AIV/Air Flow question

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

LACropCircles - 11 Mar 2004 06:12 GMT

I have a 1988 300ZX Turbo GLL that seems to be running sluggish with boost
around 4.5 to 5 pounds. It seemed as though the car was not 'breathing'
correctly. It just had that feeling like it was not getting what it needed
to get up and go. I took it to my trusted mechanic who informed me that it
was a 'contaminated' AIV (he explained it as the device going to the
air/flow meter). He told me that it goes hand-in-hand with the air/flow
meter and both should be replaced at the same time. He explained that this
could be the issue with performance, mileage (I get about 280 to the tank
full) and idle (I am experiencing a low idle of 600 revs). Before I spend
$200 on an AIV and $200 on a rebuilt a/f meter, I was wondering if anyone
had any sage advice on this matter. Do I really need to replace both? Is
this AIV responsible for all of these symptoms? Any help is really
appreciated.

Thanks-
Erik

Reply to this Message

Steve T - 11 Mar 2004 22:51 GMT

> I have a 1988 300ZX Turbo GLL that seems to be running sluggish with boost
> around 4.5 to 5 pounds. It seemed as though the car was not 'breathing'
[quoted text clipped - 7 lines]
> $200 on an AIV and $200 on a rebuilt a/f meter, I was wondering if anyone
> had any sage advice on this matter.

He speaks the truth, a bad AIV valve puts exaust gas through the AF meter
and ruins it.

> Do I really need to replace both?

Yes

>Is this AIV responsible for all of these symptoms?

The AF meter being contaminated can cause these symtoms, the AIV valve
doesn't make it run bad, it ruins the AF meter and the bad AF meter makes
the car run bad.

BTW 4.5 to 5 lbs of boost isn't enough. I believe stock boost is around 7PSI
and they can safely take 9-10 PSI.

Signature

Steve

http://www.atlantaracing.com

Reply to this Message

R.M. - 12 Mar 2004 04:38 GMT

> > I have a 1988 300ZX Turbo GLL that seems to be running sluggish with boost
> > around 4.5 to 5 pounds. It seemed as though the car was not 'breathing'
[quoted text clipped - 29 lines]
>
> http://www.atlantaracing.com

I agree with Steve. The AIV valve assemblies in these cars can get moisture
in them. When this happens, it can have a negative impact on the engine's
low speed idle. In fact, it can cause the vehicle to fail some states' low
speed idle emissions test.

R.M.

Reply to this Message

Steve T - 12 Mar 2004 21:39 GMT

> I agree with Steve. The AIV valve assemblies in these cars can get
> moisture in them. When this happens, it can have a negative impact on the
> engine's low speed idle.

Also the reed valves inside them start leaking and basically act sorta like
an EGR valve but put the raw exhaust gas through the AF meter! It's not
pretty. :-) I'd never replace an AF meter without doing the AIV valve too.

Signature

Steve

http://www.atlantaracing.com

Reply to this Message

LACropCircles - 15 Mar 2004 04:36 GMT

Thank you very much for the responses. I really appreciate that. I will
certainly get both done at the same time. Would the AIV or A/F meter rob me
of power or give me intermittent hesitation issues? The performance for the
88 Turbo seems to be less than my '82 turbo.

> > I agree with Steve. The AIV valve assemblies in these cars can get
> > moisture in them. When this happens, it can have a negative impact on the
[quoted text clipped - 3 lines]
> an EGR valve but put the raw exhaust gas through the AF meter! It's not
> pretty. :-) I'd never replace an AF meter without doing the AIV valve too.

Reply to this Message

Steve T - 15 Mar 2004 00:01 GMT

> Thank you very much for the responses. I really appreciate that. I will
> certainly get both done at the same time. Would the AIV or A/F meter rob
> me of power or give me intermittent hesitation issues?

The AF meter.

Signature

Steve

http://www.atlantaracing.com

Reply to this Message

LACropCircles - 19 Mar 2004 20:09 GMT

okay. so I replaced both units and it runs much better. For some reason, the
boost went up a little and the acceleration is equivalent with the 280ZX
Turbo. One would have thought that Nissan would have built something to beat
its predecessor. It still boggs at lights and the idle seems to be pretty
low. Yet performance and mileage seem to be better. It runs quieter too.

1) Why would my boost have increased a little?
2) Is this thing supposed to be faster than the 280ZX Turbo or was that car
an exceptional car?
3) Any ideas on the lower idle and occasional bogging?

Thank you again for the knowledge.

> > Thank you very much for the responses. I really appreciate that. I will
> > certainly get both done at the same time. Would the AIV or A/F meter rob
> > me of power or give me intermittent hesitation issues?
>
> The AF meter.

Reply to this Message

Steve T - 19 Mar 2004 21:28 GMT

> okay. so I replaced both units and it runs much better. For some reason,
> the boost went up a little and the acceleration is equivalent with the
[quoted text clipped - 4 lines]
>
> 1) Why would my boost have increased a little?

Maybe it was running so poorly it never got the turbo against the wastegate?

> 2) Is this thing supposed to be faster than the 280ZX Turbo or was that
> car an exceptional car?

It should be faster than a stock 280ZX turbo. Turn the boost up! The engine
can handle a lot more than stock boost levels.

> 3) Any ideas on the lower idle and occasional bogging?

If the idle is too low it will bog. Is the timing set right? The flat side
of the dist cap should be parallel to the intake plenum.

Signature

Steve

http://www.atlantaracing.com

Reply to this Message