'86 driveablilty dilemna

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Dec 28, 2004 | 07:09 AM

MavStallion

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Joined: Jan 2004

Posts: 79

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From: Pittsburgh, PA

'86 driveablilty dilemna

Hi, all. I have an '86, 2.9(TBI), non a/c, 5 speed with 83,000 on the clock. What's happening is that there is surging and occassional missing under load. Also, the fast idle suddenly doesn't seem to be operating. I just replaced the fuel pressure regulator as it malfunctioned. No hard starting or stalling since the regulator was replaced. The fuel pump checked out good. The filter is new and the tune up parts have only 11,000 on them. The gas mileage is normal and I do a lot of highway driving, average 20mpg. The surging is much worse when the engine is cold, but doesn't completely resolve when it warms up. The idle speed also seems to like to increase when warm and the idle has roughened up slightly. Overall, the power seems to be there.

I'm a bit stumped here and I don't have an OBD1 decoder to try and electronically diagnose the problem. What's funny is that right after the regulator was replaced, all the problems completely disappeared for a short time, but the problems mentioned above returned. The main problems with the regulator malfunction have stayed gone. Any ideas????

Dec 28, 2004 | 07:35 AM

Monty06

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Joined: Aug 2004

Posts: 1,167

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From: miami florida

q&a

you said pump. you do know that you have two pumps right, in tank pump and inline pump. the in tank is low pressure and the other one is high pressure
now on your surging question i'll get back to you i need to do some research

Dec 28, 2004 | 10:06 AM

mrshorty

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Joined: Dec 2001

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From: UT

You say you don't have an OBD1 decoder. Especially on an '86, pulling codes is the best first place to start, so I would suggest you get a "decoder". I'm going to assume you can find a paper clip or equivalent around the house/garage. You can get a cheap voltmeter or test light for ~$5 at any parts store or Walmart or equivalent. Then follow the instructions under tests at www.dalidesign.com/hbook/eectest.html or the instructions Ken00 has posted in his Tech info post (the latter look like they are taken straight out of the factory service manual). That's all you need to pull codes on an EEC-IV system.

Apr 9, 2005 | 02:24 PM

fhelmly1

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Joined: Sep 2004

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Yours sounds a little different, but I had very similar symptoms with by 2.9L 1989 Bronco II. It finally showed its hand when the fuel pump quit completely (in my driveway). Mine only has the one pump in the tank. I replaced the pump, and ALL the hesitation problems went away. I don't think fuel pressure without loading the engine tells the whole story. Incidentally, it was very easy to change the pump by cutting a 10 x 10 hole in the floor. Just use a nibbler or shears to keep from cutting into the tank. Drill holes at the corners of your cutout and cut straight lines. Good luck.

Jul 2, 2005 | 12:56 PM

884x4broncoII

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first i would do a compleet tune up plugs wires cap and rotar and fuel filter, mine had simuar simptioms when i first got it, then the ttf modual went out i replaced that and did a full tune up at the same time and now it purrs like an kitten