Engine is from a 91 camaro and runs well. I retained the factory 305 carb. Removed air pump, added shorty header, added open air cleaner, new cap, wires and plugs, gunna verify the order is right and all the caps are connected today. Followed the 350 swap guide as far as knock sensor and spark controller, its running pretty well at idle but in drive when I apply the gas it hesitates and is popping from the carb but almost sounds like the exhaust, quick short pops. The timing light i used was very old and barley worked. But set at 6° with the flat 4 plug unplugged from the distributor and will be gettong a newer light today to verify. Had alternator issues (one seemed to work then died in like 4 minutes of runtime) 2 altetnators later it looks like the gauge shows 13 volts. and I did extend a wire for the plug on the alt so i may go back and remove the butt connectors and solder. Other than that it doesn't choke or die just will not move happily. Revs kinda free but sounds like something isn't right. Do not get any clicking from the carb eith key on, all vacuum are accounted for otherwise plugged. All gauges work besides temp gauge, it stays at full cold. Bought it with a 350 in it with a broken crank so idk how it ran previously. Looking for a little point in the right direction. Thanks

 

Also bought an ecm with a prom for egr delete and slightly more aggressive timing table for the 350 tpi motor.

 

I didn't know you could still buy a PROM for a computer carb setup. Let alone with specific mods done to it.

When it "pops", is it rhythmic, like, tied exactly to engine speed? Or is it more random?

Is the temp gauge sending unit (between spark plugs #1 & #3) connected?

 

The popping is kinda relatable to throttle positioning, the further I go into the pedal(which has been mild as im afraid to hurt the new engine) and its like under a 1/4 when its starts,

The ecm and prom was purchased second hand on here from a member. I did switch back to it to see if that would change anything with key on(make the clicking noise i'm not hearing) and it didn't.

 

I extended the wire to the temp sensor, and put it on the driver side to clear the headers better. I was under the impression that sensor only controls the cooling fan, but I'm also very new to these cars and am learning along the way.

 

There are as many as 3 "temp sensors" on the 87 carb engine. I'm going to assume you still have all 3. Only 1 however, is ACTUALLY a [mr_spock] sen-sore [/mr_spock]

The coolant temp sensor is on the water outlet, right behind where the upper rad hose connects to the motor. It has a yellow and a black wire. This is what the ECM uses to "sense" engine temp. It has nothing whatsoever to do with the gauge or the fan in the carb system. What style of connector does yours have?

The coolant temp gauge SENDING UNIT (not "sen-sore") is between the #1 & #3 spark plugs. It takes a single dark green wire and a spade connector. This sends the temp reading to the gauge in the dash. It is completely separate in every way from the ECM and the fan. The same gauge sending unit has been used in GM cars that use one since the introduction of electric gauges, for as far back as I know; at least the early 50s; and up to when they started including it in the data stream coming out of the ECM in the late 90s LS engines (as far as V8s anyway; years may be slightly different for other engine types). Only change is, in the mid 70s they reduced the size of the pipe threads on it. Is it hooked up?

The radiator FAN SWITCH (again, not a "sen-sore") is in the pass side head, in the same hole in that head that would have the gauge sending unit in it if that head were installed on the other side of the engine, therefore between the #6 & #8 spark plugs. Its wire is dark green w white stripe, and the connector is a 1-pin Weatherpack. Also again, completely independent of the other functions. Does the fan work?

If you moved any of these, put them back where they belong, hook them back up to the proper wires, and find some other way to hold the wires away from the headers.

About the only PROMs I know of for these cars besides the stock ones for the various engines, was made by Hypertech, and wasn't specific to the 350 AFAIK let alone to the later TPI 350s; and one that GM released in the complete engine kit you used to could buy to put a ZZ4 into a L69 car, which was discontinued around 2000 or so. It's EXTREMELY difficult to reprogram, because the source code for it, which would have been MC6800 assembler (the chip was a MC6805 40-pin DIP if memory still serves), was never made public. Which one do you have?

I wasn't asking about throttle position, although that's a useful bit of info. I asked about its correlation (or lack thereof) with engine RPM. Some causes of popping back into the intake will be synchronized to the rotation of the engine, and some not. Very helpful for troubleshooting.

This is also a useful tidbit. The mixture control solenoid in the carb is supposed to click, maybe 10 times a second or so, when the key is turned on; then if the engine isn't started, it'll quit after a minute or so. Are you saying that it doesn't do that?

 

North Carolina SOLD - L69 8079 ECM ACFZ chips - Third Generation F-Body Message Boards

His 1987 LG4/Automatic F-body shares the ECM with the 1987/1988 LG4/L69 G-body. It's a new ECM that was introduced for 1987.

