Random misfire and power dropping out
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Mudding
Joined: Mar 2010
Posts: 217
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Random misfire and power dropping out
Granted I just did head gaskets on my engine I assure everyone that, that repair has nothing to do with this problem I'm having so let's just get that out of the way because it started doing this right before my head gaskets. (A lot of the reason why I ended up just doing them in the first place) Anyways...
Engine runs great going to work 50 miles on interstate. Out of no where the engine just starts stumbling and misfiring and has hardly any power at all. Make it half a mile and just as fast as it fell on it's face all of a sudden all the power came back and everything was good again. Left work and made it half way home before power just dropped out and engine started misfiring again.
I cleared the codes while driving a couple times. I'm getting two main codes that relate to the symptoms.
I'm getting
P0305 (misfire on #5)
P0300 (random misfire)
I had a coolant temp insufficient for stable operation code... umm.. and a couple O2 sensor circuit codes.
Just so everyone knows I installed new coil packs, new plugs, 10k mile old plug wires and did a compression test on #5 and got 120ish on a cold engine with a closed throttle body. (I don't think compression is an issue.. plus I'm getting *random* misfires)
I have a gut feeling it's my fuel pump since power came on and went away and came back on so fast... I really wanted some of you guys opinions on what it may be tho???
Again, new plugs, fairly new wires, new coils, good compression, power goes on and off like a light switch.
Oh yeah almost forgot. When everything would be running good... if I floored it or gave the engine moderate to heavy throttle it would seem to trigger the misfire/power loss so I had to drive home light-footed.
Any help would be greatly appreciated!!!
Engine runs great going to work 50 miles on interstate. Out of no where the engine just starts stumbling and misfiring and has hardly any power at all. Make it half a mile and just as fast as it fell on it's face all of a sudden all the power came back and everything was good again. Left work and made it half way home before power just dropped out and engine started misfiring again.
I cleared the codes while driving a couple times. I'm getting two main codes that relate to the symptoms.
I'm getting
P0305 (misfire on #5)
P0300 (random misfire)
I had a coolant temp insufficient for stable operation code... umm.. and a couple O2 sensor circuit codes.
Just so everyone knows I installed new coil packs, new plugs, 10k mile old plug wires and did a compression test on #5 and got 120ish on a cold engine with a closed throttle body. (I don't think compression is an issue.. plus I'm getting *random* misfires)
I have a gut feeling it's my fuel pump since power came on and went away and came back on so fast... I really wanted some of you guys opinions on what it may be tho???
Again, new plugs, fairly new wires, new coils, good compression, power goes on and off like a light switch.
Oh yeah almost forgot. When everything would be running good... if I floored it or gave the engine moderate to heavy throttle it would seem to trigger the misfire/power loss so I had to drive home light-footed.
Any help would be greatly appreciated!!!
Three Wheeling
Joined: Feb 2012
Posts: 50
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From: San Diego
Have you checked your catalytic converter to see if it has a clog in it?
I had the same thing happen to me on a sports car.
Blew a head gasket and got debris flew in the catalytic converter and clogged some of it up and when I would get on the throttle it would lose power and stumble.
Just a thought?
I had the same thing happen to me on a sports car.
Blew a head gasket and got debris flew in the catalytic converter and clogged some of it up and when I would get on the throttle it would lose power and stumble.
Just a thought?
Thread Starter
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Mudding
Joined: Mar 2010
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I could see that being the case with built up back pressure causing the vaccuum to go down but the only thing that I would ask against that is what about the power dropping off at all throttle positions and then randomly coming back alive? I mean we're talking it went from 100% power to 20% power and back to 100% instantly. Unfortunately the last time it went to 20% power it stayed there until I limped home.
Thread Starter
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Mudding
Joined: Mar 2010
Posts: 217
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Think I just found my answer. The engine feels like it's running on 4 cyls (or 1 bank)... Although it wasnt present today I had been getting a Bank 1 sensor 1 circuit failue code. When I got home tonight I watched my 02 sensor voltage readings idleing.
