Idle & Acceleration Rough - Resolved V6 Issues - Firebird Nation

Jump to content


FirebirdNation.com is the premier Pontiac Firebird forum on the internet. Supporting Members do not see the above ads.
Photo

Idle & Acceleration Rough


  • Please log in to reply
29 replies to this topic

#1 ShredDead

ShredDead

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 65 posts
  • Gender:Male
  • First Name:Chad
  • City:Columbia
  • State or Province:MO
  • Country:USA
  • Interests:Ugly Cars, Pretty Women, and Shredding on my axe.
  • Year: 1988
  • Make: Pontiac
  • Model: Firebird
  • Engine: V6 2.8L MPFI
  • Transmission: Borg-Warner T5 5-speed

Posted 06 November 2005 - 01:47 PM

Hey Readers, this is my first post after reading several that seemed to be of my problem. Hope to have some help.

I have a 1988 V6 2.8L 5 Speed with 225K miles. The car has run like a champ until the last 2 months. After I filled the tank with gas one time the car ran extremely rough when accelerating as if it was missing, kinda of like learning to drive a stick for the first time. It did this for the entire tank of gas, hell I thought that it might of been just bad gas. After running the gas out I refueled somewhere else but still had a problem. When starting the car it idles high at around 1500rpm for about a minute and then settles down to about 700-800 rpm. Periodically the tach will switch. When I come upon a time to stop the car at a red light the rpm's will still be high and then come down to its normal operating range after sitting for a moment.

I took the car in to the dealer and had them pull the codes and they told me it was my O2, MAF sensor, and my ECM. At a $600 quote I decided to do a little at a time. I replaced the O2 sensor and Fuel Filter - Still didn't fix it. Pulled the MAF sensor and had it tested, was told it was fine. Hadn't done anything to the ECM yet. Spark plugs, Wires, and Distributor Cap are only a year old and appear to be in good shape. My PCV valve has good suction.

If this is a vacuum leak how would I fix the problem myself having a MPFI and if too overwhelming, how much would this cost typically at a shop?

#2 FBN Firebird Nation

FBN Firebird Nation

    Pontiac Firebird Trans Am and Formula Fan

  • Administrator
  • 36186 posts
  • Gender:Male
  • First Name:Clark
  • City:Sparks
  • State or Province:NV
  • Country:USA
  • Year: 2002
  • Make: Transmission
  • Model: Engine
  • Engine: Engine
  • Transmission: car

Posted 06 November 2005 - 02:08 PM

Did they say why they thought the ECM was bad? I would think its the TPS or IAC myself, assuming your cars has both of these sensors. Welcome to FirebirdNation.

#3 ShredDead

ShredDead

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 65 posts
  • Gender:Male
  • First Name:Chad
  • City:Columbia
  • State or Province:MO
  • Country:USA
  • Interests:Ugly Cars, Pretty Women, and Shredding on my axe.
  • Year: 1988
  • Make: Pontiac
  • Model: Firebird
  • Engine: V6 2.8L MPFI
  • Transmission: Borg-Warner T5 5-speed

Posted 06 November 2005 - 03:57 PM

No, the dealer did not specify why they thought it would be the ECM.

Not really being a mechanic I would of thought that if it was the ECM I would have other problems acting up. But at this time no other symptoms have come to play. (Knock on Wood)

#4 FBN Firebird Nation

FBN Firebird Nation

    Pontiac Firebird Trans Am and Formula Fan

  • Administrator
  • 36186 posts
  • Gender:Male
  • First Name:Clark
  • City:Sparks
  • State or Province:NV
  • Country:USA
  • Year: 2002
  • Make: Transmission
  • Model: Engine
  • Engine: Engine
  • Transmission: car

Posted 06 November 2005 - 05:28 PM

I think it sounds like the TPS.

