NEED HELP! Codes:P0171, P0174, P0304, Symptoms inside

[taylorRichie]

So I know the codes:
P0171
Fuel Trim System Lean Bank 1
P0174
Fuel Trim System Lean Bank 2
P0304
Misfire on Cylinder 4

It started with just 171, and 174, but 304 came on shortly there after.

I cleaned the MAF and EGR, and replaced the PCV. I then ran seafoam through the gas, and Filled up with Premium. 20 miles on the tank since, and now the CEL is on, and occasionally blinking (assuming that's because of 0304 code)

My vehicle is now idling at 2500RPM!

Advice??

I was planning on Just replacing all my plugs, and hoping for the best, but figure I should post here and get advice before doing anything more.

Should I do Plugs and O2 sensors? Kind of surprised to have issues where my vehicle only has 52,000 miles, and hasn't burned any oil to date. :(

Thanks for any insight.

Richie

[pbkid]

So I know the codes:
P0171
Fuel Trim System Lean Bank 1
P0174
Fuel Trim System Lean Bank 2
P0304
Misfire on Cylinder 4

It started with just 171, and 174, but 304 came on shortly there after.

I cleaned the MAF and EGR, and replaced the PCV. I then ran seafoam through the gas, and Filled up with Premium. 20 miles on the tank since, and now the CEL is on, and occasionally blinking (assuming that's because of 0304 code)

My vehicle is now idling at 2500RPM!

Advice??

I was planning on Just replacing all my plugs, and hoping for the best, but figure I should post here and get advice before doing anything more.

Should I do Plugs and O2 sensors? Kind of surprised to have issues where my vehicle only has 52,000 miles, and hasn't burned any oil to date. :(
Thanks for any insight.

Richie

dont have any advise on the other stuff but on this, the car is almost 10 years old so is it that surprising??

[tom4bren]

Two things that will cause idle problems (that others have had problems with recently) is the Fuel Pressure Regulator (FPR) and the Idle Control Valve. I wouldn't expect either to be throwing those codes tho.

[etlsport]

i havent heard of it causing all of those issues.. but i know that a bad FPR has caused a high idle for some.. other than that... i have no idea sorry

[Jolly Roger VX'er]

The only help I can offer is that I would go over what you were working on first to make sure nothing came unplugged, unsealed, etc...before I went any further. (i.e.--EGR gasket still sealed properly, air-temp sensor still sealed properly, MAF still plugged in and sealed properly.)

I got a hunch that your 02 sensors are OK in that they are not at fault but are simply doing their job in indicating a lean condition.

The misfire though has me scratching my head :confused:
I've had a vaccuum leak cause "multiple misfire" cell because of bad pinging.

Perhaps the fuel treatment dislodged some contaminents & possibly plugged fuel filter causing lean condition? Perhaps change-out fuel filter or at least pull it and see if you can blow through it (clogged).

When my Z-34 Monte Carlo started idling at 2500 rpm's it turned out to be intake gaskets leaking. Don't know if anybody here ever had high idle because of leaking intake gaskets? Doubtful that they would start leaking just like that, right after your service done though.

When my Fuel Pressure Regulator went bad, it affected mpg and resulted in starting issues (i.e.--after engine warm, like stopping for gas and having trouble getting it to run again..taking like 3-4 attempts to restart). No codes thrown though.

IAC is easily seen in throttle body throat...see if it looks carboned up...can be easily cleaned with o2 sensor safe TB cleaner spray. Although a bad one still would need changed out.

Hope any of these WAG's help.

[taylorRichie]

Thanks for the suggestions!!

I'll check out the Fuel Filter, and then move on to the FPR, and IAC.

Maybe just replace my plugs for good measure. Perhaps I have a bad coilpack as well. ???

Any suggestions on Plugs?

====

Perhaps my EGR is gone?? Maybe the contacts on the electricals are bad? I've read a few tutorials on repairing them.

Or I suppose my MAF could be gone...

[Ldub]

Richie...

Read post #4 here: http://www.vehicross.info/forums/showthread.php?t=6940&highlight=flammable

It's a good way to check for the possibility of vacuum leaks...:_wrench:
(which would cause the lean condition)

You could try switching the coil packs side to side (#2 & #4) to see if the misfire code follows.

Good luck...:thumbup:

[taylorRichie]

Thanks dub I'll give it a go...

