Good Morning Everyone,

So...

I've got a 1997 Ram 1500 4x4 with the 5.9l V8. When I start it, it stalls out immediately. No chugging or anything else, the RPMs just drop off and it doesn't recover. It runs fine, but I've got to work the brake and throttle pedals at the same time. I have replaced the IAC previously. Before, it would be a year or so between failures. This last time was about 2 months before it started doing it again today. After seeing the pattern, my question is:

What is the background issue? What are the other potential causes for the premature failure of the IAC? And the other potential issues that could be related?

I turned the key 3 times and got these codes, in order, as presented:

12: Battery Disconnect
Direct Battery input to PCM disconnected within last 50 ignition key-on cycles. Normal if battery has been disconnected, otherwise check battery power and ground connections.

25: Idle air control motor circuits
A short is detected in one or more of the idle air motor circuits.

21: O2S Stays at center
O2S shorted to voltage
O2 sensor does not detect rich or lean condition, or O2 sensor input voltage too high. DRB will indicate which side with dual sensors. The O2 sensor signal should fluctuate under normal conditions.

25: Idle air control motor circuits
A short is detected in one or more of the idle air motor circuits.

55: N/A
End of message code. A DTC 55 is used to end all DTC messages. This code does not show on the DRB tool and indicates a completion of the stored codes on the Malfunction Indicator Lamp (check engine lamp).

That spawns another question: Why did I get 25 twice? Are there multiple IACs present?

Any help would be greatly appreciated.

V/R,

Jason


Second, I looked at the air filter, and there seems to be oil blowing on it. I've read in other posts about the plenum gasket leaking and causing idle/stall problems. Could this be the case?

 

Only one IAC. Two circuits on it though.... (not sure if that matters for the code though) There are four wires that go to it from the PCM. Somewhere along the lines, one (or more) of those wires is shorting out. That will give you some odd idle issues, as the PCM will not be able to control the IAC correctly. Fortunately, it's a relatively short run from the IAC to the PCM, so, tracing out the wires, and checking for problems isn't too much of an exercise...... If you don't already have it, grab the 96 service manual from the faq section here, it will have wiring diagrams for ya, to make life a little easier.

You have a dead O2 sensor. Need the P code to determine which one. (pre- or post- cat.)

 

Killer. Thanks. I've got the Haynes manual. Now, I just need to learn to read wiring diagrams....

Also, if the wires test out OK, I plan on doing the plenum gasket anyway (yes, I've read the end-all be-all plenum thread, but I didn't see it if it's there), could that be a potential cause of the oil on the air filter and/or the premature failure of the IAC?

 

Nah, plenum being bad may gunk up the IAC passage, but, that's about it. Oil on the air filter is more likely due to a bad PCV valve, or..... excessive blow-by.....

 

Ick. I suppose I'll have to check that out.

 

I had heard that the PCV valve ahs to be sourced from the dealer. Is that true? Are there problem with parts store PCV valves?

 

aftermarket valves do not always have the correct flow rate. PCV valve from dealer is only about 8 bucks..... and it is indeed correct.

 

Hey, thanks for the attention, man. I'm leery of the dealer, because every time I've had to go to one to get a part, it was roughly 4x the cost I would expect. I figured on it costing 20 or so from the dealer.

Also, I get a kick out of seeing someone address you by your forum handle. I'm not sure why I still think it's funny, but it gets me every time.

 

Yeah, I will grant that the dealer does have a pretty high opinion of the value of their parts....... unfortunately, there are some parts that are best gotten from the dealer.... PCV valve is a cheap example.

Yeah, I planned it that way. LOL

 

I would replace the PCV(cheapest dealer part I have found) and check and clean IAC. Clean IAC port in throttle body as well. IAC is a stepping motor. You can check ohms to make sure it is not shorted or open. Cannot rememebr valuses but should be in manual.

Disconnect battery before doing anything with any electical sesors or controls. This helps reset PCM. Some of the error codes you are seeing may be left over as PCM stores codes also. Resetting will clear this and start again.

Have you downloaded service manual from FAQ/DIY section yet? Good info.

IAC costs from $35 to $50 or so.