# some times a rough idle and back firing



## Fannin76 (Jan 1, 2014)

As the title says some times my 97 f150 with a 4.6 liter will idle rough or back fire when getting into it. Also some times it'll shake while accelerating or just feel like its completely lacking power. Any thoughts?


----------



## kimber750 (Sep 19, 2011)

Fannin76;1844574 said:


> As the title says some times my 97 f150 with a 4.6 liter will idle rough or back fire when getting into it. Also some times it'll shake while accelerating or just feel like its completely lacking power. Any thoughts?


Start with code reader. Most auto part shops will scan for free.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1844576 said:


> Start with code reader. Most auto part shops will scan for free.


No check engine lights are on though


----------



## kimber750 (Sep 19, 2011)

I would still have it checked. Just so many things it could be. MAF, fuel pump dying, bad O2, bad cat and so on. You can test fuel pressure, unplug MAF and see if it runs any different. Bang on cats. But in the end I would bet on MAF but that should throw a code.


----------



## Fannin76 (Jan 1, 2014)

It feels like its clogged up like a bad cat. Feels like I need to rev it up and blow it out


----------



## Fannin76 (Jan 1, 2014)

OK so had it read.......oh boy 36 codes. Basically needs a full tune up. Plugs,wires,rotor button and cap, dpfe sensor,02 sensor bank 1 sensor 2, 02 sensor bank 2 sensor 2, cylinder 2 misfire,cylinder 7 misfire,Fuel system to lean.....holy crap


----------



## kimber750 (Sep 19, 2011)

Fannin76;1844843 said:


> OK so had it read.......oh boy 36 codes. Basically needs a full tune up. Plugs,wires,rotor button and cap, dpfe sensor,02 sensor bank 1 sensor 2, 02 sensor bank 2 sensor 2, cylinder 2 misfire,cylinder 7 misfire,Fuel system to lean.....holy crap


Test fuel pressure, weak pump can cause a lot of those codes.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1844844 said:


> Test fuel pressure, weak pump can cause a lot of those codes.


How do you do that? And what should it be?


----------



## dieselss (Jan 3, 2008)

Don't worry about the o2 codes just yet. That might be b/c the misfire


----------



## Fannin76 (Jan 1, 2014)

dieselss;1844861 said:


> Don't worry about the o2 codes just yet. That might be b/c the misfire


Would it misfire because low or high fuel pressure


----------



## Whiffyspark (Dec 23, 2009)

Low

Autozone has a rental kit. 

Should probably be around 50 but I'd have to look it up


----------



## kimber750 (Sep 19, 2011)

Fannin76;1844876 said:


> Would it misfire because low or high fuel pressure


Low fuel pressure can cause your lean condition which will set off misfire and O2 codes.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1844898 said:


> Low fuel pressure can cause your lean condition which will set off misfire and O2 codes.


so of its low is that a bad pump?


----------



## dieselss (Jan 3, 2008)

Usually yes but could be regular, or rarely a filter


----------



## Fannin76 (Jan 1, 2014)

I changed the filter already....the regulator has the vac line with diaphragm inside?


----------



## kimber750 (Sep 19, 2011)

Fannin76;1844900 said:


> so of its low is that a bad pump?


Bad pump, bad regulator or clogged filter. You can try pulling vacuum line of regulator, that should bump the pressure. With out fuel pressure tester it is hard to say what exactly. Still could be something else. I am leaning towards fuel pump but I could be wrong.


----------



## kimber750 (Sep 19, 2011)

Seems I am a slow typist. :laughing:


----------



## dieselss (Jan 3, 2008)

Ah, I'll give you that. After surgery and all


----------



## Fannin76 (Jan 1, 2014)

kimber750;1844905 said:


> Seems I am a slow typist. :laughing:


So would this also explain the truck dying when back my trailer down the drive and manuvering it it around the conner and into position?


----------



## Whiffyspark (Dec 23, 2009)

Dude go to aurozone and get a free guage set. Anything else is just guessing and throwing parts at it


----------



## Fannin76 (Jan 1, 2014)

I'm going to tomorrow lol just run through ideas


----------



## kimber750 (Sep 19, 2011)

Fannin76;1844923 said:


> So would this also explain the truck dying when back my trailer down the drive and manuvering it it around the conner and into position?


No, my typing has nothing to do with that.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1844961 said:


> No, my typing has nothing to do with that.


Hahaha no could low fuel pressure explain that? Lol


----------



## kimber750 (Sep 19, 2011)

Fannin76;1844970 said:


> Hahaha no could low fuel pressure explain that? Lol


Yes it is possible. But still could be other things. This is why without testing it is next to impossible to say what it is with any certainty. Or you could start throwing parts at and hope for the best.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1844983 said:


> Yes it is possible. But still could be other things. This is why without testing it is next to impossible to say what it is with any certainty. Or you could start throwing parts at and hope for the best.