Quite the little gremlin... The idle issue is the main issue of worry for me... It makes it even hard to stop, my VX is trying to power brake itself. To the shop in the AM...

First I'm going to inspect and possibly swap the Fuel Filter... Then check out the FPR if the issue is persistent. (only for idle issues) then I'll swap the coil packs, check if the code follows. Probably replace plugs for good measure.

Anything else?

[psychos2]

I would check the maf sensor.If I remember right some else here had a similar issue, wire was broken or loose in the plug causing the issue. shawn

[taylorRichie]

OK... I have a new Code
P0507 - IDLE HIGHER THAN EXPECTED

Atleast this one the symptoms are true... Idle is too high :D

I replaced all my plugs, and my Fuel Filter, and now my Misfire code went away (atleast for now) And I'm not having my "Lean Conditions" codes.

I cleaned my IAC, checked all my connections (vacuum and electrical to MAF, EGR IAC etc.) But I'm not seeing anything.

The Throttle is closed, so it's not a cable or pedal adjustment that got messed up.

I ran through different readings on my Scanguage, and one think that came up was my TPS isn't registering a reading at all. I'm not sure that it does on our vehicles anyway, but if someone could confirm that would be great.

Anyone know how much a TPS is for our vehicles?

Thanks for all your help!!

Richie

The manual says use the Tech 2 for troubleshooting... Anyone want to lend me one ;)
But it looks like the only culprits are:
vacuum leak, or PCV (I just did PCV, and did the starter fluid test for leaks, found none)
Or the IAC solenoid itself.

[Jolly Roger VX'er]

OK... I have a new Code
P0507 - IDLE HIGHER THAN EXPECTED

Atleast this one the symptoms are true... Idle is too high :D


What is your VX idling at now? Is it still around 2500 rpm or is it alot closer to normal...say 50 rpms over normal?

[etlsport]

my TPS always shows up on the scangauge.. ill get some normal readings tomorrow for different situations

[Jolly Roger VX'er]

my TPS always shows up on the scangauge

I'm thinking that if his idle was just out of range (i.e. 50+rpm) it would be the IAC that was bad...but, if it is WAY out of range (alot more than 50+) & not caused by a vacuum leak...and the Throttle Position Sensor isn't showing on the scangauge...I'd be steering in that direction------>(TPS).


I had a car in the past that would kick the code of "idle higher than expected" but was only idling in excess of 50 rpm over the normal idle...it was the IAC that was bad in that case.

[taylorRichie]

It's still idling between 2500 - 3000. I can't find a vacuum leak anywhere, and I used the start fluid method. And carefully examined all of my hoses and fittings...

Is there a way to use a boost/vacuum gauge to determine if there's a leak? ie, the vacuum PSI at a given RPM?

My Scangauge doesn't return anything when I switch to TPS, it only shows

__TPS with nothing to the left of it.

[WormGod]

Mine idles in the same range from a fresh startup. It is even sneaky at times and decides to randomly do it while driving, but only when I let off the gas to come to a stop. Causes me to have to leave a longer distance between me and the car in front of me, heh. It will buck forward as I step on the brake. Very rare but I don't need to hit someone in front of me.

I have been playing around with ideas for a few months now and STILL have yet to do anything about it. I only just got a new battery this weekend to get it back on the road after a couple months, so I will be back on the case now. I have only thrown 171 and 174 previously. The funny thing is, if I clear the codes without fixing them, it will run fine for about a week. Then, the issue comes back and the codes appear again. I have concluded that a new MAF, FPR, and EGR should be on my list of things to do. I cleaned the MAF several times, but the screen isn't exactly pristine anymore. And I never did replace the FPR after the my S/C install, so that won't hurt. My EGR has been cleaned to the bone and there is no getting it any cleaner, and it is a slight disaster. Definitely won't hurt. I do not think I am gonna touch the O2 sensors unless it is last resort time. There is already a laundry list of money to be spent.

[nfpgasmask]

__TPS with nothing to the left of it.

I am pretty sure the VX does not show this. I will check my scan guage on lunch to verify.

Good luck getting her fixed up.

