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Rough idle and Running


Dman85

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I was the recent winner of a 85 2wd extra cab sold to me by a friend. He had it sitting because of running problems he couldn’t fix. So here goes.. it starts and runs ok but a little rough, but when you put it in drive it wants to die and runs really rough.. I have changed cap, plugs, wires... when listening to it I hear a rattle/gargle cling from behind the carb I think from one of the vacuum valve.. any ideas or fixes.. thanks for all your help

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Ask your friend what he thinks the problem is.  Hopefully, he is an honest friend and a good one.  Issue Maybe vacuum leak, so spray some carb cleaner around intake, carb area, vacuum hoses, and if RPM does go up there's your gremlin.  Second, I would check the base timing, 3rd maybe a carb adjust.  Good luck.

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I did spray some carb cleaner around the motor and did. Not get any idle changes. There are two vacuum valves behind the carb, what are they. One of them sounds like it is gargling/knocking. I will check the timing also.

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 You have an electronic feedback carb with a round 6 wire electrical plug at the rear right side. The wires are too short and are flexed too much sometimes causing them to break inside the insulation and giving intermittent problems with engine shake when idling. I suspect the idle cut, AKA anti dieseling solenoid, (Red wire) may be at fault. Engine off but ignition turned on/off/on/off you should hear a metallic clicking sound. Key on, wiggle the connector and the wires.... if you hear clicking there's a bad connection

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He did replace the cap and wires but not rotor.. does the EGR valve on these always sound so loud? I had it running and idling good but once you put it in Reverse or Drive it just falls on it’s Dave and wants to die unless your on the gas. I think the calves need to be adjusted also as it seems to have a lot of valve chatter. I am just confused by this. Unfortunately I have a 1 year old baby so getting a good amount of time at once to do testing is hard. Everyone has been a big help though and really appreciate it. I’m sure it’s something small and am just overseeing the problem.

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Back side of motor there are two valve one is the BTR and one is the EGR. I can reach underneath it and push up in valve and rattle will go away but engine will start to die.

 

The ported vacuum line from the carb tells the BPT  (back pressure transducer) when ERG can happen. This is under three conditions...

 

A warmed up engine (TVV thermal vacuum valve, only allow signal to pass from carb to BPT when engine ids warm)

An engine NOT at idle (no ported vacuum signal)

An engine NOT at full throttle (low intake vacuum, no ported signal)

 

EGR happens only at part throttle, part load

 

The BPT samples the back pressure in the exhaust and allows EGR based on engine load. More load.. more EGR but subject to the 3 above conditions.

 

 

 

 

 

 

Pull the vacuum hose off the EGR, the EGR is now disabled. If it still makes noise then it's faulty.

 

 

EGR valves can collect exhaust deposits and need to be removed and wire brushed clean or replaced. A dirty EGR may not close properly and leak exhaust into an idling engine. This will dilute the idle mixture and reduce power and the ability of the engine to idle properly.

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So this could be part of my problems I’m having..the loud rattling I have been hearing from the back side of motor when idling was coming from one of the EGR valve. Again while idling I could put pressure up under heather with finger and rattle would go away but engine would begin to die.

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