P0300 random misfire. Help!

[treybaxter]

I have a '97 OHV with about 200,000 miles on it. I am having random misfires, and the truck is running like crap. I am getting about ten codes on it.

P0401, 402, 1151,1152,0301,0304,0306,0171,0174,0302

when i clear them, the first ones that come back are 0300,0301,0304

The plugs and wires are pretty new, less than 10k on them. i cleaned the MAF, and the IAC. The EGR valve seems to function ok. I dont know how to check the DPFE. My fuel pressure seems a little low. about 25 at idle and about 32 with the reg unplugged. I dont have the $ to just start randomly replacing components. Can anyone help? My reading seems to lead me to a fuel pump, cat, or bad injectors. All of which would add up to be over $1,000!

Some advice would be appreciated!!!!

 

[dogfriend]

Check your coil pack. Don't just replace it (it costs >$100) - test the resistance of the primary and secondary sides. The procedure is in the Haynes manual - I have also posted on it before:

http://www.explorerforum.com/forums/showthread.php?s=&threadid=96320&highlight=coil+pack

That may not fix all of your issues, but it is relatively inexpensive and easy to check.

You might want to double check your fuel pressure readings - if you really are too low in pressure, this will lean out the mixture, which is consistent with some of the other codes you are getting.

 

[treybaxter]

Oops, i forgot to mention that i checked the resistance on both sides of the coil pack a couple of weeks ago. Thanks for the tip!

I'm thinking if i got a bad dpfe, that is flooding the intake with exhaust by keeping the egr open, then cant i just unplug the egr and test that theory?

I did unplug it btw....and it didnt help the problem, i was just wondering if that were a valid test.

thanks guys

 

[dogfriend]

Most of the posts I have seen on the DPFE have been people who got the codes and replaced the sensor to solve the issue. I'm not sure if it will cause drivability issues - it functions to measure EGR flow. If your EGR is stuck open all of the time, it could cause issues by leaning out the mixture - the EGR is only supposed to be open during warm cruise (engine warm, light loads)

I would investigate the fuel pressure issue - plugged filter, bad FPR or weak pump?

 

[treybaxter]

Replaced the fuel pump last night. For God's sake, let the pressure off before you take the filter off, and dont EVER get gasoline in your f'n ear!!! OMG! That hurt like hell!!! Truck still running rough. Going to tinker more with the EGR today. What's the best way to look for vacuum leaks?

 

[dogfriend]

See my second post in this thread:

http://www.explorerforum.com/forums/showthread.php?t=195948&highlight=propane

 

[treybaxter]

I got a propane torch, will give it a try and let ya know! Thx dogfriend.

 

[Raulsk8]

treybaxter:

Try checking the MAF asembly, mine (96 OHV) was running fine on Friday, then all of the sudden started running like crap, very low idle, shaking like crazy and backfiring if i accelerated hard... took it to Autozone came up with the following codes:

P0300
P0153
P1401
P0174
P0171

I couldn't believe i had to fix all of these codes when the truck was running fine... Don't know why but I had a hunch it was something to do with the MAF, so I decided to clean it (I mean it couldn't hurt, right?) and when I opened the hood I noticed that one of the 2 halfes of the MAF housing was loose (i guess from the vibration) i just put it back togheter and the problem was fixed! Check engine is still on (but ti was already on because of the O2 sensors) but I'm sure the first 3 codes are gone now.

Try checking this, I couldn't hurt
Hope this helps!!

 

[treybaxter]

WOW, you got lucky on that. I did take a look at the MAF. took a Q-tip full of carb cleaner and cleaned it. I read later that you should use denatured alcohol. it didnt look dirty, but i cleaned it anyway. hope i didnt damage it. Anyway, it didnt fix my problem. Does anyone know how to check the MAF electrically?

 

[treybaxter]

Also, a good friend of mine runs the parts dept at my local ford dealer, he told me that the problem was most likely a leak around the intake manifold. I sprayed WD-40 all around it and also tried the propane bottle trick, neither of these produced a difference in the idle RPMs. Any suggestions would be appreciated, i dont have the $ to just start randomly replacing components. You could easily spend $1,000 on the MAF, DPFE, cat, EGR, fuel pump, etc.

 

[uh60james]

You will probably get more help if you post this in the Stock 1995 - 2001 Explorers part of the forum.

