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

[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?



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....pic=12116&st=0
http://forum.australia4wd.com/index....ic=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.