I've got a new-to-me 1994 k1500 Suburban with an issue that's unfamiliar to me. When I apply throttle from a stop, the pedal feels very stiff. By the time I give it enough boot to move at all, revs jump up to 1500 or so, the trans lurches into gear and the back wheels skudder a bit along the ground. It takes a LOT of concentration to get it rolling without spinning the rear tires.

Part of it may be related to IACV, my idle is v. low and the idle in gear is almost off the bottom of the tach. But that wouldn't explain the stiffness in the throttle. The throttle does not feel stiff when I'm working it by hand from under the hood.

 

Any ideas why the gas pedal would be so stiff? Surely this isn't normal.

I guess I have other questions too. The tachometer, is the lowest number on it 500? It must be. This morning I went and started it up, cold idle was about 900, as it warmed up it dropped down to about 700. In gear, idle drops down to 500 or less, and I've got a little bit of a misfire whenever its below about 700. Cap, rotor & plugs are on my to do list.

Also (and probably unrelated) the oil pressure sensor (for the dash gauge) is unplugged, I can't position myself where I can see what I'm doing to plug it back in but it feels like the sensor & the plug are not the same size. Are there different size oil pressure sensors (or different oil pressure pigtails) on TBI 350 engines? And will I be able to see what I'm doing with the cap off, or will I need to pull the distributor all the way out to reach the oil pressure sensor?

 

You may have to replace your throttle cable. You might be able to lubricate it and just get away with that. If your pigtail doesn't match the sender then someone put in the wrong sending unit and that is why they left it unplugged!

 

Welcome to the forum.

Cleaning the idle air control valve might solve your low idle problem. It wouldn't hurt to check the throttle position sensor also.

 

I cleaned the throttle body thoroughly and poked around a bit more. It seems a little less touchy, but still fairly difficult to give the engine just a little bit of throttle when starting from a stop. Strangely, it doesn't feel stiff or sticky with the engine off, and I don't have that difficulty when operating the throttle from under the hood. I do think the low idle is making it lurch more than it otherwise might, and the low rpm may be causing the transmission to react also. I have a new IACV ordered, maybe I'll solve all of this.

After scratching my head for a while, and looking at pics online of what the oil pressure sender is supposed to look like, I went out and tried again. And got it to plug in! That booger is awkward to reach. Pressure seems a little on the low side, esp. with this ridiculously low idle. Maybe that's why the sensor was unplugged.

 

Solved! I think?

I replaced my distributor cap & rotor (they were crusty), checked the timing. Turns out the prev. owner set it to 11btdc, I reset it to zero. Tested the tps, in the idle position it shows .45 volts--which I understand is just a little on the low side, but it increases in a smooth and linear fashion as the throttle opens. Started it up again--whoops, I forgot to plug the spark advance back in. So I plugged it in, with the engine running--and the idle started hunting up and down. That can't be right! Shut it off, restarted, and now the cold idle is about 1500, warm idle (park & neutral) is 900. Idle in drive and reverse is a solid 700. No miss, no unsteadiness, no wondering if it's still running. And with that, several other characteristics changed dramatically. Now, when I put it in drive BAM! it's in drive, when I let off the brake it creeps, when I press on the pedal it goes. Not wait 3 seconds for it to try to decide if it's gonna go, not wait until I've revved up to 1500 and then suddenly engage the gear. And the hot oil pressure at idle is around 20, which seems acceptable.

Has anybody else had this happen? Was incorrect timing causing my ridiculous low idle, or could it have been one of the other things I did? The change is so dramatic I went looking to see if I'd knocked loose a vac line, but I didn't find one.

Further theorizing: my low idle meant the oil pump and transmission pump were both turning slower than they're supposed to. The lurching, wheel spinning acceleration from a stop (even with a light touch on the throttle) was because the transmission didn't get enough pressure at to really engage first gear until the revs come up, which was happening after the tps had already moved. The throttle is still quite firm and maybe even sticky but now it won't bother me.
Another thing I've noticed is, now all the shifts are quite harsh. I've read that if there's a trouble code set the trans maxes out the pressure which makes all shifts harsh, I could easily have set some codes while setting the timing and poking around the tps. I'll disconnect the battery to clear codes and see if that changes anything, but I'll wait for it to quit raining first. A transmission fluid & filter change is also in the works.