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'89 5th Ave. - New drama!!!

Discussion in 'F-J-M: Volare, Diplomat, etc, 1977-89' started by goair99, Mar 29, 2017.

  1. goair99

    goair99 Active Member

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    Hello again. Here is what is going on now...Since I got here 6 months ago, she has suffered from the dreaded throttle lag on tip in and especially WOT. She would buck and surge badly. WELL, I found that the return fuel hose from the fuel filter was kinked and dry rotted. SO, I replaced all hoses to and from the fuel filter. This did help greatly to reduce the lag time with throttle tip in, but not 100%.

    NOW, on cold starts she bucks, sputters and surges until half way through warm up! After warm up she seems fine. REMEMBER, all I did was replace the old hoses.

    Notes: She has a new carb that otherwise idles totally perfect in and out of gear and with or without the a/c on...
    HELP?
     
  2. goair99

    goair99 Active Member

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    Wait a minute...wait a minute...OMG I think I have the fuel filter upside down! Could this be the problem???
    I will reaffirm after work today.
     
  3. Scrounge

    Scrounge Well-Known Member

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    Fuel filter alone shouldn't be the culprit (but set it right, regardless), especially if it performs normally at operating temperatures. I suspect a choke problem, perhaps the pull-off or the rod connecting the pull-off and choke. Or the choke itself. Or maybe dirt -- you might spray some carb cleaner at key points where movement should be free.
     
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  4. valiant67

    valiant67 Rich Corinthian Leather
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    Just because it idles perfectly does not rule out a carb problem. Some things to check would be to verify the timing is set properly (doesn't take much off to create a slight hesitation), that the choke moves well (I had good luck removing the spring assembly and dousing it with carb cleaner then WD40 while moving the spring by hand), the EGR valve (remove the hose and plug it as a test).
    One problem is the crossover in the intake tends to carbon up over time, making the car run worse when cold and damp. This was worse on car used primarily for short trips.
     
    blackstratus and PCRMike like this.
  5. goair99

    goair99 Active Member

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    Once again Thanks for replying. I will look into these suggestions. The cold start was totally fine until I replaced the hoses. I just don't get it some times, it seems every time I find and fix something she starts doing something else as a result! Very depressing.

    I am jealous of my neighbor. He has a '80 Buick Park Avenue 350 4 barrel and he just turns the key waits a minute and drives off flawlessly. Then he sees my 5th buck, stall, pop and surge when I try to drive away...
     
  6. valiant67

    valiant67 Rich Corinthian Leather
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    You should be able to get there too. My 89 Fifth Avenue fired up as quickly and smoothly as my fuel injected Dakota. No stalling, no hesitation regardless of weather in Georgia. I had the same performance with my 88 Gran Fury when I lived in Ohio.
     
  7. Lee N. Burns

    Level 2 Supporter

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    Agree. Also have an '89 5th and it is capable of running 99% as well as an EFI system.
     
  8. blackstratus

    blackstratus Well-Known Member

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    I had this exact issue on a 1987 Fifth I had 20 years ago. Bucked and sputtered. Did exactly what valiant67 did with carb cleaner and got everything moving again (car sat for 6 months) and took it on some highway runs and it ran smooth as silk, cold and warm. 5 dollars fixed that one. Car ran another 3 years after that with no issues again. At that time I was worried it was the lean burn or the timing chain but tried the cheap fix first and it worked. When does that happen :)
     
  9. geraldg

    Ad-Free Member

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    A lot of the rebuilt carbs are junk I know people that have gone to thru 3 of them before getting a good one. If you can find a good carb rebuilder in your area it might be the way to go. Also if you have the lean burn computer they can cause trouble. Had a 87 that would not start a few times and read where if you tap the computer it might help and guess what it did. Got a new computer.
     
  10. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    There's a clue. Probably you accidentally disconnected, broke or moved something in the process.
     
  11. goair99

    goair99 Active Member

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    Thanks for you encouragement! I love our Mopars very much! I will first reverse the fuel filter today and report back...
     
