Idle and throttle stumbles

[91Bird305]

I have an 87 GN motor I transplanted into my 91 Firebird. I pulled it out of storage about a month ago. It has been in storage for over a year now. Initially, the car ran fine at idle and on the road. It was only recently when I took it out that I noticed the idle was rougher sounding than normal. When I took it out on the road and would give it any throttle, it would miss and sputter a bit. Not enough where it would fall on its face, but it's not running right. Some background on the car:


-Walbro 340 w/ Hotwire Kit
-Accufab 65mm Throttle Body / Plenum w/ RJC Powerplate
-72lb Seimens Injectors
-LS1 Maf w/ Translator +
-Extender Extreme Chip from FullThrottleSpeed.com
-GT6776s
-212/212 Roller
-Ported/Polished stock heads

If you need anymore info, let me know.

My scanmaster #s after the car warmed up @ idle:
02 Multivolts - 650-750 range
AF - 02
Ats - 83
L8 - 32
Clt - 172
bAt - 13.9
Int - 126
bL - 136
Ats - 85
TPS - .46
IAC - 70
MAL - 0

My iac and tps seemed high. Any other numbers stand out to you guys?

I did a resistance test on my coil pack (Car cold - 1-4, 3-6, 2-5), with the key turned on (not started - not sure if that matters) and each time it read 8.14ohms. (set to 20K). I believe it's supposed to be in-between 11-13K.

Any ideas? I'm going to try and pull my plugs soon and check to see how they look as well. I'll report back when I see how those look.

Thanks in advance!

 

[turbojd]

IAC is high at 70, should be around 10-30 when warmed up. You said it's been sitting awhile. I would pull the iac out and spray it with some carb cleaner and clean the throttlebody out also with carb cleaner.

 

[ScottHeidinger]

AF - 2 might want to check the MAF sensor. Mine is never that low.


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[626gn]

Module and/or coil pack

 

[No disintegrations]

I have an 87 GN motor I transplanted into my 91 Firebird. I pulled it out of storage about a month ago. It has been in storage for over a year now. Initially, the car ran fine at idle and on the road. It was only recently when I took it out that I noticed the idle was rougher sounding than normal. When I took it out on the road and would give it any throttle, it would miss and sputter a bit. Not enough where it would fall on its face, but it's not running right. Some background on the car:


-Walbro 340 w/ Hotwire Kit
-Accufab 65mm Throttle Body / Plenum w/ RJC Powerplate
-72lb Seimens Injectors
-LS1 Maf w/ Translator +
-Extender Extreme Chip from FullThrottleSpeed.com
-GT6776s
-212/212 Roller
-Ported/Polished stock heads

If you need anymore info, let me know.

My scanmaster #s after the car warmed up @ idle:
02 Multivolts - 650-750 range
AF - 02
Ats - 83
L8 - 32
Clt - 172
bAt - 13.9
Int - 126
bL - 136
Ats - 85
TPS - .46
IAC - 70
MAL - 0

My iac and tps seemed high. Any other numbers stand out to you guys?

I did a resistance test on my coil pack (Car cold - 1-4, 3-6, 2-5), with the key turned on (not started - not sure if that matters) and each time it read 8.14ohms. (set to 20K). I believe it's supposed to be in-between 11-13K.

Any ideas? I'm going to try and pull my plugs soon and check to see how they look as well. I'll report back when I see how those look.

Thanks in advance!

That would be fun to see you check the coils with the engine on.

 

[SCOOBY DOO]

AF and BLM's are out of whack.

 

[TurboBuRick]

AF is right on with Extender Extreme chip.

Try this:
Reset the chip (disconnect orange wire by battery for a few seconds) then do this.
Key on engine off. Go to INT on the scanmaster. It should say 12. Then switch to BL. It will prolly say 00. Press the gas till it says 08. Hold the pedal there and shut the key off. Wait a few seconds and turn the key back on. Scroll back to BL and verify 08 was stored. If BL did not store 08 then do the pedal thing again. Once 08 has been stored, go for a ride.

If for some reason INT is not on 12 post back with the number that's being displayed.

Rick

 

[Boostrules]

I have an 87 GN motor I transplanted into my 91 Firebird. I pulled it out of storage about a month ago. It has been in storage for over a year now. Initially, the car ran fine at idle and on the road. It was only recently when I took it out that I noticed the idle was rougher sounding than normal. When I took it out on the road and would give it any throttle, it would miss and sputter a bit. Not enough where it would fall on its face, but it's not running right. Some background on the car:


-Walbro 340 w/ Hotwire Kit
-Accufab 65mm Throttle Body / Plenum w/ RJC Powerplate
-72lb Seimens Injectors
-LS1 Maf w/ Translator +
-Extender Extreme Chip from FullThrottleSpeed.com
-GT6776s
-212/212 Roller
-Ported/Polished stock heads

If you need anymore info, let me know.

My scanmaster #s after the car warmed up @ idle:
02 Multivolts - 650-750 range
AF - 02
Ats - 83
L8 - 32
Clt - 172
bAt - 13.9
Int - 126
bL - 136
Ats - 85
TPS - .46
IAC - 70
MAL - 0

My iac and tps seemed high. Any other numbers stand out to you guys?

I did a resistance test on my coil pack (Car cold - 1-4, 3-6, 2-5), with the key turned on (not started - not sure if that matters) and each time it read 8.14ohms. (set to 20K). I believe it's supposed to be in-between 11-13K.

Any ideas? I'm going to try and pull my plugs soon and check to see how they look as well. I'll report back when I see how those look.

Thanks in advance!

What about the resistance test on the coil? Should it be between 11 - 13 k or is 8.14 ok? Looking for the pros to give their opinion.

 

[626gn]

What about the resistance test on the coil? Should it be between 11 - 13 k or is 8.14 ok? Looking for the pros to give their opinion.

Not a pro but will give my 2 cents anyway... that 11k - 13k ohms spec is often posted as the range where your coil pack should be but I've seen/had coils that measure fine but are still no bloody good. Sometimes a coil will get flaky only in a certain RPM range (and/or when it gets hot) but will otherwise work and test fine.

 

[91Bird305]

I know this is an old post now, but I never followed up on it after the issue was resolved and thought I'd share for when someone has a similar issue and goes forum searching.

Old gas and changing the spark plugs resolved the issue. After some discussions with my brother, who owned the car last, he apparently left it in storage for almost 2 years. Add the 1 year I had the car in storage during my transition back to Michigan and 4 months before I go out it for the spring, the gas was around 3.5 years old...so that might have been the cause? Changed the spark plugs when I put fresh gas in it, so it's difficult to tell if it was both or one of these changes that fixed the stumbling issue. Either way, car is running smooth again.