[ECM diagnostic terminal]

So, after getting tired of seeing my car sitting in my shop and going nowhere fun, I decided to delve back into this rich-running situation and found some interesting conclusions. First, the ECM has indeed been replaced at some point, with a factory remanufactured unit, part number T1226025 for what that is worth. Second, while fooling around with this the last time, I decided to check all vacuum sources for leaks and replaced all the suspect vacuum lines for good measure. I figured that a bad vacuum leak would trigger the "system" to load more fuel, causing the symptoms experienced. Nothing changed. Then I went back to sleep until yesterday. I decided to check all the vacuum stuff again, including the very visible and intact 3/8" line to the vacuum booster. But this time I plugged off the power brake booster line before changing it out to rule out possibility that the booster itself was the culprit and eureka, the engine starts and runs completely normally. The booster diaphragm apparently has an internal leak, which is adding too much air to the fuel mixture. I haven't had a chance to drive it yet to go back to the TCC lockup issue, but I think this will fix the rich running issue.

Now, I have a new problem. I can't seem to locate a ready local source for a new brake booster, its part number or what it interchanges with. I can't believe they designed a unique one for this application. I am not averse to sending it out for rebuilding, but don't have any experience with any reputable source for that either.

Any suggestions?

[What fuel pump is used in '80 Avanti?]

The part reference number is 41216. AC Delco and Airtex both use the same number. They are available everywhere.

[big ugly box under dash]

That big ugly box is your ECM (electronic control module). If your car still has its electronic feedback Quadrajet, computer controlled ignition , lock-up torque convertor and functioning "Check Engine" light, that box is what controls them. If your car has been converted to conventional carburetor and ignition systems, then it is just dead weight.

[Rear Axle Overhaul]

All of the bearings, seals, spacers, etc. are common and available from your neighborhood auto parts store. Since the Avanti assemblies were sourced over time, I would suggest that you take the axle assembly out and disassemble yourself. There are some variables to the Dana 44 that you should measure, like axle bearing surface diameter, pinion gear shaft diameter and axle spline count so you get the correct replacement parts. Take your old parts with you and ask for 1972-1980 Ford F150 truck or 1970,s Jeep CJ parts for comparison. I rebuilt mine after finding a used pegleg Avanti Dana 44 housing to replace the non-original Mopar rear end installed in my 1982 by a previous owner. For a differential unit, I bought a Detroit TruTrack geared posi unit, 3.54:1 ring and pinion, ring gear attach bolts and carrier bearings from Summit Racing Equipment. I cleaned and painted the housing and brake backing and retainer plates with POR15 and took everything to a reputable local gear shop for assembly and setup, since I have not done that before and wanted it correct. I had the brake drums turned and then put on new shoes and wheel cylinders and reinstalled the completed assembly myself. It wasn't cheap, but everything is new and correct.

Steve

[Positraction rear end]

With enough will power and money, just about anything can be adapted to anything else. The factory rear end for the 1955-1957 Chevy is a third member type. The third member was used until 1964, but the housings and axles are unique for different years (leaf vs. coil springs, body/axle width). It is not a particularly strong rear end. The wheel pattern is 5x4-3/4, whereas the Avanti uses Ford/Chrysler pattern 5x4-1/2, so you would have mixed wheels on your car. Don't switch rear ends just because you happen to have a good '56 Chevy one laying around. If you have your original Dana 44 Avanti rear, don't cut off the spring perches and traction bar mounts. It would be MUCH preferable to put in a Twin-Track, Eaton posi or Detroit TruTrac differential unit. Sell the Chevy rear and buy one of these differential options. I went through this last year, replacing an oddball Chrysler rear end that a previous owner had switched with a real Avanti Dana 44. Much better and the width will be correct.

Steve

[1967 AVANTI II CARPET SET NEEDED]

Bill,

I got my carpet kit from Automotive Interiors & Accessories, Inc. (automotiveinteriors.com). I bought their interior and trunk kit together. They are cut, trimmed and sewn pieces and there are a LOT of them (including those door panel lowers), like the original factory installation. This is not a drop-in, molded carpet set like in a "modern" car. I bought mine about 4 years ago and paid about $425 then for the complete set, interior and trunk. They are listed for $575.00 + $54.00 SH now. I lined the entire interior floor, tunnel and back wall (behind the rear seat) with Dynamat before I installed the interior set a this past spring. I have no complaints. I have not put in the trunk kit yet. The carpets fit really well and give a new look to my 1982 RQB3482. I can post some photos if you like.

