88 2.9L Misfireing/backfireing issue

[88 XLT Ranger]

"Easy steps" are fine, what are you trying to test first?

A DVOM is a "Digital Volt/Ohm Meter", the same as a multimeter.

I been doing the wire checking I can't find anything wrong thus far. I fired it up sounds great no missing or popping or running rough. I ran it up to 2500rpm's for 10 mins than let it idle at 800rpm's as I checked and moved wires it ran smooth no stumble. This is the part I don't get now if I hit the freeway going 65mph and start up the 6 mile grade before I get to the top its starts its missing/popping issue. We all know that same song and dance with this on going issue. I am not real sure what I should be testing first?

I did notice the under hood light was dim when running at idle it would go bright when at 2500 than dim again off and on. I did check the volts as it did this it stayed around 14.35 the alternator sounds bad at times like a worn bearing or bushing clunking noise. The alternator light does come on and off a lot I don't know why when the voltage is ok when testing with light on and off and hood light dim and bright


I was also thinking when it starts its misfire issue pull over disconnect the battery for 5 min than re-connect it. Would this reset the computer? maybe pin it down closer to a computer issue if the misfire goes away for bit?

 

[Mark_88]

NOTE: I don't want this to distract you from your current pursuit of the TFI and related testing...but something to check afterwards if you do not resolve this through the current steps...

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This (dimming lights) is not normal and indicates either a wonky voltage regulator, alternator, or something else is sucking up your amps. It could be a short somewhere like in the harness that was loose (inspect closely for frayed wires near metal parts).

You may have heard of those airplanes that were crashing because wire harnesses were vibrating and eventually wearing through their protective coatings causing system failures...this happens more often than you can imagine...and it may be so small a break that they go undetected.

I have personally had very similar situations where the lights would dim for no apparent reason. It was frustrating because everything worked fine except for sporadic failures...and I know I mentioned this a long time ago in one of your first posts...check the wire harness coming from the firewall to the lights/horn/starter circuit.

I know it is different on a Fuel Injected system but they are very similar...that wire harness becomes very brittle over time and the connectors start to fall apart...but you cannot see that without very careful inspection...

The main power wire on mine was frayed so badly but covered with tape and protective casing...I had to strip it right down so the wires could all be seen clearly and go over it inch by inch...but I finally found the problem and a member on here sent me a harness that fixed the problem...after fighting with it for months and not having a clue what to look for.

EDIT II: do you by any chance happen to be turning anything else on when this happens? Like your radio/cassette player...lights...signals...heater blower...wipers...anything that is not on prior to this popping event? If you can't remember...do this test...when it is running good...drive without turning anything else on...and note any changes like when you turn on your signals to exit the highway...or flash your high beams to pass someone or ANYTHING...power seat adjustments...power anything that you are turning on during the drive that may trigger this...

Again...just something to think about that you may be overlooking...

 

[88 XLT Ranger]

NOTE: I don't want this to distract you from your current pursuit of the TFI and related testing...but something to check afterwards if you do not resolve this through the current steps...

*****************************************
This (dimming lights) is not normal and indicates either a wonky voltage regulator, alternator, or something else is sucking up your amps. It could be a short somewhere like in the harness that was loose (inspect closely for frayed wires near metal parts).

You may have heard of those airplanes that were crashing because wire harnesses were vibrating and eventually wearing through their protective coatings causing system failures...this happens more often than you can imagine...and it may be so small a break that they go undetected.

I have personally had very similar situations where the lights would dim for no apparent reason. It was frustrating because everything worked fine except for sporadic failures...and I know I mentioned this a long time ago in one of your first posts...check the wire harness coming from the firewall to the lights/horn/starter circuit.

I know it is different on a Fuel Injected system but they are very similar...that wire harness becomes very brittle over time and the connectors start to fall apart...but you cannot see that without very careful inspection...

The main power wire on mine was frayed so badly but covered with tape and protective casing...I had to strip it right down so the wires could all be seen clearly and go over it inch by inch...but I finally found the problem and a member on here sent me a harness that fixed the problem...after fighting with it for months and not having a clue what to look for.

EDIT II: do you by any chance happen to be turning anything else on when this happens? Like your radio/cassette player...lights...signals...heater blower...wipers...anything that is not on prior to this popping event? If you can't remember...do this test...when it is running good...drive without turning anything else on...and note any changes like when you turn on your signals to exit the highway...or flash your high beams to pass someone or ANYTHING...power seat adjustments...power anything that you are turning on during the drive that may trigger this...

Again...just something to think about that you may be overlooking...

