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1990 16v Rough idle/backfire 700 1990

posted by  jchiodi2 on  Fri Jun 26 16:21 CST 2009
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last visit: Sat Aug 28 05:28 CST 2010
[RELATED]

It's been a while since I've worked on this thing. It was my main baby for about 2 years when times were tough. I had replaced/repaired almost every part on her, with a lot of greatt help from Brickboard. Then let it sit for two years without really running her. Got a new car! Well I'd like to get her going again, if only to get it to someone else!

When I try to start it, it will fire up for a few seconds, then chug and die. Application of starting fluid will smooth it's idle and allow me to manually get to the throttle cam so I can keep it running. It will run, roughly, as I give it gas. As I do this, it will start to lug, then backfire sometimes as it reaches around 2k-3k rpm. Letting go of the throttle, it will drop back to a very low rough idle for a few seconds then die.

The only check I've done is pinching the FPR to see if there is any effect. None noticed.

I just replaced the water pump and a burnt out starter, the starter burnt out from me trying to get it to run over the last few years, it would take a little time to get it to run smoothly, starting it only every couple of months. So the starter really got abused. I may have put some fuel preservative in the tank, but it's probably been over a year or so ago.

Any ideas where to start. I feel like a newbie at this, but just need to get back into to it...








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    1990 16v Rough idle/backfire 700 1990

    posted by  Uncle Olaf on  Fri Jun 26 18:14 CST 2009
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    last visit: Mon Oct 10 19:04 CST 2011
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    Hey John,



    Sorry to hear about your problem with the car. I would try to get some fresh fuel in the tank, if its possible. The backfiring you're experiencing makes me think there may be a fault with your radio suppression relay.

    http://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm#BackfireFailingRSR


    Have you tried scanning for trouble codes? They can be helpful, although they do not diagnose all problems. Refer to the FAQ at the top right corner of the page in the drop down menu. From my experience with this motor, I know its very sensitive about the cleanliness and adjustment of the throttle body and the cleanliness of the idle air valve. If there are any vacuum leaks (including the intake hose between the AMM and the throttle body), it can cause many of the same problems.

    Check out this section of the FAQ, it deals with drivability problems.

    http://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm

    I would look at the fuel injection relay as well the the radio suppression relay, since the bad solder joints can cause all sorts of problems. You may also want to check the condition of the chassis grounds at the front of the car, on the inside of the front fenders (left and right). These get funky and corroded and can cause a lot of trouble.

    Does it smell like gas when its running? Pull the fuel pressure regulator hose to the intake manifold and see if there is fuel or fuel odor. If you have either, the regulator is bad and should be replaced.

    You may want to see if the Air mass meter is going bad... A quick and dirty check is to disconnect it (with engine off and key out of ignition) and see if the car runs any better without it. If it does, the AMM is almost certainly bad.

    If the crank position sensor at the bellhousing hasn't been replaced, it should be. The wiring cracks and causes the sensor to fail. Its not very expensive ($30) and isn't too hard to replace if you have skinny arms.


    I hope this points you in the right direction.

    Best regards, Jon 'Uncle Olaf'








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      1990 16v Rough idle/backfire 700 1990

      posted by  jchiodi2 on  Sat Jun 27 04:34 CST 2009
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      last visit: Sat Aug 28 05:28 CST 2010
      [RELATED]

      Thanks for the reply, I replaced, while I was driving it, almost every part you mentioned. I do have to do the basics first, check for vacumn leaks, make sure of grounds, and clean throttle body and all connections, plugs, distributor etc.

      I'll check the trouble codes, and see what pops up.

      It sometimes, while holding throttle open, runs strong, like it suddenly "remembers" how it should run,lol.

      I just don't have the time like I used to, to spend a whole day going through the checks methodically.

      The thing is, it's probably worth more in parts, I had the head rebuilt, put HD Bilstiens on it, strut brace, IPD sway bars, chassis brace, rebuilt tranny, chopped the springs, new fuel pump, replaced or resolded all relays, FPR, AMM, replace the ecu, and that's a partial list! It did run pretty strong and tracked like a champ. Kinda fun to drive, and all the chassis work saved my life once. Getting cut off at 70 by a semi, swerved across two lanes, and straightened back up like a F1 race car! Oh well, those were the days.

      I'll put some time in sunday and see what I can figure out....

      thanks again,
      john








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        1990 16v Rough idle/backfire 700 1990

        posted by  Uncle Olaf on  Sat Jun 27 16:15 CST 2009
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        last visit: Mon Oct 10 19:04 CST 2011
        [RELATED]

        Hey John,




        Sorry if you have already done the stuff I mentioned ... I know how that feels, since I am dealing with that with my own car. Hope you can figure it out, no matter what you do with the car.



        Best of luck, Jon 'Uncle Olaf'







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