[Questions regarding my 1978 Avanti]

I checked out the available room between the engine and the steering box and it is obvious that there is no way that rear tube would clear using the Headman headers. The passenger side, no issues.

[Questions regarding my 1978 Avanti]

I am weighing the advantages of de-smogging my 1982 RQB3482 (stock 305/200R4, no inspection requirement in Oklahoma). The previous owner already got rid of the crossover, y-pipe and catalytic converter and installed true dual exhaust. Everything else is still installed, including the electronic Quadrajet, AIR system and computer controlled HEI distributor. I would like to do this in stages, starting with the AIR system to remove the cast iron exhaust manifolds with their air injection fittings to finish off the exhaust system. Has anyone used the Hedman Tight Tube Blockhugger headers (part number 69506) on your Avanti II? They look like a nice compact and efficient piece that would work well with a 305 and maybe later with a 350 or 383. But I would be reluctant to fork out the price of them just to be the first to try them if they would interfere with the steering column or something...and then have a dead car until finding and buying something else. The Sanderson units on "Gunslinger Bruce's" Avanti look pretty good, but these Hedman units look like they may take up even less room (making access to spark plugs, oil filter, starter, etc. a little easier?).

Steve

[Dynamat use in fiberglass structure]

Jim,

I got my carpet kit from Automotive Interiors & Accessories, Inc. (automotiveinteriors.com). I bought their interior and trunk kit together. They are cut, trimmed and sewn pieces and there are a LOT of them (including those door panel lowers), like the original factory installation. This is not a drop-in, molded carpet set like in a "modern" car. I am waiting for some warm weather before I start this project, my shop is not heated. I think that the Dynamat and carpets would also like some heat to make them more pliable during installation.

Good luck,

Steve

[Dynamat use in fiberglass structure]

I have used Dynamat material to line all of the floors and behind-seat storage in my El Camino with good success in reducing road and especially exhaust noise. This is all sheet steel structure which has a tendency to drum or resonate, transferring noise, especially exhaust of into the interior. I have a supply of Dynamat which I can use in my Avanti floors before I install my new carpet set, but I don't have any experience with it on fiberglass. Fiberglass may be a little more transparent to noise transmission, but I don't think it vibrates or resonates with the same intensity as steel which the Dynamat is primarily designed to dampen.

So, has anyone out there lined their entire floor (and maybe even the trunk) with Dynamat before and if so, are the results as far as sound deadening worth the cost and effort?

Steve

[ECM diagnostic terminal]

With the key on and engine off, the enrichment solenoid in the carburetor is cycling...so it appears it is getting at least that command signal from the ECM.

[ECM diagnostic terminal]

The 195 degree thermostat made no difference except that it runs at higher temperature now. The same rich condition, black smoke and loading up at idle and no TCC lockup. No trouble codes are being set in the ECM. I found that the O2 sensor is indeed in place back in the spring of the year and replaced it with a new one just for good measure. Also back in the spring, I switched the carburetor for another (the original stock one from my 1987 El Camino LG4 305) and the car ran exactly the same, so I switched it back. This is getting old.

On a different note, after changing out the rear end from a 2.87:1 to a 3.54:1 the speedometer is now 10% fast instead of 12% slow, according to my GPS.

Steve

[ECM diagnostic terminal]

Thanks to CaffieneRacer and IndyJimW for the information posted this week. That 1981 style connector is exactly what I have also, so obviously I have an early CCC system in my 1982 model Avanti. That is good information so I know what year Camaro parts to ask for at my friendly local auto parts store. I ran the check and found no stored codes in the ECM (12-12-12). This week, I am changing to a 195 degree thermostat to see if this thing will go into closed loop after heating up. This thing has been sitting for a while and I want to get it back on the road. This spring, I junked the mystery rear end that the PO had installed in the car and got a proper Avanti Dana 44 housing. I had to replace everything in it except the axles, but it now has an essentially new rear end with 3.54:1 ring and pinion, Detroit Eaton TruTrack differential and all new brakes, seals, bearings, bushings and everything else.

