My car idles perfectly. Very smooth, just go the timing done and I'm now pulling more vacuum. I just changed the fuel pump, strainer, fuel filter. Plugs are new, air filter is clean, TB is clean, IAC is clean, TPS is set.... W T F.
When I slightly push the gas in neutral and try to hold the RPM at 1400 or so RPM it sounds like it's choking or something and the idle falls. Problem gets less severe as I increase the throttle and by 1900-2000RPM, it will hold it perfectly. The car's pulls very strong and I'm happy with mileage (and passed emissions) so it can't be out of tune.) New coil, new distributor, new cap and rotor, 8mm taylor wires are a year old.
Anyway, when the car starts to choke and I let off the gas it drops down to like 500 or less RPM before recovering. Is my IAC bad? I can't think of anything else! Also, when I changed my distributor there is a 'thing' bolted down near the distributor with two vacuum tubes plugged into it....what is that?
All help is appreciated.


------------------
89 GTA G92
305 TPI WC 5spd w/3.45
Accel Cap & 8mm Taylor's
Custom 4" Cold Air Induction
Jet Airfoil
K&N Airfilter
160 deg stat/fan switch TB Bypass - Steel Rad
Cat back 3" Exhaust w/Terminator Muff.
HiGh FlOw Dynomax Cat
Spohn LCA's - KYB GR-2's
Moroso Crank Bolt and roller pilot bearing.
New Fuel Pump!
Autometer Vac+Oil Temp
2000 Yamaha R1 150hp 385ibs

 

The part you are talking about is the Vaccum Solenoid for the Egr Valve. Besides using vaccum to open and close the Egr it use this Solenoid. It does sound like a vaccum leak somewhere or it may be Egr. First get a can of Carb Cleaner and spray around all the Vaccum lines. If the idle picks up there's your leak. If you don't find any vacuum leaks try pulling the vaccum line off your Egr Valve and plug it. Then drive it to see if it's your EGR valve. If it's your Egr Valve that's bad replace it. Mine was $50.00 at AutoZone for a GM Egr Valve.

------------------
'87 Trans Am:
(Engine)
305 TPI
180 Degree Thermostat
JET Fan Switch
TB Bypass
Accel 300+ 8.8 Racing Wires
Accel Super Coil
Bosch Platinium Plugs
Custom Ram Air with K&N
Removed Emissions Equipment & Cat.
(Stereo)
Full Kenwood Excelon System

 

I have a Vac guage..wouldn't this show the drop. The readings are the same as when I didn't have the problem. Also, when I turn the engine off the sweep down to zero is gradual just the way it was before. If I had a vaccum leak, wouldn't it drop off quicker? (when turning the engine off)

Steve

[This message has been edited by Steve89GTA (edited April 20, 2001).]

 

Hey that's exactly the same problem my car has except that the problem goes away once the ECM goes into closed loop.

It used to be quite severe before I tuned it up. New plugs, wires, distributor, rotor, and fuel filter did make the engine a lot smoother and quieter but the problem didn't entirely disappear. Now it's become just as bad as it used to be before and the car is pretty much undriveable until the motor warms up sufficiently. The colder the ambient temperature, the worse the choking and stuttering gets. The car seems to have no power upto about 1800rpm when it's cold. In both Park and Drive, it takes a lot of pedal movement to get the rpms to 1800. In fact, in Drive it has absolutely no power until 1800rpm, where it suddenly jumps. I have to stab the gas pedal to get it moving. The increased pedal movement also translates into an increased pull on the TV cable. As a result, the transmission 'waits' before shifting and shifts late and quite hard. All in all, the freaking problem has me totally confused and is driving me nuts !!!!

Does anybody have idea what it could be besides the EGR? Wouldn't a faulty EGR set a code?

------------------
'88 IROC 305 TPI
Crappy 700R4 slushbox
Gutted airboxes
180 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel (gotta luv it)
Ram-air setup coming soon
Flowmaster muffler (puke)
Taylor SpiroPro wires
Accel cap and rotor
Ported plenum
Kills: '94 Z28, Olds Aurora V8, bunch of Mustangs, T-birds, ricers, and others who assumed a 12 year-old car would be too slow.

 

Steve where you are hooking the Vaccum Gauge up at.



