In need of guidance

[Problem]

This car has a lack of power throughout the powerband. The motor was replaced b/c of a spun bearing back in July. When I started the motor it had an idle problem and ran rough. When I unplugged the MAF the motor smoothed out. I plugged in my scanner (MT2500) and found the MAF was not responding properly when throttle position and engine load changed. I advised customer to replace.

At this point the car pulled well, it just had an idle surge, and a flatlining pre-cat 02. After some diagnostics I replaced the 02 and it began working fine (ecu restored fuel trim to near zero). Ect sensor was relating a value 40degrees below the actual coolant temp(checked with infared temp guage at ect)it too was replaced. Idle still surged. With help from Terry's Talon article I realized that even though the isc ohmed out okay and had continuity to the ecu, and I could hear it buzz when the key was first turned on, the gear was striopped like Terry said. With a new ISC the idle is okay, but the car runs like a dog.

It has good vacuum at idle, and is making 15psi by 3000rpm (maybe 2500) and holds it steadily, but the motor does not pull past that, or to it, very quickly. Pulled cat pipe down, no change(except the turbo made 20psi with pipe off).

data:
ect is at normal operating temp
under full load, and 15psi 02s go to .940
tps sweeps normally, with no spikes or drops,( but it doesn't change idle if unplugged)
MAF is pulling approx. 130g/s at wot at 3000rpm (my scanner will not display voltage)
timing advance goes to 33 degrees at this point
unplugged knock sensor no change
vacuum guage is steady at all rpms, under vacuum and boost

I am running out of tests.
Tomorrow I will replace the MAF under warranty from the parts store just for piece of mind. (I made sure the one I installed was the correct part number for a turbo motor)
If anyone has any ideas, please help.
Thank You

 

[ddavisaf]

It has good vacuum at idle, and is making 15psi by 3000rpm (maybe 2500) and holds it steadily, but the motor does not pull past that, or to it, very quickly.

Could you go into more detail about this? Is it sputtering and trying to stall out?

What are the vacuum readings at idle in kHG?
The spark plugs may not be gapped properly. They need to be NGK BPR6ES gapped at .028". Double check the routine maintenance. Filters and plugs.
If it's a manual transmission, is the clutch stock? If so are you noticing it slipping?

 

[ddavisaf]

Bolt-On ModsGreedy adjustable blow off valve Injen cold air kit w/ K&N

Make sure this is recirculated back to the intake pipe.
The BOV could be leaking at full spool causing a drastic decrease in performance. (Very important )

 

[Problem]

Could you go into more detail about this? Is it sputtering and trying to stall out?

What are the vacuum readings at idle in kHG?
The spark plugs may not be gapped properly. They need to be NGK BPR6ES gapped at .028". Double check the routine maintenance. Filters and plugs.
If it's a manual transmission, is the clutch stock? If so are you noticing it slipping?

It is not sputtering or stalling, it just seems like it has no power, like if the timing was retarded. (like if someone put the timing belt on a tooth off, but I checked it 3 times before the motor went in and once after install.)

The plugs are NGK BPR6ES, but I did not think to check the gap thanks for the tip. I will check that tomorrow and let you know what I found. Thanks for the help.

 

[Problem]

Bolt-On ModsGreedy adjustable blow off valve Injen cold air kit w/ K&N

Make sure this is recirculated back to the intake pipe.
The BOV could be leaking at full spool causing a drastic decrease in performance. (Very important )

The BOV is routed back to the intake pipe, and when I apply vacuum to it, the diaphragm does lift. Is there any other way to check it? BOV is adjustable, labeled: clockwise=harder, counterclockwise=softer. I adjusted it two turns each way, and it did not change performance in any way.

 

[ddavisaf]

Greddy BOV's have a tendency to be set to low and it can allow the pressure to escape under full boost. This happens under the "softer" setting. Turning it harder will usually remedy this. Don't turn it all the way to hard though, because it might not be able to release all the pressure in the system. Soft=slow release hard=fast release.

The intercooler. The pipe that runs from the IC to the throttle body. Is it still the plastic pipe, or is it a hardpipe?
If it is the plastic pipe still, make sure that it is bolted down under the fuse box like it is supposed to be. Otherwise when the motor flexs under acceleration it could pull the pipe off the IC a little bit causing it to leak air.
I would definately run a boost leak test at 20 psi from the turbo intake inlet. Making sure that the system can hold 20 psi for at least 30 seconds or more.
Spraying down the entire turbo track with soapy water is a good way to check for any hard to hear leaks.
Common places for leaks are the fuel injector seats, the intake manifold, the throttle body shaft seals, bov flange, etc.
Have you ran a compression test on the motor yet by chance? If so what were the numbers on all four?

