Poor performance after rebuild

[hatedonmostly]

'92 Talon TSi AWD, auto, 6/4 combo, 400 miles on a stockish rebuild. 16G at 10 psi, FMIC, 3" GM MAF and MAF Translator for mods.

After doing a boost leak test and finding 5+ leaks, the car is still performing as poorly as it was before the BLT. When driving, the turbo hits 10 psi with no problems on the aftermarket boost gauge but the car doesn't have any power when it is in boost. Sometimes it feels peppier than at other times, but nowhere near as quick as it should be. Fuel economy is also dismal.

I was thinking bad knock sensor, but the lifters aren't noisy and I haven't thrown a code while driving. Can't remember if we replaced it during the rebuild or not. Or perhaps a clogged exhaust or bad fuel pump? PCV valve hasn't been replaced since the rebuild, and a bad ISC is also causing the car to rev 500 RPM at idle. Perhaps those could be issues?

Spark plugs are new, good compression in all cylinders, etc...

 

[evil tsi]

i would say the root of the problem is the maf. i would say if you dont have a wideband, get one. use the knobs on the maft to fine tune it.

 

[bertrenolds]

Do you have anything to log with? You could be getting phantom knock because your knock sensor is bad or because it wasn't torqued down to spec.

 

[hatedonmostly]

i would say the root of the problem is the maf. i would say if you dont have a wideband, get one. use the knobs on the maft to fine tune it.

Good thinking, I never really thought it could be a MAF issue. The MAFT is tuned correctly.

Do you have anything to log with? You could be getting phantom knock because your knock sensor is bad or because it wasn't torqued down to spec.

Nothing to log with...but I was leaning toward the knock sensor as well; what does it feel like when the knock sensor starts pulling timing?

 

[91awd26]

Are there any noises (even faint noises) from the motor? I know it was probably just how my luck goes but I had the same thing going on with my car (full boost/no power) and the next day I had a rod knock. Seemed to run the same out of boost as it did at full boost. But like I said it's more than likely just my luck with cars.

 

[92AWDHX40]

Do you have a logger to use with your maft set up?

 

[mschlanglv]

Have you verified ignition and cam timing?

 

[hatedonmostly]

The knock sensor is good, it only has 500 miles on it according to my friend who helped me build the car.

Today I put in a Walbro 255 that I purchased, it started running better and actually feels like it hits boost now; albeit still not as quick as it should be. Then after a couple pulls, it started acting funny again. It has no power and feels like it has a clogged exhaust, until I hit 10 psi, then it starts to move. So basically, it's doing the reverse of what it was doing before, now it has no power until it gets in boost.

It also started overheating for whatever reason, we topped off the coolant with fresh stuff, let the motor run to work out all of the air and it's still getting hot. T-stat is good, radiator cap is good, hoses are fine, and I removed the stock radiator fan to replace it with a slim line model when I installed the FMIC. It isn't even hot here, I don't know what the deal is.

I'm going to try to get my hands on a logger in the next few days, but I don't have one at the moment...

 

[Rogi]

Bad turbo?

 

[brngrhd]

I would check cam timing too. I have had to help people with this after they did timing belts on other DOHC cars

 

[evil tsi]

The knock sensor is good, it only has 500 miles on it according to my friend who helped me build the car.

Today I put in a Walbro 255 that I purchased, it started running better and actually feels like it hits boost now; albeit still not as quick as it should be. Then after a couple pulls, it started acting funny again. It has no power and feels like it has a clogged exhaust, until I hit 10 psi, then it starts to move. So basically, it's doing the reverse of what it was doing before, now it has no power until it gets in boost.

It also started overheating for whatever reason, we topped off the coolant with fresh stuff, let the motor run to work out all of the air and it's still getting hot. T-stat is good, radiator cap is good, hoses are fine, and I removed the stock radiator fan to replace it with a slim line model when I installed the FMIC. It isn't even hot here, I don't know what the deal is.

I'm going to try to get my hands on a logger in the next few days, but I don't have one at the moment...

did you put an afpr on? you can overrun the stock fpr if you dont.

someone stated a bad turbo. this could cause your overheating problems IF the center section was cracked and you were losing coolant that way. otherwise a bad turbo is completely irrelevant.

second you say the problem started AFTER you put on a fmic, so common sense says its a blockage problem. put on a bigger fan or 2 and go from there. if it has a/c you can remove the condenser and that should help too.

another possible cause is that you are running lean, so lean that egts are too high. you say the maft is adjusted properly but with no way to log you ARE just assuming its set properly.

until you get a logger there is no way to tell for sure. best of luck to you

edit: check your knock sensor anyways, dont take your friends word for it. look to see if there is any black goo coming out of it. if there is, replace it.