  12. Chrononaut

    Chrononaut Member

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    Hey, goair99! Allpar member chrononaut here. Regarding your rough/stumbling issues on start/warmup. Years ago I owned an '85 Gran Fury ex highway patrol car that developed the same problem. Turned out to be the choke pull-off on the pass. side of the carb. When they get old the rubber diaphram inside dries out causing a vacuum leak. When this happens, the choke system doesn't work right and your car shakes, rattles and rolls 'till it warms up. $20 and ten minutes later and the problem was solved. On the civilian 318's, the timing chain sprockets have plastic teeth which wear out causing an erratic timing problem. Also the timing chains themselves stretch worsening the problem. My friend's 318 timing chain was so stretched after 100k miles, that we were able to remove it by pulling it apart then easily slipping it off the sprocket. It's a wonder it didn't jump 15 or 20 teeth! Valiant67 is correct about checking your timing. It's fast and easy to do. My patrol car ran terrible if not timed properly. Hope this helps! Talk to you later. Mopar to ya! By the way, my 'Gran was still going strong at 5000,000k on the original engine last time I saw her.
     
  13. goair99

    goair99 Active Member

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    Thanks! I just fixed the LeBaron's heater core problem, so I will see what I can find out about this one. The fuel filter is NOT reversed, I installed it correctly.

    One thing I did notice is that ever since I bought the 5th 6 months ago she has had a full tank all the time. I had to drive her a lot over the last two weeks while the LeBaron was being painted. That said, I noticed this problem started when the fuel level approached empty. Bad fuel pump??? I will start her up this morning and see what happens, I filled the tank yesterday.
     
  14. Scrounge

    Scrounge Well-Known Member

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    Where is your fuel pump? If it's bolted on the passenger side of the engine block near the front, the rough running should happen all the time if it's going bad. You can check if it's leaking when the engine is running. It's possible that you have some floating dirt in the gas tank that affects the pick-up when the fuel level is low enough. Have you examined the filler tube for rust? How long was the car sitting before you bought it? Where is the gas filter on your car? If it's between the pump and the carb, you might install another filter in the rubber section of the line before the pump and see if that improves performance.

    Still, like Chrononaut, I suspect a choke-related problem first. You might check this in your driveway: take off the air filter housing. The choke plate should be open. When you punch the accelerator pedal all the way to the floor, it should close. When you start the car, the choke pull-off should open it slightly. As the engine warms up, it should open gradually when you occasionally move the throttle. When it reaches operating temperature, it should be open wide.

    If the plate doesn't close when you punch the accelerator pedal, try to close it by hand and check for any obstruction. It could be that the fast idle screw needs adjusting, or that the rod connecting the plate to the carb needs cleaning and/or lubrication. If it closes ok, but doesn't open when the car is started, check to see if the pull-off pulls the rod to open the plate. If not, replace the pull-off (its technical name is choke vacuum diaphragm, if you happen across a young store clerk who's never heard of a choke pull-off). If it does, the rod might need adjusting. It has a small U that may be too wide; narrowing it slightly with a pair of needle-nosed pliers until it works may be your fix.

    That carb has too many vacuum lines; one or more of them may need replacing. Check all of them for leaks and/or deterioration.
     
  15. Chrononaut

    Chrononaut Member

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    Hello, goair99. I agree with Scrounge. It sounds like your fuel system is full of rust, must, crust, dust and rotten old dead dinosaurs. since you've already replaced the fuel filter, your next chore (which won't be quick or easy) is to replace the strainer in the tank. What some call the "Sock Filter". As scrounge said, rust forms in the tank and settles at the bottom. As the fuel level gets down low, you start picking that junk up, running it through your system. You won't believe how much crud collects in the tank! Moisture in the fuel rusts the tank plus the tiny particles of muck that is pumped into the gas station's tanks all wind up settling at the bottom of YOUR tank. I once replaced the tank-mounted electric fuel pump in a Dodge Shadow with way less than 100k, and when I dropped the tank, it had an inch of rusty sediment at the bottom. This rusty crud overloaded and killed the fuel pump. Also, as Scrounge suggests, check the mechanical working condition of your choke system, and inspect all vacuum lines. The little plastic ones break CONSTANTLY! Slip a small length of heat shrink tubing over one of the broken ends (if it ever happens-heaven forbid!), mate the broken ends together, slip the shrink tube over the break and heat it 'till it shrinks tight. I've repaired several line breaks on my old Gran this way. My Gran also came from the factory with a filter next to the fuel pump and one in the Q-jet carb, yet would STILL get clogged with dirt at least once a year, requiring a cleaning of the carb, and replacement of both filters. Modern oxygenated gas quickly destroys older carbed fuel systems, especially California gas. I went through three Q-Jets, two fuel pumps and about a dozen of each type of filters over the years I owned her, and the gas would boil in the pump on warm days causing vapor lock. Let me know how it goes with your 5th, and I'll talk to you later!
     