If I can get the CCC to act normal, I should have a good runner.

Steve

[1982 Rear End Information Needed]

John,

Thanks for the reply. I have sent you an e-mail separately.

Steve

[1982 Rear End Information Needed]

So I am still stalled on this rear end issue, and have had no luck locating a replacement actual Avanti Dana 44. I did get rid of those stupid spring spacers and replaced the u-bolts so the car sits a little lower in the rear, but I like the stance better now. I am getting ready to replace the interior and trunk carpeting (with a new gazillion piece carpet set I bought a while back) when I can get some warm-ish days to do so. I am reluctant to go much further with any updates to the rest of the car until I can get this rear end thing resolved. It is driveable and everything right now with the stock LG4 305 and 200R4, but this is a pretty lame setup for someone who enjoys a lot more performance than this drivetrain provides.

Does anyone know where I can get a correct complete rear end? I have tried the internet used "pay for part finder" search route and they came up with nothing but questions and no help.

Steve

[Running Rich?]

The car sprang a radiator leak (lousey old repair) last year, so I had it recored. While I was at it, I replaced the water pump, fuel pump all of the hoses and belts. I discovered then that the coolant sensor in the thermostat housing was broken off and just functioning as a plug (more of that PO stuff) with the connector just laying loose. I put a new sensor in it at that time. Later I realised that the PO had also removed the bulb from the check engine light (I guess so he wouldn't have to see it "on" all of the time). I put a bulb in it and it seems to function as one would expect if no faults are stored, on with the ignition and goes off after engine start. I have not done any ohm checks yet.

[Running Rich?]

The O2 senser is intact and hooked up. The air pump is just just venting to atmosphere, since the cat is missing, but the "system" has no way of knowing that. The fuel metering solenoid is cycling as soon as the key is turned on. Everything seems normal except the rich condition and the TCC lock-up thing. I am getting differing opinions on whether the temperature thing is a player or not. Wish I had a definate answer one way or the other...

[Running Rich?]

Okay, while I am waiting for my new radiator to show up for my '87 El Camino so I can get it back on the road, I'm trying to figure out a problem with my 1982 Avanti II. It has the stock LG4 305 and 200R4, same as the Camaro, El Camino, etc. for that year. It has all of the emission equipment installed and hooked up, except the previous owner took off the cat converter and put on true dual exhaust. It starts up and runs just fine when cold, but never seems to come off open loop operation even after it is driven, because after it is warmed up, it runs very rich, belching some black soot and loading up (trying to flood) especially at idle and the gas mileage sucks. The check engine light comes on with the key, but goes off as soon as the engine starts, so it doesn't seem to be storing any codes. They did a fine job of hiding the ALDL plug in this car...I haven't found it yet. On my El Camino (when it was still stock) the TCC would not engage until the engine reached operating temperature (the thermostat opens) and this Avanti's TCC rarely engages. It also rarely gets to over 180-185 degrees, so it may have a 180 degree thermostat. So here are my questions.

1. Will this system never go into closed loop until the temperature is up to 195 degrees?

2. Would it never store an error code until it reaches 195 degrees and then senses a fault?

3. Is it normal for the TCC to remain disengaged until the operating temperature is up to some minimum per the factory programming parameters?

I know that I could just go get a 195 degree thermostat, but it is underneath a bunch of stuff and I don't want to bother with the mess if it will do nothing to help the problem.

[ECM diagnostic terminal]

Thanks, Bob.

I will crawl under the dash and see if I can ferret out the wiring. I don't think the previous owner would have cut off the connector since everything else seems to be intact. That odd connector is a six plug thing and open on one side, so I don't know what the heck it is. The OBD1 connector should be a 12 pin unit and is pretty distinctive. These cars are like mystery novels anyway, since who knows if the 1982 models had 1982 mechanicals or something leftover from 1981??? I just figured that since it was meant to be a diagnostic tool, it wouldn't be hidden.