Checking it tomorrow. Will let u know what the psi not running, psi running and psi when I pull diaphragm


----------



## Whiffyspark (Dec 23, 2009)

To check reg you can just turn key on and see if the pressure starts to bleed off


----------



## Fannin76 (Jan 1, 2014)

Whiffyspark;1844992 said:


> To check reg you can just turn key on and see if the pressure starts to bleed off


That'll be a slow bleed of right or is that a fast bleed off?


----------



## BUFF (Dec 24, 2009)

some of your issues are very similar to what my 97 (7.5l) was doing about 2 months ago, periodically it felt like it was starving for fuel, losing power, etc..... Pulled the fuel filters and all kinds of sentiment came out of the inlet side. Replaced the filter and still having issue, checked tank vents thinking they were plugged, no issue. Pulled tanks, flushed, flushed the in tank pumps, replaced the pump pick up filters (sock), while I was at it replaced grommets and filler hose's. Got it back together and still not fixed. Finally talked to a buddy that owns a auto repair shop, he stopped by on his way to the shop with a scanner and drove it for the next couple of days. It threw O2 sensor, EGR codes but it always snapped out of it. CE light would flash or come on then go out. Just for chins he unplugged the O2senor and drove it, no real change in how it ran, checked hot lead of O2 sensor with the sensor unplugged and it was pulling a constant .8mil volt when it should fluctuate between 0-1mil volt. After all his troubleshooting he concluded the ECM was freaking out and I had sporadic a lean condition. That generation ECM is a open loop system, when sensor feedback isn't to spec it goes into a close loop mode to adjust parameters than aren't to spec, it will continue to adjust until it can't anymore then go back to open loop and continue to repeat.
According to by buddy there isn't a way to easily test the ECM for problems within it. I did have him replace the ECM and all is good now.


----------



## Fannin76 (Jan 1, 2014)

So neither of the parts stores had them in stock. So I'll try to get some results tomorrow hopefully.


----------



## Fannin76 (Jan 1, 2014)

Fannin76;1845440 said:


> So neither of the parts stores had them in stock. So I'll try to get some results tomorrow hopefully.


29 psi while running
35 while the key is in the on position


----------



## Whiffyspark (Dec 23, 2009)

Fannin76;1846197 said:


> 29 psi while running
> 35 while the key is in the on position


Sounds way low. I'll put it up on alldata tomorrow and double check for you


----------



## kimber750 (Sep 19, 2011)

Fannin76;1846197 said:


> 29 psi while running
> 35 while the key is in the on position


That should be plenty. Did you ever bang on the cats to see if anything is rattling around? Cam sensor could be the issue. Or like Buff said the ecm could be dying. Now that fuel pump is ruled out I will have to lean towards MAF. Try unplugging it and see if there is an difference.


----------



## kimber750 (Sep 19, 2011)

Whiffyspark;1846269 said:


> Sounds way low. I'll put it up on alldata tomorrow and double check for you


35-40 key on
25-35 running


----------



## dieselss (Jan 3, 2008)

That sounds low as well. It's supposed to be around 50. If I remember my gassers.
Ok then.....


----------



## kimber750 (Sep 19, 2011)

Found this, Page 8.

http://www.jameshalderman.com/links/book_adv_eng_perf_5/s_and_c/Fuel_Pressure_Specifications.pdf

I was a little off but pump should not be his issue.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1846279 said:


> Found this, Page 8.
> 
> http://www.jameshalderman.com/links/book_adv_eng_perf_5/s_and_c/Fuel_Pressure_Specifications.pdf
> 
> I was a little off but pump should not be his issue.


So you're thinking mas?


----------



## Whiffyspark (Dec 23, 2009)

It could be. You can also clean maf just incase. But unless you can see readings its a guess. I'll double check those numbers for you.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1846271 said:


> That should be plenty. Did you ever bang on the cats to see if anything is rattling around? Cam sensor could be the issue. Or like Buff said the ecm could be dying. Now that fuel pump is ruled out I will have to lean towards MAF. Try unplugging it and see if there is an difference.


No I never tried beating on the cats was trying one thing at a time


----------



## Whiffyspark (Dec 23, 2009)

kimber750;1846272 said:


> 35-40 key on
> 25-35 running


Alldata says 28-45 running. 35-45 key on engine off.

