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2G GHS GSX Shop Project- Tuning/Idle Help

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gijoe985

15+ Year Contributor
562
20
Dec 13, 2007
Grandview, Washington
Hello all,

We wanted to start a new thread for our high school shop project that has been sitting for the last half year. You can see our old threads here and here.

We have the car turning on now. We've got our timing correct and we have good compression on all cylinders now. Today when we turned the engine on it ran smoothly, but at 1600rpms. It ran well for a couple minutes, but then began to have some hiccups here and there. Eventually the idle lowered some and the idle became rough and then it just died. We tried restarting it and it idled ok and then again eventually died. Wideband originally showed us right around 14. The last time we ran it it was idling at 15:1.

We did a boost leak test and thought things looked ok. Though the psi gauge we had (attached to air gun) may not have been working well. How long does it take to pressurize the system normally? We were pumping in 50psi for 10 seconds or so and that seemed like overkill. It would hold some pressure, but again, I'm not questioning how well that gauge is reading. Sadly maintenance just came to service our compressor, so we may not have air for a few days. But we didn't hear any leaks when we pressurized it as high as we felt comfortable.

I know that the BISS will need to get adjusted, but I was waiting until it seemed to be running better.

Thoughts?
 
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1990TSIAWDTALON said:
It shouldn't idle that fast Joe. Go back now and check that the throttle cable isn't too tight, holding the plate open a bit. It should idle around 750-800 real good. Vacuum leaks or open vacuum nipple maybe? TPS adjusted correctly also? Sorry if I am redundant.
Click to expand...
Throttle cable is far too loose. Left it that way to fix later.
SAS was loosened all the way until not touching.
TPS adjusted via ecmlink.
We THOUGHT we had solved all of our vacuum leak issues, but we may need to keep checking.

I'm also working with a bunch of high school kids, so sometimes the most random issues occur. We shall see.
 
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Not likely, how about the isc being bad? have you ohm'd it out? and again if coolant isnt flowing through the fiav it will never close.
 
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I'm thinking a faulty FIAV, or throttle stop screw.

Does idle position say closed in ECM link? I can't recall exactly, but I think itll display 1 if closed and 0 if open when tracking a live log.

Otherwise I can only think of a vacuum leak causing that high of an idle and backfiring while revving.
 
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Well, we had an extra throttle body, gaskets, and new MIL spec shaft seals, so I think we're going to pull the TB off, do the trick where you just screw the FIAV in all the way (tell me no if any of you disagree with that plan) and then cap off the cooling lines to the TB. And then report back to you guys.

How's that sound? Class is 9:40-11, so we will dig in. I stuck the other TB in some carb dip to get it good and clean.
 
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Wowza, well we got the TB rebuilt today, but not installed yet. What I can tell you is that the FIAV area was filled with a black tar like substance. Quite nasty. I'm hoping that is pointing towards it being the problem.
 
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A lot of us do the blockoff and yes there is usually a lot of soot in that area. Crossing fingers that the idle will come down and let you get back to business on tuning! :thumb:
 
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Well, update, closing the FIAV obviously helped. But, after taking apart the TB, we obviously have some boost leaks now. Lots of tiny ones. The TB elbow gasket isn't sealing, BISS is leaking now (we had 2 TBs and we used the other screw), we found a couple others too. But, I'm hopeful that we are getting closer.
 
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You did put the oring back into the BISS screw, right?. I know it is a shop class, but I have used some grey silicone on the TB elbow gasket to keep it sealed if all else fails.
Keep up the good work!
 
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We never took it off. But I used the "better looking" BISS off of the two TBs, but the original one never leaked, so we just swapped them out. And we did just try some copper rtv (not really high temp, but it's what we had handy) on the TB. We swapped out a pinch type hose clamp for an actual screwed on one for the brake booster line. So, we will test today and see if the BISS is good. Then another attempt at idling properly.
 
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Gurgling from under the valve cover? Sound like oil glugging? When pressurized to 10psi.
We found new vacuum leaks. Working on those.

AFPR- there is a tiny bit leaking from the top where the adjustment screws are. Is that normal? I.e. the leaking pressure when setting it, or do we need to look inside at the o rings?
 
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Joe, something that I ran onto that you should check, is make sure the brake booster line has a one way check valve in it, however you would like to check it. My profile car didn't have one in the line and when she saw boost (and I run 40 lbs) she popped like a ballon and then leaked vacuum. Just wanted to point that out so you don't chase another gremlin!
A lot of times, those pcv valves don't seal too, so this was my remedy:
I have since put in a plastic check valve in that line and the pcv line, to keep pressure from leaking in those lines.
You can look at the working pressures and see they will hold up. I keep a couple on hand for emergencies.
https://www.ebay.com/itm/5-16-Hose-...902127?hash=item1c9c45c3ef:g:jlEAAOSwpzJaQli7 for 5/16"
https://www.ebay.com/itm/3-8-8MM-Pl...r-Fuel-Diesel-Gas-Liquid-Air-RS-/113659531385 for 3/8"

Edit: AFPR set screw should not leak, check it.

Marty
 
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Yeah, we noticed the injectors were leaking too. Well, air from around them, not fuel.

I'll post an update at the end of class today. We are seeing improvements. It is still dropping pressure at 1psi per second. I'd love to see it hold a bit longer.
 
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Change out the injector seals and you will cure the leak there. When I put bigger injectors in my car, the fuel pressure quit leaking down and it held boost pressure longer. Injector seals are cheap and pullin the rail is easy just dont drop/lose the 3 round insulators for the rail bolts and lube the new seals. :thumb:
 
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Leak locations-
Donut gasket on injector 1. Still...
AFPR (haven't addressed it yet)
Line to boost gauge. It was just one of those hard plastic lines shoved into a vacuum line with a zip tie. We tried a second ziptie, but we'll need something more secure.
Also, just noticed a tiny leak on the blowoff valve. It's a crushed 1g. It is actually from the metal, like a pinhole.

That said, we've made great improvement. It drops at a rate of about 3 seconds per psi, where it used to be less than 1 second.
 
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Silicone line is best for the boost line so it will hold pressure (yes I have seen vacuum line but it won't take my boost).The BOV shouldn't leak there so you may need to source an extra. Seen one in classifieds for $30 I think the other day. The afpr, try some teflon tape on the threads Joe.
Its all coming together nicely and glad to hear it!
 
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Well, since we got things back together we have had leaks at the fuel rail. Again, kids try their best, but this is their first time doing things. You should see my kids who are taking apart their lawn mower engines for the 3rd time because they keep making rookie mistakes. I.e. swapped valves, connecting rod on backwards, timing belt wrong, etc... They're getting quite fast at tearing one down.

Today the o ring on the fuel return line tore while being installed. They got it back on, but I haven't tried running it since.

I feel like we fixed our leak issues, or at least enough to idle well, but we're still idling at 1500 rpm, but once the car warms up it just dies. Wideband shows us at about 12-12.5:1 while we are warming up. If I try lowering the idle via the BISS it just kills it. I'm starting to wonder about the condition of my injectors. I have some 540s laying around. Maybe some 450s. We are running 880cc injectors right now, but they came with the car, so condition unknown.
 
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So, I have a set of yellow evo injectors. That we could just try swapping out to compare. (this thing does have a 280 cam on it, so that may be playing a role in our idle). The only problem with the injectors was that two were missing the pintle caps. I have some extras, but a different style. The stock ones enclose the end with a little hole, where the ones I have are pretty much just open cylinders. Would that make a huge difference?
 
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Joe, is the car currently set up to run on those 880's" ? You can swap in different injectors, that, the kids should be getting use to, LOL.
You will have to reset the injector size though so I don't know if you want to try to do that yet or not.
280 cams are reasonably big, depending on what brand, so it may have some idle issues if trying to get it to idle at 750, but it really shouldn't be idling at 1500. Check the target idle set in ECMLink and see what it says. It may be set at 1500. If so, move it down to 900 or 1000 and see how she works.
 
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1990TSIAWDTALON said:
Joe, is the car currently set up to run on those 880's" ? You can swap in different injectors, that, the kids should be getting use to, LOL.
You will have to reset the injector size though so I don't know if you want to try to do that yet or not.
280 cams are reasonably big, depending on what brand, so it may have some idle issues if trying to get it to idle at 750, but it really shouldn't be idling at 1500. Check the target idle set in ECMLink and see what it says. It may be set at 1500. If so, move it down to 900 or 1000 and see how she works.
Click to expand...

Yeah, ECMlink v2 is flashed for the 880s. I can easily go in and change it for 540s. I forget what brand our cams are. And I agree, it should still idle at much lower than 1500. I guess I was just noting that it won't idle like a stock cam.

So, it idles at 1500 with an A/F ratio of 12:1. Seems pretty healthy when idling like that. But 1) if we try to lower the idle via the biss, it dies. 2) once it warms up, it just dies. So one of my only thoughts was that maybe the injectors are having issues? I'm running short on other ideas. Compression was good, plugs are new, the boost leak test wasn't bad. I'm getting 17 "hg for vacuum, so that's decent. It'd is set at 1000 on ECMlink in hopes to get it to idle at all, we've tried lower settings too.

We may trying running it today and then pulling and checking plugs, but the A/F gauge should cover those bases. I can try another power balance test to see if the cylinders are evenly firing.
 
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In V3 Link, you have a tab that allows for "coolant offset" values. If V2 has that, it may need altered as you say when it gets warm, it dies. Does the wideband show it going lean as it dies? 14,15,18 afr's as she is dying??? If you could log it and post a log, some of the guys may be able to see it and tell you what else may be letting her die.
 
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