2004 XG350L, 124,000 miles. PO only changed the oil. When I got it, it had the Ignition Failure code and tach didn't work.

I know I am on borrowed time with the timing belt..have that kit (water pump crank sensor, alt belt, etc) on deck once I get it running again.

Since both valve cover gaskets were leaking, I decided to change them and the plugs when I replaced that sensor.

I had to replace two coil packs on account parts of them disintegrated upon removal. I also replaced the plug wires.

Since I had the upper timing cover off, I also replaced the cam position sensor.

I also replaced a couple of cracked vacuum hoses. When I removed the throttle body (actuator?), something fell out and went "tink, tink"..but didn't fall onto the ground. I can't find an exploded diagram of this part so I don't know if it was just a misc. bracket or a needed part.

I got everything back together. It starts right away but idles for just about 1 second. Codes are P102 and P113 (low input voltage MAF). I replaced the MAF (just throwing parts at it).

No change. As far as I can tell, all hoses and connectors are connected.

I have went thru it twice, touching everything I removed initially (except for the cam position sensor) and have not found anything.

Help!

I don't know what to do next.

 

The tach gets it signal from or through the ignition failure sensor.
If the sensor fails then no tach signal.

Hope you didn't throw away the used parts yet.
I would try putting the original cam sensor back in if it didn't fall apart when you replaced it.
Also check wiring, connectors, (fuses just to be thorough)

The throttle body ... hmmm ... it is over 800 dollars at the dealer but ebay has it used for much cheaper.
But, would not go throwing any parts at it yet.
The vacuum hoses could have been put on wrong??

As far as I know, the MAF wouldn't keep the engine from running.
But it might not give you power when you step on the gas (in gear)
Could try running it without the MAF sensor connected. See how it runs?

Oh, it could be a wiring problem. Trace wires for open or short.
Could also be a bad ground.
You could use an electrical schematic to help trace the wires from the MAF and the coolant temperature sensor

 

Thanks for the quick reply. I replaced the ignition failure sensor first and there were no codes and the tach worked and it started and idled fine.

Then I went on to the valve cover gaskets and other work.

Unplugging the MAF makes no difference.

I have cleaned the one ground I could find (rear engine bank to firewall).

I will take another look at the vacuum hoses but the ones I replaced are emissions related (from the intake manifold) and were very small.

Next, I will take a look at that cam position sensor. But with the codes it's throwing it seems unlikely that the cam position sensor is at fault. And I will look for that coolant temperature sensor since it is closely related in operation with the MAF.

It's a shame that it was running fine until I started working on it.

 

It appears that whatever fell out of the throttle body was the problem. I ordered a used throttle body (complete) off ebay for $100. Car starts and idles but the throttle was very sluggish and it's obvious (loud hissing) that I have a vacuum leak. Immediately after r/r the throttle body, I still had some error codes. I completely disconnected the battery and up reconnecting and starting, the codes are gone.

Now that it idles, I was able to find the vacuum line from the brake booster to intake manifold was cracked.

The cracked vacuum line looks to be available only from the dealer, got one on the way for $40.

BTW, there are no error codes at this time.

 

That's great news.
Thanks for the update