1992 camaro 305 v8 TBI idles very high and shifts at high idles - Third Generation F-Body Message Boards


TBI Throttle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.

1992 camaro 305 v8 TBI idles very high and shifts at high idles

Reply
 
Thread Tools Search this Thread
Old 08-14-2015, 11:36 PM   #1
Junior Member
Thread Starter
 
Join Date: Aug 2015
Posts: 50

1992 camaro 305 v8 TBI idles very high and shifts at high idles

I know I have posted a couple problems already, and I appreciate all those who have been trying to help. I really like my car, but it seems to have multiple problems all at once, but this is one of them that have had since I first drove and I haven't been able to figure it out yet and I don't feel it is a good thing, compared to some of the other problems I've mentioned.

Whether the car is cold or hot , it usually idles pretty high, sometimes when it warms up or sometimes before it may even warm up the idle may come down a little bit, but most of the time it is idleing way higher than it should enough that I can stop the car and take my foot off the gas and it'll go on its own pretty good. So let me explain where the idles have been at and while driving.

When I first crank it at cold, it may quickly go up to like 3000 or 3500 RPMS but then as it should come down but has been hanging out between 2000 and 2500 when cold. and if I put it in gear when cold, may idle around 1500 w/o gas just holding the brake while its in gear. Sometimes after a minute it may come down a tad but not much. when driving it let's say I put it in drive with the brake and do not touch the gas. it'll idle between 1200 and 1500, when it park it may idle between 1500 to 2000, the tach goes up faster than it actually starts to move and sometime goes up to between 3000 to just barely touching the first warning color sign I think between 4000 and 4500, before moving, it doesn't shift hard or jerks when shifting but the RPMS go way up each time and very quickly. takes a second and then it moves pretty fast, even with the loud muffler that I am trying to replace right now.

I have sprayed all sorts of stuff around the intake and check for vacuum leaks hadn't really find anything evident. I did have that knocking in cylinder 6. New spark plugs, wires, cap/rotor and ignition coil. I even replaced the control module and pick up coil, because the control module tested bad. there was a code 34 MAP sensor at one point but it never showed up again after I cleared codes and may have been in there already when I bought the car. I actually went and bought one tonight, just plugged it in to see any difference, none. I did replace the IAC because it was sort of stuck and I did have it reseat with the key on (but not the engine) but that didn't really matter. I have no other engine codes since.

I don't know why it idles so high and I am not sure what direction to go next. I thought TPS, and when the TPS goes out in my VAN (not Camaro), I know the symptoms and it doesn't spit any engine codes, it just surges up and down and sometimes trans slips or shifts hard.. but I only get high idles whether in park, in drive sitting and while moving.. the tach is way high than it should be. I did put a different fuel regulator on . ive changed the pcv valve and all my filters.

its a 305 TBI V8 engine. on 1992 Camaro. the egr valve does move when you open throttle.. it doesn't idle very smooth when just in park or sitting I mean you can feel it idleing a little rough.may be exhaust contributing there too because the muffler is loud but working on getting that changed. otherwise, I don't know what else to think. head gasket leak but I don't know. I did a coolant pressure test but that came out okay there. I have adjusted the valves. was trying to think of easier things before hooking compression hoses up to the spark plug holes and things. but I don't know what else to do. Just didn't want to replace a dozen sensors, even without engine codes (which I donot always get).
db057 is offline   Reply With Quote
Old 08-15-2015, 03:21 PM   #2
Supreme Member
 
Join Date: Jan 2011
Posts: 1,727

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

Remove the throttle body, clean all the ports & passages, & replace the base gasket. That gasket sometimes will get sucked in causing a vacuum leak.
ex-x-fire is offline   Reply With Quote
Old 08-15-2015, 06:29 PM   #3
Senior Member
 
Join Date: Feb 2011
Posts: 863

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

What is the ignition timing at idle with the brown wire disconnected?
Schurkey is offline   Reply With Quote
Old 08-15-2015, 07:43 PM   #4
Junior Member
Thread Starter
 
Join Date: Aug 2015
Posts: 50

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

Well, I had just recently, I mean like within the past week recently adjust the engine timing and it was steady at 0. when I tighten the hold-down bolt to the distributer, it slightly tends to move a tad, but I tried to hold the cap and tighten it and double check the timing, it didn't bounce around or anything so it seemed pretty steady.

