follow up to stalling Topaz

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Pdigmking - 04 Mar 2006 18:35 GMT

I'm getting multiple fault codes from an 89 topaz (2.3 with
airconditioning) Here are the codes:

13 RPM idle out of range/low:
cant control idle vachum leak,TB base idle off,idle air valve dirty or
bad, EGR stuck open
idle out of spec same as code 12

31 EVP or PFE circuit below minimum voltage
Bad EVP/PFE sensor, no exhaust backpressure (really doesn't really cause
problems) or inopperative EGR

42 HEGO (HO2S) sendor voltage high / system rich
Bad O2, bad MAP sensor, Bad fuel regulator, Leaking injectors,
restriction in fuel return line,
clogged exhaust lowering vachum

70 ECM failure
Data communication link error, bad ECM

73 Insuficiant throttle position change
No change in TPS signal, no dynamic response sets this.

95 Fuel pump secondary circuit fault
Fuel pump monitor has seen a fault in the fuel pumps or circuit

I'm wondering if I really have all these problems or if I just have three
problems. Assuming I don't have a vacuum leak somewhere (I'll test that)
I'm wondering if a bad MAP or O2 sensor could cause the ECM code?

Could anything other than a problem with the fuel pump cause the code 95?

How do you test an EGR valve?

And what exactly is a EVP or PFE sensor? I can't find a definition
anywhere.

Thanks in advance.

Paul.

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Happy Traveler - 04 Mar 2006 21:51 GMT

> How do you test an EGR valve?

It's a very simple device, operated by vacuum. Apply a handheld vacuum pump
to it and check that it doesn't leak. If you remove it, you can actually see
the valve opening when you do that. On the vehicle, fully opening the valve
will dramatically affect idle, probably causing the engine to stall. If you
don't have a vacuum pump, you could probably find an unused port on the
vacuum manifold and briefly hook to it, or put a T into another vacuum line
(just make sure not to cause a big leak in the process). If there is no
response from applying vacuum to the valve, the passageways are clogged, or
the valve doesn't work. The former is much more likely, as the older EGR
systems were prone to carbon deposits. If your 89 Topaz has never had the
EGR system serviced, you can bet that it's badly clogged. Take the valve
off, and do your best to clean the mess. You may need to remove the adapter
as well (which probably requires removing the throttle body). If you see a
lot of carbon, the valve itself will most likely be clogged too, and unable
to fully close (if really bad, this may be causing your code 13 ). With a
lot of patience and a handheld vacuum pump you can hold it open and scrape
inside. That's what I used to do. Or simply get a new one - probably around
$30 in auto stores.

> And what exactly is a EVP or PFE sensor? I can't find a definition

anywhere.
The EGR valve operates in closed-loop mode. This means that there is a
mechanism which senses what it's doing. Essentially, there are two ways:
position (EVP) or flow/pressure sensing (PFE, later changed to DPFE). EVP is
a potentiometer that simply measures how far the valve opened. If you have
it, you'll notice a small plastic cylinder (about 1" in diameter) on top of
the valve, with a 3-wire electrical connector. They rarely fail, but
everything is possible... Check that the connector is intact and the
contacts not corroded. If you have PFE, there will be a thin tube attached
somewhere along to the EGR flow path, leading to a sensor, possibly mounted
on the firewall. No experience with PFE, but its newer brother, the DPFE is
prone to failure (electronics and hot corrosive gasses don't mix too well).
Your code 31 may be due to a bad PFE, if your vehicle is equipped with one.

Hope this helps a bit.

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