Series inspired me, taking my turbo 3.4 to the track

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Aaron
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by Aaron »

Apparently I cannot. However I can plug in ground cables, and all the sudden the car is running perfectly once again.
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Re: Series inspired me, taking my turbo 3.4 to the track

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:good:
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Re: Series inspired me, taking my turbo 3.4 to the track

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I will eventually take this car to the track, but today was not the day, so I took the bike instead. A few issues with the car:

1) Ever since the original build it has done this. While cruising on the highway in 5th, if I go too far with the throttle to maintain speed, it'll dive rich, to the point that I can smell and feel the motor running poorly. I'm not sure what is happening, but it dives to 10-11:1 AFR. I have to completely let off the throttle for a couple of seconds, then slowly get back into it, but cannot go too far. Nearest I can tell it happens around 3 inHg, which is pretty easy to hit while cruising just trying to maintain speed up a hill. One possibility is that the my factory ECU is going into power enrichment, but it shouldn't be because my throttle percentage isn't that high (Maybe 60% max). Another is that the piggyback is kicking in. I have the maps set to do nothing until after boost comes on before they interrupt the MAF signal, but they don't have a sensor to know what ambient pressure is, I have to input that. This is an issue, but not as big of one yet. Just hurts MPG.

2) Ever since this rebuild, the car pegs rich on full throttle/boost. The only thing I changed was the fuel pump. It is possible my Walbro couldn't keep up and fuel pressure was dropping. It is also possible that my piggyback "lost" its maps while having a dead battery for a couple months and being unplugged for a couple weeks. But it shouldn't have. I recently legally acquired the software used to tune it (Can you believe the nazis charge for it now? Even if you already own their piggyback?). So here in a few minutes I'll try pulling the maps.

3) The brakes suck. Basically ended up doing a full fluid flush, replaced the master cylinder, and bled all 4 wheels several times. the pedal doesn't grab until the very bottom of the pedal travel, then it'll grab and I can get the brakes to lock, but it is at the floor when they do and the first 3/4 of the pedal travel does nothing but turn on the brake lights. If I pump the pedal the brakes pump up, and then the pedal feels 100% normal, but it'll lose that in just a little bit of driving and go back to going to the floor. I have no idea what is causing this. Possibly a leak, but I can't find any leaks, and once pumped up, the pedal will not "leak" down when at a stop with pressure applied.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by The Dark Side of Will »

Did you get the right "quick take up" master cylinder installed?

Have you adjusted the parking brake cables?
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by Aaron »

What MC is that? I got a reman one from O'Reilly auto parts.

I removed my parking brake and all of its components.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by The Dark Side of Will »

The quick-take-up master cylinder is '88 only and uses a quick take up mechanism similar to a single-pump-to-contact floor jack which takes up the hydraulic slack in the dual action rear calipers faster than a straight bore MC would.

IOW, if you have the same part number as they list for an '87 GT, you have the wrong MC.

Do you still have the parking brake calipers on the rear or are you running front calipers on the rear?
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by fieroguru »

You should also check for excessive run out on the rotors.
They could be pushing the pistons further into the calipers and take more pedal travel to reach the rotors.
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Re: Series inspired me, taking my turbo 3.4 to the track

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Interesting, I didn't know that, I'll check the part numbers. Any way to tell by looking at the MC?

I still have the factory parking brake rear calipers on it.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by fieroguru »

Aaron wrote:Interesting, I didn't know that, I'll check the part numbers. Any way to tell by looking at the MC?

I still have the factory parking brake rear calipers on it.
The rear calipers must have the parking brake properly set and be free of any air pockets to have a firm brake pedal.

Use a crescent wrench on the lever and rotate them to see how far the lever moves before the pads make contact with the rotor. If its more than about 3/4", then you need to adjust them closer. Without the cables, you will likely have to do this adjustment periodically to account for brake pad wear... so if you don't want to mess with this periodic adjustment, just swap to the front calipers... plus the front calipers bleed much, much easier.

The rear calipers can be a challenge to bleed as there are more areas for air pockets to collect. The most effective method is the 2 person approach with one pressing the pedal and the other cycling the bleeder screw. This method shrinks the air bubbles (compresses them) and creates some relative motion of the fluid in the caliper right around the air pocket to help move it to the bleeder. Vacuum bleeding and pressure bleeding can cause localized fluid movement from the inlet hose right out the bleeder and leave some of the air pockets in the calipers.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by Aaron »

Interesting, sounds like the exact problem I'm having. After pumping the pedal several times it makes contact and brakes as normal, but then the piston retracts again and I'm back to not making contact until the floor. I'll adjust them for now, since I hardly ever drive the car I don't go through pads very often at all.

They were bled using the 2-person method. I hate to sound like I know everything, but I doubt there's any air in the system, I spent a lot of time and fluid bleeding them.

Update on the car. Since putting the motor back in, it's run pig rich on boost, so much so that I couldn't really drive it on boost. So I took the car out to tune it on the highway. After a few pulls I at least got it running enough that I could pull through the gear on boost, but it was still rich. Well I decided to call it a night, and did a quick 1-2 run just for fun. The car dies almost immediately after, and won't restart.

I get it home, and diagnose. Fuel gauge is showing just over 1/2 tank, but the rail is dry. Probably my return line mod causing this. So I fill the tank completely, and I hear the rail get fuel, but the car still won't start. I can smell fuel out the exhaust now. I had a friend help check spark, and I do have spark.