I did tighten the TBI bolts they did tighten more (I know there's a torque and I have torque wrenches) but just wanted to see if any small adjustment might help. I could/can try and replace the gasket, it's in expensive, just might have to scrape off stuff from the old. I've done a lot of work on the Camaro I used to have (pulling intake and heads off of it over those years) but I can try that.

I did go out and buy a CTS sensor . I had no engine code, but I've seen posts about those, and it wasn't expensive, im in that process right now.
db057 is offline   Reply With Quote
Old 08-16-2015, 09:48 PM   #5
Junior Member
Thread Starter
 
Join Date: Aug 2015
Posts: 50

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

Well I replaced the TBI base gasket. It wasn't cracked or broken but hard, but I replaced it anyway. I replaced a bunch of vacuum lines as well. many easily cracked and snapped the minute I pulled on them. I changed my muffler, prob need to go have parts of the pipes welded closed, but not as noisy. I did change the CTS sensor, I haven't let it warmed up yet, but it is cold idling at about 2500 in park and about 1500 in drive. I'll go back out and let it warm up and see if it drops at all.
db057 is offline   Reply With Quote
Old 08-16-2015, 10:19 PM   #6
Junior Member
Thread Starter
 
Join Date: Aug 2015
Posts: 50

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

OKay when warmed up it's between 12.5 and 15 in park idleing, but in drive with brakes it only goes to about 1100 rpms or 1200 rpms, just about the 10 mark. and it'll drive ya if you let go of the brakes. Also can here the ignition coil buzzing again, and it goes up with the rpms (hear it better in park or when it idles past a certain point) and when you left off the noise will drop below what it was then go back up a little bit. it's not the lifters, its a whole different noise, almost more a buzzing but its from the coil because I've had my ear very close to it when it was mounted away from the engine. (but I've moved it back to where it originally went) and replaced the coil. so maybe it's a loud coil, not sure there.
db057 is offline   Reply With Quote
Old 05-04-2016, 02:33 AM   #7
Junior Member
 
Join Date: Dec 2015
Location: Pacific Northwest
Posts: 12
Car: 1991 Firebird Formula 5.0
Engine: Built L03
Transmission: WC T-5
Axle/Gears: 3.23 7.5" 10 bolt lsd

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

This sounds pretty darn familiar I have a 91 5.0 tbi and the freaking thing idled way high it often would spin the rear tires as I sat at a wet intersection and it made mountain winter driving dangerous to say the least. Try letting the car go through its idle changes when it drops as far as it's going to(you know the car best) try unplugging the tps with the car running and see if it drops. Try doing the same with your cold air charge sensor if yours has it it's the round wired sensor in the air cleaner. I replaced my cold air charge sensor and bam idle at 650 the tps made it act funny in general just an easy check if you have the means to a less primative test on these sensors go for it but this worked for me. I'd say also check iac but you mentioned you'd already replaced it.
Formula-Finatic is offline   Reply With Quote
Old 05-04-2016, 12:10 PM   #8
Supreme Member
 
Join Date: Jul 1999
Location: Adrian, Mi, USA
Posts: 1,413
Car: 1988 Pontiac Firebird Formula
Engine: 5.7 TPI
Transmission: 700R4


Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

I had the same problem in my Astro.... with a 4.3. I could not find any rhyme or reason for it... but, after breaking a bolt off in the intake when attempting to change the thermostat, I ended up having to pull the intake...... Once everything was reassembled, started it up, and it idled MUCH lower than it used to.... Thought I had done something wrong, till I realized it was now idling the way it should.
ploegi is offline   Reply With Quote
Old 05-18-2016, 10:05 AM   #9
Junior Member
 
Join Date: Mar 2016
Location: Chicago Burbs, IL
Posts: 30
Car: 1991 Formula
Engine: 305 TBI