#5

    Firebird Oil Changer

  • Validating
  • PipPipPip
  • 136 posts

Posted 06 November 2005 - 06:35 PM

Cheap idea to try would be to run a few bottles of "dry gas" in the car. It will get any water out of the tank that migh tbe there from the crappy fill up

#6 ShredDead

ShredDead

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 65 posts
  • Gender:Male
  • First Name:Chad
  • City:Columbia
  • State or Province:MO
  • Country:USA
  • Interests:Ugly Cars, Pretty Women, and Shredding on my axe.
  • Year: 1988
  • Make: Pontiac
  • Model: Firebird
  • Engine: V6 2.8L MPFI
  • Transmission: Borg-Warner T5 5-speed

Posted 06 November 2005 - 07:44 PM

"Dry Gas"? Even after several months of adding fuel and taking it to the dealer with error codes being extracted that It would come down to having water in the tank?

I read in the forums that AutoZone can read the error codes for free. Is this correct? If so I'll pull the negative side off the battery and reset the ECM to pull any new error codes. I'll do this because I did not know what these codes read when I took the car to the dealer. If the codes read either a 21 or 22 then I'll know to replace the TPS.

#7 FBN Firebird Nation

FBN Firebird Nation

    Pontiac Firebird Trans Am and Formula Fan

  • Administrator
  • 36186 posts
  • Gender:Male
  • First Name:Clark
  • City:Sparks
  • State or Province:NV
  • Country:USA
  • Year: 2002
  • Make: Transmission
  • Model: Engine
  • Engine: Engine
  • Transmission: car

Posted 06 November 2005 - 09:15 PM

Yes, I hear autozone will pull the codes for free for you. If you do that, tell us the codes and we will be able to help you from there.

#8 FAST RS

FAST RS

    Third Gen V6 Tech

  • Full Member
  • PipPipPipPipPipPipPip
  • 1218 posts
  • Gender:Male
  • First Name:David
  • City:Thousand Oaks
  • State or Province:CA
  • Country:USA
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 455
  • Transmission: TH-400

Posted 07 November 2005 - 09:17 PM

You can also pull the codes your self. Go here scroll to the very bottom to MISC its the last article it will tell you how to pull your codes and what the code means. I think you will use pins 5 and 6 not 6 and 12.

http://www.thirdgen..../thirdgen.shtml
1968 Pontiac Firebird
455 bored .30 over with TRW forged pistons, Torker 2 intake, 750 cfm Demon Carb, ISKE Cam, Mallory HyFire ignition box with a Mallory unilight distributor Super Comp Headers, 3 inch cutouts, 3 inch exhaust into Flowmaster 40 series mufflers. Almunium Drive Shaft, All new suspension Eaton Springs out back Moog up front with KYB gas Adjusts all around.


1991 Camaro RS V-6
MODS: FAST CHIP STAGE 2
MSD 6 AL, MSD COIL
CAI, Underdrive pullys.
And some stuff i cant think of at the moment.

#9 ShredDead

ShredDead

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 65 posts
  • Gender:Male
  • First Name:Chad
  • City:Columbia
  • State or Province:MO
  • Country:USA
  • Interests:Ugly Cars, Pretty Women, and Shredding on my axe.
  • Year: 1988
  • Make: Pontiac
  • Model: Firebird
  • Engine: V6 2.8L MPFI
  • Transmission: Borg-Warner T5 5-speed

Posted 08 November 2005 - 03:57 PM

Pulled the negative side off of the battery to reset the ECM this morning. Drove it to and from work and still have the same problems as mentioned, but no Service Engine Light came on.

This afternoon I took a look under the car and noticed that the Catalytic Converter is pretty banged up and deteriorating, possibly the original factory one. If this is bad, will it cause the noted problems? For I didn't see a code representing that factor. What kinda of symptoms does a bad Catalytic Converter give?