I'm going to check fuses again today (Not sure why as I'm getting fuel and spark but I will). I'm also going to check the timing belt, although I doubt this is it as the motor sounds normal when cranking. Any other ideas? Also, the motor doesn't pop or hesitate when cranking. There's absolutely nothing there, just cranks and cranks like there's no fuel or spark.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by The Dark Side of Will »

It's flooded.
Still sounds like an umetered air leak. You're running speed density, right?

What piggyback do you have? I've never heard of a piggyback running "right"... just close enough to not be a PITA to drive.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by Aaron »

I cranked it for a good 20 seconds with the throttle wide open, not even a pop. It's now sat overnight, and still does the same thing, doesn't even try to start.

It's MAF only, but the only place it's getting un-metered air is via the PCV line, so breather goes from inlet tube pre turbo and MAF, to the valve cover. PCV goes from PCV port to catch can, then to a check valve, and then to the intake manifold.

Mine ran fairly well, I had no complaints. It doesn't change the tune at all until boost comes on, and despite the limitations it still coped well. Limitations are I can only make changes for 500 rpm and .5 psi increments, and the piggyback doesn't have a way of establishing ambient air pressure, so I need new maps for significant altitude changes. But I had no problems holding a steady A:F ratio and getting that exactly where I wanted it.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by Aaron »

Thanks Will for the prompt replies, you've been extremely helpful.

Timing belt is tight and centered on the cogs, and looks brand new. I'll check rotation as soon as I get another pair of hands.

Noticed something else, and I'm sure I'll catch all kinds of shit for this, but oh well. The 4-pin connector coming out from the front passenger corner of the decklid, where does this go? I can't find the other side of the plug. Which would probably explain why my decklid release button doesn't work. Ha. But shouldn't be anything that would cause the issues I'm having, especially when it's done 120 miles problem free up until a couple days ago.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by The Dark Side of Will »

The body harness that goes from the bulkhead pass-through to the C500 connector has a branch that connects to the decklid connector (which I think includes the "ajar" switch for the decklid as well).

MAF only? I thought GM used MAP/MAF combo on everything since 1990 (I know the '165 based controls were MAF only, but those suck)

In the car's current condition, it has fuel pressure and has spark. You've verified (via noid light, stethoscope or listening with a screwdriver in your ear) that the injectors are firing, right?

If it has fuel, air and spark, but still doesn't run that means either ignition timing or mixture is WAY off.
You say it was running, but running rich after the last hardware change, so we can rule out ignition timing.

What has happened is that something has degraded or failed (or a threshold has been reached) which causes problems. By "threshold" I mean something like the fuel trims in the ECM are maxed out or split excessively or something similar.

That leaves mixture. Due to the restriction in the PCV valve, not a lot of air flows through the PCV circuit, so it's not a huge unmetered air leak. Your no start/poor run condition is probably not related to the PCV system, especially since the car ran since any work was done on the PCV (unless a hose has come off, or an elbow cracked or something went wrong that makes a gross leak)
Is your return line blocked? How's your fuel pressure? Does your piggyback compensate for injector size (IE, are you running larger injectors than your ECM is programmed for and trimming the fuel with your piggyback)? Could your piggyback's injectors settings/maps have been screwed up?

Your MAF is plugged in, right?
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by fieroguru »

Is the coolant temp sender for the ECM plugged in? It might think its -40 below and dumping lots of fuel to compensate.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by Aaron »

I'll look for that decklid plug, however I'm not overly confident I'll find it lol.

The 3.4 DOHC had 3 ECU iterations. 91-93 was OBD1 MAP onoy, 94-95 is OBD1.5 MAF only, and 96-97 is OBD2 MAF and MAP. I'm running the 1.5 version, it gives me SFI and a heated O2 sensor with what is essentially an OBD1 computer.

I think it has fuel pressure, I have to remove the intake manifold to physically check how much, and I don't want to do that if I don't have to. I also haven't checked injectors yet, I'll do that as soon as I get a helper. I'm leaning toward fuel pressure. Just too coincidental for two things to fail at the same time.

Ran fine with the PCV setup the last 120 miles, so that's out. I assume return line is ok, again ran fine the last 120 miles. Piggyback is not adjusting for my larger injectors, the factory ECU was programmed by Darth to do that. MAF is plugged in, as was coolant temp. I'll check both MAF and CTS for wiring faults, but I doubt they're the problem considerino neither one is a part that causes catastrophic failure of the system.
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by Aaron »

Ok so I thought it had fuel pressure. Today I turned the ignition on, pump ran for a few seconds as usual, and then I cranked the engine about 5 seconds to check the timing belt. Marks I made on the timing belt were gone, so the belt is spinning.

I then went to remove the fuel line to try and empty the tank. Not a single drop of fuel came out of it, and it should've been at full pressure after that. So I definitely have a problem with my fuel tank/sending unit assembly. I'm not sure if it is because of my genius modification or not.

So car is up in the air, waiting until I can find that assembly at a junkyard. All Fieros had the same pump housing assemblies correct?

Thanks guys!
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by The Dark Side of Will »

Can you really not get to the fuel pressure test fitting without disassembling the intake?
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by Aaron »

Ya really. It's partially my fault. I turn the fuel rail around backward on my install so I could easily run the fuel lines down the passenger side of the engine, as there is way too much crap and heat on the drivers side. Well that puts the fitting underneath the intake manifold unfortunately.

Are all the Fiero fuel sending units interchangeable?
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Re: Series inspired me, taking my turbo 3.4 to the track

Post by The Dark Side of Will »

Yes, AFAIK. I think only the pump was different between the MPFI and TBI cars.
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