Bank 2 Sensor 1 - .035ish volts (350mv)
Bank 1 Sensor 1 - .895ish volts (895mv)
I found this
"
Bank 2 Sensor 1 - .035ish volts (350mv)
Bank 1 Sensor 1 - .895ish volts (895mv)
I found this
"
After an engine has ran through its warm up period (O2 sensor has no effect on engine operation while the engine is cold), the ECM then looks for the O2 value. The 0.450 volts mark is considered almost universally as the midway point or crossover point for O2 sensor operation. If the signal is on the rich side (above 0.45 volts), then the ECM will answer with a lean command (reducing injector pulsation), or if the signal is on the lean side (below 0.45 volts) then the ECM will answer with a rich command (increasing injector pulsation). The amount of injector pulse correction is proportional to the voltage seen by the ECM at the O2 sensor signal wire. The higher the voltage the more the ECM reduces on-time to the injector. The lower the voltage the more the ECM increases the injector on-time. The ECM is constantly doing exactly just that, slightly increasing and decreasing injector pulsation. The constant adjustment is what gives the O2 sensor signal the switching appearance (sine wave) on the scope screen."
So from what I gather my Bank1 Sensor1 sensor is readin MAX voltage saying that bank 1 is way too rich so the ECM is cutting fuel to bank 1 as much as it can.
The sensor failed to the high (rich) side so the ECM is cutting fuel on that bank and is actually causing a lean condition on bank1 since the 02 sensor is saying IT'S RICH! which in turn causes my random misfire code (lean mixtures cause misfires) and cyl #5 (same bank) code. I could be totally wrong but I think I may just need to replace my bank1 02 sensor! haha Reaching?
Last edited by GARovee; Feb 14, 2012 at 11:44 PM.
Super Moderator
Joined: Jan 2011
Posts: 16,322
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From: Savannah Georgia
see OBD2 info.pdf - ON-BOARD DIAGNOSTICS BOSCH M5.2.1 ENGINE MANAGEMENT (4.1 M) PDF (Adobe Acrobat files) Download. for a download of the Bosch manual on your ECU, this is not part of the RAVE. It contains the codes, an explanation of how they are monitored, and exact volt readings that make up each range of parameters.
Last edited by Savannah Buzz; Feb 15, 2012 at 06:55 AM.
Super Moderator
Joined: Nov 2009
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From: Arkansas
So from what I gather my Bank1 Sensor1 sensor is readin MAX voltage saying that bank 1 is way too rich so the ECM is cutting fuel to bank 1 as much as it can.
The sensor failed to the high (rich) side so the ECM is cutting fuel on that bank and is actually causing a lean condition on bank1 since the 02 sensor is saying IT'S RICH! which in turn causes my random misfire code (lean mixtures cause misfires) and cyl #5 (same bank) code. I could be totally wrong but I think I may just need to replace my bank1 02 sensor! haha Reaching?
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Mudding
Joined: Mar 2010
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I downloaded the pdf, buzz. I'll go over it when I get home from work. Thanks.
Jafir, the rover started doing this right before I did the head gaskets... I just put the intake back on a couple days ago so I know the intake bolts are good and tight. I ordered an 02 sensor (what's $60 bucks?) for that bank yesterday. I'm going to get a vac gauge and see how my vaccuum looks while running. I guess if I find no vaccuum leak or low vaccuum and the 02 doesn't fix it I'll be on to a fuel pressure test... which I dread because I don't know if you can even do it with the 2003 style upper intake plenum on the engine. That thing is rediculously huge and in the way of everything.
Jafir, the rover started doing this right before I did the head gaskets... I just put the intake back on a couple days ago so I know the intake bolts are good and tight. I ordered an 02 sensor (what's $60 bucks?) for that bank yesterday. I'm going to get a vac gauge and see how my vaccuum looks while running. I guess if I find no vaccuum leak or low vaccuum and the 02 doesn't fix it I'll be on to a fuel pressure test... which I dread because I don't know if you can even do it with the 2003 style upper intake plenum on the engine. That thing is rediculously huge and in the way of everything.