TOPIC: 1999 Hyundai Accent- Idle issue

I’m working on my 1999 Hyundai Accent 1.5L w/throttle body

Put the groove in the throttle body and found a few things happening.

The problem is the engine will not idle properly. It may simply be that the IAC decided to fail while I was doing this.

If I set the idle screw up high enough to keep a high idle it is okay except for an occasional hiccup.

Took the car out for a run to see what else is happening. Found that initially it wants to bog down for a second then pick up the rpm’s.

It also seems that as long as the butterfly is in the window of the groove, the vehicle will accelerate. If I push it past that point it will

reach about 40mph and act as if it had a speed limiter installed.

Not sure what to think of this but I will continue to beat on it until something happens.



Karl Fortner
Gadgetman Tacoma
Tacoma, Washington

Hi Karl,
Did you reduce and/or reroute the idle air pathway on the Hyundai?

On this model it has an Idle Air Control that takes air from the intake plenum ahead of the Throttle body and routes it to the manifold directly.

There is also a passive PCV connection at the front of the Throttlebody about an inch ahead of the butterfly.

I plan on finding out today what happens if I restrict or alter the flow on th PCV.
Not sure what to do with the IAC.

Thanks

Karl

First of all, don't alter the passive crankcase ventilation. The vehicle needs upper end ventilation and there is no benefit to change it. The idle air pathway could be restricted to a 1/8 to 3/16 of an inch diameter opening. You would then go through the ECU conditioning process. If it doesn't run well (usually when cold), open up the throttle plate slightly with the adjustment screw. What this does is reduces the amount of air bypassing the plate forcing more over the Groove which enhances the Groove's effect. Let us know. Good post.

Okay, I took a step back, reviewed what I had done and from thaat made some derived conclusions.

It did not make sense to me that the mod should have any effect on the engine idle taking into account that the fuel is being delivered by injection at the exit of the manifold ports. That being the case , the only thinkg affected by the groove would be the air intake, when the throttle is opened and the throttle plate engages the groove.

I did as Ron advised, pulled the throttle body off the engine to inspect it and had a second pair of eyes also inspect it. What we found was a very small hole to the outside which was actually located in a tucked away part of the casting. Cleaned it up and applied JB-Kwik to the area and reinstalled after totally cured.

The idle is better but still has some inconsistencies, plugged in the OBDII reader, checked for pending codes and discovered that the Throttle position sensor was flagged.

Which explains why I can remove the connector from the sensor, manipulate the throttle and it all reacts the same.

Have a throttle position sensor on order.

Will update when I have results.

Karl Fortner
Gadgetman Tacoma (Youtube)
Tacoma, Washington

Hey Karl. Thanks for the update on your TB.

Whenever anyone finds something "not right" after reinstalling their throttle body one should ALWAYS be willing to check their work. Of course, most times it will simply be the computer adjusting.

Karl, you did all the right things. If it's still a little rough, then you may have missed a spot! Check it with a flashlight behind, looking from both the outside and then the inside.

It may take a little longer, but it's always better to check it than replace it.

I don't think there's anything wrong with your TPS, my friend. I suggest (once you're SURE you haven't left a hole or OTHER LEAK (gasket, hose, et al) in the TB reinstall) you just drive it for a day and see what happens.

This error code is not uncommon. About 1 in 20 I do shows the code, although that number is greatly reduced by multiple restarts. I restart the engine at least 15 times, not touching the accelerator pedal until at least 10 minutes of run time, and 5 restarts.

Many restarts reduces the likelihood of the error. (considering the install was good and no burn-throughs!)

Keep up the good work, Karl!

Ron

Update on the 1999 Hyundai accent.

Capped off the PCV connection at the manifold, rerouted the line to the passive intake.

I tried restricting the IAC line as suggested, the idle was better but still had issues maintaining idle after a deceleration.

I did notice that the MAF sensor was reporting .995lbs instead of the original 1.8lbs. With that bit of information I made use of another example of "things you can do" and wrapped a thin strip across the MAF sensor to reduce the amount of air that it would report to the computer.

This actually worked out to the positive. The engine idles smoother, still a little touchy on deceleration when just revving the engine but is fine when you decelerate via downshifting.

The other part of it basically points to the amount of fuel that was being delivered. With the higher MAF value the computer determined that more fuel was required to accomodate the air intake, by reducing this number the computer has reduced the amount of fuel it is delivering. I know this because one of my tests included taking a clean white clothe, dampening it and placing it snuggly over the exhaust pipe. Before the change the clothe after 30 seconds over the pipe had a black circle showing the unburned fuel. After the above adjustments, that same test comes back with a clean white clothe without the black circle.

Oh yeah, I also ripped the original gasket off the manifold (mylar material), purchased gasket material and cut a regular gasket to replace it and permatex'd both sides prior to putting the throttlebody back on. (Didn't know they still made that stuff... it's been awhile!)

Took it for a short run, felt pretty good... just a matter of seeing how the computer break-in will go.

Almost forgot, also regapped the plugs from .045" to .055"

Karl Fortner
GadgetmanTacoma (Youtube)

GadgetmanNebraska here, Try, try, try, and try again. This sounds so much like what I have done before. Good information. Very very important to find all vacuum leaks.

A little vacuum leak can make a big difference. Keep uo the great work Karl!!!