Diagnosis steps & tools?

[thergen at svn.net]

I had a similiar problem -- hunting/unstable idle only when warmed up on
an '87 2.8 Cavalier (MAF).  It turned out to be the O2 sensor. Clean the
IAC passage and pintle also.

Funny, the O2 sensor was not even in the $800+ list of things to replace
as suggested by the Chevy dealer after 1.5 hours diagnostic time ($).

Tom

On Mon, 8 Feb 1999, Terrill Yuhas wrote:

> 
> I have a '90 Chevy Beretta with the 3.1L V6 that I'm looking for some
> diagnostic suggestions.  Basically when the engine is warmed up, it hunts
> for an idle.  It never stalls but it sounds like it's misfiring.  I'm in
> the process of figuring out which scantool to get so I took it to the
> shop.  Mr. Goodwrench ran some diagnostics and said everything was fine.
> I took the service advisor out for a spin and showed him what it was
> doing.  His reply was that this is something that is designed in.
> 
> The biggest problem is I'm now getting close to failing idle emissions
> tests so I figure this isn't really a "designed in" idle hunt.  Rather
> than chase it with parts, I'm looking for any suggestions on where/what
> tools to get so that maybe I can see what's going on.
> 
> I don't know which scantool is adequate.  I was looking at either the Auto
> Xray or the Actron Scantool.  The others I saw were thousands of dollars.
> Not knowing what a "Mr Goodwrench Diagnostic" consists of, I wonder if any
> of those hobby scantools would tell me anything.
> 
> I also looked at the Diacom but I always get ten-year-old brochures when I
> contact them for info.
> 
> I've been toying around with EFI for a little while, so I figure this will
> really get my feet wet!
> 
> Thanks,
> 
> Terrill
>