Car Bucks Violently; Code 81

[Marccus]

My '89 SHO bucks violently when I open the throttle while in gear. It runs fine in neutral and fine in reverse. I'm getting a code 81.

" '89: Insufficient IAS output voltage change when solenoid
activated. "

So I need a new IAS valve? The round cylinder like thing right behind the throttle body?

 

[Marccus]

Anybody??

 

[VortecGT]

IAS? I would try cleaning the MAF and see if that helps.

 

[Marccus]

I replaced the Inlet Air Solenoid Valve and I'm still getting code 81.

The car bucks like crazy while in gear but the engine runs fine while in neutral and while opening the throttle in neutral.

I get a backfire sound from the exhaust.

I am also now getting codes 18 (spout circuit open) and 59 (low speed fuel pump circuit open).

Any ideas on what to do next?

How about replacing the PCM (Powertrain Control Module - computer) or the other thing under the flap at the front of the engine near the fan - the CCRM or IRCM (something like that). I'm really showing my ignorance here.

Replace the oxygen sensors?

Any advice would be appreciated.

 

[Marccus]

OK. Code 81 is gone. The secondaries electrical connector was disconnected and I reattached it.

But I'm still getting codes 18 (spout circuit open), 59 (low speed fuel pump circuit open), and 67 (A/C NPS circuit).

I know I can ignore 67.

And the spout connector is in.

What does code 59 mean as the car runs fine in neutral so there cannot be a fuel pump problem?

Any advice appreciated.

 

[jayro]

Not too familiar with the 2 digit codes, but I believe the fuel pump one just means the car stalled at some point. Have you done any work on the car recently? Did this just all of a sudden come up?

 

[Marccus]

I just replaced the clutch with Nick Chrimes in San Jose Friday and Saturday. Drove home from San Jose, CA to Bakersfield, CA with no problem at all - car drove perfectly.

Woke up the next day, after driving about 100 yards, the car starts bucking violently when in gear. Engine ran very rough; backfiring from exhaust. Had to cruise back home by getting some speed and then coasting in neutral.

I don't know what could be causing this. Engine runs fine in neutral. Clutch ran fine for 240 miles all the way home from San Jose to Bakersfield.

If I can't find the problem, I'll have to get rid of it and get another car. I only have one car and now I'm taking the bus to work and can't go anyplace else .

How about replacing PCM and IRCM?

 

[rubydist]

1. make sure all the grounds to the engine were reattached properly after the clutch work.

2. make sure the pcm connector is properly attached and tight.

3. disconnect battery to reset codes - leave disconnected overnight to be sure its all cleared.

4. run idle reset procedure.

5. double check all vacuum lines to make sure no vac. leaks.

 

[Marccus]

Well, I'll try all that. But why would it run fine for 260 miles from San Jose to Bakersfield with absolutely no problem? I stopped to gas up and eat something so I did turn off the engine and restart it and still had no problem. All it did was sit overnight!

 

[Marccus]

'89 w/470K

Can anyone else help or provide advice?

Do you think the problem is with the clutch job or the transmission? Since I have no problem when the engine runs in neutral but it bucks violently when in gear, could the clutch be binding or could there be something wrong with the transmission?

Do you think the car is just toast at this point and can't be fixed?

How about the DIS?

 

[Frisbeeguy]

Check out this thread from awhile ago... maybe it'll help?
http://www.shoforum.com/showthread.php?t=118453
http://www.shoforum.com/showthread.php?t=118453
Good luck - my cars running O.K. these days.

 

[Marccus]

Thanks. I'll try a new Camshaft Position Sensor.

Rockauto does not list this part.

Where can I buy a new Camshaft Position Sensor online?

 

[SHOuMINE]

this is similar problems i had with my SHO when i bought it, landed up needed new cats ( were clogged) and new spark plugs (had garbage bosch plugs in it) replaced with autolite and, problem sloved

 

[Marccus]

I just had new cats installed about 4 months ago in order to pass smog check. And the plugs are the correct Autolite plugs that everyone uses for the SHO so I think I'm alright there also. Plus it runs fine in neutral - no engine problems.

 

[jayro]

I Plus it runs fine in neutral - no engine problems.

In neutral there is no (or very little) load on the engine. With oil in my plugwells my car would run fine in neutral, but the second a load was added it ran terrible. It sounds like something came unplugged or a ground came loose. If something came loose that allows air into the engine post MAF this could happen also.

 

[220ksho]

Sounds to me like something is happening when the engine leans back (in forward gear under load). Check to make sure the DIS module isn't too close to the dampener mount and that it isn't cracked. This could mean that your rear subframe mounts are loose, or an engine mount is compromised.

Engage the parking brake and put the car in gear, ease up on the clutch and watch for excessive engine movement and any interference.

Hope this helps, it happened to me...

 

[Marccus]

I have aluminum subframe mounts and shonut reinforced motor mounts. But it rode perfectly for 260 miles from San Jose to Bakersfield, CA, so it seems to me that it's not motor mounts or subframe mounts, but that a sensor or the PCM went on me once I finished the trip.

 

[Frisbeeguy]

Thanks. I'll try a new Camshaft Position Sensor.

Rockauto does not list this part.

Where can I buy a new Camshaft Position Sensor online?

The good one I got from NAPA. The one that was not good was from O'Reilly's.

Here it is at RockAuto: http://www.rockauto.com/catalog/raframecatalog.php