Bart

[Jolly Roger VX'er]

Just found some relevant threads in case you didn't already see them:

http://www.vehicross.info/forums/showthread.php?t=12563&highlight=maf

http://www.vehicross.info/forums/showthread.php?t=10328&highlight=high+idle

http://www.vehicross.info/forums/showthread.php?t=7106&highlight=maf

http://www.vehicross.info/forums/showthread.php?t=12726&highlight=idle

http://www.vehicross.info/forums/showthread.php?t=12058&highlight=idle

http://www.vehicross.info/forums/showthread.php?t=8222&highlight=idle

http://www.vehicross.info/forums/showthread.php?t=7069&highlight=idle

http://www.vehicross.info/forums/showthread.php?t=6599&highlight=idle

http://www.vehicross.info/forums/showthread.php?t=3007&highlight=idle

http://www.vehicross.info/forums/showthread.php?t=1300&highlight=idle

[taylorRichie]

Thankya thankya thankya...

Looks like the IAC is going to be the culprit... as corroborated by the man links you sent...

Most people on here have referred to it as the Idle Control Valve, or ICV which is probably why my searches for IAC didn't come up. But your searches for IDLE showed a lot...

I'm going to go disconnect my battery for 30 minutes to get a fresh restart (apparently needed after messing with the IAC) and then if the issue persists (expected) then I'll pick up an IAC, Part#8-17112-648-0 (for anyone's future reference)

[nfpgasmask]

Richie, I was wrong, my scanguage does indeed show a reading for the TPS!!!!

Bart

[taylorRichie]

uh oh... I guess I better reset my computer (disconnect battery) and then check the scanguage again...

Man it'd be nice to own the tech 2 tool...

Thanks Bart!

I'll keep everyone posted on my findings, I'm sure you're all on the edge of your seats.

[nfpgasmask]

uh oh... I guess I better reset my computer (disconnect battery) and then check the scanguage again...

Man it'd be nice to own the tech 2 tool...
Thanks Bart!


What kind of scanguage do you have? Is it like mine?

http://www.nofuture.com/myvx/mods/vector.jpg

What is the "tech 2" tool?

Bart

[taylorRichie]

Yeah I have the same scangauge...

And the TECH 2 tool is the $3,500 tool mechanics can plug into your car and get tons of information, reset sensors, ran diagnostics, manually adjust solenoids etc. So they can make sure they're functioning, etc. etc. etc. The CD Manual has full routines for trouble shooting specific issues, and checking if different components are faulty.

We basically guess based on symptoms where the tech 2 can verify the condition of a lot of components without even popping the hood. ie full control over the IAC, they can say adjust to 30% (or whatever) and if it doesn't work, they know it's bad.

[taylorRichie]

Replaced the IAC, and Disconnected, my TPS, then started the car, shut down, plugged it back in after codes were thrown, plugged it back in, and now my TPS is reading on my Scan Gauge.

Also my IAC fixed my issues, with one caveat... My Idle is only low when it's in gear?? The vehicle acts completely normal when in Reverse or any forward gear, but when I put it in park it goes to 2,000 RPM.

My stopped in gear RPMs are about 850, before they were like 1500-2000 and trying to powerbrake. But not anymore.

Any ideas on what would cause an increase in IDLE but only in Park and Neutral?

I'm getting no codes so far (15 miles or so).

So far here's my repair list:
Cleaned MAF
Cleaned EGR
Replaced IAC
Replaced all Plugs and properly gapped them
Replaced Fuel Filter
Replaced PCV
Checked all hoses for vacuum leaks (found and fixed one small one, actually not even sure it was able to suck air, but there was definitely a small tear near a hose connection)

Verified all coil packs with an Ohm Meter.

?????

[tom4bren]

Are your gear select indicators on the dash indicating correctly? The tranny should be signaling the ICV to adjust for the tranny being in gear or out. It sounds to me that it's sending the right indication but the ICV is still not reacting quite right.

Did you replace your ICV or replace?

[taylorRichie]

I replaced the IAC with a brand new one.

Well I may just bring the car in for a diagnostic :(

All Original Codes Came back:
P0171
P0174
P0304

Doesn't make sense to me...

I swapped the coilpack with a different one, to see if the code would follow... It didn't, and all my coils (all six) check out with a Multimeter...

:(

Could a vacuum leak, logically, cause a misfire, and not only a misfire but one on a specific cylinder?

[Jolly Roger VX'er]

Replaced the IAC, and Disconnected, my TPS, then started the car, shut down, plugged it back in after codes were thrown, plugged it back in, and now my TPS is reading on my Scan Gauge.