So it's defiantly on the low side


----------



## Fannin76 (Jan 1, 2014)

Whiffyspark;1846851 said:


> Alldata says 28-45 running. 35-45 key on engine off.
> 
> So it's defiantly on the low side


So even though its still in spec do you think that could be the issue? I'm going to laser check the cat todau


----------



## kimber750 (Sep 19, 2011)

Whiffyspark;1846851 said:


> Alldata says 28-45 running. 35-45 key on engine off.
> 
> So it's defiantly on the low side


Lower side of spec but still within spec. IMO fuel pump is not the cause of his issues. So very hard to diagnose somethings over the internet. If he wants to replace the pump I am sure it wouldn't hurt.

Also without scan tool we are just guessing at any sensor it could be and it could still need multiple things after having 30 some codes.


----------



## BUFF (Dec 24, 2009)

kimber750;1846904 said:


> Lower side of spec but still within spec. IMO fuel pump is not the cause of his issues. So very hard to diagnose somethings over the internet. If he wants to replace the pump I am sure it wouldn't hurt.
> 
> Also without scan tool we are just guessing at any sensor it could be and it could still need multiple things after having 30 some codes.


If I was to toss parts at it without truly diagnosing with a scanner I'd replace the MAF. It's cheaper, the pump maybe on the low side but it is working and you don't have to drop the fuel tank.


----------



## kimber750 (Sep 19, 2011)

BUFF;1846909 said:


> If I was to toss parts at it without truly diagnosing with a scanner I'd replace the MAF. It's cheaper, the pump maybe on the low side but it is working and you don't have to drop the fuel tank.


Agree, MAF and cam sensor. Also general tune up. Maybe have fuel injection system cleaned.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1846916 said:


> Agree, MAF and cam sensor. Also general tune up. Maybe have fuel injection system cleaned.


I ran some STP through it a few weeks ago helped some I'm going to get some CRC cleaner for the maf and is the can sensor easy to get to or no


----------



## Whiffyspark (Dec 23, 2009)

kimber750;1846904 said:


> Lower side of spec but still within spec. IMO fuel pump is not the cause of his issues. So very hard to diagnose somethings over the internet. If he wants to replace the pump I am sure it wouldn't hurt.
> 
> Also without scan tool we are just guessing at any sensor it could be and it could still need multiple things after having 30 some codes.


I agree with you. Just pointing it out. It's hard to diagnose anything on the Internet lol


----------



## kimber750 (Sep 19, 2011)

Fannin76;1846923 said:


> I ran some STP through it a few weeks ago helped some I'm going to get some CRC cleaner for the maf and is the can sensor easy to get to or no


Again I would just unplug MAF and see if there is a difference in how it runs. Runs worse, good chance MAF is working. Runs better, good chance MAF needs cleaned or replaced.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1846927 said:


> Again I would just unplug MAF and see if there is a difference in how it runs. Runs worse, good chance MAF is working. Runs better, good chance MAF needs cleaned or replaced.


I think that's the winner. It'd running way better


----------



## BUFF (Dec 24, 2009)

Fannin76;1846923 said:


> I ran some STP through it a few weeks ago helped some I'm going to get some CRC cleaner for the maf and is the can sensor easy to get to or no


BG Products https://www.bgprod.com/catalog/gasoline-fuel-system/ have treated me very well. I run their 44k through my system in my gas truck about every 10K miles and their 244 through my diesel.


----------



## Fannin76 (Jan 1, 2014)

Fannin76;1846960 said:


> I think that's the winner. It'd running way better


Also its not smoking nearly as bad


----------



## Fannin76 (Jan 1, 2014)

BUFF;1846961 said:


> BG Products https://www.bgprod.com/catalog/gasoline-fuel-system/ have treated me very well. I run their 44k through my system in my gas truck about every 10K miles and their 244 through my diesel.


Do that sell it at advance or auto zone


----------



## Fannin76 (Jan 1, 2014)

ok so i guess i unplugged my map sensor? but i took both that and maf sensors out and cleaned the piss out of them the maf was caked with mud much like everything else on this truck. Im starting to think this used to be a mud truck.....its everywhere lol


----------



## BUFF (Dec 24, 2009)

Fannin76;1846988 said:


> Do that sell it at advance or auto zone


I don't go to Advance or Auto Zone my local Napa and CARQUEST stores sell it.


----------



## kimber750 (Sep 19, 2011)

Really hoping you meant outside of MAF was caked with mud and not the inside.


----------



## Fannin76 (Jan 1, 2014)

inside the wires were caked. i mean it wasnt a mud plug but the wires were completely covered with dry mud


----------



## kimber750 (Sep 19, 2011)

Fannin76;1847095 said:


> inside the wires were caked. i mean it wasnt a mud plug but the wires were completely covered with dry mud


You do realize that means all that crap was going into your engine. Does it even have an air filter? Flood recovery?


