Backfire and loss of power.

[mudflies]

Hi ranger folks:
Im looking for some direction. I dont have a lot of money so throwing parts at this is not for me. So here it is: 93 3.0 4x4 automatic. 93,000 km. I bought this truck and drove it home 4 hours. It runs good if youre on the gas but seems to lose speed if its just cruising. I can hear and feel it back firing intermitently if im cruising at say 80kph. It will then run smooth and proper for a bit then more backfire and lose of power. If you floor it, it runs like it should. At low speed it seems like you have to push harder on than gas than you should (not my first ranger) to get up to speed. Also idle goes up to 2500 rpm sometimes when put into park. Flashing cel when back firing. I havent pulled the plugs yet (tmorrow). The plug wires look fairly new. The coil looks stock/original. Motor oil has no moisture in it. Im open to any sugestions. Im going to pull the plugs and clean maf and intake tmorow. Any pointers would help. Thanks.

 

[RonD]

1993 3.0l will still have a distributor and use the TFI spark system.

Backfires can be caused by Lean fuel mix, or poor spark or spark timing.

Lean mix is an actual "back" fire, air/fuel mix ignites as it enters a hot cylinder while intake valve is still open so explosion comes "back" out of the intake manifold, this usually causes vacuum hoses to pop off the intake manifold, so check if that has happened

More common is a "backfire" out the exhaust, this is caused by a cylinder misfiring, so the air/fuel mix was not ignited/burned, it is then dumped into the exhaust manifold where it is ignited by the next "firing cylinder's" hot exhaust, so explosion comes out the tail pipe.

So yes, check all the spark plugs, keep them in order so you can see if a specific cylinder might need a better look.
The tip of a spark plug can tell you what is happening inside that cylinder.

You need to set the base timing for the distributor, so you need to get a timing light.
1993 3.0l will use a remote mounted TFI module(it was usually on the distributor)
Look on(or inside) the radiator support, looks like this: http://www.therangerstation.com/tech_library/images/remote_tfi1.jpg

Reason you need to locate this is because you need to find the SPOUT connector so you can set the base spark timing.
One of the wires from the computer to the TFI module will be the SPOUT(SPark OUT) wire, computer uses this wire to Advance and Retard spark timing.
To set base spark timing you need to disconnect this wire, same as vacuum advance was disconnected on older distributors to set base timing.
So there is a SPOUT connector on that wire just for this purpose.
Google: ford ranger spout connector
So you know what they look like

Then watch this short video: https://www.youtube.com/watch?v=cLYT7cTxY6A

Base timing should be set at 10deg BTDC

Once spark system has had it's tuneup you can move on to possible fuel issues

Yes, cleaning the MAF and IAC(idle air control) valve is always a good idea

 

[mudflies]

RonD
Thanks for your reply. I didnt have time to work
on the ranger today, but i did pick up 6 new plugs. Had to work on mammas toyota echo today. Rotted exhaust. Missing donut at manifold. No hoist, no torches, no welder and no desire (on her side)to buy new parts (2001 echo with 385,000 km) makes for a long day. On to the ranger tmorrow.

 

[mudflies]

Hi ranger owners
So heres where i am. New plugs, new cap and rotor. Still have a slight miss at idle and a misfire under load (2500-3000 rpm). Misfire is less noticeable in "drive" as oposed to "overdrive" but is still there. When misfiring, cel flashes but then stays off when misfire stops.At operating temp, i unplugged maf and there was no change in idle. Any guesses from the gurus? Again 93 3.0 4x4 93,600km. Also all 6 plugs i took out looked good, light tan color and no deposits on them. HELP PLEASE.

 

[RonD]

Flashing CEL means engine damage could occur, and is often seen with misfires

Also means you could have some codes in memory
1993 Ranger will use 3-digit codes
Code list here: http://www.therangerstation.com/how-to/ignition-charging-computers/obd-i-diagnostic-trouble-code-dtc-applications-ford-3-digit-codes/

How to get the codes via flashing CEL seen here: https://www.youtube.com/watch?v=RVbDHOiuKpQ

It is not hard to do, finding the OBD connector in the engine bay is the hard part, lol.

 

[mudflies]

Ok. I will look into the links you provided. Thanks.