Cascade Crew

BluFbdy

So randomly my car likes to idle higher than usual around 1500-2000 rpms, when this happens i do the good old IAC cleaning and tps adjustment which usually fixes the issue.

Pulled my IAC, cleaned it out and used lithium grease on the pintle, put it back in and reset my minimum air, my tach is iffy so ive always just set the screw to the farthest out where it will idle without choking out. put it back together started it and it was fine, idle was at around 1000 which isnt ideal but its better than nothing. shut the car off, started it again 2000 rpms.

So i broke out my fluke and checked my TPS, .55 volts closed, 4.23 at WOT, normal. ran it through the range and it increased properly no jumping or sticking, decreased the same. TPS seems to be in good shape.

Broke out the carb cleaner and cleaned the hell out of my TBI, nothing too major in the IAC passage just small buildup, no chunks or crud one shot of cleaner made it shine, sprayed down the whole tbi to clean off that light brown crud. Tried the IAC reset again, 1000 ish idle. shut it off and started it again FREAKIN 2000RPMS!!!

SO one more time, broke out my timing light and checked it, dead at 0*. Reset the IAC, without relying on the tach i just adjusted it until the car was barely getting enough air, just enough to run, shut off the car, pulled the paperclip, plugged in the IAC. Same thing. low idle then ridiculously high once i put it back together.

WTF is going on here? Im gonna lose my mind. The IAC is reacting the way it should when i look down the passage way, hit the gas it sucks in and moves back out when the idle drops.... im at a loss ive done a full TPS,IAC, timing check and TBI cleaning but the little bastard keeps giving me the middle finger.

Help??? Confused

MrMike98 · Member Joined: 18 May 2010 Posts: 231 Location: Bremerton

I had an intermittent high idle issue- traced it to TB main blade shaft was wore -so that the TB was not returning to same spot ever time-
fixed it by adding an extra throttle return spring-

also vacumm issues can cause an idle problems.

aaron_sK · Posted: Wed Oct 10, 2012 7:02 pm Post subject:

TB can be rebushed to solve that problem. Easy to check for: just grab the throttle shaft and try to move it.

BluFbdy · Posted: Wed Oct 10, 2012 8:57 pm Post subject:

I don't think its the plates, I can push the throttle forward against the screw with no idle change leaving towards a vacuum leak because its consitebt 2000 rpms until u put a load on it then it drops, if I leave it in 5th at 40 mph it makes for a sweet cruise control though lol

Gotta find time to hunt down the leak, I left the house at 4am today and didn't get home til 6 tonight, and its cold as hell for me so night time work outside isn't gonna happen

Twilightoptics · Posted: Wed Oct 10, 2012 10:07 pm Post subject:

Dewey and I had this issue. I don't remember the fix though. Maybe he does.

DBL_TKE · Posted: Wed Oct 10, 2012 11:17 pm Post subject:

I had this issue with my '85 as well. And of course I can't remember what I did to remedy it.

BluFbdy · Posted: Thu Oct 11, 2012 4:22 am Post subject:

Sweet its the amnesia problem lol I'm hoping the weather breaks when I get off work so I can hunt down a possible leak, apparently the base gasket on the tbi can be the culprit, I reduced most of my vacuum lines so there's less to check over, gotta snag a propane torch and start hunting around, I'm hoping its not the China walls

Twilightoptics · Posted: Thu Oct 11, 2012 6:51 pm Post subject:

BluFbdy · Posted: Thu Oct 11, 2012 7:41 pm Post subject:

Anyone know what the iac is supposed to do when idling? I know it moves in and out during driving, when I reset it, its closed the hole on the throttle body, idled fine when I start it right after because it doesn't move from that position, on the second restart it will come close to closing but not all the way, and then I get a high idle. It's gotta be a vacuum leak but I cut down most of my lines a while ago I've traced them all and found no leaks...I'm stumped. I was told to use a propane torch and check all areas because it would work better than carb cleaner, that's safe right? Oh and my when isn't hooked up, is it possible its leaking from there?? Internally that is, I'm grabbing at straws here I'm totally stumped.

aaron_sK · Posted: Thu Oct 11, 2012 8:16 pm Post subject:

BluFbdy · Posted: Thu Oct 11, 2012 9:15 pm Post subject:

Damn auto correct when was supposed to be EGR, fair enough on the propane lol as far as the base gasket goes I think I ruled it out, used wd40 and sprayed around the base, the bubbles from the spray didn't suck inward towards the throttle body they dissipated as usual, beyond that spot any other places I should look?

BluFbdy · Posted: Sat Oct 13, 2012 11:37 am Post subject:

This is a video of whats going on, click it and it will take you to my photobucket to watch it

Twilightoptics · Posted: Sun Oct 14, 2012 5:50 pm Post subject:

Few things: Make sure the TPS isn't getting stuck.