----------



## Whiffyspark (Dec 23, 2009)

Yikes that's not good


----------



## Fannin76 (Jan 1, 2014)

kimber750;1847218 said:


> You do realize that means all that crap was going into your engine. Does it even have an air filter? Flood recovery?


Um I think it was a mud run truckive changed the oil a few times doesn't seem to dirty maybe I should sea foam it


----------



## BUFF (Dec 24, 2009)

Fannin76;1847247 said:


> Um I think it was a mud run truckive changed the oil a few times doesn't seem to dirty maybe I should sea foam it


 You take a truck you use for creating revenue mud racing?


----------



## Fannin76 (Jan 1, 2014)

BUFF;1847348 said:


> You take a truck you use for creating revenue mud racing?


Me god no. I bought if from my brother he bought it from another guy. My brother never drove it that much. I'm saying I think it was a mud truck because when I installed my plow mount I had to clean the frame out it was packed with dirt


----------



## Fannin76 (Jan 1, 2014)

BUFF;1847348 said:


> You take a truck you use for creating revenue mud racing?


I said I think it was. I said I changed the oil a few times in response to number saying that muds gotten into your engine


----------



## BUFF (Dec 24, 2009)

fannin76;1847355 said:


> me god no. I bought if from my brother he bought it from another guy. My brother never drove it that much. I'm saying i think it was a mud truck because when i installed my plow mount i had to clean the frame out it was packed with dirt


ok..........


----------



## Fannin76 (Jan 1, 2014)

BUFF;1847373 said:


> ok..........


Still running like **** after cleaning it. Hasn't back fired since though but just no power still


----------



## Fannin76 (Jan 1, 2014)

And every time I slow to an idle it wants to die


----------



## Whiffyspark (Dec 23, 2009)

Unless you have a friend wth a scanner take to a shop and have it diagnosed. We're just throwing darts at a board with no Bulls eye.


----------



## Fannin76 (Jan 1, 2014)

Whiffyspark;1847989 said:


> Unless you have a friend wth a scanner take to a shop and have it diagnosed. We're just throwing darts at a board with no Bulls eye.


Its going to my cousins shop next week. I was trying to avoid that because I don't have the money right now but I'll be real broke come Nov. If I'm sitting on the couch


----------



## Fannin76 (Jan 1, 2014)

Fannin76;1848081 said:


> Its going to my cousins shop next week. I was trying to avoid that because I don't have the money right now but I'll be real broke come Nov. If I'm sitting on the couch


There are no catalytic converters on this dang thing


----------



## Fannin76 (Jan 1, 2014)

well motor is toast.... no compression in the rear cylinders and an oil leak which is most likely from a hole in the piston or rings being destroyed.


----------



## BUFF (Dec 24, 2009)

Fannin76;1855217 said:


> well motor is toast.... no compression in the rear cylinders and an oil leak which is most likely from a hole in the piston or rings being destroyed.


You never pulled a sparkplug to check the burn when you first started to troubleshoot this problem?


----------



## Fannin76 (Jan 1, 2014)

I pulled them and they needed changed for sure so with the oil leak I just decided to take it and have it fixed and tuned up but I never did a compression check myself.


----------



## BUFF (Dec 24, 2009)

Fannin76;1855509 said:


> I pulled them and they needed changed for sure so with the oil leak I just decided to take it and have it fixed and tuned up but I never did a compression check myself.


Always start with the basics.......
You brought it to a shop for a tune up and they never mentioned the motor is toast?


----------



## Fannin76 (Jan 1, 2014)

BUFF;1855516 said:


> Always start with the basics.......
> You brought it to a shop for a tune up and they never mentioned the motor is toast?


Its at my cousins he just had a chance today to look at it.


----------



## kimber750 (Sep 19, 2011)

So what ya gonna do now? Scrap or drop a engine in?

Mud in intake was a really really bad sign.


----------



## Fannin76 (Jan 1, 2014)

4.6 out of an 02 130,000 miles 600 bucks. I'll make more then that on one property one push getting an engine


----------



## kimber750 (Sep 19, 2011)

Fannin76;1855550 said:


> 4.6 out of an 02 130,000 miles 600 bucks. I'll make more then that on one property one push getting an engine


Make sure you clean all parts you transfer over.


----------



## Fannin76 (Jan 1, 2014)

kimber750;1855558 said:


> Make sure you clean all parts you transfer over.


My cousin is going to install. He's a pretty reputable shop so I have full confidence. I just hope I get it back before the first storm


----------



## Fannin76 (Jan 1, 2014)

Fannin76;1855566 said:


> My cousin is going to install. He's a pretty reputable shop so I have full confidence. I just hope I get it back before the first storm


holy crap was just able to pick it up today. its running great now!


----------

