Engine Stumbles at WOT

[TomoHawk]

I got my car back!

I finally got the new fuel rail on, the fuel lines plumbed, and after I put the spark plug wires on (in the right order), it started right up. Just no cold-start valve (it leaks), but I can give it a crank or two until it starts spouting gas, just enough to start, then unplug it so I can drive. New cold-start injector ordered. New fuel & vacuum hoses too.

So I got it to the gas station (on fumes) and on the way there, I noticed that if I push the gas pedal all the way down, the engine stumbles (loaded or not). 1/2 or 3/4 down is fine with good power, but all the way down stumbles with a burbling sound(runs rough).

Could it be the ignition timing? With new vacuum hoses, it's got more vacuum for advance, so it could be advancing too much and stumble? I'm not so sure about this as it happens even with no load or on the freeway. Haven't got a timing light- I'll go borrow one Wednesday.

Maybe the TPS switch? It's supposed to add gas at WOT, but that gives you a rich mixture which would still run smooth. Could still be the TPS because it's connected directly to the gas pedal.

What else could it be? I had the AFM off to clean (Deoxit) the connectors & check the spring tension. Used DeOxit 100 on just about every connector on the engine. Just not the Headlight (ran out )

I will have to go check the connections again during the day.

thx

[LanceM]

Doubt that it is timing, sounds fuel related. Don't know EFI very well but I would check fuel pressure, TPS, and the AFM. You can check the TPS with an ohm meter, don't know about the AFM.

[Mr Camouflage]

Mybe you need the new TPS coversheet? (office space joke).

but seriously,

what is WOT? (Wde Open Throttle perhaps?)

and what is TPS?

[TomoHawk]

WOT: wide open throttle, foot to the floor

TPS: throttle position switch

I'll be into the EFI bible book soon, or the FSM, after I try a few things.

The only thing I wasn't able to do is to disconnect the harness from the ECU, to DeOxit the connector, or trace some wires.

thx

[TomoHawk]

I think it's the TPS or something in the computer that's connected to the TPS, because when I disconnected the TPS, the engine worked normally. I will have to look at how the TPS or hooks into the computer, or what's associated with it.

thx

[PrOxLaMuS©]

it's the TPS

[240ZX]

Sounds like your muffler bearing are shot! If you disconnect the framajammer from your BFM, it should solve the problem. Or, manybe if you turn your MUSIC up loud enough you won't notice it any more. Hey, I know! Squirt some liquid wrench all over the engine and then add a lit match......problem gone. Yah, thats the ticket!

[240ZX]

it's the TPS

Does TPS translate to.....TomoHawk's Perpetual Stupidity?

[chickenwafer]

^^ okay, now that was good

It could be the knock sensor. My buddies TBI Chevy is currently having problems with it and it causing the engine to "stumble" at WOT. His TPS is also shot, along with a few other things.

I agree with 240ZX- the framajammer on the BFM, the one that connects to the YTC the OJT- those are bitches

(i need this good laugh)

Dave

[TomoHawk]

It's a combination of the TPS and the AFM. Disconnecting the TPS smoothes things up, up to a certain RPM , then it will smooth out again to 7,000 RPM. It jives with the resistance reading I took of the resistance line inside. It was smooth at the ends, and all jumpy in the middle. A new AFM goes on the wish list.

Thanks for the (confirmation), PrOxLaMuS.

Dave-

My 280Z doesn't have TBI. It has direct port injection. Much different from a Chevy.

240ZX is his own fanclub. Only he enjoys own own dumb jokes.

[chickenwafer]

TomoHawk- I knew it wasn't Throttle Body Injected- I was just pointing out. You still have a knock sensor, don't you?

[240ZX]

TomoHawk, you can bank on the fact that I am not alone in my candor about you!!!