#10 FBN Firebird Nation

FBN Firebird Nation

    Pontiac Firebird Trans Am and Formula Fan

  • Administrator
  • 36186 posts
  • Gender:Male
  • First Name:Clark
  • City:Sparks
  • State or Province:NV
  • Country:USA
  • Year: 2002
  • Make: Transmission
  • Model: Engine
  • Engine: Engine
  • Transmission: car

Posted 08 November 2005 - 04:01 PM

A bad catalyic converter will cause poor running, lack of power, poor gas mileage, and sometime a sulfer or egg smell.

#11 FAST RS

FAST RS

    Third Gen V6 Tech

  • Full Member
  • PipPipPipPipPipPipPip
  • 1218 posts
  • Gender:Male
  • First Name:David
  • City:Thousand Oaks
  • State or Province:CA
  • Country:USA
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 455
  • Transmission: TH-400

Posted 08 November 2005 - 04:14 PM

That very well could be your problem.
1968 Pontiac Firebird
455 bored .30 over with TRW forged pistons, Torker 2 intake, 750 cfm Demon Carb, ISKE Cam, Mallory HyFire ignition box with a Mallory unilight distributor Super Comp Headers, 3 inch cutouts, 3 inch exhaust into Flowmaster 40 series mufflers. Almunium Drive Shaft, All new suspension Eaton Springs out back Moog up front with KYB gas Adjusts all around.


1991 Camaro RS V-6
MODS: FAST CHIP STAGE 2
MSD 6 AL, MSD COIL
CAI, Underdrive pullys.
And some stuff i cant think of at the moment.

#12 ShredDead

ShredDead

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 65 posts
  • Gender:Male
  • First Name:Chad
  • City:Columbia
  • State or Province:MO
  • Country:USA
  • Interests:Ugly Cars, Pretty Women, and Shredding on my axe.
  • Year: 1988
  • Make: Pontiac
  • Model: Firebird
  • Engine: V6 2.8L MPFI
  • Transmission: Borg-Warner T5 5-speed

Posted 08 November 2005 - 07:14 PM

This evening I dismantled the IAC and noticed that it was somewhat carboned black. Taking Carb Cleaner I cleaned the valve pintle with a soft bristled toothbrush. Before reinstalling the IAC valve I made sure that the distance between the tip of the pintle and the housing mounting surface was LESS than 1-1/8". I also cleaned the electrical connection with "CRC - QD Electronic Cleaner"

Started the engine and allowed it to reach operating temperature then turned it off.

Tommorow morning I'll see how she acts.

As for the Catalytic Converter - No smell of sulfer or eggs but other poor conditions that Bob stated are present.

Edited by ShredDead, 08 November 2005 - 07:14 PM.


#13 ShredDead

ShredDead

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 65 posts
  • Gender:Male
  • First Name:Chad
  • City:Columbia
  • State or Province:MO
  • Country:USA
  • Interests:Ugly Cars, Pretty Women, and Shredding on my axe.
  • Year: 1988
  • Make: Pontiac
  • Model: Firebird
  • Engine: V6 2.8L MPFI
  • Transmission: Borg-Warner T5 5-speed

Posted 09 November 2005 - 07:50 PM

Started the car this morning and let it completely warm up before driving. Temperature outside was pretty cool and I had only a few hesitations in the acceleration after cleaning the IAC valve. But this afternoon was a different story. Temperature outside was humid and the car just ran like hell, even after letting the engine warm up.

So what could it be?

#14 FBN Firebird Nation

FBN Firebird Nation

    Pontiac Firebird Trans Am and Formula Fan

  • Administrator
  • 36186 posts
  • Gender:Male
  • First Name:Clark
  • City:Sparks
  • State or Province:NV
  • Country:USA
  • Year: 2002
  • Make: Transmission
  • Model: Engine
  • Engine: Engine
  • Transmission: car

Posted 09 November 2005 - 08:56 PM

Have you tested the TPS? Don't rely only on the codes. Sensors can be defective without throwing a code. So what you need to do is test them or replace them. I am not familiar with the 2.8, but others are and I am sure they will have other suggestions for you.

