4.0 top revs 3k.

[Drivin` Dave]

started it up yesterday and it fired right up and died. restart and same thing. Held it to the floor and it went up to 3k and holding it there it started to pulse between 3k and 2k. any ideas?

 

[Drivin` Dave]

not showing any codes. just wont run.

 

[alwaysFlOoReD]

I think there is a rev limiter when in park or neutral.

 

[Drivin` Dave]

I think there is a rev limiter when in park or neutral.

I think you are right, but the rev limiter doesn't explain the start and stall situation. it starts and just dies unless you hold the gas pedal down. it runs smooth at 1k but dies when i take my foot off. Think it might be the IAC.

 

[JoshT]

Like @alwaysFlOoReD said, your 3K RPM limit is most likely a REV limiter.

As for it dying, but running with throttle opened... I'd probably be checking out the idle air control valve (IACV).

EDIT: You replied while I was typing, but I think you're on the right track. The IACV bypasses the throttle body and controls air intake at idle. If it isn't opening, you aren't going to get enough air to idle. By actuating the throttle you are manually doing the same thing.

 

[Drivin` Dave]

Like @alwaysFlOoReD said, your 3K RPM limit is most likely a REV limiter.

As for it dying, but running with throttle opened... I'd probably be checking out the idle air control valve (IACV).

EDIT: You replied while I was typing, but I think you're on the right track. The IACV bypasses the throttle body and controls air intake at idle. If it isn't opening, you aren't going to get enough air to idle. By actuating the throttle you are manually doing the same thing.

I will get a new valve tomorrow. No codes, no fuses blown, just a mystery to me. happened all at once. Thanks to you guys for the imput. I am 85 and can't do as much as i used to. LOL

 

[JoshT]

I'm assuming that by no codes, you mean there is no Check Engine Light (CEL). There are conditions required to set codes and not all codes will trigger a CEL. This is probably oversimplified, but...

An abnormal condition (IE: missifre or lean condition) sets a "soft code". Unless it's something extrememly critical and detrimental to the engine, it usually takes repeated triggering of the same soft code over a couple of drives to set a "hard code". The hard code triggers the CEL.

If the engine starts and dies immediately, it probably isn't going to meet any of the conditions required to set a code. Honestly I'm not sure if codes even exist for the IACV.

 

[Drivin` Dave]

I'm assuming that by no codes, you mean there is no Check Engine Light (CEL). There are conditions required to set codes and not all codes will trigger a CEL. This is probably oversimplified, but...

An abnormal condition (IE: missifre or lean condition) sets a "soft code". Unless it's something extrememly critical and detrimental to the engine, it usually takes repeated triggering of the same soft code over a couple of drives to set a "hard code". The hard code triggers the CEL.

If the engine starts and dies immediately, it probably isn't going to meet any of the conditions required to set a code. Honestly I'm not sure if codes even exist for the IACV.

thanks, i had forgotten about the soft code. all the info from this app has helped me a lot.

 

[Drivin` Dave]

Like @alwaysFlOoReD said, your 3K RPM limit is most likely a REV limiter.

As for it dying, but running with throttle opened... I'd probably be checking out the idle air control valve (IACV).

EDIT: You replied while I was typing, but I think you're on the right track. The IACV bypasses the throttle body and controls air intake at idle. If it isn't opening, you aren't going to get enough air to idle. By actuating the throttle you are manually doing the same thing.

Replaced the IACV and still starts and stalls. I agree the rev limiter is causing the 3k max rpm. Any other ideas? if i can get it to my mechanic maybe he can run a smoke test.