 

[JohnJ]

Given my record on this forum, remember to take my words with a grain of salt. I'm wrong at least as often as I'm right, probably more.

Has the check engine light been on for a while before the running problem arose?

If so I would expect that the p1401 is unrelated (probably bad DPFE, do a search for a conclusive test) and caused the light to come on. The actual running problem and other codes then would be caused by either a severe vacuum leak or a bad MAF.

If the light came on at the same time the running occurred, then you're more likely looking at a damaged wiring harness or much less likely physically stuck open EGR valve.

An intake gasket seems unlikely as your misfire and lean codes represent both cylinder banks.

Don't forget to check compression on an engine with that high mileage, especially if the problem seemed to develop over time from minor to major.

/Carburetor cleaner may be less likely to cause an open flame than propane
//Ethyl ether is great for open flames

 

[treybaxter]

Well, long story short, my wife was going to work the other day and called me. The truck was barely going, missing like crazy. I told her to take it on in to the ford dealer and tell them to analyze it. I came on and switched rides with her and waited a few hours before the service manager came over and told me the news. No compression on 3 and 4, need a new engine. I was thinking holy crap since 3 and 4 are on opp sides i knew it wasnt a head gasket. So i limp along back home 25 miles at about 35mph. Next morning i take out the plugs (i can tell the mechanic never pulled them) and check compression. Not great but all over 100 psi. I go and get a cheap set of plugs and wires b/c a couple of the plugs are obvously shot. It ran like a champ, no codes flashing at all. I later called ford back and they gave me my $100 bucks back for a bad diagnosis. about 100 miles later i did get a lean code back, but no more flashing CEL and no more misfires. No telling how many ppl ford has told to get a new engine when they just needed plugs and wires. My biggest mistake i think is that the wires i put on just 10,000 miles earlier, i did not put on the lube so the boots had popped off the plugs a bit, causing major problems. Thanks to all that gave me such good advice!!

 

[06ebEXPLORER4.0]

just FYI.....

the P0300 is a general random mis-fire code. Just telling you that there is one.

P0301 is indicating a problem with the #1 cylinder, P0304 is indicating a problem with the #4 cylinder.....

should help with future diagnosis

 

[5litersplorer]

Another note....my 5.0L was showing a misfire #3. I had done some work to the top of the motor (replaced rotten coolant pipe). I had to unplug three fuel injectors to gain access. The retaining clips for the wire plug broke. i pushed them back onto the injectors and they seemed to want to stay, however, a couple months down the road the truck began to misfire intermittently.
After changing 3 sets of wires and two sets of plugs, I finally remembered the coolant pipe job. I went back in there to find the injector wires had worked loose. I used a small ty-wrap (tricky job) to hold the fuel injector wires on and it hasn't missed a beat yet and that was a year ago!

 

[Europin]

Given my record on this forum, remember to take my words with a grain of salt. I'm wrong at least as often as I'm right, probably more.

Has the check engine light been on for a while before the running problem arose?

If so I would expect that the p1401 is unrelated (probably bad DPFE, do a search for a conclusive test) and caused the light to come on. The actual running problem and other codes then would be caused by either a severe vacuum leak or a bad MAF.

If the light came on at the same time the running occurred, then you're more likely looking at a damaged wiring harness or much less likely physically stuck open EGR valve.

An intake gasket seems unlikely as your misfire and lean codes represent both cylinder banks.

Don't forget to check compression on an engine with that high mileage, especially if the problem seemed to develop over time from minor to major.

/Carburetor cleaner may be less likely to cause an open flame than propane
//Ethyl ether is great for open flames

@JohnJ
I have this problem and check engine light been on for 2 years .. now I’m having these problems...:

2002 Ford Explorer with 150k miles. Have done maintenance mostly myself. For last 2 yrs the check engine light has been on and would occasionally go off. Code check said was an o2 sensor so I blew it off. As of a month ago I noticed lack of power while driving. Pedal down to floor and car wouldn’t budge, slow off the start etc. When stopped at stop light brake pressed car throttle seemed to increase and decrease as if I pressed the gas when I didnt. Got code checked again this time p0300 cylinder 2 misfire and (another code) random misfire showed up.
I changed the plugs - nothing changed
I changed the wires - nothing changed
I changed the ignition coil pack - nothing changed


Any help with this issue would be a great HELP.
Thanks