 

[hatedonmostly]

Bad turbo? I doubt it, it spools fine...
However, it spools almost too quickly, for example it will get up to 5 psi from driving like a grandma just to get up to the speed limit. Kind of sounds like a bad wastegate actuator...

The CAS was set with a timing light, but only when I put it on the logger will it show if there is a problem with the timing.

did you put an afpr on? you can overrun the stock fpr if you dont.

someone stated a bad turbo. this could cause your overheating problems IF the center section was cracked and you were losing coolant that way. otherwise a bad turbo is completely irrelevant.

second you say the problem started AFTER you put on a fmic, so common sense says its a blockage problem. put on a bigger fan or 2 and go from there. if it has a/c you can remove the condenser and that should help too.

another possible cause is that you are running lean, so lean that egts are too high. you say the maft is adjusted properly but with no way to log you ARE just assuming its set properly.

until you get a logger there is no way to tell for sure. best of luck to you

edit: check your knock sensor anyways, dont take your friends word for it. look to see if there is any black goo coming out of it. if there is, replace it.

AFPR? How does that work?

Coolant was boiling out of the overflow, so I will try to get another fan on it to see if it helps.

The MAFT is dialed in according to the instructions, but who knows if that's how my car wants to be dialed in.

 

[brngrhd]

yeah id really check cam timing not ignition timing. the fact that it spools to fast and has poor power i bet your cams are off.

 

[hatedonmostly]

How do you adjust cam timing vs. ignition timing? I can't say I've heard either of the terms, so I'm not familiar with which is which.

 

[brngrhd]

How do you adjust cam timing vs. ignition timing? I can't say I've heard either of the terms, so I'm not familiar with which is which.

cam timing is with the timing belt make sure all your timing marks are right.

 

[natural laser]

yea when ever the timing belt was last changed you may of gotten the cam timing off and that could be causing the issue.

 

[evil tsi]

im pretty sure cam timing has nothing to do with it. if his timing marks were off, he would hit the valves being that the 4g63 is an interference motor. look at what i stated before

the apfr, is the adjustable fuel pressure regulator, the stock fpr cant handle the extra flow that the 255 puts out. some would argue that it does but if you look at the upgrade path it states you SHOULD have one to run the 255

 

[hatedonmostly]

im pretty sure cam timing has nothing to do with it. if his timing marks were off, he would hit the valves being that the 4g63 is an interference motor. look at what i stated before

the apfr, is the adjustable fuel pressure regulator, the stock fpr cant handle the extra flow that the 255 puts out. some would argue that it does but if you look at the upgrade path it states you SHOULD have one to run the 255

You're right, it's definitely experiencing a fuel issue. I'm just having problems with tuning. If I lean out the tuning on the MAFT (WOT set to F) it runs better in the lower RPM range but runs out of fuel up top when it's in boost. When the MAFT is set to 0 for WOT it pulls hard in boost because it gets plenty of fuel, but lags from running so rich. I can't find a way to tune it so I have low end and top end. MAFT settings are as follows:

AUX 0
Base 4
Idle 0
Mid -1
WOT -1

 

[LiquidX]

Fill out your profile so we can better assess your "tune"

You mentioned you took the stock radiator fan out? Why, was there not enough room for it to fit? What brand and size of fan was it replaced with, and what CFM does it pull?

An AFPR (adjustable fuel pressure regulator) is installed to change or verify fuel pressure at the rail. Generally when installing a larger fuel pump from stock, you put on an AFPR to make sure that your fuel pressure is at the proper pressure. If it's off, you will have fueling issues since the ECU is making calculations using Xpsi fuel pressure and you are actually using Ypsi pressure.

Do you know how a wastegate work? It only opens up when you has a determined pressure and that allows excess exhaust to be routed away from the turbine wheel to slow down the spooling so you can maintain your selected pressure/flow.

So you have a logger, read your fuel trims to help with setting the MAFT and also what was the coolant temp when it was boiling out of the overflow? Did you make sure the rad cap is good and sealing well? Pressure test the coolant system and make sure all air is out?

Mechanical (cam) timing is setting the belt and ensuring that the cams, balance shafts, crank, and oil pump are phased correctly by lining them up with their appropriate marks. After setting the belt you need to rotate the motor over by hand to make sure everything is still lining up when it's at #1 TDC. It can take up to 6 full rotations to get all marks to line up.

Ignition timing is done by hooking up a timing light per the instructions. Generally you hook up to the #1 spark plug wire, power wire, and ground the gun. You'll need to ground the timing pin so the ECU sets timing at 5* BTDC (instead of having it jumping around) and rotate the CAS (passenger side of the intake cam) so when you trigger the light on the crank pulley, it will flash at 5* BTDC which is shown on the lower timing cover. There is a notch cut on the crank pulley, that is the marking used to set ignition timing.