Help: Car bogging down and backfiring!

JAZ 5.0 · Oct 23, 2005

I need some help to figure out what's wrong with my car. The problem is that it bogs down and backfires. I'll drive and it will bog down usually only do it under 1500 rpm at lower speeds. Then it will backfire and drive normal, it backfires throught he exhaust. Sometimes it just bogs down with no backfire and then pick up as if nothing is wrong. This happens for about 15 minutes before the CE light comes on. Once the CE light comes on, it stops bogging down and backfiring. Problem is, once I turn the car off and back on again the CE light isn't on anymore so I can't get that code. I've checked for codes anyways but the scanner shows nothing with KOEO or KOER tests.

So far I've changed: plugs, fuel filter, air filter, new distributor w/module and pickup, coil, tps, and IAC but the problem is still there.

The car is stock only with after market exhaust. Any suggestions or help would be appreciated.

Bladez5_0 · Oct 23, 2005

Try unhooking your MAF. Guy I work with had almost exactly the same issue with his F150. He had to get it replaced and viola it was all better. 6 different mechanics couldn't figure it out. Also try unhooking the 02 sensors.

JAZ 5.0 · Oct 23, 2005

Oh ya, I've also replaced the O2's as well. I had a feeling it was the MAF but wasn't sure. I'll disconnect it and see how it runs. I'll see if I can replace it; anything better than stock that I should get?

Bladez5_0 · Oct 23, 2005

There are lots of different MAF's you could go with but to be honest until you do something that requires upgrading injectors I wouldn't upgrade it because any difference is not worth the cost.

JAZ 5.0 · Oct 23, 2005

Cool, I'll be looking to get a stock replacment. Also, my car sometimes has a sudden miss. It'll miss at one light and then go away at the next.

jrichker · Oct 23, 2005

Code 66 MAF below minimum test voltage.
Insufficient or no voltage from MAF. Dirty MAF element, bad MAF, bad MAF wiring, missing power to MAF. Check for missing +12 volts on this circuit. Check the two links for a wiring diagram to help you find the red wire for computer power relay switched +12 volts. Check for 12 volts between the red and black wires on the MAF heater (usually pins A & B). while the connector is plugged into the MAF. This may require the use of a couple of safety pins to probe the MAF connector from the back side of it.

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

http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp

The Shape · Oct 23, 2005

I have this exact problem with my 2.3 coupe daily driver. Only difference is mine only does it when cold. Now that the weather is changing if I jump in the car on a cool morning it will do just as you described it wil bog down badly and backfire then the CE light pops on. If I pull over and let the engine warm up it will run fine, also if I cut it off then restart it the CE light goes away. I also don't get any codes when I try to scan it. All I get it code 111 all clear.

JAZ 5.0 · Oct 23, 2005

Well actually mine does it more on a cold start than after it's warmed up. It's been cooling off here too, so it's cooler than normal. But it still continues to do it after it's warmed up, but by then the light comes on much sooner and so it doesn't do that as often. I'll try to change my MAF sometime this week and post the results.

Shakerhood · Oct 24, 2005

JAZ 5.0 said:
I need some help to figure out what's wrong with my car. The problem is that it bogs down and backfires. I'll drive and it will bog down usually only do it under 1500 rpm at lower speeds. Then it will backfire and drive normal, it backfires throught he exhaust. Sometimes it just bogs down with no backfire and then pick up as if nothing is wrong. This happens for about 15 minutes before the CE light comes on. Once the CE light comes on, it stops bogging down and backfiring. Problem is, once I turn the car off and back on again the CE light isn't on anymore so I can't get that code. I've checked for codes anyways but the scanner shows nothing with KOEO or KOER tests.

So far I've changed: plugs, fuel filter, air filter, new distributor w/module and pickup, coil, tps, and IAC but the problem is still there.

The car is stock only with after market exhaust. Any suggestions or help would be appreciated.

Backfire = Out the Induction System

Afterfire = Out of the Exhaust

JAZ 5.0 · Oct 26, 2005

Got MAF yesterday, I'm going to try to install it today. I'll post if this cured my problem or not.

cardudeusa · Oct 26, 2005

Mine does something similar. Every now and then it will backfire a few times and sputter, then its gone. It only does it when the car is cold as well.

JAZ 5.0 · Oct 27, 2005

Ok, new MAF installed and NOTHING! It didn't work; it still does the same thing. CE light still comes on. So any other suggestions of what it could be? It's getting really annoying and seeing as that I need to pass inspection next month I need to get it fixed. The only other thing I've noticed is the smell of gas like the older carbureted cars. This is even after driving it for 15 minutes. So anything else....?

DmnStr8 · Oct 27, 2005

Try your TFI module. My notch did the same thing last year. Drove me crazy.

JAZ 5.0 · Oct 27, 2005

The module has been replaced. I bought a MSD distributor new w/ module and pick....

jrichker · Oct 28, 2005

Go back and fix the code 66. The probability is that you have a wiring problem. All the information you need to isolate the problem is in the code 66 test path I posted.

gcwh02 · Oct 28, 2005

I have the same problem too... it only happens when the engine is cold... I know i have a short in my ground cable and i have no clue if that is the problem... I have a new distibutor and module so thats not my problem b/c i have had that problem before too... I am going to get the short in my ground fixed even if its not the problem but I will let you guys know my solutions too..

JAZ 5.0 · Oct 28, 2005

Well if it was code 66, then wouldn't it be a hard code. I mean if the MAF was giving me a problem, then wouldn't the scanner pick it up. Also wouldn't the CE light stay on? The scanner is picking up nothing and the CE light always turns off when the car is off. I'm starting to think the problem is lying in my fuel system...

JAZ 5.0 · Oct 28, 2005

Ok, well now sitting on the passenger side, I can more clearly hear the "poping". It's actually coming from the air box and not the exhaust like I thought before. I don't know if that makes any difference..but maybe someone could chime in.....

Shakerhood · Oct 29, 2005

JAZ 5.0 said:
Ok, well now sitting on the passenger side, I can more clearly hear the "poping". It's actually coming from the air box and not the exhaust like I thought before. I don't know if that makes any difference..but maybe someone could chime in.....

Well now that you have a Backfire and not an Afterfire, it may be easier to figure out. There seems to be unburnt fuel in your induction system in order to make it Backfire, maybe there is an issue with timing or spark.

JAZ 5.0 · Oct 29, 2005

well timing was set with new distributor, but I will check it again. As far as spark, well everything has been changed...well except for the wires, but those are only 3 years old max, ford racing. I just might replace those too....

Help: Car bogging down and backfiring!

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