Issues w/ my 87 GN

[Gru1986]

Ok, first and foremost, I am a huge newbie, so please forgive me if I say anything newbish. I just got my GN a couple of weeks ago, so I'm not yet familiar with all its nuances. Anyway, here's what's going on with my GN:

The main problem is that my GN will occassionally die on me after decelerating to low RPMs. It tends to happen after driving around for a few minutes. I'll slow down for, say, a speed bump, or to make a turn, and the engine will quit on me. It's starts up fine afterwards, though.

The other, less significant problem is that my GN is sluggish, at least compared to other near-stock GNs. The last owner thought it might be because the transmission is old (which, I think, could also be the reason why the engine is dying on me). In addition to that, however, I think there may be an exhaust leak. I can smell fumes coming from the engine compartment, especially when I accelerate quickly. I don't know if that's normal for a GN, but because the motor's gotten louder in the past few days, it leads me to believe it's a leak. Are there any places in particular where I should check?

Just as a sidenote, the exhaust system is not stock... I'll have to dig through the receipts to find out what it is exactly. The engine was also rebuilt a few thousand miles ago... I can post more info if necessary. Thanks!

[Gary Wells]

I knolw exactly squat about these cars, but could the dying after slowdown after acceleration be due to an aftermarket performance chip. I beleive that some aftermarket performance chips used to die in reverse when the rpm went down. Just a thought , and probably not a valid one.

[white shadow]

New guys are usually well taken care of here at "turbobuicks.com".These guys are very nice and forgiving and that makes owning a t-buick great compared to going over to a website like "realoldspower.com"where they eat each other just to stay alive!!!
Welcome aboard.
TTT.

[ES]

1) See if you can get a scantool to give us some info
2) Look for exhaust leaks / cracks at the driver's side header.
Since the engine was rebuilt make sure the header bolts are tight
3) Run some GM Top Engine cleaner in, it will show you where alot of leaks are.
4)Put zip ties on all vacuum lines,wastegate lines and t-bolt clamps on the other hoses


Exhaust leaks will cause poor spool up pour performance

On the transmission, I would add a cooler, overfill by a quart, and use Honda Transmission fluid. I did this and stopped my transmission from flairing up.

[Gru1986]

There are no aftermarket chips on this car, so that's not it - thanks for responding, though! I believe all the relevant hoses were tied down after the rebuild, but I'll double-check. The bolts are all right... I don't think there would be any problems directly related to the rebuild work; the guy who did it was very competent. I will start checking for cracks, though... I hope it's not the header... As for the transmission, it already is overfilled, though I'm not sure what the fluid is exactly. The tranny's just plain worn out, I think, but I'll look into the cooler when I get it rebuilt/replaced. Thanks for the suggestions and the warm welcome!

[stealth908]

i'll bet the dying at deceleration is a combination of the IAC and the TPS being out of tolerance. when i first got my car i didn't have a scantool, and this is how i set them up...

first, turn the IAC set screw (d/side throttle body, looks like curb idle set screw) to about 1 1/2 to 2 threads showing on the end of the screw.

then get a voltmeter and with the motor running, use the positive lead to probe the top wire of the TPS connector, i think it's blue. the negative lead goes to ground. the reading should be .42 volts +/- .02 . if it's not you have to loosen the two TPS screws just loose enough to move the sensor, and set it to .42 by moving the TPS towards the front of the car and pivoting the top. once you get it then have someone mat the gas pedal and check for atleast 4.50 volts no more than 5.0 volts. adjustments are the same as for idle. this will probably take a while to get right.

why do you think the tranny is bad?

[WLDWST]

Stealth908 could be right. When I first bought my T, I had the same problem. When I would idle down to a stop sign, it would shut off. The cure for mine was this: I bought a Scanmaster, set TPS and IAC and it disappeared.

Also, if your budget allows, get a new chip for your combo. Some of the old chips are obsolete. Some have too much timing for todays fuel. Chip technology has advanced greatly. I suggest Eric @ http://www.turbotweak.com/

First and foremost, buy a Scanmaster. I have Turbolink and a Scanmaster. In my opinion, both are great, but the Scanmaster is a permanent fixture in my car. As a newbie, that should be your first investment. Knock retard is your enemy. No Scan tool = Big Money Repairs.
There are many excellent vendors out there.Many sponsor this board. I am sure there are several that sell the Scanmaster.
I have purchased plenty of parts from Mike@ Fullthrottle, with excellent service. His prices are very competitive.

http://www.fullthrottlespeed.com/Dyn...CZYW73&Cc=SCAN

[Gru1986]

Well, on the tranny, I took the last owner's word for it. He was saying it probably needs to be replaced/rebuilt within the next 15k or so, so it's not that it's bad, but with a 140k miles on it something is apt to go wrong. It seems alright to me, but what do I know?

I'm definitely getting a Scanmaster, but which chip, specifically, do you recommend for a stockish car? Also, a friend of mine was urging me to get a blow-off valve for the turbo, any problems with getting one?

Edit: I forgot to mention the transmission has a (very) minor leak.

[Gru1986]

Also, regarding the Scanmaster, is there anyplace where I can find like benchmarks for a stock GN? I would like to have an idea of what readings are acceptable for these cars.

[Ttype83]

A chip is one of the last things that you do. A good tune is first, next and/or same time a scan tool. If you are going to drag race take it to the track after a good tune and see were you sit. After that is when you start to mod. If you don't know were the car sits how do you know how much you've improved it???

[WLDWST]

Originally posted by Ttype83
A chip is one of the last things that you do. A good tune is first, next and/or same time a scan tool. If you are going to drag race take it to the track after a good tune and see were you sit. After that is when you start to mod. If you don't know were the car sits how do you know how much you've improved it???

I wouldn't say a chip is the last thing I would do, but it is good advice to get the thing sorted out first with a Scanmaster and take care of any sensor malfunction codes. Exhaust and vacuum leaks also steal power. No need for a blow off valve either.
( Turbo farts are cool.)

P.S. Try this site. It is the Bible of Turbo Regals everywhere.
http://www.rennie-macintosh.com/resources.html

[Lonely WE-4]

maybe your tcc solenoid is bad, a locked converter would cause the dying and the sluggishness. happened to me on one of my old cars

[Ormand]

Check out Full Throttle Speed, there is a sale on Scanmasters, but only until the end of the month, so you don't have long! You may also need a new fuel pump, if previous owner did not upgrade, but that's not needed to keep it running. Just needed if you want to push it. The stock fuel pump will lean it out, even with the stock chip, turbo, and injectors, and then something will go BOOM!

[Gru1986]

Well, I found the leak in a matter of seconds... turns out one of the bolts for the pipe on the back of the turbo went AWOL, so that the other came loose and the entire thing was unseated... that explains a lot. The TPS's voltage is dead-on, but I'm having trouble finding the screw for the IAC... the IAC motor is not stock, though... I'll keep poking around the throttle body. And the scanmaster has been ordered. Thanks again!

Edit: typo