The next this I would check would be the wastegate on the turbo. Make sure that it is sealing properly. Remove the o2 housing to check this.
If it's not it may take it longer to build up to full boost. Or an exhaust leak pre turbo could cause the slow buildup.

Was there any change in performance after the MAF had been replaced?

 

[Problem]

I took your advice and replaced the plugs. They were NGK BPR6ENK, which has two prongs, similar to Bosch platinum +4, but with two prongs. I put in the BPR6ES, plugs gapped to .o28, and the car began to break up after 3500 rpm, which it did not do before. where the previous plugs making up for a weak ignition. Should I check the waveform of the secondary ignition voltage for each cylinder. Thanks for help so far. I am trying to gather the components to make a boost leak tester.

 

[Problem]

I applied 10 inchesof vacuum to the wastegate actuator and it didnt move. if it was stuck open or closed could this cause some of my problems

 

[Spyydie98]

The wastegate, which is normally closed, should open when when applying boost pressure instead of vacuum. Try applying pressure to the wastegate and at some point, the pressure will overcome the internal spring and cause the actuator arm to open the internal wastegate flapper. A stock 1g could open around 9-11psi. A stock 2g can open as high as 11-12psi.

That is, IF it is working properly. It should stay closed and the boost going over and under the spring's pressure design will open and close it.

 

[ddavisaf]

The wastegate like Spyydie said shouldn't open unless under boost.
Sputtering and such symptoms usually indicate a boost leak in the system somewhere. A boost leak test is what I think is needed at this point. Spray soapy water over the entire system including the intake manifold, injectors, throttle body, bov, and everything that is in the pathway of the intercooler piping.
Also, yes, test the secondary voltages of the ignition coil and the transistor pack.
If in fact your wastegate isn't sealing properly do not bend the bracket. Simply reinstall it with washers until the flapper closes completely.

 

[JessesTalon]

I've read your post a few times and either im going blind or something but I did not see anywhere what kind of car it is your working on (seems as you are a tech asking for help on a customers car so im assuming its not your 96 gst your working on)

A complete list of Mods as well as year and make of the car would help greatly in finding a way to fix your problem.



From what I gather though it sounds to me like the cat is clogged.

just taking off the cat on a stock car should not cause 20 psi.

Does the car have any mods? like boost controller, I think the cat has something to do with the power problem, possibly idle as well.

 

[infamous1]

i dont have many mods just a injen intake and greddy type s blow off

 

[JessesTalon]

i dont have many mods just a injen intake and greddy type s blow off

Well the stock cat might be clogged up/bad I suggest replacing it with a high flow or getting rid of it alltogether. even if it isn't "the problem" your still getting the benefits of a higher flowing exhaust system.

 

[Problem]

I've read your post a few times and either im going blind or something but I did not see anywhere what kind of car it is your working on (seems as you are a tech asking for help on a customers car so im assuming its not your 96 gst your working on)

A complete list of Mods as well as year and make of the car would help greatly in finding a way to fix your problem.



From what I gather though it sounds to me like the cat is clogged.

just taking off the cat on a stock car should not cause 20 psi.

Does the car have any mods? like boost controller, I think the cat has something to do with the power problem, possibly idle as well.

In my profile you can find the information you are looking for. The 96 gst is not mine. I dont own a DSM. I disconnected the cat. i.e., ran it with and open header. Although the car made 20psi there was no increase in performance, the motor still did not want to rev up. Any other ideas.

 

[Problem]

The wastegate like Spyydie said shouldn't open unless under boost.
Sputtering and such symptoms usually indicate a boost leak in the system somewhere. A boost leak test is what I think is needed at this point. Spray soapy water over the entire system including the intake manifold, injectors, throttle body, bov, and everything that is in the pathway of the intercooler piping.
Also, yes, test the secondary voltages of the ignition coil and the transistor pack.
If in fact your wastegate isn't sealing properly do not bend the bracket. Simply reinstall it with washers until the flapper closes completely.

I am trying to locate the apparatus to put together a boost leak tester. I found some ideas in one of these forums. I have access to a leak-down tester and am trying to incorporate it into my test to provide consistency and accuracy. I will get back to you with the results of my coils and transistor. Thanks for sticking with me so far. Your help is greatly appreciated.