Also my IAC fixed my issues, with one caveat... My Idle is only low when it's in gear?? The vehicle acts completely normal when in Reverse or any forward gear, but when I put it in park it goes to 2,000 RPM.

My stopped in gear RPMs are about 850, before they were like 1500-2000 and trying to powerbrake. But not anymore.

Any ideas on what would cause an increase in IDLE but only in Park and Neutral?

I'm getting no codes so far (15 miles or so).

So far here's my repair list:
Cleaned MAF
Cleaned EGR
Replaced IAC
Replaced all Plugs and properly gapped them
Replaced Fuel Filter
Replaced PCV
Checked all hoses for vacuum leaks (found and fixed one small one, actually not even sure it was able to suck air, but there was definitely a small tear near a hose connection)

Verified all coil packs with an Ohm Meter.

?????


wow...you've got a toughie! Before you go any further..even though I read your last post showing that the codes came back...just to be sure that you have a correctly adjusted IAC:

My only experience with IAC's involved replacing one on both an '88 fiero and a '96 Z-34 Monte Carlo. Both came with instructions with the replacement IAC showing that you adjusted the pintle length to a prescribed dimension in the instructions. I remember something like 1 and 1/8th" with a ruler. I Don't know what yours for the ISUZU 3.5 is supposed to be set at?

secondly...after replacing on the above listed cars, my instructions said to go through a routine to allow your computer to re-set the IAC. It was something like turning the key on...then off...and then starting & driving the car at a set speed for a set time (i.e. 38mph for like 10 minutes....can't remember the specifics!).

I googled "resetting IAC, ISUZU" and the only relevent thing I read was this link. Please pay attention to post #5 and post #16. (Bear in mind this refers to to a 1997 3.2L V6!)

http://forum.australia4wd.com/index.php?showtopic=12116&st=0
http://forum.australia4wd.com/index.php?showtopic=12116&st=15

I hate to see you spend too much chasing this problem...the plugs were probably well worth replacing even just for routine, preventative maintenance.

If it wasn't for stores being so fussy about returns of electrical components....I'd recommend changing the MAF just as Psychos already has because your problems started after you cleaned it and it can cause lean conditions which can yield misfires (although as you said..hard to believe on the same cylinder!).

I'm about out of WAG's on this....you might just benefit from a good diagnostic! My mechanic is my last resort when I can't figure things out!

[taylorRichie]

Thanks for the advice...

I did follow the instructions on replacing the IAC per the CD Manual... Measured and set the length of the pintle. No need for the fuse removal because I had the Battery disconnected.

I'm leaning toward MAF or EGR... We'll see what the dealer says... When I get around to taking it in :( shrug.

[WormGod]

I'm leaning toward MAF or EGR... We'll see what the dealer says... When I get around to taking it in :( shrug.

I am leaning towards either or both. Come tax time, I am replacing both of mine and throwing in a new FPR to boot.

I reset my codes this weekend and took it out. I never got the over-rev, which I usually do. I noticed both Sat and Sun, the CELs would not throw until I was at highway speed and let off of the gas. Very curious but it at least leads me down the road to fuel/air operations.

[etlsport]

Thanks for the advice...

I did follow the instructions on replacing the IAC per the CD Manual... Measured and set the length of the pintle. No need for the fuse removal because I had the Battery disconnected.

I'm leaning toward MAF or EGR... We'll see what the dealer says... When I get around to taking it in :( shrug.

have you tried checking your air-fuel ratio? you should be able to program the scangauge to show it.. mine always reads 14.3 (or is it 14.7... i cant remember)

[taylorRichie]

I haven't tried programming the Air Fuel.. Not even sure how...

----

@Worm

I looked at replacing the the FPR, but couldn't figure out how to get that relay that's on top of it off. And the book said, remove relay.... Didn't really help me figure out how to remove it.

I think I'm dropping it off at the stealership tomorrow.. :(

I'll have them diagnose and me repair.

[etlsport]

the fpr replacement was pretty easy.. im not sure what relay you are talking about... but the black box comes off with two bolts one on the side and one facing the firewall.. there is a fantastic write up on here somewhere, if you cant find it i think i have a pdf version of it on my computer... also try sending a pm to circmand.. i think last i heard he had the paper version of the write up and the modified allen wrench that makes things much easier

[Mrcln1]

I'm going to watch this thread closely cause I just started having the same problems yesterday.....uggg:confused:

[taylorRichie]

Thanks ETL... That black box is the relay...

