240 Merc EFI issue

[timeouttom]

240 Merc EFI issue - TPS problem?

I have a 2004 Challenger 1800 with the 240 EFI Merc. When engine is warm and at or near idle speed, I get a single beep at anywhere from 5 to 25 second intervals. Immediately after the beep the engine speed goes up slightly and then back down to idle. I've looked at the beep codes and this doesn't fit any listed pattern. I temporarily disconnected the temp sensors for both heads, with no change in the beep pattern. Water from the telltale is warm with good flow.

I don't get this issue at speeds other than idle or close to idle. Engine runs great at speed.

Any suggestions? Thanks in advance!

-Tom

(EDIT) - After some more research, I am thinking this may be a throttle position sensor problem based on the intermittent nature and the fact that it occurs only at low speed. Thoughts?

 

[Dr Honda]

That's a strange one. A random beep isn't anything "real". So... it's not going to help. But something is tripping the alarm.

Since it's a 2004... you probably a Gen2 engine... and it's computer is smarter than the Gen1... so Yes... I would be inclined to think it could be a TPS going bad, since the RPM's are jumping around.

If you need a TPS... I have a new one I'll sell you for half price. I bought it to see if it could be made to work on the Gen1 engines. The Gen1 TPS is almost $500 !!!! And the Gen2 is around $120. Needless to say, it's TOTALY different. (Electrically and physically)

 

[timeouttom]

Thanks doc! I'm feeling fortunate to have the Gen II TPS. I'll gladly buy the part you have - let me know how you want to proceed.

I think that I read if the TPS completely fails, the engine is reduced to idle. If I disconnect the TPS and this stops the beep I get at idle, would this confirm that the TPS is in fact the issue?

Thanks again.

Tom

 

[Dr Honda]

I would unplug the TPS, and put a meter on the center, and either one of the other terminals. Then have someone slowly open, and close the throttle. It should give you a perfectly smooth reading. (Resistance, up and down) If you see a spot where it jumps (or goes to crazy) Then that's a bad spot in the traces inside.

I'll PM you the details on the TPS.

 

[timeouttom]

Update: installed the new TPS and she's running great! Thanks for the guidance doc!

 

[Dr Honda]

glad could help.