IM already removed? Time to clean the EGR passage

Figured i would try posting the whole story to see what you guys think.

My son just bought a 1996 mx6 ls with 140,000 miles with automatic transmission. He got in the car in the morning and had a check engine light. He went to Autozone to check the code. On the way, the car, for a moment, hung up and would not shift past 2nd or 3rd. RPMs shot up then it shifted fine. It did not happen again. Autozone checked the code and said it was an intake sensor. Autozone dude sprayed some cleaner in the intake. He sprayed maf air flow sensor cleaner on the mas air screen. Car was off when he sprayed the cleaner and cleared the code thru the checker.

Check engine light went off and stayed off. He went to play golf. The car sat for 6 hours at the golf course. When he got in it to go home the check engine light had returned and the car was hanging up in 2nd/3rd again. It would not shift and just kept reving up. So he drove it home at about 35mph. He tried it a few more times later in the day, with the same result. He checked the tranny fluid to find it low, so he topped it off. Then tried the car again. Same result. So he took it to a shop. The tech said the code was for the map/boost/baro sensor. The tech said the car went into limp mode and it would not allow the car to go past a certain gear/speed. He called around and the part was not available from any of the parts stores. So he called the dealer and it was $350.

He found the part on Ebay, ordered it, installed it. Disconnected the battery to clear the codes.... Now the check engine light has stayed off for now, but the car will still not shift past 2/3rd. It just climbs in RPMs. He is taking it back to the shop now, but I want to know is this common with this sensor. Could the new one be bad and just not throw a code yet, but keep the car in limp mode?

So my question is this? Do the symptoms match the part failure? Could it be the sensor? Or could it be what I have read in searching... the passage to the EGR could be caked with carbon? Or willl carbon in the intake always throw a code! I want to try to help him, but he lives over an hour away. So any suggestions you have would be awesome. I hate for him to just change the sensor and neglect the passage if it causes the same symptoms.

Thanks you guys!

Yeah I did the same thing yesterday, I opened it up to find it so badly built up with grime and gunk in there it was incredible, isn't the best idea to spray tb cleaner into the actual intake because obviously yeah it'd just pull off all the grime in chunks and would just cause further problems, but scraping out all that stuff is a good way to go, i used some tb cleaner to help me get most of it off

Heres my picture of how it was when i opened it up, the side that i pulled off was actually almost twice as bad as this, but i didn't get a photo..




Pretty damn bad.. She runs alot cleaner now that i've cleaned it all up though

Looks familiar. Just did mine a few weeks ago. It gets on these and the throttle body facing the same way.
Is this all coming from the EGR exhaust gases ? I didn't notice any change in performance, but EGR
systems seems happy.

Take it slow if you've never done car work before. Don't damage any very (very) delicate aluminum threads. Don't crack plastic pieces, after all these years they will break easy. Don't pry anything unless it's a last resort.

First, make extra sure you've removed all the bolts that are preventing separation of the parts. Get a printout of an IM removal guide, try to think of what you might be doing wrong before you go breaking something. Try to find the factory repair manual (it is not too terribly hard to locate a link via google) and see what info it can give you.

Spray some penetrating oil on the parts and let it sit. Get a plastic deadblow hammer (or something like it) and tap with some force all around. Spray more oil. Hit it again with a just bit of force but make sure the bolts are NOT ENGAGED WITH THE THREADS when you do this, i.e. they are backed out of the hole.

And, yes, you remove the accelerator cable. You use one hand to rotate the throttle cam it is attached to, maybe one half turn. Look carefully with a light and you'll see that on the end of the cable, there is a little metal cylinder that slides into a hole on the throttle cam goes around. You need to use your other hand to get the cable out of that little hole, you need to rotate that cylinder and the wire will clear a slot on one side of it and slide it on out. Voila.

You will need to install a new intake manifold gasket (set of two) along with a new throttle body gasket. With the intake manifold off, now is an *excellent* time to replace the two O-rings that are on the passengers-side end of the two metal coolant pipes that sit right smack in the middle of the engine underneat the IM. Those O-rings will leak coolant and ruin your knock sensor. You can get replacements at the dealer, or just find a "seal" shop in your town that has many different types of O-rings, if you live in a large city there should be one.

I have a new EGR valve, new 02 sensors, all new hoses, new catalytic converter,
and still am getting high numbers on the test:

Low rpm
HC 136 ppm standard 222 ppm result
N0x 1045 ppm standard 1222 ppm result

High rpm
HC 132 ppm standard 212 ppm result
Nox 945 ppm standard 1075 ppm result

Car runs good, premium fuel, timing is at good at 10 degrees. If you retard the timing
do you get better results ? No check engine light codes on.

I have never changed the PCV valve or those 2 hoses (the short one and the very long one going to the back of the engine). Can that be causing high HC and Nox ? Do those hoses get plugged or narrowed over time by the stuff
running through them ?

The new EGR valve helped a lot to lower Nox, but still not low enough.