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

Just went through something similar with my 91 TBI firebird, Was idling at 1500 and ROUGH. Turns out a few things were wrong - vacuum leak from a cracked line, TPS was way off at idle, and IAC wasn't functioning correctly. If you haven't already I highly recommend going through the idle setting procedure on the how to pages, it helped me because while everything was wrong I was able to set a correct idle, which quickly was lost. Replaced the IAC, did the procedure again and got down to about 800 idle. Noticed TPS was off and replaced that, which was the final key. for me TPS voltage needs to be around .53-.55 at idle and 4.00+ at WOT.
Geekium is offline   Reply With Quote
Old 05-23-2016, 08:47 AM   #10
Junior Member
 
Join Date: May 2016
Posts: 1

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

Quote:
Originally Posted by Schurkey View Post
What is the ignition timing at idle with the brown wire disconnected?
Would this be the same on a 92 Chevy pickup with a 305 tbi, but running 350 injectors, computers, knock sensor, and esc module. I'm having to run it 30 degrees off tdc on cylinder one to make it level out and have a top end and bottom end
ddwh is offline   Reply With Quote
Old 05-23-2016, 10:36 AM   #11
Senior Member
 
Join Date: Feb 2011
Posts: 863

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

Quote:
Originally Posted by ddwh View Post
Would this be the same on a 92 Chevy pickup with a 305 tbi, but running 350 injectors, computers, knock sensor, and esc module. I'm having to run it 30 degrees off tdc on cylinder one to make it level out and have a top end and bottom end
So instead of setting the timing at "0" which is factory spec, you're setting the timing at 30 degrees advanced?

I guess that's telling you that your advance system is faulty.
Schurkey is offline   Reply With Quote
Old 06-07-2016, 09:26 PM   #12
Junior Member
 
Join Date: Jun 2001
Location: Bumphucked Egypt
Posts: 19
Car: 91 Firebird Formula WS6
Engine: 305
Transmission: 700r4
Axle/Gears: 3.27 9 bolt


Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

You did pull the wire when you set the timing right? The one near the blower motor


iac idle screw in too far. Read the section on setting it

My 91 305tbi used to do same thing. Low and behold old dead vacuum line near the charcoal canister was bad. Check the hoses a 26 year old car has plenty of bad ones... I replaced all sorta of parts. Iac tps,map, you name it heck even. New edelbrock intake and egr. And it was a simple vacuum leak.
Chris67rs is offline   Reply With Quote
Old 03-16-2017, 09:20 AM   #13
Junior Member
 
88BlackFormula's Avatar
 
Join Date: Jan 2017
Location: Rhode Island
Posts: 23
Car: 1988 Pontiac Firebird Formula
Engine: 305 TBI
Transmission: GM TH700R4

Re: 1992 camaro 305 v8 TBI idles very high and shifts at high idles

Is your accelerator return spring broken/disconnected/missing? It would connect to somewhere along the edge of the driver's side valve cover

Mine was missing and I replaced it with a universal one from Autozone. It cut my idle from 1100 to 500 rpm when idling in gear, and from 1100-1500 to 700 rpm in park.

My setup is a bone-stock 88 Firebird 305 TBI with the TH700R4 if that helps for comparison purposes.
88BlackFormula is offline   Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Sputter on acceleration 92camaro350cci TBI 8 10-14-2015 10:29 AM
RPM inconsistent when blower motor turned on buckeyecelt Tech / General Engine 3 09-24-2015 06:50 AM
High Idle and new Hum Noise db057 TBI 1 09-22-2015 08:14 PM
Flashing security light junior419 TBI 12 09-22-2015 04:19 PM
Timing Chain Changed, Car Won't Start db057 TBI 8 09-06-2015 09:11 AM


Go Back   Third Generation F-Body Message Boards >
« 1992 350 tbi | Tbi »

« 1992 350 tbi | Tbi »
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Advertising
Featured Sponsors
Vendor Directory

1982 Camaro '82 || 1983 Camaro '83 || 1984 Camaro '84 || 1985 Camaro '85 || 1986 Camaro '86 || 1987 Camaro '87 || 1988 Camaro '88 || 1989 Camaro '89 || 1990 Camaro '90 || 1991 Camaro '91 || 1992 Camaro '92


All times are GMT -5. The time now is 12:36 AM.


All content copyright 1997 - 2014 ThirdGen.org. All rights reserved. No part of this website may be reproduced without the expressed, documented, and written consent of ThirdGen.org's Administrators. We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: