Ok, heres the problem. My 350, which is in really good shape, runs like a dog. It ran like a top in the '79 Z28 it came out of, but ever since it went into my '83 with all the CC parts that the L69 came with, it never ran right, and got absolutely horrid gas mileage (about 150kms on a full tank). There are no leaks of anything, anywere... vacuum, oil, gas... nothing leaking. As for parts, this is whats been replaced:

- New cap and rotor
- New plugs (twice now)
- Rebuilt CC Qjet by my uncle
- New knock sensor (350 part)
- New O2 sensor
- New fan switch
- New temp sensor in thermostat housing (I think thats what that is)
- Most emitions removed because they were wrecked anyway

Me, my dad, and my uncle (both have alot of experience with sbc's) have been trying to get this 350 to run right since it went in, with no luck.

The only thing I can think of is maybe the TPS... how do I test that, and if necessary, how do I adjust it?

 

BTW, the symptoms are something like this... kinda rough idle (like a big cam idle, but its not a big cam), its really "soggy" feeling at low rpm, and just generally runs and feels kinda rough up to about 2200 rpm where it smooths out somewhat. Up to about 2000, it does vibrate quite a bit. Sometimes enough to make my CD player skip (but thats another problem for another day). It also gets really horrid gas mileage... about 150-200kms on a full tank of 87.

Any thoughts?

 

You can test the TPS with a voltmeter; check the 3 terminals on it with the key on and engine not running, you'll find ground, 5V, and a voltage that varies as you move the throttle; the variable one should go from about .6 -.65 V at idle, up to 4V or more at WOT. It should increase smoothly, with no jumps or dips. There's a little screw thing to adjust it (behind one of those spun-in plugs) but it essentially never needs adjustment once it leaves the factory.

I doubt that's your problem.

Sounds to me more like one intake valve is too tight.

 

You might want to check the M/C solenoid while you are at it. It is it messed up your fuel mixture will probably be messed up. If it is good and the TPS is good and you have a new o2 double check the MAP sensor also.

Also most people who have replaced a 305 with a 350 in a ccc car follow Chevy's lead. Chevy had a kit to replace a 305 with a 350 in the carbed cars that would still be emissions legal in 49 states. They don't sell the kit anymore but they still sell the parts. A lot of Camaro guys and Monte Carlo guys have done this.

It boils down to this. To put a 350 in with the CC carb you need:

87/88 ECM
ZZ4 PROM
Spark Module
knock sensor

(There were many more parts in the Chevy kit like the zz3/4 shortblock but these parts are what makes a moderate 350 work well)

87/88 ECM for carbed cars is p/n 1228079. It is a faster ECM than yours and to my knowledge is the only one that can run the zz4 PROM. I found one online for 20 bucks.

ZZ4 PROM PROM made by Chevy for their 350 package p/n 24502456 90+ bucks from a chevy dealer. ouch.

Spark module made by Chevy for the 350 package p/n 16128261

Looks like you already changed the knock sensor.

with this setup people have claimed better idle, throttle response, and much better shifting with an automatic.

Since the ECM controls the M/C solenoid and the timing it would probably be a good idea to go ahead and replace these parts especially since they are supposed to be plug and play.

I have tightened an intake valve too much and I think you would know that by now. That allows burning fuel back into the intake manifold and usually causes an nice backfire through the carb! it really wouldn't rev either.

Glen

 

Find a chip meant for an early 80s 350 9C1 cop car. With a mild 350 like that it should be fine. The only thing is, I don't believe the chip is causing your problems. It sounds like your timing is off. Those harmonic balancers are terrible for having the outer ring slip moving the timing mark. It sounds to me like your timing is too retarded. The other thing I recommend is hooking up a dwell meter and checking the dwell of the mixture control solenoid and adjust the IAB and mixture screws until you get the dwell in the right place. You can also check the operation of the ECM, O2 sensor, and Mixture solenoid by introducing a small vacuum leak. The dwell should decrease in this case. If you hold a clean shop rag over the top of the carb, you should see an increase in dwll(leaning the system out by keeping the metering rods down longer) The final thing you can do is swap the secondary metering rods to DRs and use a F hanger. Make sure the map sensor is working. You can check its function by connecting a hand vacuum pump to it with the engine idling. If you pull a vacuum on the map it should idle faster. If you release the vacuum it should idle slower. Finally it should maintain vacuum.

 

Ok, so just for $hits and giggles, I checked my TPS. I checked the ground (top one, right?) and got 5V dead on. Ok, so far so good... I checked the middle one, and it read about .6V at idle. Again, so far so good...

Now I pull the throttle open slowly, and.... nothing. It just stays at .6V all the way from idle up to WOT. Could this be my problem, or did I not test it right?

 

What about the 3rd terminal?

 

I tried the 3rd and got no voltage out of it... whats the 3rd for?

So, now that its been established that my TPS is a POS, can I adjust it to correct it? Or does it have to be replaced?

 

One more thing (just making sure I tested it right)

I unplugged the plug from the carb, and tested the voltage on the connector, not on the carb. But how would the voltage change if I open up the throttle without this plug connected?

 

you need to leave it plugged into the carb and check it by tapping into the back of the connector while it's hooked up. a scan tool can typically read the TPS voltage as well....at least on metalicamaro's TPI car I was helping him with it showed up on a snap-on scanner. Made adjusting it easy as pie.

 

How do I check it with a voltmeter with it plugged in? And how do I adjust it (if needed)?

 

The connector MUST be plugged in to correctly measure the voltage.
Use sewing needles, stick the needles into the wire insulation. (Don't let them touch each other)
Measure the voltage between the bottom and middle wires.

Question: Is the ECM alive? Does the Check Engine light come on if you start the car with a sensor unplugged?

 

Yea, the ECM seems fine. Unplug anything and the Check Engine light will come on. Did that when I unplugged the distributor a few days ago as a matter of fact. Its got no error codes stored either.

I checked the valves too, as RB suggested, and they are all lashed fine. None are over-tightened.

I don't really need a 350 computer do I? I've never heard of that!

 

Ok, so I checked the TPS voltage again (the right way) and everything seems fine... ground was 5V, the middle wire was .6 at idle and smooth to 4V at WOT.

I got no voltage from the 3rd wire.. is that a good thing, or not a good thing?

 

The third terminal should be grounded I believe, so no voltage there would be correct.

 

Ok, so my TPS appears to be healthy then.

I don't really have to get a 350 chip do I? With all the 350 parts, like the knock sensor, etc.. the L69 ECM should work fine with the 350, shouldn't it?

Is there anything else I could possibly check? I'm 99% sure its computer related, because thats what I left for last... I've checked everything mechanical, like valve lash, ignition timing, no vacuum leaks, plugs are good... and all that stuff checked out!

I'm really getting frustrated with this CC carb and distributor... its really tempting to just drop on the regular Qjet and VA distributor that came out of the '79 Camaro.

 

I was just thinking... is there maybe anything I could test on the CC distributor? I know its timed right, but something to check and see if its actually getting a signal from the ECM?

 

Put the timing light on it with the ECM plugged in. It should be very advanced, like a vacuum distributor hooked up to manifold vacuum. It might appear to jump around a little on you.

 

Are there any parts in the distributor that could be bad if it doesn't act as you described?

 

MSD ignition and a holley carb will probably cure your problems..........it did mine

 

Thats alternative #2

But I want to get what I have running right if I can. I've thrown too much money at computer parts lately, and would like to be able to use them.

 

Ignition control module, coil.

Also possible are trigger wheel and pickup coil.

 

So should I just yank the whole distributor out and check everything? Is there a way I can test those parts?

 

as a genral rule, if it starts up & runs & doesn't kick codes, then the module & pickup coil are fine, i have seen some after market modules cause some strange problems though.
things that will cause poor preformance & bad fuel mileage,...
normally these won't cause it to run ruff,..
i would look at exhaust, is it clogged?
ing timing, someone mentioned the outter ring on the balancer can slip & cause the timimng to be low but check as though it is right.
make sure you have it wired right, there is a certain way you can wire the plugs so that it winds up with low power & run some what ruff but not so bad as to act like it is wired wrong.

i ran my 83 m/c with a .30 over 350, mild cam, eldenbrock intake, & ported & polished heads useing all the 305 computer parts & carb with no problems.

 

OK,
So the TPS is good. That was the first question you had.
To answer your next question, no you do not need a 350 ECM/chip to get this thing to run correctly. Later on, a custom chip can unlock a few extra HP, but we need to get the car running OK first.
I’m happy to see someone try to keep their CC carb. When it is working properly, it provides excellent fuel mileage and throttle response under widely varying driving conditions.

Before we start some kind of online electronics troubleshooting school for CC distributors, there is something we need to understand. The distributor is part of a “closed loop- feedback system” made up of:
1. a running engine
2. sensors monitoring the engine
3. a computer reading the sensors, then adjusting control signals sent to the Dist and Carb
4. the Dist and Carb, which supply fuel and spark to the engine to keep it running.

This means that if you don’t see the timing changing with engine speed (using a timing light like five7 recommended), you can not assume a problem in the Dist. A bad ECM, sensor, or mechanical problem with the engine can all affect timing.

What we need to do is “break the feedback loop”. This VERY easy to do on a CC carb system. Start the car and warm it up, short the ALDL pins A to B with the engine running (exactly as when you check for stored codes, except this time with the engine running).
The engine idle should smooth out, VERY, VERY SMOOTH. No codes should flash, not even 12. If it does flash any codes then something is wrong.
What is happening is the ECM goes into a simplified open loop mode. It ignores most of the sensors and sets the timing fixed to “base” (10 deg BTDC on a L69, zero deg on a LG4), and sets the carb M/C dwell to a fixed 30 deg. (or 50% duty cycle)
If the idle is still rough with the pins shorted, I would first try adjusting the timing slowly in ether direction and see if that helps. If not, set it back to 10 deg.
Next thing is check the Carb. You’ll need to find an old clip on tachometer that also measures “Dwell” with a setting for 6 cylinders (or an oscilloscope).

I have some questions:
Is the Choke flap opening all the way when the car is warm?
How does the car run when first cold started and the choke is closed?
Does the ECM store codes when the ignition is Off? The ECM gets both a switched 12 volt power supply and a continuous 12 volts straight from the battery. Did you remove the battery supply to clear code from when the Dist was unplugged?

 

Weak distributor components won't set codes unless the ECM isn't getting pulses or is causing another system problems. The module/coil caused very poor performance and mileage on my nephew's '86 LG4. It didn't set a code until it finally quit running.

 

- Yes, choke works just as it should.

- Kinda rough and shakey, but stable.

- What do you mean? When the engine is off, or when the key is out?

- No.

 

five7kid, thats why i said " as a general rule", 95% of the time
when there is a problem with the pick up (no start) or module you get a code 42 or it's a no start. i have seen a few that the pickup checked good but were bad & the car would still run.
with delco modules i have seen maybe 10 that would still start
& run without codes but the module was bad. i can't even guess how many new aftermarket modules i have tossed in the can because of some strange run problem.


Air_Adam, five7kid mentioned the coil, i was thinking he was talking about the pickup coil, my bad. after re-reading i see you didn't replace the ignition coil, low output from it can sure cause what your having.
you also said that it does vibrate quite a bit, im taking that to mean not as a missfire, but as if the engine is out of balance.
try this, start it up & rev the engine up to around 3000 rpm & then turn the key off & let it come to a stop, do not turn the key back on while the engine is still turning, is it smooth coming back down or does it still have the vibration in it?

 

Double post.

 

No, I havent replaced the coil. Think that would help much?

As for your idea, that might work, but I doubt thats very good for the engine. I would think that could make it start dieseling, no?

As for the vibration, I'm thinking it could be just crappy motor mounts, because the 305 that came out of the car "felt" exactly the same.

BTW - Why does no one rent out timing lights anymore? I was asked about one at work, and I didn't see any on the rental tool shelf, so I asked about it, and they don't rent them anymore, but no one can tell me why?

 

a new coil would help only if your old 1 is weak, for a quick test, you can pull a wire off of 1 plug & put the blade of a screw driver with a good plastic handle on it into the plug wire where it goes on the plug & then lay it on the fender or on a windshield wiper arm & start the engine up, then holding the screw drive by the handle as far away as you can get from the metal part of it, ease it up, it should easily jump a 1/2+ inch gap with no problem. if it won't jump at-least a 1/2 inch gap then you do have some weak ignition parts. seems like your system should be able to jump a full 1 inch gap like this, but i haven't checked 1 like this in so long i don't remember for sure anymore.

reving it up & turning the key off won't hurt it, unless you turn the key back on before the engine has stopped, which would probably take out the muffler & maybe the cat. also, it would only need to be done 2 or 3 times tops. you do it when the engine is cold, not warmed up, if you do it when it's warmed up then it may diesel. it's hard for me to describe what to look for, in person it would be no problem even with bad mounts. if it has a harmonic imbalance coming down then there is the possibility that the outer ring has shifted on the balancer & if that has happened then a timing light won't do you much good. because you said the old motor felt the same we can disregard a balance problem.
someone had said a way to set the timing without a light, it will work & get the timing pretty close. the outer ring can shift enough as to not cause a balance problem but still cause problems getting the timing right.

on the light rental part, it may because that most cars built in the last few years have no provision to set the timing.