A member here had that ECM with the stock L69/Automatic chip for a Monte Carlo SS plus two additional chips that were stock except with EGR trouble codes disabled but with a functioning EGR system and with EGR trouble codes disabled and the EGR system disabled and removed.

For $40.00 you couldn't hardly pass it up. A known good working "8079" ECM and 3 L69/Automatic chips.

I sent him links in PM to a (NOS) Genuine GM "Delco" 10456018 knock sensor and matching (NOS) Genuine GM "Delco" 16128261 electronic spark control module.


GM Delco Knock Sensor 10456018

GM Delco ESC Module 16128261 (ANUC)


His 1987 LG4 F-body uses the same "8079" ECM as was used in the ZZ3/ZZ4 Camaro H.O 350 engine conversion kit. The new knock sensor and ESC module are the same ones used in that kit for the 5.7L engine.

His new engine is a 1991 iron head F-body 5.7L L98 with a 9.7 to 1 compression ratio. He couldn't use the knock sensor for that engine because the 1990 to 1992 L98 didn't have an ESC module and the knock sensor is a different impedance and the knock filter is on the CALPAK in the ECM.

His 1987 LG4 is just a 1987 peanut roller cam LB9 TPI long block with a CCC Q-jet system and CCC small cap HEI distributor. A 1987 L69 5.0L H.O. is just a 1987 hot cam LB9 with a CCC Q-jet and a CCC small cap HEI. I figured a chip for that is a lot closer to a 1991 9.7 to 1 L98 than a 1987 9.3 to 1 LG4.chip. The 1987 L69 and the 1991 L98 share 6 degrees of base timing with an aggressive timing curve and a 369 Ignition Control Module. The 1987 LG4 has 0 degrees of base timing with a lame timing curve and a 048 ICM.

Neither the LG4 nor L69 chip are going to be 100% optimal for the 1991 L98 engine. The L69 chip should be way closer than the LG4 chip though.

I figure it will be a little off cold start open loop and cold off idle and part throttle open loop. When the engine gets warm enough to go into closed loop with everything working right and the ECM getting good and fast data from the sensors the ECM should keep the engine at the programmed AFR by adjusting the mixture control solenoid 10 times per second. WOT open loop the MCS should go full rich on the primary side, and the secondary side is the same as a normal Q-jet and will need a richer metering rod and hanger assembly.

Any chance for all of this to work well the CCC Q-jet is going to have to be working right, and the ECM is going to have to be getting fast and accurate data from the Coolant Temperature Sensor and the Oxygen Sensor. The CTS we don't know what it is doing if anything at all and the stock 1 wire O2 sensor is going to work for sh*t way down far away from the head on an uncoated raw mild steel shorty header. The O2 is going to have to be converted to a heated 4 wire O2 sensor to deliver fast & accurate data to the ECM. Otherwise, it will be slow & lazy dropping back into open loop all the time.

I'm tired and my eyes are blurry now. Nap time. Be back laer on.

 

I did not know that. My late little brother's 87 MCSS had the same old one just like my 83... we even swapped em once when he was having trouble with something. Didn't fix it, butt plugged right in and worked fine.

TBH the amount of "authority" that the computer has over anything in that system, besides ignition timing, is kinda ... limited. It's not like EFI where the computer can command the fuel all the way from basically zero to wide open; it's more like about ± 15% or so, limited by the carb itself.

As far as base timing, any yutz can fix that, even me. In fact that's the first thing to do to ANY LG4 car to wake it up, whether in one of these cars, or a Caprice (my wife had one of those... about 84 I think, damn nice car, butt it got stolen out of a McDonald's parking lot in about 92 or so), or whatever. It's free and only takes about 30 seconds. Butt yeah, I don't think GM ever released ANYTHING for that system that was "optimal"; it was all heavily emissions-crippled. Regardless, that's all good stuff to know.

 

Ok, got off work finally, buddy was doing driver side... we were excited, got 5 and 7 mixed. It actually can drive now, midrange is still doggy, haven't braved anything over 50% as i know its not totally right. Temp didn't rise at all and was blowing heat out of the vents. So ill trace those wires back, my choke light was on the entire drive assuming cause it hasn't seen temp. Alternator can trip that light i hear but its charging and im about to verify that

 

I can't even count how many times over the years I have got #5 & #7 crossed. Even done it with labeled sparkplug wires.

 

14.5volts so I think its time to try and rebuild this e4me, does the solenoid that clicks stop clicking when it fails? Or maybe its just plugged? I know its a plunger type de richner deal, maybe its stuck? The temp sensors are both new, along with a new thermostat. Gas is likely a year old, i use non oxy but idk about previous owner.

