502 MPI Adj
 

95 502 mag mpi - idle adjustment -
there are 2 allen head screws in the bottom of the throttle body,
I beleive they are for adjusting each throttle plate -
can anybody help with the adjustment of these 2 screws ?

Problem is motor does not want to idle in gear. I believe these screws are out of adjustment. Have checked the IAC sensor, the TP sensor and they test fine. Please help.

:confused:

Don

Don, Im not positive on this but I think if you try to adjust idle on a computer controlled motor the computer will just reset back to the factory spec. i.e. turning the screws won't help.

Eric

Whoo, hondatv. I don't think these adjusters are going to change anything unless they are loose and have moved. There are other things that need to be checked. What about the MAP sensor? What about fuel filter? What about fuel pressure? What about timing? I don't mean to pessimistic, but I see alot of people chasing the wrong problem. There are alot of other things that can cause this type of behavior, such as a vacumm leak. OK so when did this start happening, or has it been a slow progression. What has changed since it idled ok. There are alot of great people on the OSO board with alot of knowledege. Many people here have probably had the same problem at some point in time, so if you can give us some info we will try to help you out.

Welcome to Offshore Only!;)

hondatv,

look for a little filter near the IAC motor. it might be dirty.
If so the IAC motor will just keep searching.

Is the IAC motor accessible by taking off the flame arrestor? I may need to check mine.

more info....
 

28 eliminator & others,

Motor idled fine last year, had to rebuild, motor is now 30 over,
same cam, added MSD box, MSD coil, EMI exhaust, ASM computer mod,
air filer and fuel regulator. Motor runs fine, idles fine in
nuetral. When put in gear idle is rough, wants to stall.

I tried adjusting the two screws for primary and secondary throttle
plates- thought would work like a carburator throttle plates.
Are there some type of spec for the adjustment for air to the IAC ?

Have tested the IAC, TP, MAP, fuel pressure, timing, idle and 3000
under load. All fine. Will have to check on vacuum (my guage is
broke). Thanks for all the help - this is a great site, lots of
knowledge.

Don

Don,

The idle is controlled by the computer. It regulates air flow through the IAC ( idle air control ) motor. The screws on the throttle plates are for adjusting minmum air. They should not be touched. I am not sure what they are set at, but I do know that trying to raise the idle that way will not work. Is it possible that Arizona Speed lowered the idle somehow when they re-programmed? Do you have another e.c.u. to try to see if it cures the problem? Another possibilty is that there is dirt under the i.a.c. Sometimes the air hole that goes from the i.a.c. into the plenum gets dirty, but I doubt it since you said the motor is fresh.

Thanks for a place to look. I did not take the TB apart there may be some trash in that hole. Will check and clean. I will also check for the filter that jdelo talked about. If I am understanding this right those 2 screws are linkags stops. When I adj those two screws I am opening or closing the throttle slightly, which tells the TP sensor that the throttle is open slightly, in turn tells the ECM the throttle is open slightly and allows the RPMs to raise.
I understand this is not the way the system is designed to work, but it's the only way I know to bring my RPMs up. It does bring my RPMs up but the motor starts to surge when I get to a certain point. I guess I can kick my own a$$ for ever touching those two screws. Anyone know how to adjust the screws (where should they be set)?

hondatv, I would call to ASM and ask to talk to the programmer about the issue. I would bet he will have some good ideas about what may cause this, and possibly programming also. As far as the adjusters, I don't have a clue how to adjust them, but I would try to get it back to a good idle out of gear like it was. If you are going to pull the TB, there probably is a setting of gap between the throttle plates and TB. I just don't know what it is, but I can look in my book and see if it is in there(that's a stretch).
I am pulling my TB off soon to put on a new one from whipple, so I could measure the gap on a stock one for you. OK back to the problem, what is the RPM at idle? If it is 600-800 then you don't want it any higher and air/fuel mixture seems to be the issue if it idles ok until you put it in gear. Or the timing maybe off, what is it at? A vacumm leak of any kind will cause this problem on any motor. Buy a new vacumm gauge it may tell alot. The little filter near the IAC motor might be a good place to look(Hmmmm I didn't know about that. Thank sjdelo) When you find the real problem, the adjuster settings may not be that critical.
Welcome to the fun world of troubleshooting!:D Do some messurments and give us the results, then we can help out more.

hondatv

Checkmat454MAG is correct. the ECU sends out pulses (counts) to the IAC. The IAC motor is supposed to match these counts.

If that air hole is dirty the IAC motor will just keep searching to match want the ECU is sending out. It is possible that ASM set the counts to low.


jdelo