SN95 rough idle/throttle kills the engine

[MikeS]

This prevented me from running race 4 at TWS.

Now taking a look at it to see if I can get the car running for Hallett.

Car has a ragged idle then when I hit the throttle it dies.

Car ran about the same with TPS hooked up and not, so I replaced the TPS with no better results.

Thoughts on where I go next? Motor is a 4.6 2v if that makes a difference.

Thanks for any tips.

[cobra132]

The idle is controlled by the idle air intake valve. You will need to check it. Make sure there are no vacuum leaks. Then clean the mass air meter, check all connections and test all of the other sensors. The Haynes manual has a good protocol for this. If that does not work remove the 4.6 and install a 347 with a Holley 650.

[Rsmith350]

Had a similar issue and it ended up being a MAP sensor

[edrock96GT]

Check your TPS wiring to make sure there isn't a break anywhere in the circuit. Just from seeing how tight it was at TWS, it's possible it may have been yanked out somewhere. Based just off of what you described (same results with TPS hooked up and disconnected), it sounds like the PCM has no idea where the throttle is and when you open the throttle it just leans out and dies.

Robert. Our 2V Ferds don't have them MAP thingys. :D

[MikeS]

Tomorrow I'll clean the MAF and check the harness at the TPS. I'll bet it's one or both of those.

[MikeS]

Most likely was a dirty MAF. Now running like a top.

[AI#97]

another thing to look for is the fuel pressure sending unit on the driver fuel rail. They can go bad and are known to be crappy parts. They aren't cheap either. I went through 1 and kept a spare in the tool box. Thankfully, that is all behind me and now I have a whole new list of unknowns! LOL!

If you MAF got dirty....best figure out why so it doesn't do it again! ;)

[marshall_mosty]

Some people over-oil their cotton gauze filters (K&N, etc). For our environment, the oil isn't really needed because we change our oil so often that the particulates from the bit of dust/dirt that contaminates the oil is flushed away.

Michael and I both run cotton/gauze filters with no oil and haven't seemed to have any issues related to that.

The oil on the filter can be sucked into the air stream and get on the two MAF wires causing the heated wire not to cool at the proper rate.

[MikeS]

The reason the MAF got dirty was that I lost the air filter, most likely during a bumpy off-track excursion. More accurately, it was knocked loose and was sitting loose in the fender.

All's well now. Rigged something up that I believe will prevent this happening again.