Thanks Mark

When it does misfire I think I have radio on and heater on at times. I will try it with nothing on see what it does. I did look the wire harness over on the drivers side firewall to headlights. There was one wire going from harness to side marker light that looked to be burned in half but both ends not touching or near metal. I unplugged the battery let it sit for a few hours before driving it the hood light when running was dim than once I reved it up 2500 it went bright

 

[88 XLT Ranger]

Test failed

I had everything off drove it same results I got home turned the headlights on reflecting on the garage door. I noticed a faint flickering of them and the hood light rpm's at 2K. I took and un-plugged the Temp sensor the lights went real dim I fired it ran that died I tried again turn the key on lights where dim fired it up ran than died. I turned the key on all power to the truck went off I plugged the sensor back up disconnected the battery than hooked it back up nothing no power at all within 10 seconds power came back on. I fired it up runs the same that wasn't a bright idea I guess

Maybe I should get a new Temp sensor it controls fuel and timing that may be the issue what do you guy's think?

 

[Spott]

Test the temp sensor. That's what I think. The temperature sensor does not control fuel or timing.

It seems very weird that unplugging the temperature sensor would cause the lights to dim.

Sent from my XT1254 using Tapatalk

 

[88 XLT Ranger]

Test the temp sensor. That's what I think. The temperature sensor does not control fuel or timing.

It seems very weird that unplugging the temperature sensor would cause the lights to dim.

Sent from my XT1254 using Tapatalk

Spott

My understanding on this Temp sensor after looking through fuel injection tech library and asking the auto shop it controls fuel and timing. When I got home I disconnected the battery for 5 min than re connected it fired it up still running rough. I shut it off disconnected the temp sensor two wire connector on intake above thermostat. I turned the key on the lights inside went dim I fired it up it ran 5 seconds and died I tried again same thing the third time I just turned the key on all power went off. I checked the battery cables all good and tight battery volts at 12.45 I re-connected the temp sensor after 10 seconds all came back on and it fired right up. I am wondering myself why it would do that it may have shut the computer down it being disconnected


"Here the info I found on the ECT sensor"

The coolant temperature sensor is used to measure the temperature of the engine coolant of an internal combustion engine. The readings from this sensor are then fed back to the Engine control unit (ECU), which uses this data to adjust the fuel injection and ignition timing


From the FITL

The ECT is third in command in the hierarchy of EFI sensors, this means this sensor is very important when calculating fuel ratios and timing curves. This is because of simply chemistry; fuel and spark are constants in the equation. Air is the biggest variable in combustion; it changes density greatly over a range of temperature. So keeping track of the changing temperatures of the incoming air and the engine in which it is burnt becomes very important

 

[Spott]

Please allow me to clarify: The temperature sensor does not control fuel or timing. The temp sensor reports temperature to the engine computer, which uses that information to control fuel and timing.

To test the temperature sensor:
1. With the engine cold, unplug the connector for the temp sensor.
2. Set your multimeter to the 20,000Ω or 20KΩ setting, or the next larger setting if you don't have that one.
3. Touch the meter probes to the pins of the temp sensor, one probe to each pin, making firm contact. Makes sure the probes are not touching each other or more than one pin.
4. Read the value from the meter. If the meter says"OL" or "OR" or has a single 1 in the first position, or a blinking digit, or some other non-numeric value, then change settings to the next larger Ω setting and try again, until you get a value or run out of larger Ω settings.
5. Plug the temp sensor back in.
6. Run the engine until it gets up to normal temperature (whatever is normal for your engine, even if it's somewhat below halfway on the gauge).
7. Turn off the engine and, before it cools, unplug the connector to the temp sensor.
8. Reset your meter to 20KΩ if you changed it.
9. Touch the meter probes to the temp sensor pins, and read the value again, still doing so before the engine cools.
10. Post your results, or anything unexpected, or any steps you don't understand.

Ideally, the meter should show around 20.0K when cold, and 2.0K when warm. (Technically that's 20,000 and 2,000 "ohms (Ω) of resistance", if you're curious.)

If your temp sensor has results significantly different from these values, then it is bad and you can replace it with the knowledge that you're solving a problem.

Sent from my XT1254 using Tapatalk

 

[88 XLT Ranger]

Please allow me to clarify: The temperature sensor does not control fuel or timing. The temp sensor reports temperature to the engine computer, which uses that information to control fuel and timing.

