Very odd problem -- can't find the solution. Help!

[Kindred]

All right, here's what's going on. When I tap the gas pedal ever so slightly from an idle, the car revs up to about 1500, sits at 1000 for several seconds, then finally drops back down to normal. It makes driving kind of annoying, because when I pull it out of gear, the engine again drops down to 1000-1500. The car stumbles badly under a light foot, but seems to drive better if I'm rough with it. There is much less power between 2-3k rpm, but from 3500-5500 the car accelerates the same as it always has. I've also noticed at highway speeds that I seem to have less power at full throttle than half throttle. If I'm cruising at around 80 and I floor it, the car will lose power, but I'll ease right back up to 80 if I let up off the gas.

I've changed the O2, fuel filter, and TPS, no fix. I've experienced no loss in fuel economy. It seemed to me like a vacuum leak, but I've checked the lines with starter fluid and tried capping them off one at a time with no change in performance. It does not backfire, but it does idle a bit rough. That could be related to my capping off the throttle body coolant lines. There's some chatter coming from under the hood, but I'm thinking it's just valve lash as it usually goes away when the engine has some time to warm up. The plugs and wires are less than a year old. I replaced my head gasket at the beginning of this year with no problems until recently (the last month and a half). Timing, sensors, etc...what can it be? Any ideas?

[bbrown]

I'd focus on the carburetor next.

[gdawgs]

Sounds like it's fuel injected to me.

It sounds fuel/air related to me rather than electrical(spark electrical) although you shouldn't rule it out. Just because plugs and wires are new, doesn't mean one can't be bad. I've seen plugs go bad shortly after installing and have even seen them bad right out of the box.

Double check for air leaks between the air filter and throttle body(another good way to check for leaks is to use a propane blow torch, just open the valve (but don't light it), if the propane gets sucked into the engine, it will speed up. Not as messy as liquids).

I'd yank the plugs and take a peek as well. Plugs are cheap, could just replace right away.

Could also be a loose/bad connection somewhere. I had a Neon(POS) that had a bad connection at the wire harness going into the TPS. Had to bypass it, then it ran great.

How bout a plugged Cat or muffler. This could also create the full throttle symptoms that you have.

[Kindred]

The car's fuel injected. My cat and muffler are both punched out. I still have yet to check the timing or plugs, but I'm on vacation this week and I'll probably break into the engine bay tomorrow afternoon. I'm wondering if it might be my ECU. I've been running with an alternator that's been dropping voltage. I know older electrical components are sturdier than the ICs of today, but I'm not sure how much. If my voltage dips to 9-10V on a regular basis, will that cause damage to the ECU components?

[gomer]

Low voltage will cause erroneous operation (voltage mods are a typical method to induce "glitching" into processors) but generally won't harm automotive circuits... Festy's have "old style" alternators that can run 100% duty cycle ,, what is really dangerous is running a car with a low duty cycle "computer controlled" alternator (most are 20-25%) with a battery that can't maintain a charge ... you'll fry the alternator in that case.

[Kindred]

All right, I went out and did a once-over on the car. Plugs all look good, though a little on the lean side. Crank pulley looks like it's wobbling a little bit. I tried tightening the nut, but that didn't fix it. It's probably a warped pulley because there's no oil leakage. That would explain the intermittent rattling sound I hear as well, since it doesn't sound like valve lash. Checked the vacuum tubes again with a bottle of propane, nothing. Fuel pressure is 1-2psi on the low side, but barely within tolerance. Made sure everything on the intake was tightened down. Coil is good. All four wires are getting good spark.

Any more ideas? The problem hasn't gotten worse yet, but I need to tackle it before it does. It's my only transportation and I've got to do a lot of traveling next month.

[Kindred]

I've been told that if the fuel pump is running one or two psi below the rated limit, it can cause the car to run like shit. Is this true?

[mechanicaldj]

Just for giggles , check the idle air control valve to the drivers side of the throttle plate on the lower intake manifold, for vacuum leaks and try cleaning the air valve side of the motor with gum cutter or even unplug it and see if there is any changes.

[getitqwik]

WHEN it DIES keep me in mind, I buy junkers. getitqwik@hotmail.com As far as solving your problem, I know there are many people on here that jump to other areas but in my humble opinion, you need to disconnect the MAF connector and on the side with the rubber boot on the wires you need to peel the boot down without tearing it and push the individual wires all the way back up to seat in the connector. THEN connect back to the stationary side of your connection and after you have in place, push the rubber boot back up snug and remove all the mess you made trying all the other repairs....start the car. Should run better now. The connections for the MAF are now solid and it will do what it was designed to do! If you are really bored you can clean both sides of the electronics connectors with ELECTRONIC CLEANER only, however the problem is that one or more of the wired slipped down. Let me know if you got it going.

[Champ 98]

Had the same prob a couple years ago with our 1991 1.3 fuelly, had replaced damn near everything including the fuel rail and it turned out to be a sticking MAF, simply remove it and check it for smooth operation then lube it with WD40.