I have an '89 Iroc-Z with the L98. Current mods are in my sig. It shakes at idle kind of roughly. What could be causing this? It runs great while driving but at idle it shakes. I adjusted the TPS and IAC but still no good. I also checked the firing order and its ok. Also my cruise won't hold at any speed and surges sometimes as if I floored it. Could there be a vaccuum leak? If so how it test for it?
Thanks for any help!


[This message has been edited by My Slow Iroc-Z (edited October 01, 2000).]

 

Any help please???

 

your web site is updateable now...check ur email

 

Here's my sig!!

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1989 Iroc-Z L98 Original engine-58K miles!!

SLP 1 3/4 SS headers, Hooker Areochamber catback, no cat, BBK AFPR, Hypertech 160* fan switch, ported and gasket matched plenum, TB coolant bypass, relocated MAT sensor, screenless MAF sensor, K&N filters, Accel cap and rotor, Taylor SpiroPro 8mm wires, Bosch Platinum plugs, Mobil 1 Synthetic 15W50 motor oil, and more to come...
Best ET- 14.24@96.76MPH / 2.17 60ft on street tires with the crappy B/W 2.77 gears.

Homepage currently under construction: http://www.iit.edu/~wicktho/len

 

now that I clicked on the send button you should have the addresses for the site

[This message has been edited by TwicK91 (edited October 01, 2000).]

 

I sprayed TB cleaner on all the vac hoses, cruise servo, egr valve, pvc valve, all intake gaskets/plenum gaskets, and charcol canister, but the car did not increase in idle. I dont understand why it shakes. I recently did the tuneup about a month ago but that didn't help the shaking eighter.

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1989 Iroc-Z L98 Original engine-58K miles!!

SLP 1 3/4 SS headers, Hooker Areochamber catback, no cat, BBK AFPR, Hypertech 160* fan switch, ported and gasket matched plenum, TB coolant bypass, relocated MAT sensor, screenless MAF sensor, K&N filters, Accel cap and rotor, Taylor SpiroPro 8mm wires, Bosch Platinum plugs, Mobil 1 Synthetic 15W50 motor oil, and more to come...
Best ET- 14.24@96.76MPH / 2.17 60ft on street tires with the crappy B/W 2.77 gears.

Homepage currently under construction: http://www.iit.edu/~wicktho/len

 

My car shakes at idle too Guess its an 89 thang, heh.


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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-Rebuilt 700R4 Tranny
With the goodies to go

-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)

 

There had to be something wrong, I'm sure GM didn't let them out the door like this. Any help is appreciated.

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1989 Iroc-Z L98 Original engine-58K miles!!

SLP 1 3/4 SS headers, Hooker Areochamber catback, no cat, BBK AFPR, Hypertech 160* fan switch, ported and gasket matched plenum, TB coolant bypass, relocated MAT sensor, screenless MAF sensor, K&N filters, Accel cap and rotor, Taylor SpiroPro 8mm wires, Bosch Platinum plugs, Mobil 1 Synthetic 15W50 motor oil, and more to come...
Best ET- 14.24@96.76MPH / 2.17 60ft on street tires with the crappy B/W 2.77 gears.

Homepage currently under construction: http://www.iit.edu/~wicktho/len

 

Anyone???

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1989 Iroc-Z L98 Original engine-58K miles!!

SLP 1 3/4 SS headers, Hooker Areochamber catback, no cat, BBK AFPR, Hypertech 160* fan switch, ported and gasket matched plenum, TB coolant bypass, relocated MAT sensor, screenless MAF sensor, K&N filters, Accel cap and rotor, Taylor SpiroPro 8mm wires, Bosch Platinum plugs, Mobil 1 Synthetic 15W50 motor oil, and more to come...
Best ET- 14.24@96.76MPH / 2.17 60ft on street tires with the crappy B/W 2.77 gears.

Homepage currently under construction: http://www.iit.edu/~wicktho/len

 

My lg4 shakes like mad right off of idle,,, it's not just a l98 thing.

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<A HREF="http://anzwers.org/free/gta" TARGET=_blank>87 Firebird
84 Camaro</A>
Virtual Racing

- intelligence is learned, ignorance is universal

 

Anyone have any thoughts as to where I should start to fix this?? Vader??? Anyone????

 

My car shakes ever since I put in the new engine. Mornings worse then afternoons. The mounts looked good when I had the engine out and I am sure it is balanced correctly.

Didi it just start for no reason, or were you changing something and then it started the next day? If so, what were you working on? I know it shook like mad when I put the wrong length pushrods in once...

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane...

-=ICON Motorsports=-

 

You could have a fuel leak. If possible hook up a fuel gauge and check your pressure. Also you might want to replace the fuel filter. On a TBI car I seen where the pressure regulator was leaking causing an over rich condition. Your PR could be doing the samething.

