Poorly running 89 mtx

[milehigh89mtx]

After getting the car back from the alignment shop after some extensive suspension work, I was having some problems with the engine. Poor gas milage (about <10mpg), running about ~80% hp according to my seat-of-my-pants dyno, occasional backfire through the intake, sputtering/bucking under load and while keeping steady. Seems okay after secondaries open at about 4k rpm, but I have been trying not to push too hard. No oil or water in plug wells, wires all seem to be firing, all vacuum lines seem to be intact. I cleaned the MAF and got new 02 sensors about 100 miles ago. I ran the self-test, and received some sporatic codes.

KOEO- 11 System checks OK
Stored- 63 Throttle Position Sensor (TPS) signal too low TPS 66 Vane Air Flow (VAF) or Mass Air Flow (MAF) signal low - VAF MAF Transmission Oil Temperature (TOT) signal low (possibly grounded)

KOER- 12 Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too low) - ISC

Cylinder Balance- 9 System checks okay

I don't know if this will help, but the day after it started running rough, I needed emissions, and it passed as such: HC GPM 1.4 Limit 3.0; CO GPM 7.0 Limit 20.0; NOx GPM 2.9 Limit 6.0; CO2 GPM 379.4

I don't have a whole lot of money to throw at it right now, so I've parked it for a while. Any help to test/diagnose the problem would be appreciated so that I can be halfway sure before I throw a bunch of parts at it. Thanks!

 

[jessemachone]

Oil in plug-wells?

 

[haggarSHO]

replacing the tps should fix your bucking/sputtering and the backfire - I had the same problem. but I didnt get the same code.
they're only like $20-30 i think.

 

[Mels]

When mine was doing the exact same thing, it ended up that after a couple years my Pro-m 75 had gone bad.

Put the stock MAF back in, reset the computer and haven't had that problem since.

If you were closer I'd lend you another stock maf to try.

Maybe try gently cleaning yours, mine ended up being the electronics.

 

[milehigh89mtx]

As I said, I did clean the MAF. I used brake parts cleaner, should I try with carb cleaner or electronics cleaner? While trying to diagnose, I did try driving with the MAF unplugged with no change. Could that point to a failed sensor? Where could I get a replacement, and/or which upgrade is recommended? In regards to TPS, A few times I got the code 77 - Goose test not received, until I re-read the directions. After that I didn't get 77 anymore. Could the problem still be the TPS, because it would be awesome if that was it. Cheap+Easy= Happy Birthday Boy.

 

[milehigh89mtx]

Round Two......

Okay, so I pulled all of the spark plugs, and I did find a little oil in the plug wells, but I don't think it was enough to cause misfiring. I changed out the MAF and coil pack with some junkyard items, and converted the "cone" filter back to the paper one with the air box. I also did a compression test, with over 160 in all cylinders. My fuel economy has improved, and so has my idle. The sputtering is still there, and I still feel a lack of torque, and I am still getting popping/backfire through the intake when taking off from a start. After pulling codes again (after clearing), I got 12 - Idle Speed control not working properly, idle set too low. I was going to try a new TPS, maybe new CPS. I am going to change plugs and wires after replacing valve cover seals/pllugwell seals. Any other ideas?

 

[SHO#7]

IIRC backfire through the intake is due to a lack of fuel and a backfire out the tailpipe is due to too much fuel. I do not think you have a fuel delivery problem, but dont rule it out. A fuel pressure test would surely not hurt. Most part stores will lend you the tool.

Are you resetting (sp) the computer after you replace parts.

Try to run it without the maf plugged in too. See if it runs better.

Mike

 

[93rev2sev]

Things to check...

Unplug the MAF...it's the best way to tell if your issues are MAF related. You problems will be magicly gone if the MAF is the culprit.

Explain HOW you cleaned your MAF. Did you remove the sensor? Did you spray off the the little wires? Brake cleaner is NOT recommended for cleaning the MAF. I'll be very surprised if unplugging the MAF does not help.

 

[milehigh89mtx]

I got a junkyard MAF out of a thunderbird (matching part #'s), cleaned the wires on sensor itself and plug connections with electronics cleaner, dabbed some dielectric grease on plug, no improvement. Drove with MAF unplugged, no diff. Could I be looking at a TPS or CID? Or would it throw a code? I dunno, my wallets on a bit of a diet, so I guess I should save up for VC gaskets/SP well gaskets/plugs/wires, huh?