1988 Ford Ranger 2.9 Missing

mjs

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Make
Ford
Model
Ranger
Year
1988
Miles
200 +
Engine
2.9 liter v-6
My ranger starts fine then starts to miss after it warms up. approx. 10 min. Changed distributor,control module,cap,rotor,wires,plugs,coil.Checked fuel pressure which was 35 psi. book says thats normal. Newer fuel pump as well as fuel filter. Also have a donor truck with parts so I went and changed out the TPS ,IAC valve after I cleaned it and the manifold pressure sensor. Still has the miss after it warms up. So I decided to run it down the road and the truck has intermittent surges and struggles to reach speeds of 55 mph or above. I have no clue to what might be wrong. Also there is no check engine light on.Any help greatly appreciated. Thanks in advance.
 
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billr

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Sounds like a vacuum leak or faulty ECT sensor/circuit; but I would also try blocking off the EGR ports. Do you have an electrical multimeter? With this old OBD1 beast you may have to be creative to get "live-data" and avoid lots of parts-swapping.

I gotta ask... have you checked compression?
 

mjs

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Sounds like a vacuum leak or faulty ECT sensor/circuit; but I would also try blocking off the EGR ports. Do you have an electrical multimeter? With this old OBD1 beast you may have to be creative to get "live-data" and avoid lots of parts-swapping.

I gotta ask... have you checked compression?
Ect sensor is the only thing I did not look at. No EGR valve,blocked off by plate. Did not check compression. yes to the multimeter. Also tried to find vacuum leak several times. thanks
 

NickD

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1982 Chevy P-30 did not have an EGR valve either, still burning unleaded gas with that much greater combustion chamber of 2,700*F as opposed to 2,100 with leaded gas and the compression was great.. These things sure got a lot of carbon build up under the intake valves, Seafoam took care of that.

Hard, to tell with these trucks, do you have fuel injectors or a carb? EPA was never concerned about trucks, just little cars like a VW.
 

mjs

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1982 Chevy P-30 did not have an EGR valve either, still burning unleaded gas with that much greater combustion chamber of 2,700*F as opposed to 2,100 with leaded gas and the compression was great.. These things sure got a lot of carbon build up under the intake valves, Seafoam took care of that.

Hard, to tell with these trucks, do you have fuel injectors or a carb? EPA was never concerned about trucks, just little cars like a VW.
fuel injection and did the seafoam spray also but was wondering if I need it again. thanks
 

Mobile Dan

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You might have a problem with Dist rotor indexing. This means that your spark has to jump a gap that is too far under some conditions because the rotor/spark timing puts the rotor tip too far away from the pin inside the Dist cap at the moment that the spark is fired.

Does that Dist have a vacuum advance device?

"Miss at idle after warmup"...did you do a power balance test? With proper precautions, remove plug wires one at a time to see how that action affects idle speed and quality.
 

billr

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I missed that, since the dizzy was replaced it may now be in wrong. You may have traded one dizzy problem for another.


Do you know how to back-probe the ECT sensor and read voltage across it? If so, get a reading with the engine cold and then with it fully warmed up and post results. I assume you do not have a scanner that shows live-data, correct?
 

mjs

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You might have a problem with Dist rotor indexing. This means that your spark has to jump a gap that is too far under some conditions because the rotor/spark timing puts the rotor tip too far away from the pin inside the Dist cap at the moment that the spark is fired.

Does that Dist have a vacuum advance device?

"Miss at idle after warmup"...did you do a power balance test? With proper precautions, remove plug wires one at a time to see how that action affects idle speed and quality.
No vacuum adv,and no with the balance test. Indexing is one thing that came across my mind. I made sure the rotor was in the exact position when I put it in.
 

mjs

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I missed that, since the dizzy was replaced it may now be in wrong. You may have traded one dizzy problem for another.


Do you know how to back-probe the ECT sensor and read voltage across it? If so, get a reading with the engine cold and then with it fully warmed up and post results. I assume you do not have a scanner that shows live-data, correct?
No scanner.Just going to repace ECT because of its age. I consider it good preventative maintenance.
 

billr

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No centrifugal advance either, I presume. So what "exact position" did you have the rotor in? It should point to the cap tower when the crank is about 25 BTDC

PS: be sure the connector contacts for the ECT sensor cable are tight and not corroded.
 

mjs

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No centrifugal advance either, I presume. So what "exact position" did you have the rotor in? It should point to the cap tower when the crank is about 25 BTDC

PS: be sure the connector contacts for the ECT sensor cable are tight and not corroded.
Hmmmm! Thats interesting to know about the rotor.No centrifugal adv. but I know they took out the dist. to change head gasket years back. Ill have to take a look. thanks
 

mjs

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UPDATE. I removed the connection to the oxy sensor. Now runs pretty dam good but no light comes on until I drive down the road. still runs good down the road. when i shut it down the light goes out. Just wondering if something is up with the computer or just a bad O2 sensor...
 

billr

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Connect a voltmeter between the O2 sensor signal wire and engine/chassis ground. Use long leads, so you can observe the voltmeter while driving the car. The O2 sensor should "toggle" back-and-forth from a reading below .45V to a reading above .45V, at a slow (1-2 Hz) rate. Typically, the reading will go down to .1V and up to about .8V, but as long as it distinctly "crosses" .45V the exact min/max are not important. If it is "stuck" either high or low, let us know the reading. I assume this is a simple 1-wire O2 sensor, but even if it is a heated one with more wires, that crossing .45V on the signal is still what it should do.
 

NickD

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Some one at GM was smoking crack telling to gap your sparkplugs at 0.062" with that new HEI system. Not the only gap, larger one between the distributor rotor and cap.

Been gaping my plugs for auto at 0.025" for many years, motorcycles and chainsaws more like 10 to 17 mils to avoid a missfire. My plane and boat used multi-ground electrodes, those cannot be gapped, but could keep clean with a ground walnut shell blaster.

Ignition system points was a far superior system, condenser, actually a oil filled capacitor was in parallel with the primary of the autotransformer of the coil. When the points opened, formed a resonant circuit that produce a series of positive and negative alternations for a rather long spark line. But points would wear out, newly formed idiot group call the EPA want transistors to be used of longer life, but they are all unipolar. Only one tiny little spark that lasts perhaps a tenth of a microsecond. Far better system used a 500 volt capacitor triggered by an SCR that generator a similar spark line. But would cost around ten bucks in production, bean counters said, one tiny transistor switching 12 volts was enough, so this is the kind of crap you are getting today. Your only recourse is to cut that large gap, voltage is greater, but the current is so weak, combustion hurricanes can blow it out.

Just saying don't blame engineers, we care, but the bean counters have control. But even they have to listen to the DOT and EPA, before 1972, engineers with brains had a say, and so much for the land of the free.

Ha, if an insurance company finds you are using other than your vehicles recommended spark plugs, can claim this is the cause of some idiot running a red light for an accident rather than that drunken idiot.

This country is sure going to hell.
 
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