shanesaw
NAXJA Forum User
- Location
- Ramona, CA
I had the exact same problem in my '87 and it ended up being a bad fuel pressure regulator. Diagnose by checking fuel pressure at the rail.
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Backfiring in the Intake Manifold
- Thread starter mrpeepers
- Start date
krelja
NAXJA Forum User
- Location
- New Jersey
My 98 would backfire through the intake due to the upstream o2 sensor heater ckt being f-ed up. At first I thought it was just the o2 so i replaced it, but I still had the codes but now for both o2's. The codes went away but the problem still would come up. I started pulling fuses under the hood and found a couple blown changed them out codes gone and no backfire or small stumble anymore. My problem would only arise when I first started the heep. When i first started driving it would hesitate a little backfire through the intake then from then on out it would run fine no loss of power or mpg.
mrpeepers
NAXJA Forum User
- Location
- Phoenix, AZ
i finally rented a fuel pressure gauge.
At the on postion the guage sees no increase in pressure. I start the car and the pressure slowly builds to ten psi, then i have to restart and it finally works its way up to 15 psi starts and idles around 20 psi. When driving it never goes above 23 psi and drops as low as 18 psi.
What is normal operation psi 31-35 lbs? Is that a bad fuel pump or leaky hose on the fuel pump?
At the on postion the guage sees no increase in pressure. I start the car and the pressure slowly builds to ten psi, then i have to restart and it finally works its way up to 15 psi starts and idles around 20 psi. When driving it never goes above 23 psi and drops as low as 18 psi.
What is normal operation psi 31-35 lbs? Is that a bad fuel pump or leaky hose on the fuel pump?
winterbeater
NAXJA Forum User
- Location
- Royal Oak, Michigan
The leaky hose could do that.
mrpeepers
NAXJA Forum User
- Location
- Phoenix, AZ
PROBLEM SOLVED
Finally resolved the issue. Bad Fuel Pump. At ignition I have 30lbs PSI at Idle anywhere from 31-36 just like the manual says. Starts immediately now, no backfiring, no hesitation under pressure, and I actually have fuel at the fuel rail squirt out if I press on it. Prior to installation, I had no pressure at ignition and 21 lbs at idle and 19 under load. If your problem is similar Auto Zone has the Fuel Pressure gauge to test this out for a rental deposit.
This problem became apparent after changing a fuel filter. I think the old filter was crappy and clogged and had created back pressure to keep it going, when I changed it out the fuel pump showed it's true colors.
I'm not the most mechanical guy, so any fix without a shop charge is a win in my book. Case closed on this one, don't need to worry about getting stranded anymore, runs like a champ.
Edit: I checked the hose in the fuel tank connected to the fuel pump and it's to my knowledge this pump was stock through 170k miles, the hose had no holes at all.
Finally resolved the issue. Bad Fuel Pump. At ignition I have 30lbs PSI at Idle anywhere from 31-36 just like the manual says. Starts immediately now, no backfiring, no hesitation under pressure, and I actually have fuel at the fuel rail squirt out if I press on it. Prior to installation, I had no pressure at ignition and 21 lbs at idle and 19 under load. If your problem is similar Auto Zone has the Fuel Pressure gauge to test this out for a rental deposit.
This problem became apparent after changing a fuel filter. I think the old filter was crappy and clogged and had created back pressure to keep it going, when I changed it out the fuel pump showed it's true colors.
I'm not the most mechanical guy, so any fix without a shop charge is a win in my book. Case closed on this one, don't need to worry about getting stranded anymore, runs like a champ.
Edit: I checked the hose in the fuel tank connected to the fuel pump and it's to my knowledge this pump was stock through 170k miles, the hose had no holes at all.
brendon800
NAXJA Forum User
- Location
- Woodland, Pa.
I can't stand bringing up old threads, BUT...
After searching and searching, this is the thread that got my Jeep fixed!!!
My symptoms were:
Backfiring through the airbox.
It would only DRIVE decent when giving it a HAIR bit of throttle on a level road.
I would have to MASH the pedal to the floor to move up ANY sort of hill. Otherwise, it would spit, sputter, backfire(through the airbox).
Idles pretty well perfect.
When starting, it would crank for longer than usual.
I started with replacing the O2 sensor, then a fuel filter, then a FULL tune up, cleaned the IAC and throttle body, then adjust the TPS, sea foam through the oil, gas AND vacuum lines. Of course, none of that fixed my problem.
Found quite a few threads on other forums with the same EXACT problem as me, but the threads just died leaving me with no help. THANK YOU ALL for keeping up with this thread!!!
I replaced the fuel pump and MY GOD, the little "filter" on my old fuel pump was BLACK. I don't know if I would've just replaced that part if that would have helped, but I figured a new fuel pump couldn't hurt and I couldn't be happier!!!
Thanks again!!!
-Mike-
After searching and searching, this is the thread that got my Jeep fixed!!!
My symptoms were:
Backfiring through the airbox.
It would only DRIVE decent when giving it a HAIR bit of throttle on a level road.
I would have to MASH the pedal to the floor to move up ANY sort of hill. Otherwise, it would spit, sputter, backfire(through the airbox).
Idles pretty well perfect.
When starting, it would crank for longer than usual.
I started with replacing the O2 sensor, then a fuel filter, then a FULL tune up, cleaned the IAC and throttle body, then adjust the TPS, sea foam through the oil, gas AND vacuum lines. Of course, none of that fixed my problem.
Found quite a few threads on other forums with the same EXACT problem as me, but the threads just died leaving me with no help. THANK YOU ALL for keeping up with this thread!!!
I replaced the fuel pump and MY GOD, the little "filter" on my old fuel pump was BLACK. I don't know if I would've just replaced that part if that would have helped, but I figured a new fuel pump couldn't hurt and I couldn't be happier!!!
Thanks again!!!
-Mike-
