Basically stock, except; hot wire/Walbro 340, cold air kit, TT 93 chip, Impala MAF/translator (on, on, 0n, off/Base 3), shift kit. Seems to run well, except idle is rough. Shows 12 psi boost under full throttle. Recent 1/8 mile time slips with factory tires were; 10.12/69mph, 9.89/70mph, 10.00/73mph. No missing, stuttering or anything obvious. Vacuum @ idle is 18" in park and in gear is about 14". TPS/IAC are about right. Starts instantly cold, takes a few seconds when hot after setting a while. Also, gas mileage is poor, around 12. No black smoke. 106K miles. Factory injectors. I feel like I am pulling an invisible trailer. Where do I start?
Why is my 87GN so slow?
- Thread starter rays87gn
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Bescurred
BOOSTED SHAMU v2.0
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Do you have a scanmaster? On factory tires and 12 psi of boost I wouldn't expect more than a mid 9 second pass if you're lucky
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U start by posting scan tool results.
Far too many possibilities as to the problem, to start guessing.
Far too many possibilities as to the problem, to start guessing.
turbo39151
anycoloraslongasitsblack
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^^That. And everyone knows that the 1986 models are faster. 
Yep^^That. And everyone knows that the 1986 models are faster.
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x2 on what chuck said, it shouldn't be that slow, that's around high 15s in the 1/4.
hensleyt
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12 PSI is what my 87 had when I first got it ,Boost solenoid plumbed incorrect ,had a plug over the vent side
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You have omitted one piece on important data and that is your 60' time which may not be very good?
When my car was new in 1987 with the original crap Goodyear tires it would be a good day when I could run a low 15 sec. time with the stock 15-16 PSI, but obviously it did not have 106K miles and I do not remember getting a 14 sec. time slip until I changed to better tires!
When my car was new in 1987 with the original crap Goodyear tires it would be a good day when I could run a low 15 sec. time with the stock 15-16 PSI, but obviously it did not have 106K miles and I do not remember getting a 14 sec. time slip until I changed to better tires!
You need a Scanmaster first of all.
Have you done the spring cleaning on the car? Here is a link to the guide to help. http://www.gnttype.org/maint/basics.html
What size and brand of tires are on the car?
What are the settings of the TPS/IAC? What did you use to read them?
Do you still have the stock exhaust system with the cat converter and mufflers? Just taking a wild guess here if it is the stock cat converter on the car it's clogged.I had that happen on a stock 87 Turbo T and the car couldn't get out of it's own way it was so slow. I bought it that way and had a dealership replace it along with the downpipe it made a world of difference it was like driving a different car.
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corsair231
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I bet 3-4 more pounds of boost would make it seem a lot snappier.
Using Pathfinder Monitor 4000E, got following readings; Idle rpm varies between 875/1000, O2 cross settled at .000, o2 v-.11/.8, TPS-.48, IAC-.025/.032, LV8-032, MAT-129, MAF-.006, BLM-133, ADV-37/38. At first during idle, closed loop and rich/lean switching. After idling a while, went to open/lean and stayed. Idle is rough, with intermittent "misses". Drives nicely on the street. Exhaust is aftermarket with split duals from the convertor. Tires are original equipment size Goodyear and traction is not my problem. It is a street car. My boost shows 12 psi. Nick mentioned 15-16 being stock. Why would I have only 12? Hensleyt mentioned checking the boost solenoid. Where is that and what do I check? Appreciate all the information from everyone, (even you '86 owners).
Wonder why the open loop idle goes lean? Your other numbers look pretty good, TPS couild be a tad better set to .40 to .42 key on engine off.
BTW, I don't think your car is slow at all, based on your description of what it has and how it's set up. You are after all running quite low boost and a street chip.
OEM size tire are totally useless for traction either at the strip or street. I know, I've retired my car from racing and running stock size Goodyears.
As for what is stock boost, I disagree that 15 was stock. 15 was the top limit of the original boost gauge so the factory would not have the c# ar boosting to the top limit of the bar graph gauge. FYI, both of my GN's came originally from the factory making 12# which was the orig. stock setting.
to give you a comparison, just before I retired mine from racing (11.6's @ 117.5 in the 1/4) I took it to the local 1/8 mile track. My car is now detuned from racing trim but I'm still able to run 20# of boost because of my tune and big front mount IC. It ran 8.0 flat through the 1/8 (forgot the mph but I think it was arouind 85-86) with a 2.0 60'.
So for what you have and how you're set up, you're not far off at all.
BTW, I don't think your car is slow at all, based on your description of what it has and how it's set up. You are after all running quite low boost and a street chip.
OEM size tire are totally useless for traction either at the strip or street. I know, I've retired my car from racing and running stock size Goodyears.
As for what is stock boost, I disagree that 15 was stock. 15 was the top limit of the original boost gauge so the factory would not have the c# ar boosting to the top limit of the bar graph gauge. FYI, both of my GN's came originally from the factory making 12# which was the orig. stock setting.
to give you a comparison, just before I retired mine from racing (11.6's @ 117.5 in the 1/4) I took it to the local 1/8 mile track. My car is now detuned from racing trim but I'm still able to run 20# of boost because of my tune and big front mount IC. It ran 8.0 flat through the 1/8 (forgot the mph but I think it was arouind 85-86) with a 2.0 60'.
So for what you have and how you're set up, you're not far off at all.
hensleyt
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Boost solenoid ,passenger side valve cover , should be no pluges one should be vented
TT chip should say timing and boost
TT chip should say timing and boost
My solenoid had a "cap" on one nipple and the other goes to the "Y" hose to the turbo. The capped nipple has a ridge to hold a hose or something. Why would the factory put a nipple there if it is supposed to be open to the air? I took off the rubber cap for the picture. Should I leave it off?
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That cap renders the boost controller inop. U have something else controlling it?
hensleyt
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did that help ?
It's been raining since your message, but I made a foam cap to put over the nipple. Finally got to drive today and boost went from a previous 12 max to 14! Feels much better. I'll give it some more testing this week, if the rain doesn't start again. Many thanks!
