. Here are the things I've read, or thought of myself.
Grounding- The car had a horrible light throttle bucking when I first got it. Once I cleaned up all the engine bay grounds, the problem was gone, and hasn't returned. I do know that the exhaust grounds are in place, but I have not attempted to clean them. I have also not added any additional grounds.
Injectors- I ran a bottle of injector cleaner through the system to see if that would make any difference, but it didn't . Is there any way to confirm that an injector is misbehaving, without removing it to have it tested? Will you get a check engine light if one gets too screwed up? This is the most worrisome possibility, since I assume the surges would be the motor going lean. As we know, lean = $$$$ Would a wideband A/F meter show an injector problem like this?
Boost leaks- I don't see the boost gauge fluctuating along with the surges, but I haven't completely ruled this out.
Plugged pre-cat, or main cat- I'm not quite sure what the symptom of a plugged cat is. Could this be my problem?
Thanks for reading though this, and giving it some thought. If you have any suggestions or comments, I'll be most happy to hear them.
Thanks,
10-27-2002, 07:17 PM
#2
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Join Date: Jan 2002
Location: New Jersey
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Originally Posted by 13brv3' date='Oct 27 2002, 07:59 PM
.....Now that I have 10 psi of boost (trailing to 7 at redline), I have a light to moderate surge that starts around 5500 rpm and lasts till redline. This was NOT there before I picked up full boost, and I hoped that the plugs, wires, or fuel filter would take care of it, but no joy. ....
as you stated:
"light to moderate surge that starts around 5500 rpm and lasts till redline"
my initial response would be...its your second turbo kickin in ....
typically a good pattern will have you at 4500 for the second turbo at 10psi...
tapering to 8psi around 6000rpms and holding..
10-27-2002, 07:31 PM
#4
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if hesitation is the intended word...
my first guess would be exhaust restriction.....precat
boost pressure drop and hesitation at high rpm band ... typically at 6k+ are symptoms of a clogged pre/maincat..
my first guess would be exhaust restriction.....precat
boost pressure drop and hesitation at high rpm band ... typically at 6k+ are symptoms of a clogged pre/maincat..
10-27-2002, 07:33 PM
#5
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Join Date: Sep 2002
Posts: 46
I guess I need to work on my description. What I mean is that the transition (10-6-10) happens right at 4500, and it's pulling strong and smooth until about 5500 rpm. Somewhere around that point, it feels like the power sags, then comes back, then sags and comes back, etc, until redline. I was really expecting this to be a bad plug wire or plug since it feels like an ignition miss.
Hopefully, that's a better description.
Thanks,
Hopefully, that's a better description.
Thanks,
10-27-2002, 08:00 PM
#7
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Originally Posted by vosko' date='Oct 27 2002, 08:34 PM
amp might be right you might have a BLOWN secondary turbo....
since were on that topic....check your secondary turbo housing...
look for hairline cracks...source of the leak may also be due to a leaky gasket...
although exhaust loss unlikely produces the hesitation you feel...
it would be a gradual boost pressure loss
by the way...when the hose job was done...were the restrictor pills placed back?
10-27-2002, 08:14 PM
#8
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Thread Starter
Join Date: Sep 2002
Posts: 46
Well, the secondary turbo compressor housing seems to stay oily on the bottom. I can't tell exactly where it's coming from, but it doesn't seem too bad. I haven't inspected the turbo aside from what you can see with it installed, but they are original 84k mile turbos.
The hose job was done because I had 10-5-5(trailing to 2 at redline). It turned out that there was one hose off (charge control at LIM), and several that looked cracked and leaking. I verified every hose location, check valve, solenoid, and tank while doing the job, so I'm sure it's right. Much to my surprise, the pills were right where they were supposed to be, and I put them back in the new lines. I realized that 6 is a little low for transition, but that's been the least of my problems so far. I do still occasionally go back to 10-5-5 for reasons unknown, but it's very intermittent.
BTW- was my description what you'd call "hesitation" ?
Thanks,
The hose job was done because I had 10-5-5(trailing to 2 at redline). It turned out that there was one hose off (charge control at LIM), and several that looked cracked and leaking. I verified every hose location, check valve, solenoid, and tank while doing the job, so I'm sure it's right. Much to my surprise, the pills were right where they were supposed to be, and I put them back in the new lines. I realized that 6 is a little low for transition, but that's been the least of my problems so far. I do still occasionally go back to 10-5-5 for reasons unknown, but it's very intermittent.
BTW- was my description what you'd call "hesitation" ?
Thanks,
