Can anyone think what would cause this? Backfire/popping, driving me nuts!

[1993SSP]

Ok guys, This problem is about to really piss me of
I can be driving my car at a steady RPM, 2000 in 4th for instance, then when you push the gas or gear down and mash on it the engine has a backfire/sputter in the exhaust for a second and it smooths out. I found a bad place in the 02 sensor harness, fixed that and replaced the fuseable link in the harness near the firewall, cleaned every connector in the engine bay and put WD40 on them and still does it! Ive got my fuel pressure set at 38lbs warm idle with vaccum off, Anyone think of anything that may cause this, Im all out of ideas!

 

[Black 93 Fox]

Check your timing, plugs, wires, cap, rotor. How long has it been since you did a tune up?

 

[darkarrow]

Try cleaning your MAF sensor, i had a similar problem and cleaning the MAF sensor solved the problem, good luck.

 

[1993SSP]

this is a fresh build, 1000 miles on engine. Im kinda leary of cleaning the maf, any tips on cleaning it, it's a pro-m unit

 

[Stangtamer]

hey i had the same problem and it could be one of three things that i experienced...1. wrong size spark plugs 2. fouled plugs, wires, etc. 3. or the worst of them all...bent valves. Do you have problems starting when the car is cold? i pulled my motor out to and took my heads in to have them checked...one side was not sealing and the other side had two bent exhaust valves...it made my computer go crazy since it reads a certain amount of air going in and out of the motor...with bent valves its gonna go crazy...do a compression test and leak down test...you'll be able to evaluate your problem much better this way

 

[jrichker]

this is a fresh build, 1000 miles on engine. Im kinda leary of cleaning the maf, any tips on cleaning it, it's a pro-m unit

There are three parts in a MAF: the heater, the sensor element and the amplifier. The heater heats the MAF sensor element causing the resistance to increase. The amplifier buffers the MAF output signal and has a resistor that is laser trimmed to provide an output range compatible with the computer's load tables.

The MAF element is secured by 2 screws & has 1 wiring connector. To clean the element, remove it from the MAF housing and spray it down with electronic parts cleaner or non-inflammable brake parts cleaner (same stuff in a bigger can and cheaper too).

The MAF output varies with RPM which causes the airflow to increase or decease. The increase of air across the MAF sensor element causes it to cool, allowing more voltage to pass and telling the computer to increase the fuel flow. A decrease in airflow causes the MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow. Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and tan/light blue) or at pins 50 & 9 on the computer.

At idle = approximately .6 volt
20 MPH = approximately 1.10 volt
40 MPH = approximately 1.70 volt
60 MPH = approximately 2.10 volt

Check the resistance of the MAF signal wiring. Pin D on the MAF and pin 50 on the computer (dark blue/orange wire) should be less than 2 ohms. Pin C on the MAF and pin 9 on the computer (tan/light blue wire) should be less than 2 ohms.

There should be a minimum of 10K ohms between either pin C or D on the MAF and ground.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

Dump the codes and see what the computer says is wrong…

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35

 

[Boss 351]

Ok guys, This problem is about to really piss me of
I can be driving my car at a steady RPM, 2000 in 4th for instance, then when you push the gas or gear down and mash on it the engine has a backfire/sputter in the exhaust for a second and it smooths out. I found a bad place in the 02 sensor harness, fixed that and replaced the fuseable link in the harness near the firewall, cleaned every connector in the engine bay and put WD40 on them and still does it! Ive got my fuel pressure set at 38lbs warm idle with vaccum off, Anyone think of anything that may cause this, Im all out of ideas!

hehe I have that problem with my carb! If I mash the gas, the engine will sputter, backfire and just won't go! If I press slowly, above 3000rpm the car will run somewhat strong. Turns out I didn't have enough fuel, so I tuned the carb for more fuel and it works better now (need a new carb, this 10 year old POS pisses me off!)... What's your timing set at?