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1988 dodge w150 idle problem

Discussion in 'Pre-1994 trucks, commercial vehicles' started by upser145, Jan 16, 2017.

  1. upser145

    upser145 Member

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    I recently discovered I had a coolant leak from my intake gasket on my 1988 dodge w150 360 engine. so I pull the carb and the intake and put in all new gaskets, no more leaks but I am having problems with the truck idling now I have the stock quadrajet carb and i adjusted the idle on it enough where it would idle but it seems like i have to turn it up faster then i should have to to keep it idling in gear. also sometimes when its in gear even when its idling good it'll backfire and cut off. it runs good when I am going down the road its just idling rough, is it likely i just need to keep adjusting the idle until i get it right.
     
  2. pt006

    pt006 Active Member

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    I would start by checking all the vacuum hoses for cracks or leaks. Replace the pcv valve. Check the routing of the vac hoses. There should be a diagram under the hood.
     
  3. ImperialCrown

    Level III Supporter

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    Welcome to Allpar. Is the backfire out the tailpipe or out of the carb? What color are the spark plug tips?
    I thought that the truck transition to EFI was during 1987 1/2? What is your build date? Did someone put a carburetor/intake on this?
     
  4. pt006

    pt006 Active Member

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    IC; 1988 was a mixed year for Dodge pickups. The V-6 and 318's had fuel injection. The 360's still had carbs. Doesn't make sense to me.
     
  5. upser145

    upser145 Member

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    Most of the backfire is out the carb. however once or twice after i cut it off it'll backfire out the tailpipe. they still used a carb stock on my engine it was the last year they did so I believe the carb and everything is stock. I will check my spark plugs and report back in a few.
     
  6. upser145

    upser145 Member

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    Also I wasn't having this problem until I pulled the intake and the carb and put new gaskets down
     
  7. ImperialCrown

    Level III Supporter

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    This is important information and could be your whole problem. The EFI heads and intake manifolds were different. Do you think that they may have given you EFI engine gaskets instead?
    I can try to look up Mopar OEM part #'s later.
     
  8. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Or he created a vacuum leak during re-assembly.
     
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  9. upser145

    upser145 Member

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    I believe I had the right gasket I can try to find the box they came in and match the part numbers up. I believe it was a vaccum line on the front of the carburetor that was causing the majority of my problems, got it hooked up right and it seems to be backfiring less on me. only really backfiring when I turn the engine off. I think that is because I need to adjust the idle down a bit. I'm gonna keep playing with it and I'll report back
     
  10. upser145

    upser145 Member

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    After some research I am thinking i got the right gasket
     
  11. pt006

    pt006 Active Member

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    Your truck could be dieseling. There are 4 adjustments to set the idle. I'm not familiar with your carb, but the old [70's] Chevy carbs had a solenoid mounted on the carb bracket and when the key was turned to 'run' the plunger would push out. This set the idle speed of a hot engine. It was adjusted by turning the plunger 'hex' to raise or lower the rpm. When the car was turned off, the plunger would retract, the throttle plates would close, and the engine would starve for fuel.

    There was an almost hidden screw that kept the throttle plates from fully closing inside the bores. This prevented the throttle plates from binding/locking in the bores.

    There is a screw that adjusts the idle speed when the engine is warming up/ till the choke plate is fully open.

    There are 2 idle MIXTURE screws that control the rich/lean setting. They may be plugged or capped and the plugs would have to be removed to get to the screws.

    good luck
     
  12. upser145

    upser145 Member

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    The almost hidden screw you mention would it be on the drivers side and take something like a t15 head? if that sounds right and i use the idle solenoid to set the hot idle what should I set the hidden screw to?
     
  13. ImperialCrown

    Level III Supporter

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    I would find a service manual for adjustment information. Chiltons and Haynes aren't the best and are pretty vague sometimes. Factory, Motor and Mitchell manuals are usually much better.
    Some main public libraries have manuals going back to the '80's and earlier. They may not be on the shelf, but in the backroom. Ask.
    Our downtown library has a subscription to Alldata for patron use @ 50ยข per 1/2 hr. You can print out what you need.
    Some idle solenoids in this era had an A/C idle adj Allen screw underneath the visible Flathead adj screw. After setting the A/C idle, the regular screw was put back in and curb idle (A/C off) was set. Most technicians wouldn't think to look for this:

    0900c15280251a58.gif

    At 29 years-old, I would think that the carburetor idle mixture screw plugs have already been drilled out and adjusted. I find many adjusted too rich and that causes other issues. Slightly lean while maintaining good idle quality is best. Always follow the service manual procedure. Don't try doing it by ear.
     
