97 Conti Issues

[germz1986]

Hey guys and gals, I have a 97 Continental.

It keeps throwing P0174 and P0171 (bank 1 & 2 Lean). The car has 102k on it.

I have had some idle problems with it, and some power problems as well. trouble idling at all, or having no power what so ever missing like crazy.

I have replaced the plugs and wires with motorcraft parts, replaced the MAF, Coils, and also the O2 sensors. The fuel injectors are fairly new and have less than 30k on them.

Car is my wifes daily driver, she goes through about a 1/2 tank of gas a week. We always buy gas from the same station. I put a can of Sea Foam in the tank @ every oil change.

Since the coils and wires replaced, have not had any idle issue or lack of power. Still throwing lean codes though.

I have an engine vacuum gauge, I have about 18 in Hg vacuum at idle. I have done a smoke test looking for vacuum leaks, I have found none.

I also have an idle "swell" of sorts, it varies from 850~1100 kind of like if you have the ac on, but it does it all the time.

When its not acting odd, it runs like a top, pulls hard, idles smooth and is generally a great car. But when its not running right, sometimes have a hard time getting it to start and idle, and then once i get it to run halfway well, it has no power, doesn't want to accelerate past about 45mph.

 

[Town]

Your engine has 2 features that may cause your problems:

1. The Idle Air Control (IAC) valve provides a variable amount of air to match engine load and speed at idle. The solenoid can get sticky from deposits and cause a lopey idle or failure to increase engine idle speed under load, i.e. power steering at low speed parking, or A/C turning on, etc.
2. Intake manifold runner control can cause performance problems. The low speed runners (up to 3,000 rpm) are open all the time, and a second runner per cylinder opens after 3,000 rpm when the PCM opens a control valve. Sometimes those control valves can stick so that the second runner is open all the time and lower speed performance suffers. The two runners open at the same time at lower engine speed may cause excess air into the engine and poor performance. Usually there is a DTC set and the check engine light goes on when the runner control mechanism fails.

The throttle position sensor could be worn resulting in the PCM hunting for a setting. This could account for dead spots in acceleration.

Your vacuum gauge reading suggests there is no vacuum leak.

Good luck.

 

[germz1986]

The IAC and TPS are both new. I had to replace the Intake manifold gaskets about 10k miles ago. While I had the IMRC plates off the engine, I cleaned them and lubricated them with Seafoam

Ty for suggestions.

 

[Town]

Did you replace the actuating solenoid for the intake runners while you had it all apart?

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[germz1986]

Hello Town,

I had the car at my lincoln mechanic on saturday. He has determined that the intake is pulling air, I had replaced the intake manifold gasket set when I first bought the car for the same reason. It seems that the previous owner may have gotten the car hot and has warped either the intake manifold, imrc plates, heads or all of the above. I will be disassembling the intake this comming weekend as i cannot get the gaskets before Thursday.

 

[Town]

Thanks for the update. It is surprising that you have an intake leak while your engine is capable of pulling 18 inches of mercury at idle. A warped head(s) will usually show up as a head gasket problem with low compression on adjacent cylinders or a coolant leak/burning coolant or oil in coolant (or vice versa). I cannot see how a warped head would allow extra air or create a problem at the intake gasket and not affect the head gasket.

I was not sure how the intake runners worked on the DOHC so I looked up the procedure. It is different to the 4.6 3 valve engine system. So I attached the intake manifold remove and install procedure.

Good luck.

 

[germz1986]

Thank you town for that pdf,

While the car was at my mechanic he had done a compression check on it, said everything was spot on. I tore it all down over the weekend, will be taking the intake manifold and the imrc plates to a local machine shop for clean up and and inspection, and if need be milling to ensure flatness.

Will report once I have it back together.