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  16. goair99

    goair99 Active Member

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    Update: Busy week! She starts right up cold now, no problem. Remember, I filled up the tank with Shell V-Power 93 and added my usual Lucas ethanol treatment.

    So this tell me that she does not like being run with a near empty tank. I still get the surging while under WOT and medium acceleration...All rubber vacuum lines are fresh and in there proper places. I will have to check out the hard plastic lines soon.
     
  17. AHBGuru

    AHBGuru Active Member

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    Basic diagnostics first:
    Air, spark, fuel.

    - Clean air filter.
    - Champion copper plugs, RN12YC, .035 gap. 7° +/-2° BTDC timing (ESC hose off and plugged at carb). 650 RPM curb idle, 800 step-up, 1200 fast. Check timing chain for stretch, check harmonic balancer for slippage, check vacuum advance for proper function (raise RPM gradually up to 3000, total timing should be 52°+ BTDC).

    - The fuel system on F/M/J cars seems to be the only real problem area. Check the main 5/16" feed line from stem to stern for leaks and overall condition. Replace leaks with short lengths of EFI fuel hose and screw clamps. 1/4" return line is supposed to help reduce vapor-lock. Nylon sock on end of fuel pickup tube is often missing or blocking the tube. Fuel pumps on LA motors often don't give any warning before expiration, but occasionally may send a signal at higher RPM - though the tall gears in retail M bodies don't typically get into those engine speeds. Replacements only seem to last a year or so, regardless of brand.

    Your rebuilt Holley 6280 may or may not have the ethanol-resistant seals and gaskets. Unless you know for certain what you have, run the good stuff.

    - Lean Burn.

    Never a more controversial subject in these cars.

    From 1981 on up, the system actually had two names (components): Electronic Spark Control and Electronic Fuel Control. The computer contains both circuit boards and runs the whole show from that. With a 28 year old car, the computer is the last thing to diagnose, after you've checked out your tune-up areas first. Then check all vacuum hoses and even sensor and solenoid connections for leaks/continuity. What was true in 1989 is still true today - 95% of the time, the computer isn't the problem. However, the next myth to bust is the cost of that computer: most 2bbl computers for sale through Rock Auto are a good bit less than $150. You cannot hack the car with a 2 or 4 bbl electronic ignition conversion for less than twice the price of that computer, if you're using new/rebuilt parts. Plus, you gain ZERO in performance and mpg if the car is already running fine. Rick Ehrenberg's Tech Archive is full of those kinds of horror stories.

    As Valiant mentioned, the 2bbl cars often carbon up at the crossovers, and one may have to yank the intake and take it in for a good rogering.

    For the A998 transmission, it originally called for the 7176 fluid, now superceded by Mopar +4. Use that with a new filter, the new Mopar rubber gasket, adjust the bands and kickdown rod per spec. It wouldn't hurt to regrease the rear axle bearings and use a good Valvoline pumpkin fluid.
    Front hubs take Mopar Green Snot grease. Adjust them up tight. Timkens for replacement.
    Make sure the caliper ways are filed smooth. Firm Feel carries every conceivable suspension part. It's easy to set these cars up good and tight, but they will not ride well afterwards. I had one Fury that I had so tight, you'd feel it if you drove over a dollar bill.

    Lastly, one "mod" that *is* definitely worth the expense is a Canadian Y-pipe
     

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