#15 FAST RS

FAST RS

    Third Gen V6 Tech

  • Full Member
  • PipPipPipPipPipPipPip
  • 1218 posts
  • Gender:Male
  • First Name:David
  • City:Thousand Oaks
  • State or Province:CA
  • Country:USA
  • Year: 1968
  • Make: Pontiac
  • Model: Firebird
  • Engine: 455
  • Transmission: TH-400

Posted 10 November 2005 - 12:54 PM

I also think you can adjust your TPS on your year car. When i get home let me see if i can find the article on it.
1968 Pontiac Firebird
455 bored .30 over with TRW forged pistons, Torker 2 intake, 750 cfm Demon Carb, ISKE Cam, Mallory HyFire ignition box with a Mallory unilight distributor Super Comp Headers, 3 inch cutouts, 3 inch exhaust into Flowmaster 40 series mufflers. Almunium Drive Shaft, All new suspension Eaton Springs out back Moog up front with KYB gas Adjusts all around.


1991 Camaro RS V-6
MODS: FAST CHIP STAGE 2
MSD 6 AL, MSD COIL
CAI, Underdrive pullys.
And some stuff i cant think of at the moment.

#16 ShredDead

ShredDead

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 65 posts
  • Gender:Male
  • First Name:Chad
  • City:Columbia
  • State or Province:MO
  • Country:USA
  • Interests:Ugly Cars, Pretty Women, and Shredding on my axe.
  • Year: 1988
  • Make: Pontiac
  • Model: Firebird
  • Engine: V6 2.8L MPFI
  • Transmission: Borg-Warner T5 5-speed

Posted 10 November 2005 - 03:13 PM

I added one bottle of Valvoline's dry gas yesterday afternoon and drove it a little last night, still had some hesitation.

This morning the weather was pretty cool and I had only a few problems going into work. Noticed that I my way home tonight that the car was starting to feel pretty good with only a couple of burps here and there, but the weather is still cool.

Maybe I did have some condensation in the fuel like "Fastbird" had mentioned. If this is the case, what a beating around the bush. How long does "Dry Gas" have to be in play before this can be ruled in favor or against?

Hey Fast RS, I would still like to know the how-to on adjusting my TPS if this problem still is the case.

Thanks

#17 FBN Firebird Nation

FBN Firebird Nation

    Pontiac Firebird Trans Am and Formula Fan

  • Administrator
  • 36186 posts
  • Gender:Male
  • First Name:Clark
  • City:Sparks
  • State or Province:NV
  • Country:USA
  • Year: 2002
  • Make: Transmission
  • Model: Engine
  • Engine: Engine
  • Transmission: car

Posted 10 November 2005 - 03:29 PM

I would think it will take a full tank before you know if that was the problem or not. Have you tested the TPS? Has the car had a tune up lately?

#18 ShredDead

ShredDead

    Firebird Tire Changer

  • Full Member
  • PipPip
  • 65 posts
  • Gender:Male
  • First Name:Chad
  • City:Columbia
  • State or Province:MO
  • Country:USA
  • Interests:Ugly Cars, Pretty Women, and Shredding on my axe.
  • Year: 1988
  • Make: Pontiac
  • Model: Firebird
  • Engine: V6 2.8L MPFI
  • Transmission: Borg-Warner T5 5-speed

Posted 11 November 2005 - 03:40 PM

No I haven't had the time to test the TPS but tommorow is Saturday and then time shall be on my side. After this is resolved I will then have the car tuned-up.

I did find this article on adjusting the TPS -- Hope it is not too lengthy.

Switch Types |
There are a few different TPS design types: switch, potentiometer and combination. The switch type, not surprisingly referred to as the throttle position switch, cycles on and off through its range. It is usually "on" (has electrical continuity) at throttle close, or idle. Just above idle it is "off" (loses continuity), and stays that way until wide open throttle is reached, where it is then "on" again. While operating in the middle area, where the switch is off, other sensor inputs provide the computer with the data it needs to maintain smooth throttle response and good driveability. This type of sensor is usually adjustable.

