1G Fuel Pressure

[undefined0000]

I'm probably going to get flamed for this, but I have honestly searched all over, but I also have a strange situation.

I just bought a 92' Talon TSI AWD. It has an aftermarket FPR, apparently a 16g turbo (no way to confirm) and that's basically all I know. The car idles terribly and I've been playing around to try and fix it. What it does is when its in park, the idle shoots up for a few seconds, and shoots back down, works it way up and continues. I'm assuming ISC (Just discovered today). Gonna mess with that tomorrow morning.

The next thing is that when I'm getting on the highway or just accelerating fast, it feels like the car gets stuck at a certain RPM. Kinda the same feeling when I would hit the 105mph governor in my 97 Grand Am.

I was assuming it was the FPR not being set correctly. So today I bravely played with it. I started the car up and let it warm up (I also put it in reverse and pulled the E-Brake so the idle was steady) and at idle, it seems like its in the 45-50 psi range and when I pulled the vacuum hose off, it was near 60 or so if I was reading it right. That seemed REALLY high to me, so I tried lowering it and when I put the hose back on, it sounded like the injectors were ticking, so I turned it up little by little and ended up back where I started. Then I tried increasing it a bit and it started running like crap, so I just left it alone.

I did recently put a new TPS sensor on there and no difference. ALSO when I'm driving and I let go of the gas, it does the idle surge as stated above while I'm moving for a bit, then evens out and it goes away if I rest my foot in the accelerator. There is probably an answer to all of this somewhere, but I really couldn't find it.

This is also my first turbo car, I've only owned GMs before this. 92 Cadillac Deville and the 97 Grand am GT 3.1. So this is a whole different ball game for me.

 

[JusMX141]

What injectors are in the car?

Base fuel pressure for a 1G is 37.5psi, but certain injector brands flow-test at a higher pressure therefore a higher fuel pressure must be run in order to achieve an accurate tune.

 

[undefined0000]

No idea, would I be able to check somehow? This car has had several owners and the one before me only has fragments of its history :/

And is that pressure with or without the vacuum line in?

 

[JusMX141]

Always set base pressure with the vacuum line disconnected. Once you connect the vacuum line, the pressure will likely read lower as this is the car's way of correcting fuel pressure at idle through vacuum from the intake manifold.

 

[undefined0000]

Alrighty, thank you thank you. If I pulled an injector out, would I be able to find a model number of some sort?

 

[JusMX141]

Aftermarket injectors aren't easy to identify- OEM injectors may be able to be identified by color.

 

[undefined0000]

Sounds good, I'll pull one out tomorrow and snap a pic so it can be gandered upon. I'll compare against the OEM injectors myself.

 

[greekgodchaos]

Always set base pressure with the vacuum line disconnected. Once you connect the vacuum line, the pressure will likely read lower as this is the car's way of correcting fuel pressure at idle through vacuum from the intake manifold.

Quick question on this I feel needs clarification; do you need to plug the vacuum line with your thumb or something while you adjust the fuel pressure or do you just leave it unplugged?

 

[talonsnwbrdr]

apparently a 16g turbo (no way to confirm)

http://www.dsmtuners.com/forums/articles-turbo-system-intercooler/313105-16g-serial-numbers.html

Looked at this and realized I have a genuine Evo III Big 16g

 

[undefined0000]

Quick question on this I feel needs clarification; do you need to plug the vacuum line with your thumb or something while you adjust the fuel pressure or do you just leave it unplugged?

I've only seen people plugging it while they adjust. I believe its because it simulates WOT. I could be very wrong though .

http://www.dsmtuners.com/forums/articles-turbo-system-intercooler/313105-16g-serial-numbers.html

Looked at this and realized I have a genuine Evo III Big 16g

Where might I find the part number? The guy did say "Big 16g" so I guess I believe him more. He was a turbo newbie as well, so I don't think he could have pulled it out of his butt, but you never know.

 

[drive-maniac]

Is your car automatic?
Your injectors should be grey tops (390cc).
If your car is manual - blue tops (450cc).

 

[undefined0000]

It is automatic, and thank you for that info!

 

[undefined0000]

Alrighty, so I've gotten the fuel pressure right, and I even went ahead and replace the throttle body gaskets. Still no difference. I replace the throttle body gaskets because I noticed that there is a snake in my engine bay somewhere (hisssssssssS) and its near the throttle body. I covered my hand over the throttle body and it dimmed the sound, and I did it between the throttle body and valve cover and it had more of an effect. Would this be bad intake manifold gasket? I'm not overheating or losing coolant (so far as I know), but it still runs like poop. Should I go through the bother of taking that all apart to replace the gasket?

 

[Spin Daily]

if you have leaks in the TB area; might as well do a complete boost leak test on the rest to find the other leaks you might have as well.

Also, if you think you are running a 16g variant i would hope the previous owner is running something bigger than the stock 390's!

 

[undefined0000]

What's the easiest home-made way I can do a boost leak test? Would the cigar trick work? Or something else that costs around $20 and that I can do in the college parking lot, because that's my garage for the next 4 years. Also I have no way of confirming the bigger turbo, so I'm not even sure.

Also, would it be bad to spray some throttle body cleaner around to try and hunt down the leak? I read that stff isn't good to use with boosted engines

 

[Spin Daily]

Boost Leak Testing 101: Building the tool. - YouTube

video shows how to make a cheap tester, then use a air compressor from any gas station if you don't have one . You need to Go about 5lbs above what you want to run your boost at. Use a bottle of soapy water to spray on all intercooler couplings and vac hoses to find leaks.

 

[undefined0000]

So is it possible to have too much fuel pressure going though? To compensate for my boost leak, I have just been increasing the fuel pressure so it runs half-decent. Its at about 49-51 at idle. Could I kill something by doing this? Its not blowing black smoke or anything. Thanks.

 

[JusMX141]

Depending on the type or brand of injector. Some injectors are actually flow-tested at higher pressures from the factory; you either need to find out what your injectors are both brand and size-wise, or send them out to have them flow-tested so you can achieve a proper tune.

Basically the amount of fuel an injector will flow will go up with more pressure or decrease with less pressure. A 550cc injector that was rated at 45psi may only flow 460cc at 37.5psi but almost 600cc at 50psi....but you have no way of knowing that without getting them flow-tested. As you can see, it's complicated.

 

[undefined0000]

Thank you for that. Sure is complicated!

Another question, I noticed that the vacuum line for the FPR had no suction, so I rigged it right to the intake manifold for a vacuum. Would bypassing that electronic solenoid thing make a difference. I'm talking about the thing that's mounted right near the break fluid reservoir.

There are 2 black units with 2 vacuum lines on each. What is its exact function? I can't find anything on it.

 

[Colt4G63 also]

Thank you for that. Sure is complicated!

Another question, I noticed that the vacuum line for the FPR had no suction, so I rigged it right to the intake manifold for a vacuum. Would bypassing that electronic solenoid thing make a difference. I'm talking about the thing that's mounted right near the break fluid reservoir.

There are 2 black units with 2 vacuum lines on each. What is its exact function? I can't find anything on it.

Geez, it seems to me that's your whole problem right there! Run that AFPR hose directly to the manifold! You don't need the fuel pressure solenoid attached to the hoses at all.

PS. Since you said you changed the TPS, you should test the signal voltage, and adjust the TPS for a closed throttle voltage of about .63V, then set the base idle set screw until you have proper idle with the idle speed control motor position sitting at around +30.

 

[undefined0000]

That's what I did! But what's the other side for? There was blue hoses for fpr and red hoses for setting else.

So here's a video of my car on a cold start, running like complete crap, opinions?

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