Hi all, over the last year or so, my year 2000 Grandeur (XG300) has occasionally popped up the CEL with the following effect on the car:

1. Car still drives normally, but when stopped and in park or neutral the idle speed goes up from the normal 700 or so rpm to around 1100.

2. Strong smell from the exhaust like unburnt fuel (smells like coal/coke burning). Engine is obviously running on a VERY rich mixture.

3. If I turn the engine off and wait for 20 seconds or so I can re-start and all is back to normal with no CEL until the next time.

Just recently this has been happening more and more often to the point where I've taken it to my service center (not Hyundai, but very capable) and they have found the following codes:

P1159 Variable Intake Motor Malfunction / MAF sensor?

P0100 MAF sensor?

They replaced the MAF sensor but the problem persists.

The air cleaner is almost new and the intake manifolding etc has been tested for leaks etc.

The car has only clocked up 82000 klms and is generally in great condition

I've noticed that the CEL will reliably come on within 2klm of a cold start, indicating that the warming up process can cause this error.

Also, the fault can be reliably induced by a prolonged (more than 7 - 10 secs) downhill run. In other words, throttle closed and high vacuum situation in the intake.

Has ANYBODY had the same symptoms as above and are there any other components that could be causing this.

Thanks for any help you can give!

Rick

This post has been edited by Essex: Jan 26 2010, 10:44 PM

I'm new to the XG (Just bought a 2002) and car maintenance/repair in general (first car), but I'll throw some ideas out and see if they help.

(I'm a total computer geek, so hopefully my troubleshooting skills will transfer.)



Suddenly rich + check engine light = confused powertrain-control module.

- sensor acts up, so PCM has to guess the fuel flow
- PCM guesses rich to protect the engine (better to run rich than lean)
- reboot causes the PCM to check it's sensors again. If the sensor is only intermittently bad, the engine will run fine. (suggests wiring problem, hopefully just a loose or dirty plug)



Reliably? Yes! That's great news. (In the computer world at least it's called a "reproducible" problem.) The next thing I'd try to do is plug in a laptop-based scanner, start logging sensor values and record one or more cold starts and a couple down-hill runs. Try to make it happen on tape so you and your mechanic have more information to work with.



Good news: http://hmaservice.com has troubleshooting guides indexed by problem code. All you have to do is register, sign-in, and click "DTC."
Bad news: it only goes back to the '02 XG. Hopefully it won't be too misleading.

(On the 2002 XG350)

P1159 means that the ECM cannot get confirmation that it has successfully changed intake geometry. I'm not sure that would be enough to make the engine run rich, but it's probably worth a check, especially since the motor is easy to get to and you've already replaced the MAF.

The '02 manual doesn't have an entry for P0100, but -1 -2 and -3 are three different MAF sensor checks. A failure here would definitely require the PCM to guess what the correct fuel flow should be--without the MAF it doesn't know how much air the engine is getting.

Best of luck.

Thanks for detailed reply wildweathel, I reckon you're on the right track with...

"P1159 means that the ECM cannot get confirmation that it has successfully changed intake geometry. I'm not sure that would be enough to make the engine run rich, but it's probably worth a check, especially since the motor is easy to get to and you've already replaced the MAF."

That's where I'm gonna go next!