The potentiometer type of TPS is a variable resistor, effectively supplying a gradually increasing supply of voltage to the computer as the throttle is gradually opened. Usually the voltage operating range is from about one-half a volt at idle, to five volts at wide-open throttle. These sensors are usually not adjustable.

The combination type employs elements of the switch and "pot" type of sensor. Early designs were often adjustable, later designs are not.

Stop and Adjust |
You may already be imagining what kinds of failure and maladjustment scenarios are possible with the different types of sensors. We'll get there momentarily, but no discussion of proper diagnosis and adjustment of the TPS would be right without first addressing the throttle stop, and throttle cable adjustments.

The reason that these adjustments are so important is that if they are incorrect, that is they are holding the throttle plate open beyond specification, the TPS will not be able to give an idle (throttle closed) signal to the computer. Driveability symptoms that result include poor startup, engine stall after startup, poor idle, engine stall at idle, poor throttle response at throttle "tip-in" or possibly even engine "ping." Besides those things, you may also discover that you are unable to access the vehicle on-board diagnostic tests, and/or unable to properly set the ignition timing!

While it may be true that adjusting the TPS may correct some of these symptoms caused by a maladjusted throttle cable or stop, the throttle plate would still be admitting more than its share of air at throttle close. This will cause the idle air control valve to operate out-of-parameter, which will lead to similar, if not new and unusual problems. If the TPS is not adjustable, the throttle cable and stop adjustments are even more critical.

Rules of Thumb |
It's best to consult the service manual for specifics on any adjustments that we are about to discuss, but here are a couple of rules of thumb: To make sure that the throttle cable is only as tight as it needs to be, have a friend push the accelerator pedal to the floor (with the engine off, please!) and then adjust the cable so that the throttle plate just reaches the fully open position without stressing the cable.

As for the throttle stop adjustment, while it may look like an idle speed adjustment, if it has a direct effect on throttle position, don't use it as such. Set it so that the throttle plate is only held open enough to prevent binding of the throttle plate in the bore. At that position, the throttle cable should have at least a little slack in it, so that the throttle can consistently return to its stop. Do not proceed until these relationships are correct.

Regarding TPS adjustment, most TP sensors are adjusted at throttle close. Generally speaking, if the other adjustments are O.K., and the sensor is otherwise fully functional, getting this adjustment correct will finish the job.

Setting switch-type sensors will require the use of an ohmmeter. On some European models however, a pronounced click from the sensor should be heard if the throttle is opened just a bit from fully closed, and again at wide open throttle. Adjust the switch so that this occurs, but its still a good idea to double-check with the ohmmeter. Combo-type sensors are usually adjusted the same way as switch-type sensors.

Setting potentiometer-type sensors will require the use of a voltmeter. You'll really need the service manual for the exact voltage spec, as well as the correct wires to connect up to. This type of sensor is usually set with the ignition on, engine off.

Sometimes problems will show up during the adjustment procedure. They may point to a malfunction in the sensor, a wiring problem, or perhaps a computer problem. If you're feeling confident and adventurous, with the help of the service manual and a digital volt/ohmmeter, you might even be able to tackle those problems too.

#19 FBN Firebird Nation

FBN Firebird Nation

    Pontiac Firebird Trans Am and Formula Fan

  • Administrator
  • 36186 posts
  • Gender:Male
  • First Name:Clark
  • City:Sparks
  • State or Province:NV
  • Country:USA
  • Year: 2002
  • Make: Transmission
  • Model: Engine
  • Engine: Engine
  • Transmission: car

Posted 11 November 2005 - 05:39 PM

It could actually be your spark plugs and wires which are causing this problem.

#20

    Firebird Tire Changer

  • Validating
  • PipPip
  • 99 posts

Posted 11 November 2005 - 09:48 PM

Yea, Bob is right thats what was wrong with mine until i took it to shop and got charged $180 to change them you might want to check them out, it fixed my car, it might work for you also




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users