To test the temperature sensor:
1. With the engine cold, unplug the connector for the temp sensor.
2. Set your multimeter to the 20,000Ω or 20KΩ setting, or the next larger setting if you don't have that one.
3. Touch the meter probes to the pins of the temp sensor, one probe to each pin, making firm contact. Makes sure the probes are not touching each other or more than one pin.
4. Read the value from the meter. If the meter says"OL" or "OR" or has a single 1 in the first position, or a blinking digit, or some other non-numeric value, then change settings to the next larger Ω setting and try again, until you get a value or run out of larger Ω settings.
5. Plug the temp sensor back in.
6. Run the engine until it gets up to normal temperature (whatever is normal for your engine, even if it's somewhat below halfway on the gauge).
7. Turn off the engine and, before it cools, unplug the connector to the temp sensor.
8. Reset your meter to 20KΩ if you changed it.
9. Touch the meter probes to the temp sensor pins, and read the value again, still doing so before the engine cools.
10. Post your results, or anything unexpected, or any steps you don't understand.

Ideally, the meter should show around 20.0K when cold, and 2.0K when cold. (Technically that's 20,000 and 2,000 "ohms (Ω) of resistance", if you're curious.)

If your temp sensor has results significantly different from these values, then it is bad and you can replace it with the knowledge that you're solving a problem.

Sent from my XT1254 using Tapatalk

Thanks Spott

I appreciate you getting back to me and making it more clear on the temp sensor and how it works. On my multimeter I only have KΩ there is no settings I went ahead and tested it just now cold it is at 35.83 on the digital readout. I can't test at normal operation temp until noon tomarrow will wake everyone up. I hope this info will be of some use on my issue these sensors are no cheap I wont buy one unless its bad

 

[Andy D]

A 2 wire CTS is about 15 $ for the one that fits my BMW. It has a Ford (Bosch) fuel injector connector. The proper test is a PITA . Easier just to swap.

 

[Lisa J]

Wanted to let you know EBAY sells auto parts cheaper than stores. Most are free shipping. I had simulor problems with my ranger. I replaced distirbutor cap for $7, rotor for $3 and ignition module for $14.
I also replaced my fuel regulator because it started leaking. Idled really high because I forgot to hook up vacuum lines. Hook up line same problem.
I replaced the IAC and it ran good for 4 days. I drove it about 30 minutes and it almost stalled on freeway. Took me 2 hours to travel back home.
I also ordered parts from Rockauto. Replaced egr and sensor and MAP. Runs much better BUT after 40 minutes it hesitates when I give it gas. I let it coast and try again and it goes. So I still have something wrong.
There is also a egr pressure feedback sensor also called DPFE sensor that causes hesitation and misfiring when bad.
Also check fusable links one goes to oxygen sensor. This caused someone elses ranger to idle badly and stall.
Good luck

 

[88 XLT Ranger]

Thank you Lisa & Andy

I appreciate your info I got the readings from my Mutimeter (Spott) on the Temp Sensor. Engine cold is 35.83 and at normal engine temp is 1.864 I checked it a few seconds latter is was 2.058. I have no idea if that is good or faulty. I have a little RadioShack Mutimeter it only has the KΩ there is no settings

I fired it up cold today it was popping/missing I un-plugged the battery for 10 seconds hooked it back it went away. As soon as I got on the road got into the throttle it started popping/missing. I drove on the back road in low gear about 2K no popping or missing up a steep road some 3 miles. Now before I got to the top the darn popping missing again. I pulled over disconnected the battery for 5 min hooked it back no go still popping missing. I though re-setting the computer would clear it up

 

[Spott]

Well, your tests seem to indicate that the Engine Coolant Temperature sensor is working correctly, so you've eliminated that as a source of the problem.

Your little Radio Shack meter is just fine for troubleshooting; one of my meters is the same or similar. I included the settings info in my instructions because some meters have those, but your meter automatically changes to the best setting based on what it's measuring.

Sent from my XT1254 using Tapatalk

 

[Andy D]

According to values for the 528e CTS, at 68F 2.2 k ohms, 176 F , warm idle, is .3- .36 k ohms . What the test doesn't take into account is a 30 yr old unit maybe making and breaking internally. Thats why I would go with a new one.

Carbon tracking inside the distributor can cause similar trouble. Or a wire end somewhere has frayed. When it breaks, the engine will die, not just falter.

 

[88 XLT Ranger]

Thank you Spott & Andy

I started up this morning popping /misfire real bad I had a hard time keeping it running. I did this all the way to town the second time I re-started it in town it started running perfect again. I got home popping/missing again I shut it off 10 min later I put the code scanner on turned the key only I got code (96) I re-tested with key on again code (96) I did it once more I code (11) system pass I fired it up running perfect again


Code 96

Thermactor air system problem right passengers side air flow will not bypass or fuel pump (FR) circuit failure or high speed fuel pump relay circuit failure. I am not sure what this all means?

 

[88 XLT Ranger]

"I am still trying to sort this out"

Code 96 "Fuel pump relay" might have short in it? there is also a Computer Control Relay. One has a green bottom the other brown how would you test the relay?