 

I think I have that fan wire on the knock sensor down below...

 

I appreciate the replies, loooooong day at work. And have a toddler im soaking in our first child, so between that and the car its been hectic. I will take in all the temp sending unit and sensor info, mine for the ecm is a plug on the thermostat housing like you described. I for sure have a wire that wasn't accounted for that i thought was ac.. ill assess and get back tomorrow hopefully. I greatly appreciate all of the help and input. This site literally made this swap so much easier!!

 

Was thinking about picking up a dwell mwter to go through the carb after i take a stab at rebuilding it(bought a rebuild feom the local parts store) and see what happens. Can you use a decent volt meter instead of a dwell? I know very little about them, first priority is getting the gauge and fan working through when i get time.

 

Found the correct sending unit i dont have, will put the fan sender back on the pass side, and install my gauge sender today! Appreciate the help, I let it run a bit at idle and it warmed up and got pressure but never kicked the fan on, without the gauge I didn't leave it running long though.

 

The fan should come on when the coolant temp - actual, as measured by something that's real test equipment, NOT the dash gauge - reaches a little over 230°F. Should turn off when it cools down to about 210°F. So, check it with your IR gun, pointed at the head near the fan switch, before giving up on it.

 

And choke light stays on entire time. Idk why. Would that be a symptom of a stuck choke?

 

[QUOTE=sofakingdom;6573995]The fan should come on when the coolant temp - actual, as measured by something that's real test equipment, NOT the dash gauge - reaches a little over 230°F. Should turn off when it cools down to about 210°F. So, check it with your IR gun, pointed at the head near the fan switch, before giving up on it.[/QUOTE

I guess I dont get the real test equipment, the dash gauge is a one wire like the fan switch. Anyways, do the fan, and gauge switch stick into a water jacket? Dont know if im going to lose some coolant in the process.

 

No. Not exactly necessarily.

That light is ACTUALLY the Alternator light. The way all that works is, the electric choke stays operated (choking, as if the engine is cold) if there's no power fed to its heating coil; and the circuit is set up (details vary by year) such that if the alt isn't alt-ing, the choke gets no power, so that it doesn't heat up if, say, you're sitting somewhere with the key on to listen to the radio or whatever. For whyever, probably to assuage the emissions gestapo, they labelled the light with an "emissions" warning (if the choke stays closed on a warm engine, it runs SUUUUUUUPER RICH, like black smoke and gallons-per-mile rich) instead of telling the poor victim what's ACTUALLY wrong with the car. So there are things that can go wrong with that circuit that will light the light, butt in general, if that light comes on, it's because the alternator isn't working.

REAL test equipment, like, an infrared thermometer (I realize they're just STUUUPID expensive, like https://www.harborfreight.com/121-in...ter-63985.html or something similar, butt sometimes there's just no substitute for cubic $$$), instead of the wavy-pointer "sporty" trim package thing in the dash. Or, a REAL tachometer. Or, a REAL digital voltmeter. About all the dash trim is good for is, "it used to read this butt now it reads that, I guess it's time to check something". The "numbers" they show are totally unreliable.

 

Im getting 14.5 at the batt when running, so ill go through the two red wires i extended for the alternator plug. Will pick up a nicer infered temp gun as i need one anyways

 

Yeah if the wiring has been "improved" around the alternator, that's definitely a potential factor in this matter, like it appears to be elsewhere as well. Best to leave the wiring alone unless it absolutely cannot work as-is, and even then, it really helps to know what you're doing before altering it.

 

Appreciate the help but I dont think a well placed butt connector for a few single small gauge wires is going to cause many issues. Also i dont lack the ability there either, but nice of ya to assume.

 

Remembering where stuff goes that was never hooked up either isn't my strong suit. But here we are. Part of buying a project and learning. But splicing and soldering I've been doing for decades.

 

I wasn't. Don't have to. It's already plain to see.

Maybe not a "well-placed" one. A MISplaced one, different story. "Wires i extended for the alternator plug" for example: shouldn't have been necessary at all. The alt should be in the same place on the 350 as it was on the 305, and the wiring is the same in any case, IFF the 87 alt was used.

Best to know what you're doing before doing it. Doesn't usually turn out well to just dive in and start changing stuff and moving it around without knowing what it is and does. And I'm not referring to the mechanical aspects of operating a pair of dykes or a crimp tool or even a soldering iron.