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89 GTA
350
K&N air filter
Flowmaster muffler

 

Well I got the car two years ago, and when I bought it, it shook but not as noticably. I believe the fuel pressure is fine because when I put the AFPR on I checked the pressure and watched it after I turned the car off, it held for about 10min and then dropped slowly. The fuel filter was replaced about 1 year ago. The motor mounts seem fine because when I dropped in the headers the engine was high enough so I didn't have to raise the engine, they just fell in.
Anyone else?? Could this be because of the screenless MAF, no codes are stored and SES light is off.

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1989 Iroc-Z L98 Original engine-58K miles!!

SLP 1 3/4 SS headers, Hooker Areochamber catback, no cat, BBK AFPR, Hypertech 160* fan switch, ported and gasket matched plenum, TB coolant bypass, relocated MAT sensor, screenless MAF sensor, K&N filters, Accel cap and rotor, Taylor SpiroPro 8mm wires, Bosch Platinum plugs, Mobil 1 Synthetic 15W50 motor oil, and more to come...
Best ET- 14.24@96.76MPH / 2.17 60ft on street tires with the crappy B/W 2.77 gears.

Homepage currently under construction: http://www.iit.edu/~wicktho/len

 

It could be your EGR vavle is stuck open. With the engine off see if you can move the valve by hand. There should be windows on it that you can put your fingers in. If move then start the car and try moving it again. If the engine slows down then it is might be okay. Try that and let me know.

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89 GTA
350
K&N air filter
Flowmaster muffler

 

Maybe it's just an '87 thing, but look at the vacuum lines at the vapor canister. Mine (particularly the bigger one) come off sometimes when working on the engine. You don't suspect them since they're far away from the engine and out of your usual field of view.

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'87 IROC 5.7l TPI - original owner!

 

I checked the vac lines when I sprayed the card cleaner all over. All tight. I looked at the EGR valve but can't really see any windows. Do you have a pic or something? Wouldn't I get a code if the EGR valve was going bad? Wouldn't the engine change RPM when I sprayed the carb cleaner on the valve when I checked for vac leaks?

 

Any other ideas??

 

?

 

You might have a burnt exhaust valve, or bad rings. Does it burn any oil?

James

 

Mine is doing that and I have a vacuum leak.

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TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

It doesn't burn any oil. Not even a blue puff at startup. Exhaust is clear except when its cold. I checked 3 times for vac leaks but can't find anything. How would you burn an exhaust valve??? The car runs fine, very dependable, and has been taken care of; regular oil changes/maintaince.

 

Anyone?

 

Well, as someone mentioned before, you could have a poorly seating EGR valve...tough to diag, without pulling it and inspecting...

Could be a faulty injector.

Could be ignition related.

BTW, I've got it too...a slight miss at idle...I'll change the EGR valve and while the plenum is off...send the injectors out for cleaning and matching as well.

 

Mine has done several "shakey idles" One was it would rev up, and fall to a near stall, then back up,...That was several vac lines+EGR. Fixing the vac leak smoothed it out some, enough to be able to drive and ignore, but not enough to fool the sniffer (Out here in Montgomery County Pensylvania, we have CA emmissions) Replaced it a while ago (what a pita....the temp diag switch on the old one wouldn't come off...ended up breaking it, and having to drive 3 hours to get a new one!)
The most recent shake my car had was the whole thing wold bounce! It looked like I ahad a chick in the back seat Only at idle was it noticable though. That turned out to be ignition related. The idiot who owned the car before me had left the ignition coil sitting out. Me being lazy, and not having realized what would happen if left untreated, left it there too. Well, the coil started to break down, and was just not generating enough spark all the time. I replaced it w/ MSD 6A box (no rev limiter) and an MSD Blaster SS coil. It is still a little rough...I need to replace the plug wires to...
Home this helps. BTW they were right about the egr tests, although I know of no window to get at it w/o pulling at least the plenum. Mine was so bad, you could shake it and have the plunger move! While I had the intake apart, I sent it out for cleaning. Can't hurt!
Hope you get it worked out.
Corry

 

It is not that it shakes once in a while but it shakes all the time.....

 

Well I guess you guys are out of ideas or don't give a fukt anymore...Thanks!!

 

sht man, what the hell are we supposed to do, You kinda have to be there to diagnose something like this, Make a wave file or something.......or take it to a mechanic, sometimes sht like this just happens, It's not that we dont want to help, its just that ther are so many possibilities to diagnose without being there!

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91 RS W/carbed 350, Vortec heads, performer rpm, Comp cams Xtreme energy 280 grind. BFG Drag radials. 3.42 posi,Corvette servoed 700r4, ****ty stock converter
13.24@104

 

I have the answer,at least one of your piston skirs are blown off.I have seen 3 sb chevys that had a rough idle.After checking the usual we tore them down.The oil pans had skirts in them.You are the proud owner of a big boy L98 with a mini skirt.Just pull the pan off and see.