Tough revving problem.

[TweeT91109]

OK so I just finished rebuilding this motor. Got it in and started after figuring out a few wiring issues. It starts right up, and goes right to 950-1000 RPM's. Perfect right....Well I go to try and rev the motor and absolutely nothing happens, it just continues to hold its perfect idle. I thought maybe the butterfly wasn't opening, but I removed all the piping, and looked inside the throttle body and the butterfly opens. I thought maybe there was a shop towel stuck in the piping, from when I took it all off....maybe to cause a blockage. But there was nothing. Now i'm thinking it has to be something to do with one of the following the TPS, MAF, or more wiring problems, to one of those. Here is a video to show exactly what i'm talking about. Has anyone had this problem before, how was it resolved. Any other things I should be looking into? Also the ECU only throws the code 41 for TPS.

 

[hvyman]

Sounds like afm. Check your codes.

 

[IJ.]

Sounds like afm. Check your codes.

Tweety PM'd me on this one and it's something I've never seen/heard of before but agreed if the AFM was somehow jammed shut the engine would behave this way!

Click the pic it's a Vid Link!

 

[IBoughtASupra]

Ian, if the AFM was jammed, unplugging it would put it into some fail safe. It would cause the motor to only rev to somewhere around 3000RPM as a fail safe.

So unplugging the AFM and trying to rev the motor, should allow it to rev but have a fuel cut at around 3000RPM.

I have never ever seen anything like this. Someone told me as I have asked around, it could be something blocking the intake or exhaust ports. Just saying but I am not sure if that even sounds correct.

He said his timing is on spot with all the lines correctly lining up. Whenever adding air to a motor, it should rev, even if some sensor input is missing, it might not rev cleanly but it should do something.

He is full throttling his motor and the darn things is just relaxing.


:aigo:

 

[IJ.]

I mean mechanically jammed as in the flapper won't move and it's choking the engine (or there's a rag in there somewhere)

There is 0 throttle response, usually if it's a fuel/spark issue it'll fall in a big hole soon as you open the throttle.

 

[IBoughtASupra]

That's what I am saying. There could be a rag blocking the runners but blocking all six?

Air is not making it down to the valve through the throttle body, but it is making it down there through the ISCV. Hmmm. Could be a rag INSIDE the manifold?

 

[TweeT91109]

I have removed all piping and the upper intake plenum, and there nothing in there....

 

[TweeT91109]

Sounds like afm. Check your codes.

I have checked codes and the only thing it throws is 41 (TPS)

 

[Poodles]

Ugh, hmmm...

Could be a TPS issue, but it would have to be in addition to other issues. Try disconnecting the TPS.

 

[Dan_Gyoba]

AFM doesn't have a flapper, and even then it should TRY to rev when you open the throttle.

RPM depends on how much air (therefore fuel) you can put through the engine. The other place that it could be plugged is the exhaust side, manifold, turbo, downpipe, exhaust. Plugging that will have the same effect as closing the throttle side of things.

If it's AFM, then the air will still be getting there, just not metered, but it should still rev, particularly at part throttle. It'll throw codes, and go into limp home mode.

Only thing that the TPS would do is limit revs to 2000 RPM, where it would drop back to about 1000, and that's if IDL is shorted to E2. (Happened to me. Was annoying. Disconnecting the TPS sort of resolves it, but RPM didn't drop right when you closed the throttle to shift.)

So if what you're getting is FCO every time the engine starts to rev, look at the TPS. If it won't rev at all, start looking for blockages on the hot side of the engine. (Stuck turbine in the turbo maybe?)

 

[IJ.]

Sorry never owned a stock GTE and was going of my old GE AFM...

This one has me stumped and why I asked Tweety to post a thread on it.

I can't even think of a way I could make an engine run this way on purpose.

 

[hvyman]

Forgot to plug Afm in once wouldn't rev. Also buddy's car stopped revving in te canyons once and it was the Afm and 2 codes popped up.

Pretty sure it's the Afm.

Anyone near you tweet that you could try swapping with?

 

[IJ.]

Won't rev without the AFM plugged in but they do fall in a big hole if you open the throttle, his doesn't and that's what has me confused..
(be cool if that's all it is)

 

[Poodles]

I have no idea what would happen if you disconnected both the AFM and the TPS, but it's worth a try.

 

[Dirgle]

Since this is an off the wall problem, I'll shoot out an off the wall idea.

What if the ISCV was locked in full open or the plunger was missing for what ever reason. So the engine was getting all the air it could handle and it was trying to manage the idle speed through ignition timing and fuel injection events. Then even if you opened the throttle it wouldn't matter because it already as all the air it can use with the retarded timing and fuel. And it wouldn't bother accelerating the engine if it was receiving a false TPS signal. It wouldn't know the throttle valve moved.

It's a really out there idea, and may have no merit in our reality.

What wiring issues did you have to fix?

 

[Dan_Gyoba]

I'd suggest that a manifold vacuum gauge would be rather telling in that event, since the car should idle with ~12-15 inHg vacuum. That amount should drop when the throttle is opened. If vacuum is less than specified, then there's more air in the manifold than the engine can take advantage of for whatever reason. If it does not drop when you press the gas pedal, then the throttle valve isn't making any difference.

 

[TweeT91109]

I'd suggest that a manifold vacuum gauge would be rather telling in that event, since the car should idle with ~12-15 inHg vacuum. That amount should drop when the throttle is opened. If vacuum is less than specified, then there's more air in the manifold than the engine can take advantage of for whatever reason. If it does not drop when you press the gas pedal, then the throttle valve isn't making any difference.

Well that makes since, but even with there being more pressure then it can handle, then it would still react in some manner correct. Revving incorrectly, or falling on its face and stalling.

---------- Post added at 07:16 PM ---------- Previous post was at 07:08 PM ----------

Since this is an off the wall problem, I'll shoot out an off the wall idea.

What if the ISCV was locked in full open or the plunger was missing for what ever reason. So the engine was getting all the air it could handle and it was trying to manage the idle speed through ignition timing and fuel injection events. Then even if you opened the throttle it wouldn't matter because it already as all the air it can use with the retarded timing and fuel. And it wouldn't bother accelerating the engine if it was receiving a false TPS signal. It wouldn't know the throttle valve moved.

It's a really out there idea, and may have no merit in our reality

What wiring issues did you have to fix?

I had to wire a separate wire to the inside of the cabin to get power to the batt., B+1, IG, and FP of the ECU pinout. So the harness was pretty much garbage, so I have one in the mail right now from Van off of here. If that doesn't solve it ill be moving to replace the MAF, and TPS.

 

[Dan_Gyoba]

Check AFM wiring first, and I'd still like to know what the manifold vacuum is.

 

[TweeT91109]

Can I just give you the pull off of the boost gauge? Cause its T-lined into the vacuum block thats right of the intake manifold.

 

[Dan_Gyoba]

That'd be perfect. And what it does when you open the throttle.