Unplugged TPS -> Bucking. Normal?

[Andy348]

My original problem was that I couldn't rev past 3500-4000rpm, but now with the TPS unplugged, I can go up higher.

New problem is that when I let off throttle after hitting higher RPMs, the car bucks and bogs down like crazy. Could this be because of my unplugged TPS or is it a seperate issue?

[jlevie]

A bad WOT switch in the TPS would cause a loss of performance above 5000rpm, but I can't see a bad TPS causing your 3500rpm problem. Nor would a bad TPS cause the problem you have now. Something else is wrong. I think I'd start by testing the fuel system.

[Andy348]

My new external fuel pump does make a decent amount of noise, so that could be the culprit. I don't have a fuel pressure gauge so I'm getting it done by a local garage early next week.

In the mean time, what else should I check?

[7pilot]

With the TPS disconnected, you will have driveability problems transitioning from idle to load, and also on closing the throttle on coast to idle.
You'll be lacking power at the top end.
Similar driveability issues can result from a bad ICV and airleaks(if it stalls).
If prior to the TPS disconnect, your complaint was the problem at 3500-400 rpm you may want to ensure that the road speed signal from the dash to the DME unit is intact.

m

[Andy348]

With the TPS disconnected, you will have driveability problems transitioning from idle to load, and also on closing the throttle on coast to idle.
You'll be lacking power at the top end.
Similar driveability issues can result from a bad ICV and airleaks(if it stalls).
If prior to the TPS disconnect, your complaint was the problem at 3500-400 rpm you may want to ensure that the road speed signal from the dash to the DME unit is intact.

m

Is the road speed signal a wire that goes from the tachometer to the ECU? I've got a couple wires that do not connect anywhere in the glovebox (did b25 swap) yet I figured I'd tackle those once I've got the car running well.

[Kershaw]

cap and rotor.

[Andy348]

I just disconnected the battery for five minutes, then reconnected and went for a 20 min drive. For 10 mins the car would rev all the way up to the redline, yet for the last 5 minutes it would cut out and start bucking at:

1st gear - approx 3200rpm
2nd gear - approx 3700rpm
3/4/5 gear - dunno

Keep in mind that thats with a 2.93 diff and the tachometer could be slightly off.

I bought a fuel pressure gauge so I'll check that tomorrow but I really doubt thats my problem, now that the car functioned fine for the first 15 mins.

Also, could be unrelated/placebo, but it seemed like the engine would tick louder after the problem started. Both my friend and I both noticed this.

So whats my next step? I'm thinking I'll try and check the TPS, check the CPS resistance and clean out the ICV. I'll also try and clean out the ICV just for kicks.

[Kershaw]

have you checked the cap and rotor?

a friend of mine could only low rev and it would buck like crazy. replaced the cap and rotor and that was it.

[Bimmerista]

My eta had a bucking issue at one point & it turned out to be the TPS.

[Andy348]

have you checked the cap and rotor?

a friend of mine could only low rev and it would buck like crazy. replaced the cap and rotor and that was it.

How do I check the cap and rotor? I have an eta one but I heard it doesn't have an impulse sensor so I doubt it would work.

I'll look up how to clean the TPS or test it and I'll do that tomorrow.