------------------
'87 Trans Am:
(Engine)
305 TPI
180 Degree Thermostat
JET Fan Switch
TB Bypass
Accel 300+ 8.8 Racing Wires
Accel Super Coil
Bosch Platinium Plugs
Custom Ram Air with K&N
Removed Emissions Equipment & Cat.
(Stereo)
Full Kenwood Excelon System

 

I'm really not to sure but I would suggest cleaning the IAC.



------------------
'87 Trans Am:
(Engine)
305 TPI
180 Degree Thermostat
JET Fan Switch
TB Bypass
Accel 300+ 8.8 Racing Wires
Accel Super Coil
Bosch Platinium Plugs
Custom Ram Air with K&N
Removed Emissions Equipment & Cat.
(Stereo)
Full Kenwood Excelon System

 

My Vac guage is hooked up to a vac line that runs to the Cruise control. I beleive if comes off the TB (a T fitting). I checked all hoses in question and replaced them...maybe my motor is going. So much for Mobil 1

 

btt

 

My formula woudl do this, and it wasn't a vacum leak. it was the idle air contol. Don't give up too soon- double check the egr for movement, ie plug it up and see if it does the same thing. Also adjust the iac. is it throwing a check engine light? if so, do you know how to pull the codes?


STeve

------------------
86 Firebird, LG4, t-tops, 2.73 open rear, SLP 3 inch cat back exhaust, catco cat, 1inch carb spacer.

Current Plans: 342 posi disk 10 bolt rear, rebuilt/fixed up tranny with a trans go shift kit, vette servo, and some other goodies...,cowl induction hood, lowering springs, sfc, and new formula wheels, and tires.
Hopeful list- mild 350, headers, and a t56

My Webpage- Battle of the birds, My own Thirdgen Page, still under construction, http://www.geocities.com/soares711/index.htm

88 Firebird Formula- deseased 2/9/99- 305 TPI, SLP 3 inch exhaust, SLP Intake runners, SLP cam, 3.45 BW disc brake posi, WS6, NOS, and all that good stuff, 13.8 on the motor, 12.89 on NOS and slicks! Hit by what else!?!? a FORD EXPLORER!!!!!!

 

Nope, doens't throw any codes. In neutral, I can raise the RPM easily to 1500 RPM, then it bogs down slowly and sounds like it either isn't getting enough fuel, spark, or something. I've checked vac lines and replaced most that would be in question. IAC is clean and adjusted and the TPS is adjusted. These two items are my next replacement issue, if it still does it then it's going straight into Lake Ontario. At least the suckers can use it's clean seats to spawn!
OH, my fuel canister has a dent in it..could this be leaking some Vac pressure? I noticed the lower Vac line from the TB comes down to the canister...

POS!

Thanks again...

[This message has been edited by Steve89GTA (edited April 24, 2001).]

 

Hey, Steve, try cleaning your IAC valve. There's instructions on how to do that someplace on the board here. Nice to see another TFM'er on the boards.

------------------
--
Kevin-87 Firebird 2.8 A4
Ported Intake, K&N, !Cat, Cutout coming soon...
Best 0-60 10.26 seconds...for now

 

Oh, and my o2 sensor is new as well...
BTT

 

I ain't trashin' it yet!

 

I had a similar problem. It ended up being a clogged cat. I removed it and the car runs btter then it has in awhile. Goo luck.

 

But I just passed emissions (pretty good too) so I don't think my Cat is blocked. It only has about 5000 miles on it!
It's a Dynomax high flow unit.

 

Can I unplug my TPS and see if the bog is still there? Will my car even run with this unplugged? (TPI)
I've checked the TPS with an ohm meter and the increase/decrease is stead when moving the blades in either direction..but that doesn't mean anything underload I guess. Can I just unplug it (only for testing measures). I'll buy a new one if necessary.

--------

[This message has been edited by Steve89GTA (edited April 27, 2001).]

 

I took the car out last night and after it warmed up she's starting to run like A$$. I'm losing at least (or what feels like) 20hp when the car is fully warm. When I just get off the freeway, it feels like a monster but after sitting in traffic for a bit, it all goes to $hit. My clutch chatters more, car has less power, damn.
POS.

[This message has been edited by Steve89GTA (edited April 30, 2001).]

 

Any luck on these problems? My car is suffering form something similar... lacks power until around 1800-2000 RPM... just wondering if anyone found anything out?

