Hi everyone!

I haven't been on the site for a while, I used to post under CamaroDrvr before the site went down. Anyways The Q-jet on my LG4 carb & ECMed 360ci is dumping fuel like it's draining out the bottom of the carb which it could be but there are some other weird symptoms along with it. With the dwell meter hooked up it stays around 10 on the 6cyl scale all the time. I'm getting a new dwell meter tonight to make sure mine isn't broke. Normally at startup it stays at 40 then once it warms up it starts swinging right around 30. I've played with the idle mixture screws and the air bleed and they don't make any difference. I can't get it over half throttle with out it falling flat on it's face and anywhere near there it's over 900mv on the O2 sensor which I just changed out which is the same as the old O2 sensor. I've got the idle screw backed out 3 turns and the air bleed backed off either a half or 1 1/2 turns from bottoming out. This atleast let me drive the car around at part throttle without boggin, it's ideling rough and burbleing but so far no back fires.

I jumpered the ALDL connector and it shows a 12, while jumpered the dwell shows a constant 30 on the 6 cyl scale. As far as I understand it a 10 on the dwell is the ecm trying to lean out the A/F mix correct?

Thanks

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'84 360ci WS6 Berlinetta
Fastest Berl In Ahhh De Lan!!

 

Just fixed up a CC QJet on my brother's 85 IROC this weekend so I'm fresh on this subject.....

I'm not absolutely certian but I beleive the duty cycle shows M/C solenoid "ON" time. Turning the M/C solenoid "ON" pulls the rods DOWN, leaning the mixture. So a low duty cycle would be consistent with a very rich mixture.

The real question is WHY? Why is your ECM trying to make things so rich? Is it not seeing the O2 voltages correctly? Is the O2 dead and lying to the ECM? Are you even getting into closed loop mode? Engine temp must be over 66*F and the O2 over 600*F to go into closed loop. THose are the only two conditions that must be met for closed loop.

Hope that helps some.


[This message has been edited by Damon (edited May 29, 2001).]

 

Ok I know a 30 on the dwell is 50% duty cycle but is 10 a higher or lower duty cycle. I thought it was a higher duty cycle trying to lean out the carb since startup enrichment is a 40 on the dwell. I'm kinda confused about which end of the meter indicate rich/lean.

Thanks

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'84 360ci WS6 Berlinetta
Fastest Berl In Ahhh De Lan!!

 

You have the simplest CCCS problem in the world to diagnose, your TPS is misadjusted/shot.

Whena TPS is bad, basically the ECM thinks you are at WOT all the time. If your ECM thinks you are at WOT, you are in open loop and the computer will command full rich from the MCS. What's really weird is that CCCS cannot diagnose a bad TPS itself. I've only seen it throw a code twice on 2 different cars with TPS's that were off for months, and then only after letting it idle for very extended intervals. CCCS is that f ucking stupid, lol!

What you need to do is this:
#1 - verify bad TPS by hooking aDVm between the middle and bottom wires on the connector on the front DS of the carb. With the throttle closed (not on the fast idle cam) it should read 0.5V. If it reads above 0.75V things start going to hell. If it read ~4V there is a good chance yours is shot, not just out of adjustment.
#2 - You'll need the tools to adjust it whether you have to replace it or not. Im bored so i did the legwork, you need this: http://www.thexton.com/catalog/fuel/fuel_1.htm , scroll down to PN 362 at the bottom, you need that.
#3 - You need to remove the cap over the TPs adjusting screw. Get a small drill bit and carefully drill into the cap, it't just to the right of the acc. pump arm pivot on the airhorn, little round plug on an angle in the casting. CAREFULLY drill into it, but do not apply force to the drill bit or you will push the plug all the way in, making removal a PITA. Once you have alittle hole, screw like a drywall screw in, then pul the plug out with pliers.
#4 - Adjust it. If you can't get it to 0.5V w/ the throttle closed, and/or the voltage jumps arond when you move the throttle it is bad and needs to be replaced.

#5 - IF it needs to be replaced you may want to get your hands on a manual cuz you have to remove the airhorn. Its not that hard, after a little practice i cold do it with the carb ON the car, but i wouldn't recomend it.

And thats that. With a good TPS you'll be back idling smooth, getting TPI killing gas mileage, and your engine will be happier from not being so rich and loaded with carbon.
...ed

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Ed Maher - Moderator @ The Carb Board
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

Thanks Ed!,

I was so depressed earlier today since my Berl was reduced to a hundai excel performance wise because I couldn't figure out why I was running so rich, now I feel alot better now that I know that it's something simple. I've even got a spare TPS I saved from my original carb sitting in a box in the garge if this one is shot. I already pulled the air horn off the other day thinking the float was messed up or the lean stop was misadjusted. I'll test the tps tonight. From what you and Daemon wrote I'm assuming that a dwell numerically lower than 30 like the 10 is the ecm richening up the mix and a numerically higher number like the normal 40 at startup would be the ecm leaning out the mix?

Thanks again everyone =)

Randy

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'84 360ci WS6 Berlinetta
Fastest Berl In Ahhh De Lan!!

 

Well the plug stripped out and is now stuck around the adjusting screw, the TPS from my old carb somehow got the plunger snapped off, and I can't get a volt meter reading off the bottom and middle wire on the tps. I'm going to get a pair of weather pack connectors and 2 spade connectors and make an adapter to go between the wireing harness and the tps so I can get a voltage reading without messing up the connector or pokeing into the wires.

It's driving well enough to get me around to work etc so I'm not too worried since I can still cruise 90 mph at 1/4 throttle even if I need to down shift instead of flooring it to pass.

I put the new dwell meter on it last night and it shows a constant 35. I need to hook both up and see if they read the same.

Here's my current plan. Hit the junkyards saturday grab a couple of air horns and TPS's or whole carbs if I can find one like mine. All I've seen so far were oldsmobile and buick Q-jets but the air horns Look identicle I'll just try to match the casting numbers. Anyone know if that will work? I want a few spare air horns since I'm not the most coordinated person and I can't drive to work if I drop my airhorn and mangle all the tubes etc.

Thanks
R

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'84 360ci WS6 Berlinetta
Fastest Berl In Ahhh De Lan!!

 

Told you to be careful, lol.

As far as interchanging airhorns, you'll just have to check. I actually ran an airhorn from a different casting #, different year, and from an obviously different application (the baseplates had different ports) on my 85 after i did the same thing lol. Of course, the butcher mechanic that i am managed to screw that one up too, but i modded it so i could still adjust the TPS.
If all else fails, here is how you mod it. You drill a *small* hole through the top of the airhorn casting right next to where the TPS adjusting screw lever is. You then find a small screw for that hole. You ten play with spacer shafts and lengths on the screw till you find one that lets you screw it in to adjust it and isn't still sticking out and in the way of the air cleaner.
Yeah, it's much cleaner to get another airhorn. Keep this in mind, some CCCS airhorns you find will have a VERY limited opening to the secondary AV. AVOID THOSE. You can probably mod them to open fully, but it is possible that it will have spring bind as pointed out by Damon.
...ed

 

Hey- while I'm thinking about it....

Getting the TPS reinstalled wrong after having the air horn off is easy to do. There's a little metal "pushrod" about 1/2" long that goes from the under side of the accelerator pump arm to the TPS pluger itself. It just kinda "floats" between the two and its a PITA to get everything to line up when you are trying to drop the airhorn down the last 1/4" or so. The pushrod tries to fall out the bottom of the airhorn as you are assembling it. If it does that it's EASY to get the TPS plunger wedged in unnatural ways, and obvoisly get bad TPS readings.

I found replacing the small o-ring that seals the pushrod up where it goes through the top of the airhorn with a fresh one helps hold on to it better so it won't fall out. But that's a PITA to replace, too! So I smeared a little thick grease on the pushrod before isntalling it. That let it sttick where it was supposed to long engouh to get the carb assembled without wedging the TPS assy.

I suppose you could also take off the accelerator pump arm and then drop the pushrod in from the top AFTER you isntall the air horn. But that would be too easy, wouldn't it?

Still, having a second set of hands helps a lot.


[This message has been edited by Damon (edited May 31, 2001).]

 

I actually found that 1/2" long push rod in my primary drivers side venturii I didn't know what it was so I put it in a box. I went to Napa and bought 2 rebuild kits for $18ea I got the tool Ed gave me a link to for $22 it's under a new part number and looks different but the old style was discontinued I'll post that part number this weekend.

I also got the TPS style weather pack connector male and female and the pins that go into them. I'm going to connect them back to back to go inbetween the wireing harness and TPS or any other sensor that uses that style connector with some plastic sheilded Spade connectors in the middle of the wires to hook a volt meter up to so I can test voltages alot easier.

Thanks Guys
R =)

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'84 360ci WS6 Berlinetta
Fastest Berl In Ahhh De Lan!!
WWW.SDFB.ORG

[This message has been edited by WS6 Berlinetta (edited June 01, 2001).]