Also, since the car has a 180 degree thermostat and a re-cored radiator, it runs pretty cool. That said, the torque convertor clutch rarely locks up, so that could be related to this same issue. The computer may want more heat (195 degree thermostat?) or it just may be the open loop situation. I am tempted to trash all of it and get another distributor and non-feedback Quadrajet, but that wouldn't really improve performance much with a stock 305...and would cost more than it is worth if I can get the stock system working. Put in a 383 stroker and headers and then the story changes a lot...

Steve

[ECM diagnostic terminal]

My 1982 Avanti II (RQB3492) has been running extremely rich, black smoke, loading up, poor fuel economy, etc. The previous owner pulled the bulb out of the "check engine" light, annoying I guess, but I put one back in to attempt to extract trouble codes from the computer. All of the pollution control equipment is intact, with apparently an LG4 305 and electronic Quadrajet (except maybe the O2 sensor was removed when he changed to dual exhaust and eliminated the cat converter) so the system should throw come codes. These LG4 305s are no powerhouses, but are normally smooth, economical engines for everyday use. I think it is running open loop, some cripple-home default setting, so it will get around but doesn't run like it should. My problem is locating the diagnostic connector. They are usually are under the driver's side dash (like my El Camino) and ther is an odd connector under there, but it is not like the "normal" ones that GM used 1982 and later, so my scan tool plug does not fit it. Am I looking in the wrong place or did they put some kind of earlier or oddball connector in these Avantis?

[1982 Rear End Information Needed]

Okay, so I took some pictures and went web surfing for more data and I believe someone has transplanted a Mopar 8-1/4" rear end in this car. I haven't pulled the wheels to measure hub-to-hub yet. I don't know if a well built Mopar is stronger or weaker than the Dana 44 that is supposed to be there, but the cost to upgrade the Mopar to Twin-Track is probably less than to acquire a proper Avanti Dana 44 to rebuild, but definitely not if I have to narrow this unit while it is out. My problem remains the width issue, which brings me back to my original question...

What is the flange-to-flange (wheel surface interface) width of a stock Avanti unit?

I have stock 15X6 wires (4.00" backspacing) with 225R60's and they just seem too close to the fenders to me (see attached photos). There is a lot of room on the inside of the fenderwell for more tire, but the wheel choices get really slim when you need to go more than 4.00" on the backspacing, and that is with a 6" rim. I already made the mistake of mis-measuring the backspacing on a wheel and thus have a new useless set of American Racing Tork-Thrust II's that would look really good on the car if they would fit.

Any information or suggestions are welcome.

Thanks,

Steve

[1982 Rear End Information Needed]

While investigating a rattle in the rear suspension of my '82 Avanti II (RQB3482), I discovered that the mounting bracket for the RH traction bar had broken loose from the differential tube (bad weld job). Looking closer, I found that the weld was so bad that it is impossible that it came from the factory that way. All of the other brackets (spring perches and opposite side T/B mount) have similarly globbed weldment. The brake lines don't attach to tabs factory-style. That being said, I have not yet done further research to identify what kind of rear axle I actually have here. It is an open differential (not posi-track, twin-track, whatever) type, which is not so good for such a nose heavy car. The centering step on the axle flanges are slightly larger than the holes in the wheels (both the wires and the steel spare), making wheel installation a press-fit situation. Also, the tires seem a little too close to the fenders for my taste (don't need tires rubbing fiberglass). My intent now is to decide if this thing should just be cleaned up, re-welded and upgraded to twin-track or replaced with something more appropriate, either a Dana 44 from a donor Avanti or another stronger unit with the same wheel bolt pattern from something else.

What I do need to know is:

1. What is the flange-to-flange (wheel surface interface) width of a stock Avanti unit?

2. If I used a disc brake rear, would I need to eliminate the brake proportioning valve?

3. Does anyone have a source for a good stock replacement Dana 44 (prefer 3.55:1 twin-track, dream on...)?

4. Is there a better "bolt-in" choice identified (hub-to-hub width and bolt-pattern critical)out there than the Dana 44 originally sourced?

I am not trying to break the bank, but I an not trying to go on the cheap, either. I want a foundation rear end in case I decide to ditch the weak-kneed LG4-305 for a strong, streetable 350 or 383 stroker.

Thanks for the help,

Steve