My Engine Has a Bad Miss! And it's WEIRD TOO!

[SHO_ROLLER]

Ok, here's the story. About a week ago, my alternator went. I had it replaced but when I got the car back, it missed between idle and 2400 RPM's under heavy throttle in 2nd through 5th. I thought it might need some fuel system cleaner so I ran a bottle of Slick50 through it. It seemed to clear up, but over the past 2 days, it does it REAL bad in all the gears. But get this, after 3900 RPM's, it clears up! I don't get it. Now, keep in mind I haven't changed my fuel filter in about 70K miles . Someone PLEASE give me an idea of what this might be! Oh yeah, to top it all off, my TOB went and my flywheel seems to be missing some teeth!! :grits teeth: but I really love this car...............

Thanks in advance for any help

Anthony

 

[Dr. Tweak]

Plugs/wires?

 

[DHMag]

Plugs/wires?

or oil in plug wells ?

 

[SHO_ROLLER]

or oil in plug wells ?

Nope, just checked 'em

 

[JaySHOguy]

Check the plug for the MAF sensor.

My '89 had worked itself loose, but still looked like it was connected.

Unplug it, plug it back in.

May help to clean the MAF with some Electrical Motor Contact cleaner, too.

 

[GR8WYT]

Code Reader

Check the codes. Beg, borrow or buy a code reader. You can get one from the local parts store for under $40.

I had a similar problem recently and it turned out to be plug wires.

Good luck.

 

[BeautifulDisasterSho]

I replaced my alternator not too long ago because it was bad also. The car ran fine for a while but then started missing like mad throughout the powerband. It ended up being a bad battery causing the computer to not work correctly. Check that maybe.. good luck!

 

[Off Road SHO]

At 3900 your secondaries are opened by the computer telling the IMRC (intake manifold runner control) to block off the vacuum from the plenum from going to the two vacuum actuators that reside on each side of the intake. With out that vacuum present, the shaft springs are free to snap open the butterfly valve secondaries. I would check to make sure none of the vacuum hoses are pinched cut or loose. Also check the one way vacuum canister on the back plenum, It can only be plugged in one way for it to work properly. If you take it out and shake it and hear something rattling around inside, the one way valve flapper has snapped off. Replace it.

Also at 3900, I believe your computer tells the fuel pump to run at full speed. You might not be getting full pressure at the injectors (because of a plugged filter), until the pump cranks up to full.

I watched a gas pump company service the filter in a gas pump once and was amazed at how heavy the old filter was (about 15 pounds!). When I asked about it, the service guy said it was all sediment from the tank, and that when the gas filter became too clogged, it went into by-pass mode, just like an oil filter. I now change my fuel filters regularly, whether it's needed or not.

Tom

Good luck

 

[BeautifulDisasterSho]

The secondaries actually open at 3,950 with a slight delay so 4,000.

If it's a miss it's probably electrical. But if it's just a lack of power then change the fuel filter first because it has a lot of miles on it.

 

[FrOsTyShO]

The miss your having sounds exactly like what i had. I tried two different sets of plugs and checked everything possible. On my car it would miss below when the secondaries opened in all gears and then be fine in the upper rpm range. It didn't miss if i just barely hit the accelerator down. What fixed my car was i had a bad TPS. Didn't throw any codes for the tps, just other ones such as bad pcm and other things not related. It actually turned into on my car that after i tried the plugs the car woudn't start at all. So i unplugged the tps and the car started up. If your car is running i wouldn't reccomend driving with the tps unplugged. Do as the others above me said and then try replacing the tps. It's cheap and might be the culprit.

 

[FrOsTyShO]

Check out the thread i posted ~~~>

http://www.shoforum.com/showthread.php?t=7288

Try all of the suggestions the guys gave me.

 

[SHO_ROLLER]

On my car it would miss below when the secondaries opened in all gears and then be fine in the upper rpm range. It didn't miss if i just barely hit the accelerator down. QUOTE]

Yep, that's EXCATLY what my car is doing! Where can I buy a TPS and how much do they cost?

Anthony

 

[masho95]

You should really check the TPS with a multimeter before replacing it for no reason. Probe the output wire while slowly opening the throttle body. The TPS should read from ~.6V to ~4.5V If it doesn't drop to zero volts anywhere through the throttle body plate opening then the TPS is ok.