I modified an allen to get to it... but it's still a pain to get to the screw facing the firewall...

I'm still going to be dropping my VX off at the dealership, just to be safe, and possibly save me some money (replacing things that don't need it :)) I'll keep everyone posted.

[Mrcln1]

Any update??? I'm having the same issues and no luck???

[WormGod]

FINALLY, ordered a new MAF, FPR, and EGR. Considering an alternator after all that is replaced. I am hopeful these items take care of the 171 and 174 and I will definitely post results.

[WormGod]

Good news. FedEX delivered my goods today so the VX will hopefully getting a mild tear down to get the goods in. FPR, EGR, and MAF all nice and shiny. I will certainly post updates on how well these treat the 171 and 174. Keeping my fingers crossed that the o2 sensors aren't part of problem.

Wish my Green drop in filter came today, but no luck. Such is life.

[WormGod]

Well, it was a "no go". Changed out the FPR, MAF, and EGR, reset the codes last night. Drove it around all day running my errands and catching up with some friends. Ran wonderful. Really felt like she was breathing better. Upon jumping in to leave to come home this evening, she sputtered on startup and stalled a couple times in park. Next thing ya know, "CEL". Same issues as before the parts swap. 171 and 174 remain.

I got her home and let her sit running at idle in the driveway while I tinkered around a bit more. I found that when i wiggled some wiring, the idle RPM would dance around some. I may want to look at some of the rewiring I had to do when I extended lines for the S/C install. Something may have come undone over time or something.

I may just go ahead and add the o2 sensors to my TO DO list next.

I am seriously losing patience (and wallet fat) with VX maintenance. :(

[Jolly Roger VX'er]

I got her home and let her sit running at idle in the driveway while I tinkered around a bit more. I found that when i wiggled some wiring, the idle RPM would dance around some. I may want to look at some of the rewiring I had to do when I extended lines for the S/C install. Something may have come undone over time or something.


THAT is where I think your problems lie. I would be really looking into the wiring as it sounds like it is "imitating" the symptoms of a bad MAF.

[WormGod]

THAT is where I think your problems lie. I would be really looking into the wiring as it sounds like it is "imitating" the symptoms of a bad MAF.

Indeed, it all came down to wiring. Squeezing on the TPS line/wires would oscillate the idle rpms. Plus, it threw a TPS CEL code, so that was GOOD. So, I knew where to look....

Now, dig this....

Last night, I tore it all down again. Pulled all vacuum lines, pulled all wiring harnesses, and removed the S/C. It appears I have found the villain playing castaway in my engine. Under the S/C plenum I found a family of well-done field mice and a handful of medium-rare babies. ALL wiring that was anywhere near that area was chewed right down to the copper. I am surprised my problems weren't 10X as bad as they are now. Luckily, it doesn't appear that they chewed on any vacuum line, gaskets, etc.

I shop vacc'd out what was left of the bastards (sorry, I had cell phone pics but they didn't come out, heh) and cut all new wiring. Started soldering my wires again and hoped to have it all done but sadly, I couldn't find my shrink tubing, so work came to a halt.

While on this subject, the stock wiring is absolutely HORRIBLE. Cheapest damned wire I have ever worked with. Thin, brittle, and not easy to work with. I get this crap done (and hope it solves my plethora of dodgy problems) and then it's off to solving the trannie/mode switch/clunk. *sigh*

[VehiGAZ]

Little bastard mice!! They have caused me a lot of grief too. I'm afraid to start up the 928 each spring for fear of where they've built a nest and will the thing catch on fire once the engine warms up. I've had them in the VX, in my wife's old car, in the Mini Cooper... EVERYWHERE.

[Jolly Roger VX'er]

Little bastard mice!! They have caused me a lot of grief too. I'm afraid to start up the 928 each spring for fear of where they've built a nest and will the thing catch on fire once the engine warms up. I've had them in the VX, in my wife's old car, in the Mini Cooper... EVERYWHERE.


Yeah, in the past I would find half-eaten hickory nuts on top my Supercharger!

Had baby red squirrels in my heater (blower) fan.

Lost my underhood insulation to mama squirrel to build said nest in (blower) fan.

I've had good success since by periodically driving it and moving it to different spots in the yard/driveway. Seems to keep the critters off balance!