High Idle/Backfire issue.

[deeb]

so i finally got the oil pressure situation straightened out...

couple more things to address:

1) the truck idles pretty high when in park/neutral (1500-2000 rpm). i have searched all around under the hood looking for any vac leaks, ive even tried spraying some carb cleaner looking for any leaks. i drilled the cap off and tried adjusting the idle control screw also, its tightened all the way- still idling high.

2) when in gear the idle goes down to around 1000 rpm which im happy with, but when the idle is down, i hear a misfire coming from around the passenger side ex manifold, maybe down to the cat.

3) the vehicle is generally sluggish- which im thinking/wondering is a result of the misfire stuff? maybe air/fuel ratio is off?

ive switched the plugs and inspected/sprayed down the wires for any arcing.

im stuck...anything else i should be looking into?

thanks
chad

[greg409]

what fixed the oil press?

My '97 idled high - I tried all the suggested remedies (clean IAC, replace IAC, checked thoroughly for vacuum leaks, etc.)
I resolved it by blocking the air passage inside the throttle body that leads to the IAC --

I formed a piece of alum to block the opening, it extends out & folds around the edge of the throttle body,
then the rubber flex connector & clamp hold it.
works great and I don't have to pay dealer to reset my IAC idle.

(50% of the new IAC's will end up @ dealer to reset ECU, I've read.)

I can set idle by moving alum to expose tiny opening.

(you shouldn't mess w/idle screw, it's been said)

luck,greg

[lauderdalerover]

i had the same issue two weeks ago!! revving around 2000, thought it was a vacuum leak. nope! The hose coming from the plenum chamber expands blocking the throttle linkage. Its only a fraction, but its enough to cause the high rpms. Check it by pulling the hose a little, and you should notice the drop in rpms. I replaced that hose, and what do ya know. no more high rpms

[osiristheclown]

Is the CEL lit? Do you have codes?

[deeb]

Originally Posted by osiristheclown

Is the CEL lit? Do you have codes?

yup CEL is on. occasionally it blinks! P1313 and P1414
weird thing about it, was when my buddy scanned it, he cleared the codes and it ran a little better. then, the next day it was running crappy again.

Originally Posted by greg409

what fixed the oil press?

it ended up being a clogged oil cooler on the battery side of the radiator. i just put some carb cleaner and pressurized air through it. cleaned it right out.

[osiristheclown]

P1313 is catalyst damage bank A IIRC. I haven't a clue about P1414. Have you put oxygen sensors in this truck ever? The blinking CEL is bad news, usually a plugged cat or complete failure of an oxygen sensor. Your truck is calling for help. The only way to the bottom of this is going to hands on troubleshooting. If you haven't already, download the RAVE and start testing sensors with a DVOM. Oxygen sensors would be a wise investment even if they don't cure the issue, you may need to put some cats in too. Do the basics like fuel pressure/injector leak down first and go through the ignition system. What do the plugs look like? Are they black and wet?

[greg409]

Originally Posted by deeb

yup CEL is on. occasionally it blinks! P1313 and P1414
weird thing about it, was when my buddy scanned it, he cleared the codes and it ran a little better. then, the next day it was running crappy again.


it ended up being a clogged oil cooler on the battery side of the radiator. i just put some carb cleaner and pressurized air through it. cleaned it right out.

Did I wonder about that on another site to you?

Also, I bought NTK brand o2 sensors for my '97 several years ago - spliced same color coded wires into the harness.

they were around $40 ea I think & work fine

luck,greg

[deeb]

Originally Posted by greg409

Did I wonder about that on another site to you?

Also, I bought NTK brand o2 sensors for my '97 several years ago - spliced same color coded wires into the harness.

they were around $40 ea I think & work fine

luck,greg

good call on the 02 sensors.

maybe on a different forum. i tend to double dip when i need help asap. like this thread

so i got the misfire issue taken care of. stupid me, assumed plug wires were good when they werent.
now, however idles higher than ever (2500ish) i have taken IAC and TPS off and cleaned them both really good. is that little plunger from the IAC supposed to move. it wiggles a little.
also, took the intake hose off and cleaned out throttle body really well. paid extra attention to the little holes inside.

have chased vac lines all over with propane and carb cleaner- no leaks anywhere.

base idle reset? is it possible to do without a T-4 or something like that?