------------------
Owner of a 1989 IROC-Z Camaro, a.k.a. "The Babe Magnet". Painted a cheap metallic blue that chips off all too easily and covers over the IROC-Z decals on the doors, also has non-leaking T-tops, ps, pw, power rear hatch, working A/C. Mods: SLP intake runners, gutted MAF sensor, adjustable fuel pressure regulator, modified air spoil, 3.27 posi rear end.
Broken stuff: rear spoiler brake light, driver side lock, power antenna, tilt steering, rear end bushings, cracked passanger side ground effect, washer fluid tab, leaking exhaust and a rotted through muffler that sparks when the car bottoms out while driving like any 17 year old does.

 

I've tried everything listed here and nothing cured my problem. I plugged up one at a time..
-brake booster
-EGR
-Fuel canister
Cleand IAC and adjusted TPS. Sprayed WD 40 everywhere and no change in idle. Car runs like a$$ when fully warmed up but the off idle condition is pretty much the same. Really bad when dead cold but I guess that's normal.
I think I'm just going to go ahead and change the IAC, TPS and CTS since they're all 13 years old anyways..

Steve

[This message has been edited by Steve89GTA (edited April 30, 2001).]

 

How about a fuel lIne near the exhuast ?


Weak Pump, ect.


is it when the car is physically warm, Or just running for a while ?




------------------
60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Reader's ride -> My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

Well, my exhaust before the cat is stock so there isn't any problem of heat soak on the lines. The fuel pump was replaced last week.

Maybe when the guys did my timing they screwed with that assembly near the distributor. I think it has two vac lines running to it. Are these expensive to replace?

 

BTT

 

did you ever say if you checked the timing or not?

might also try a fuel pressure gauge, could be a problem, even though its new.

 

Yep, timing is bang on. Did it after the distributor change. I've had this problem for about a year now. Last night I picked up a TPS and a CTS. They didn't have the IAC in stock or I would have got that too. I'm just sick of that damn bog down low but I'm extremely happy with the cars performance in the top end this year.
Will Update.

 

Have you tried disconnecting the MAF sensor, my car had a similar problem, 89 5spd GTA, wouldn't idle cold at all, after it was warm then it was be horrible at like 500 or less RPM. If I floored it, everything was fine, but part throttle and idle were bad. Try your MAF sensor.

 

Did you actually pull the codes or are you just not seeing the check engine light? It sounds stupid but my damn check engine light was burned out and in reality was throwing a code for along *** time. I assumed no codes were present when they were, stupid me for not trying to pull them sooner and seeing that it was burnt out....

If I was guessing at the problem the CTS would be one of my first. Hope that fixes your prob since you just got a new one.

------------------
Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

[This message has been edited by Ray87Z (edited May 02, 2001).]

 

Didn't have time to put them on last night, but I will tonight (The TPS & CTS). I MAF is only 2 years old (Bosch), I hope it isn't busted!
My SES light works fine, it comes on when I power up the car. I just got an SES code from a bad pickup coil not too long ago so I know it works fine. There are no codes stored in it...just the usuall 12.

 

Well, changed the TPS and this didn't help the problem any. Tonight, I'm going to go ahead and change the CTS (Too damn hot yesterday, car wouldn't cool down in this heat wave weather we're having).

 

Changed the CTS sensor and that didn't help any either. I read a few articles on the net about a lean condition present that may be causing the bog...but, my problem may be a little different. On all the posts I read with a similar problem, they get on the gas and feel the bog. My car's RPM jumps pretty fast without any bog...it's only when I try and hold it around 1500rpm (or so) that it will begin to bog down. This is why I feel it when I'm putting along. Otherwise, power is great!

Please help...I'm outta options...EGR? How the hell did I pass emissoins if this didn't work?

 

I guess i can live with it until I pull the motor next year.

Thanks.

 

Honestly, my WAG would be the MAF has some kind of issues. That it runs fine all the time, except steady state low rpm/load just doesn't make sense. Any real problem that was ignition/fuel related would get worse with more load/rpm. A bad MAF could easily screw you up in this situation, cuz airflow is low, thus if it is going bad a low airflow situation might be too hard for it to measure properly, thus completely screwing your injection/timing with it's bad readings.
...ed

------------------
Ed Maher - Moderator @ The Carb Board
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

I haven't touched the relays yet, do you think this could be the problem? I've read some time ago that the MAF sensor has two relays (burnoff and another) which sit beside the fuel pump relay. Should I bother to change them?