Getting a copy of the FSM for your car might be a GREAT place to start. Not easy for a 87 model butt not impossible either, may just take a bit of patience. Won't tell you about whatever "improvements" may have been made in the interim as seems likely, butt, is invaluable for figuring out what does what and what goes where (or did originally anyway), especially if it was already out of place before you got it. May help avoid doing things like plugging the wrong connector onto something, or help figure out why warning lights are on, or even more, how to put stuff back where it belongs if it's already been disturbed.

Beyond that, all the knowledge you need is here, if you're willing to be humble and admit that you're ready to learn, rather than ... all that other.

You'll find that the 305 you pulled out and the 350 you're putting in, are all but IDENTICAL on the outside; meaning, all the electric parts, accessories, brackets, hoses, etc. from the 305, will transfer right over to the 350 long block. Hopefully you still have both. A 91 350 has completely different all of that, especially on the front of the motor; for example, the 91 water pump, in its accessory drive system, is designed to spin the opposite way from the 87 system, and won't pump anything if the 91 pump is driven by the 87 belts; butt the 87 stuff will all bolt RIGHT UP to the 91 long block, and all the wiring and everything else will just drop right back into place and work as well as it ever did. Were I in your shoes that'd be the very first thing I'd do. Since the engine is evidently already in the car, that makes it a bit harder at this point, butt still, that'll help keep you out of mix-match hell. Without knowing whether you did the changeover yourself, or it came to you partially done, or what, it's hard for me to know or even guess whether all of that that should be done, has been done; just, that it's pretty much a necessity.

 

Whats this port thats circled for? Shpuld get a chance to rebuild today or tomorrow. Just curious

 

I don't know. I don't have factory service manuals for anything older than 1988 and 1987 was the last year for a carburetor on a 3rd gen.

You have eliminated the EGR system and by installing the headers you have done away with the EFE system and the AIR system. You are going to have some vacuum hose and wiring harness stuff left unused.

Where is the wiring harness and connector for the mixture control solenoid at?

 

Went to the Thermac on the original air cleaner snout.

That being missing, as it is, would tend to explain why the mixture control solenoid doesn't click; and would also therefore explain at least some of the poor gas mileage and other driveability problems as well. I kinda think the wires running just barely across the bottom left of that pic, and the connector kinda stuck all up in the choke linkage, are supposed to go there.

I'd recommend not "rebuilding" anything just yet. Get it all wired up right, with minimal to zero "improvements" FIRST, and see where that takes you.

 

That was plugged in, just was taking it apart, never clicked cars running extremely rich.

 

Right: of course it would.

When the solenoid operates, it pulls the metering rods (which are tapered) down into the jets, which moves their thicker portion into the orifice, thus decreasing the area for fuel to flow through. It also opens the idle air bleed valve, which decreases the strength of the "signal" pulling fuel into the idle circuit. That's how the ECM controls the mixture. If it's not getting operated, then it stays at full rich.

Measure the resistance between the 2 pins of the connector on top of the carb. Should be something in the neighborhood of 75 to 100 ohms or some such, I can't recall exactly off the top of my head. Exact # isn't critical here; we're looking for something more like, is it zero, or some reasonable number like that, or infinite (open).

 

Yea i agree, although some things were misplaced before my purchase it is all the same and has been pretty straight forward. The choke liight doesnt come on as much but im pretty sure my carb is leaking into my intake and a carb rebuild seema like a good place to start. The connections are basic and the harness's were already moved all over so didnt have a great start point. The factory emissions and everything was trying to retained to a point but itll eventually get a t56 and likely hei distributor and get rid of the ecm eventually but haven't decided. The helpa been great. Will ohms test my alt connections but there's alot not working with the carb as is.

 

Could be. That's EXTREMELY common. Butt a "rebuild", by itself, won't fix that, and isn't necessary to deal with it; it can eeeeeeezily be fixed with the carb still almost completely assembled.

No, not those; the mixture control solenoid ones on top of the carb.

Might also want to check for the presence of 12V on the pink/blk wire that goes to that plug, with the key in Run. Won't matter whether the engine is running or not.

 

Ok, I figured the rebuild would replace the seal or gasket causing the leak, progress will be slow but I will surely use this info and update. Its in its storage spot for now in the garage which is very open for working on it. But northern MN is getting cold and snows close by. I am eager to learn about these carbs and figure it all out here! Thanks

 

Also got 2 of these same carbs for 40 on marketplace so I plan to dig into one a little for fun and I was missing a linkage for the passenger side of carb.

 

The leeeeeeeks in Q-Jets that leeeeeek into the intake, aren't gaskets.

Do an Advanced search on this site for my userID and the phrase "well plugs" (including the quotes).

BTW, your rear gears would have been 2.73 originally. No guarantees that that's what's still there, of course; butt that's how it would have started out its life.