running problems/ MAF?

Csirny

Registered User
So after trouble shooting codes for the last few weeks I'm still getting 51(temp sensor) which is a new piece I also tested the IRCM with a tester I bought it was good and the sensor appears to be fine from my ohm testing. Now for code 56 (MAF) I'll spray it down with contact cleaner and it's good for a few days then it's a problem again. I tested the MAF ground and voltage output. Seemed OK. The issue I'm still having is a hanging idle and when I punch it it stalls then goes. ( I'm making boost as soon as I hit it but no increase in rpm some times the RPM will drop off then it will go) I had a friend behind me watching and it puffed black smoke. I have no modification to the fuel system. Stock throttle body and MAF housing. The car is a 1990. I'm getting really frustrated and could really use some more help with this. I've tested everything that was suggest in my previous post about the issues with the codes. Please help
 
Tell us about your air filter....stock paper, recently cleaned and oiled K&N, none... ?
 
Hi KMT.
Thanks for still reading my posts. This car keeps out smarting me. I started drinking more. just feeling defeated here.
Anyway the air cleaner is a k&n knock off that came with the ebay special cold air intake. Its fairly new. one thing i did find out on accident is the car seems to run a little better (the idle is lower. still hangs a little then falls to normal) with the vacuum actuator on the intake plenum going into the engine unplugged. originaly i noticed the vacuum line not connected and plugged it (wasnt sure where it came off of yet) than today I was looking and noticed it came from this actuator. after i connecter it the hesitation was much more prominent and the idle would jump to 2000/2200 and then slowly fall off. The actuator pulls wide open at idle while connected, if this is correct i dont know. anyway I plugged it again the idle might bounce to 1500 and then fall off to 800 alot faster than with it plugged in. also the car runs with no problems cold and for about 5 minutes until these issues start showing. im not sure how the computer works with this but im guessing its running some kind of pre set or closed loop programming.
 
The reason I asked is, the deal w/the filters that can be cleaned/oiled is that there can be a risk of excess oil bathing and contaminating the sensor wire in the MAF. It's simple enough reach in with filter removed and spray a compatible cleaner to spruce things up.

That actuator is the boost bypass. Vacuum pulls it one way to allow defeat boost at idle, part throttle - no vacuum and it moves the other way, allowing boost to build. If the actuator isn't doing it's job, you can experience bucking... And yes, it should pull all the way at idle. If the diaphragm in the actuator is leaking, you'll have a vacuum leak which miiiiighttttt affect idle. If it was totally blown out, tho, it wouldn't pull.
 
Thanks for the input. The air filter is untouched by me. It's the way I bought it. I'll try hooking a vacuum pump to the actuator tomorrow and see if it holds vacuum. I am a little suspicious of this piece because of the lower idle with it unplugged. I'm thinking I should double check all my vacuum lines as well. Thanks again for all the help. Ive been learning a lot about trouble shooting these cars from reading your responses. I'm trying hard to get everything running well for the auto-motion car show in Wisconsin dells at the end of may.
 
So far so good. I checked the actuator this afternoon and it seems good. The only thing I do different was I disconnected the battery for a while I got about 30 miles on the car with no problems so far. Will see if it lasts
 
Still running good! I finally got code 51 cleared ( temp sensor) I replaced the sensor again. I think the first was bad. (Seems to be my luck with parts from the auto parts stores out here lately) The fan would turn on high as soon as the guage would get past the blue mark. Now it comes on at M on NORM. I checked with my IR thermometer and that's about 210* I believe this is the low speed also. Now well driving my temp hangs right around the middle of the guage. Not use to seeing the car run this warm it never usually got passed the first white mark. Everything is running good and no CEL though.
 
i see alot of us mn12 owners in WI...........kinda nice when i cruise and run into a few..god, i gota get another mn12 v8
 
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