High idle no vacuum leaks

[illinidorry]

Just got my truck shipped to my base a couple weeks ago. Unfortunately she's been sitting for the majority of the last 2 years just being started and taken to the store by a friend. Since I've had it when I start it it'll idle in the 1500-2500 range. Once it put it in gear it will drop to 800-1200. Most but not all the time while driving I can feel the truck doesn't want to sit at a low rpm and will kick down aggressively when slowing down. Sometimes when I start it if I put it in gear to drop the rpms then back into park it will idle relatively normal in the 800-1200 range. Couldn't track down any vacuum leaks, haven't been able to test my IAC. or TPS. yet. BUT, if I rev it either with the pedal or throttle body it will often jump up and sit at a high idle again. Could it be a worn, dirty throttle cable or a gunned up throttle body? Truck is a 93 150 w 302 and AOD.


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[locopny]

Look at your IAC. Sometimes you can clean em up. They aren't that expensive either. That was my first thought anyway.

[illinidorry]

Yea I tried cleaning mine today. Doesn't appear to have changed the situation. Might just throw a new one in.

[Seattle FSB]

Test your TPS with a DVOM. These sensors sometimes develop dead spots from wear, usually in the most used lower range. At any rate, you should be running Diagnostic Trouble Codes for any additional information.


Throttle Position Sensor Testing, Replacement and Adjustment

[epsgunner]

I've got a similar issue going on with my 1993 with 5.8L..

I tested the IAC yesterday and I got 10.2 ohms..

I checked today with carb cleaner spraying everything (including the vac canister) with a vacuum line and the lines... got nothing..

My idle is also 1400-1800 rpm in P/N, and drops to say 1000-1150 when in a Drive gear..

It drives and appears to shift fine on the highway.. so I don't thinks its the TPS asmost report stalls when that goes..

Someone else had some issues and say maybe the EGR vacuum solenoid may cause this as well..

I too am seeking suggestions on which way to go next..

IAC, TPS, EGR solenoid??

[omp]

Have you tried tightening all the intake/TB bolts. Had similar on mine, could not find a leak, finally I started turning the bolts and a few of em turned more than two turns. Solved most of my high Idle. Of course now that motor is being pulled for other reasons.

[epsgunner]

There is 6 total (5/16") and one is a T40 correct?? and I read 12-18 ft lbs max..

I have a T40 in 1/4" and some extensions.. maybe I will try that tomorrow before work..

[rwrankin]

Vacuum leaks can come from the most unsuspecting places. I would use a smoker to make sure.

[epsgunner]

Originally Posted by rwrankin

Vacum leaks can come from the most unsuspecting places. I would use a smoker to make sure.

Whats a smoker??

[rwrankin]

Sorry. A vacuum smoke test. It is a machine you plug into a vacum line and it will shoot a white smoke into the system and helps you detect leaks.

http://inspectusa.com/smart-smoke-de...=price_grabber

Shops will do it for you for $50-100

[epsgunner]

Well I went out today to attempt the jumper on the ODB1 connector to read my CEL flashes.. and it doesn't light up.. figures.. hence the no CEL lights being on.. I just ordered the $26 ODBI 3145 Reader from Jegs.. should be in the mail soon.. this is the only thing making me NOT want this truck..

[BroncoBuff777]

Originally Posted by epsgunner

Well I went out today to attempt the jumper on the ODB1 connector to read my CEL flashes.. and it doesn't light up.. figures.. hence the no CEL lights being on.. I just ordered the $26 ODBI 3145 Reader from Jegs.. should be in the mail soon.. this is the only thing making me NOT want this truck..

my truck is doing the same thing but not as bad....I replaced my o2 sensor this morning and got an improvement, my tps has been changed, manifold gasket, pcv valve and tube, coil, dis, rotor, plugs, & wires, ect, thermostat, fuel filter, I checked for vacum leaks and havent found any......Whats weird is when i pump my brakes in park my idle goes up.Also my brake booster where it attatches to the master cylinder is leaking so maybe check that out...Let us know if you found the fix and i will do the same..... I suspect my egr or evp is the culprit though.

[epsgunner]

Some other guy had a bad EGR vacuum solenoid that caused a HIGH idle issue.. they cost like $45-60 but my local AZ and Advance say special order..

I will be keeping everyone posted as to what I find with my engine..

[illinidorry]

No news from me yet. I've been real busy. I was in the truck today though and it's weird. Starting it in park, truck will immediately idle at 1800-2300. Put it in gear then back to park and it will idle at 1000 for seemingly until it runs out of gas. Put your foot on the gas pedal and vroom up to 3k and if you shift into gear and back into park it will jump back up to 3k.

[broncomine]

brake boosters create vacum leaks also on the inside. it can be all the time or when you apply your brakes

[toysforme1]

Should be able to plug the vac lines one at a time to eliminate a craked line, booster and solenoid. I found on mine the IAC wasn't closing enough. Tried to clean in but ended up having to replace it.

[epsgunner]

Got the Equus code reader #3145 in today..

Only 1 code after warm up...

In KOEO test... just code 121.. Closed throttle voltage higher or lower than expected..

So it sounds like the TPS.. I didn't have a 2nd hand to do the KOER test to help turn the wheel and push the brake pedal stuffs..

With that info and the IAC doing 10.2 ohms in testing, I'm thinking 99% TPS..

Should I try cleaning it out with some FI/Carb cleaner 1st by removing the intake snorkels?? or just do the TPS??

The truck has been sitting on/off since 2006 (last registration)..

[Mikey350]

Before you change the TPS, read this excellent write-up by SeattleFSB:
http://www.fullsizebronco.com/forum/...t=ultimate+tps

And at the risk of incurring the wrath of Steve83, next time you have an extra $25, buy the extension cable for your Equus 3145, it's worth being able to run the tests from the driver's seat.

[epsgunner]

Got the BWD EC1015P part in hand and yanked off the TB..




Heres the inside picture.. alot of oily sludge/crud..



Tomorrow I will clean and replace the TPS and see what happens.. going to gingerly clean the IAC since its all off the truck..

[epsgunner]

I cleaned the IAC carefully as not to get anything up past that post that goes into the solenoid/motor.. I also noticed the part that moves seems initially stuck in leaving the plastic middle piece 'open'.. after a few minutes and some Qtips with cleaner.. it freed up..



I also cleaned the throttle body on the inside since I was installing the new BWD EC1015P TPS anyway (which may have given me the code 121).. use some soft rags and smidges of carb cleaner.. (I know TB cleaner is supposed to be used, but at 168K miles I dunno and thats what I had here)..



My idle ice cold is 1100 RPM in P.. and then drops to about 900 RPM when warmed up for a minute or 3.. then in D I get about 750-800.. seems fixed.. Took a 2 minute ride in the back parking lot and goosed it to check response.. seems good as well.. going to test drive in abit down the road..