What's the Coolant Temp Sensor read for the ECM?

1. Check the Throttle Position Sensor (TPS) for any low voltage glitches.

2. Check the alternator output for AC voltage in excess of 0.2 volts, excessively high or low DC voltage.

3. Check IAC wiring and connections.

I've had a few IAC connectors go to crap and one of the wires break at the connector.

Also, a new IAC doesn't mean it's good. :O)

BluFbdy · Posted: Sun Oct 14, 2012 6:21 pm Post subject:

Checked the tps with my meter and with tunerpro, neither have any sticking or any out of order increase or decrease, ill have to check the ac voltage on the alternator though, I have pretty much eliminated the iac being bad because it goes in its full range when the motor is shut off. Dunno if that sounds right but it makes sense to me lol as for the cts its on point with my engine temp, I can run a datalog from cold to warm for you and post it up to see if anything is out of place, luke looked at it for me and said he can't spot anything weird but to get a second opinion because he's learned by trial and error also lol

Wiring seems to be in good shape too I haven't dove into the harness but I was seeing voltage on 2 pins and ground on 2 pins which runs the coils so it seems to be in order

BluFbdy · Posted: Sun Oct 14, 2012 11:09 pm Post subject:

ok so i ran a log, started the car no fan no nothing, just motor running, ive seen a few....issues with the tps already.

I began by turning the key on and running the tps through the range to show its operation

Started the car and let it sit while the log ran, around the 12 minute mark i flicked the ac to max to turn my fan on and then started to punch the gas to see if there were any red flags.

-12:10 to 12:23 the tps movement is reflected by the rpm, equal spikes on the graphs.

-12:30 theres a similar but much less spiked result, just a light press of the pedal.

-12:50 to 13:08, engine rpm is spiking because im hitting the gas and tps is chilling at a nice .57 volts. Evil or Very Mad

-13:48 when i shut the key off, every signal flatlined like expected. Then i turned the key on and ran the tps around a bit and it had range again..... Confused

-started the car at the 14:35 mark and the tps doesnt reflect the rpm as well as it did toward the beginging of hitting the gas.

So....despite my testing with my meter and the good response of the tps in the begining of the datalog can i assume that the tps is the culprit here? i dont get why the tps would jack up my IAC operation but thats definitely not right for it to be sitting at .57 while im hitting the gas.

I used the;
AXKW BIN for 91 5spd tbi
61v3.xdf
61.adx*

dunno if you need those to see the log but if the more experienced tunerpro users could review this and see what ive posted and either confirm/deny my thoughts id appreciate it, im attatching the xdl file to this post so you can bring it up

*EDIT* ok apparently xdl files arent allowed..... so idk what to do at this point lol id still like for someone who is more tuning literate to see this thing because im just learning on a crash course curve with this stuff
TIA

Dewey316 · Posted: Mon Oct 15, 2012 5:53 am Post subject:

Random thought, as TBIs are known to wear the butterfly bushings.

When it does the high idle, if you blip the throttle hard a couple of times, does the idle drop?

BluFbdy · Posted: Mon Oct 15, 2012 6:25 am Post subject:

That was my first reaction was to mess with the throttle lol no luck though, the tbi was rebuilt in 08 and I'm not getting any play on the butterfly shaft the idle drops when I cover the iac hole or attempt the reset and its at 0 steps which is why I thought I isolated it, I know cts can interfere with it can the tps do the same if its nit responding like the log is showing?

aaron_sK · Posted: Mon Oct 15, 2012 7:27 am Post subject:

Two things:

Did the problematic CTS wiring get shortened/replaced? If the ECM think's it's -20* out it will idle high. Laughing

As Paul mentioned the IAC valve does much more than control the idle. It works in conjunction with the TPS, and if the TPS is dead-zoning it will not respond properly.

BluFbdy · Posted: Mon Oct 15, 2012 8:39 am Post subject:

Cts wiring hasn't been modfied, the sensor read incrementally up to 200 on the log, I had an issue a while back where the pin wasn't getting full contact but that was a dead giveaway because it was reading -40* C lol that's been fixed, so tps is shot apparently, good thingheres tests with a meter right? Rolling Eyes

I'm kinda of torn on this because the tbi system is so slow to react with datalogs I can't wait to use the speed density one where I can log and see without a doubt because its quicker lol even on he older ecms datalogs are accurate right? I just wanna make sure this is my issue and its not a glitch

Twilightoptics · Posted: Mon Oct 15, 2012 11:15 am Post subject:

Update thst ecm to EBL and be happy. Speed density just means Map sensor based fueling instead of Maf sensor based.