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  14. AHBGuru

    AHBGuru Active Member

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    1988 was the first year for TBI, 302 heads, and hyd rollers on the 318 for trucks ('85 for retail M bodies, except they stayed carb'd).

    1989, the 360 light duty engines got the same changes, but a few applications kept the QJet.
     
  15. AHBGuru

    AHBGuru Active Member

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    I'm gonna take a stab at this, since I've put several 360's into M bodies using the QJet.

    You can goof things up pretty bad if you put the gaskets on backwards (easy to do), or if you don't torque things in sequence and in steps. Barring all else, you could have an issue there.

    Improving one area can sometimes cause problems with another, such as the carb or timing, which may have been tuned to compensate. Double check your timing, vacuum hose unplugged, idle stop solenoid grounded. Make sure the timing chain is good. A weak coil will cause issues, too.

    After that, double check for vacuum leaks and vacuum hose routing. Then, check the mixture. You need a mixture adjustment tool (cheap, most auto stores) with the proper "slot" for the QJet. With the engine at correct curb idle speed, timing properly adjusted, shut her off. Lightly seat the screws (turn to the right looking at the front of the carb/engine). Bring each screw out maybe 2-2.5 turns each (as evenly as possible). See if she'll start. Keep the choke open (take it off fast idle cam). Shoot for the leanest, smoothest idle you can get. Put a Delco kit in it if necessary.
    On Mopar QJets, you adjust the curb idle and the idle solenoid separately. The solenoid is just a kicker that bumps up the idle a bit to handle A/C and electrical loads. I've built and used many of these, and have never seen one set up like some TQ's with only the solenoid.

    One last thought - Mopar Action had some really good tech from Dr Ebooger about flat tappet cam failures. If you can't get her to run right, you may have wiped a cam lobe.
     
  16. 2012srtchallenger

    Supporter

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    Sounds like vacuum leak,I would get can of carb cleaner with pipette,warm engine so choke is open,start spraying carb cleaner down intake manifold sides,around carb and along vacuum hoses.if there is a leak the idle will pick up.look in this area for vacuum leak
     
  17. KevinBlack366

    KevinBlack366 New Member

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    Which gaskets did you use? Fel pro has steel ones and the rubberized or whatever ones. The steelies are prone to leaking. I have sucessfully used them, but I've also had serious problems with them sucking air and oil on a different application.

    Separately...Someone mentioned there being a difference between EFI heads and carbed heads, that there was a possible gasket change. What was the difference? I was always under the impression the heads were the same up until they went over to the magnum layout in the 90s. I ask this because I'm dealing with some odd ball stuff on my 1989 EFI 360, and want to be sure I didn't mess up there.
     
  18. ImperialCrown

    Level III Supporter

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    The Mopar parts catalog lists 3 different intake manifold gasket set part number possibilities for a 1988 360 (5.9L) w/4-bbl, depending on the intake manifold casting number found on the casting. It was a complex year, maybe due to changeovers.
    I'm sure that aftermarket gasket selection is less confusing, but you still must be sure that you have the right ones for the job.
    The Mopar part #'s given here may be superseded or discontinued. They are still a good reference for comparison. If the old gaskets are still around, they may also offer a good comparison for dimensions. Thicker gasket material may be more forgiving for vacuum leaks.
    If the heads are shaved or planed, that can also affect the angle of the 'V' where it seals against the intake runners.
    See figure 9C-800, Item #1 in the 1988-89 truck catalog here (large 27mb folder):

    http://oskin.ru/pub/chrysler-dodge/manuals/Chrysler_Service_Parts_Catalog/CD1/81-96/88t.PDF
     
  19. pt006

    pt006 Active Member

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    I came up with 1 part number from an old source that fits both an 88 360 4 bbl and an 89 TBI 360. It is 4397 642.

    Your idle speed should be set at 800 RPM unless your sticker says otherwise. First check the solenoid. Put the fast idle stepped cam on its highest position. Put a weak elastic or a friend's finger on the solenoid. Turn the ign. key on and off. The plunger should move up and down. If OK, with ign off, unscrew the 'hidden' screw and watch the throttle lever retract. When it stops retracting, screw in the 'hidden' screw until the throttle lever starts to move. Then screw it in a 1/4 turn more. This is my own method that worked in the past.

    Start and run the engine till the choke is fully open. Adjust the solenoid screw to get the idle speed close. Then adjust the idle mixture screws. Try to keep them even with each other. Readjust the solenoid screw. If the truck ran smooth before the intake swap, you might have other problems.
     
  20. upser145

    upser145 Member

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    Now I have got it to idle fine but i noticed the anti dieseling solenoid does come on when the switch is turned on but after about 45 second the plunger appears to lose power and drops back down. Is there any other component that could cause this or do i just need to most likely replace the solenoid .
     

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