bigalpha
Moderator
- Location
- Tucson, AZ
Oh, I forgot about the RenX files. I need to go through that. Thanks for the reminder.
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Erratic idling
- Thread starter bigalpha
- Start date
bigalpha
Moderator
- Location
- Tucson, AZ
If I cover the IAC hole while the truck is idling then it should die, right? If not, that's indicative of a vacuum leak?
Assume vacuum leak causing high idle, good TPS and good IACV. If I disco the TPS, should the IACV kick in and fix the high idle?
Assume vacuum leak causing high idle, good TPS and good IACV. If I disco the TPS, should the IACV kick in and fix the high idle?
- Location
- MilkyWay Galaxy
There is always a vacuum leak through the CCV lines (by design), not sure if it is enough to keep engine running with IAC blocked.
bigalpha
Moderator
- Location
- Tucson, AZ
So I was re-reading the RenX thread again.
Could a bad TPS/IACV cause a consistent high idle in P and N but not any drive gear (D, 3)? In a drive gear, it keeps a steady, high idle.
In D and N, it immediately jumps up real high and stays. What is the idle related to being in gear?
Could a bad TPS/IACV cause a consistent high idle in P and N but not any drive gear (D, 3)? In a drive gear, it keeps a steady, high idle.
In D and N, it immediately jumps up real high and stays. What is the idle related to being in gear?
- Location
- MilkyWay Galaxy
In gear the TC stops to slip around 1000 rpm and loads the engine down.
bigalpha
Moderator
- Location
- Tucson, AZ
This must explain the delay. Turn on the truck, and it idles really high. Drop it into 'D', and about a second later, it kicks into gear, the truck lurches forward and the idle goes down (no surging or anything).
I'll have some free time this weekend to go more in depth and work on it. Hopefully it's something easy like loose manifold; somehow, I doubt it.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
You are looking for an idle rpm of 725-775, in DRIVE, when fully warmed, about 15-20 minutes after starting.
Your idle will be higher in Park and Neutral, of course.
- Location
- MilkyWay Galaxy
While I do have other problems with my Renix, I have a steady idle, in P, D, & N, and it increases about 150 RPM with the AC on to about 750, and about 600 with out the AC on. Mine settles in after about 5-10 seconds after a start at about 900 to 1000 rpm.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Your base idle is too low at 600 rpm. Your base idle should be 725-775, in D, engine and transmission fully warmed, NO accessories. A/C on idle should be higher to compensate for load. Cold idle will be higher, of course.
I think you should give the TB base idle screw an adjustment, as 600 no-load idle is way too low.
I think you should give the TB base idle screw an adjustment, as 600 no-load idle is way too low.
- Location
- MilkyWay Galaxy
I am happy with 600 rpm minimum at hot idle. So why do you feel that 600 is too low, other than the FSM lists 700-725 rpm?
I should mention that it was 250 to 300 at one time, LOL.
joe_peters
NAXJA Forum User
- Location
- Grants Pass, OryGun
Just an educated guess, but I would say your 600 rpm idle is too low and the IAC is not going to compensate for something so out of spec, perhaps the source of an "erratic idle"?
bigalpha
Moderator
- Location
- Tucson, AZ
Yeah, my idle is way above that (no dash tach yet, though). I was trying to figure out why the idle was somewhat lower in a drive gear as opposed to higher in P or N.
The engine will idle up between downshifts, too, since there is a small delay in the downshifting process. I already replaced the TPS with new and calibrated it. It made no difference so I put the old one back on.
The engine will idle up between downshifts, too, since there is a small delay in the downshifting process. I already replaced the TPS with new and calibrated it. It made no difference so I put the old one back on.
bigalpha
Moderator
- Location
- Tucson, AZ
I tested the constant 5V connection at the TPS and it shows 4.86V. Is this enough to screw things up?
- Location
- MilkyWay Galaxy
4.86 V supply from ECU to TPS is fine. More likely that one or more of your grounds is loose and dirty.
bigalpha
Moderator
- Location
- Tucson, AZ
I bought a new B- to block ground wire from 5-90. The ground was missing insulation.
I stuck my finger over the opening for the IACV and the engine idled down to what I assume is the proper operating idle speed. It didn't stutter or try to die when I covered that hole. Does this mean there's a massive vacuum/air leak somewhere?
I stuck my finger over the opening for the IACV and the engine idled down to what I assume is the proper operating idle speed. It didn't stutter or try to die when I covered that hole. Does this mean there's a massive vacuum/air leak somewhere?
- Location
- MilkyWay Galaxy
Yes.
bigalpha
Moderator
- Location
- Tucson, AZ
I checked all of the upper manifold bolts on the intake manifold. Are there lower manifold bolts that I have to check by laying on the ground and come up from under it?
- Location
- MilkyWay Galaxy
Unfortunately yes.
bigalpha
Moderator
- Location
- Tucson, AZ
Bummer. Something tells me those are a real PITA. If one or more of those lower bolts were loose, would it be hissing?
- Location
- MilkyWay Galaxy
Pita..., What was your first clue?
Might hiss if loose enough, hard to hear small leaks. Keep in mind some of those bolts hold the intake and exhaust at the same time. Those bolts are notorious for getting loose.
A stethoscope or just a long piece of vacuum hose used as a stethoscope can help you hear small leaks.
