Greetings all, I tried searching first but had little luck, here is my question: My 91 Sovereign has 170k miles and only a couple thousand by me, but I recently developed a problem with the trans shifting. It’s an AT car but when I shift manually the engine won’t rev much over 3,000rpm – it’s hard to describe because it feels like it’s slipping because the car definitely stops accelerating, but the rpm’s won’t go higher like a true “slip” would - they just reach a certain point and stays there. It will shift the moment you back off the gas pedal and shifts hard. For 2 to 3, or 3 to 4 it is the same, even 1 to 2 with Sport on under WOT.

The engine almost seems as if it’s starved for fuel but it’s very steady without coughing or stumble. I replaced the tranny filter and fuel filter for good measure but neither had any impact. So I don’t know if the engine is just starved under load or if the trans is not shifting correctly; it seems to pull perfectly fine up until just over 3,000rpm. Not knowing this was bad for the tranny I have revved it over 2000rpm in park, but now know that’s a no no. Any suggestions would be greatly appreciated! (No failure indicator lamp btw)

 

ixfn:
To clarify... Does the transmission shift normally when used in the fully automatic mode rather than when you shift "manually"? Also, you indicate the transmission warning light is not illuminated, but do you perhaps have a check engine light?
Scott

 

Hey Scott, thanks for the reply. It shifts fine in auto mode; normal shift points and firmness absolutely. However it's shifting before 3,000 rpm this way. Check engine light IS on for an unresolved 39 code (EGR temp sensor?).

 

ixfn:
Sorry, further clarity... So, for a while you were shifting in the manual function and it would allow you to rev over 3K, but now it won't, right? If it had acted like this the whole time, my instinctual response was going to be - maybe it's normal. I know that sounds dumb... But I'm not sure how much higher than that it is allowed to rev before being limited by the transmission mode in some way. (I never use that function, and I can't quite check for you at present because my car is still in winter storage.)
Another idea might have to do with the shift knob linkage itself - perhaps worn or stretched? I also had a weird thing happen with the rotary switch on the side of the transmission. It wouldn't allow me to shift out of low gear, but would rev up to a certain point - kind of like you are describing - and it would seem to "stall out". Ended up being that switch - sometimes called the "PRiNDL" switch.
I can't quite see on the FF39 might be related to this, but who knows! Thank goodness, though, you've got normal shifting in auto.
Scott

 

I can only go from what happened to my XJ40. Years ago I had the FF39 code and the car went into limp mode which means it will not rev over 3000.

Although you can still drive it in Auto mode which may seem to mask the problem.

In my case, it was the wire connector on top of the thermostat that had broken, I made a temp repair with tape 6 years ago.

Check your wiring connectors in this area.

 

Scott, yes that clarification is accurate - I would pull it to 4,000 or so then shift and it was fine. My car is in storage as well, I'm trying to look into this now to resolve it when better weather comes

Excellent info Richard, I will do so. It does rev freely over 3,000 in park or neutral though.

 

Just for the sake of closure the fuel pump was the culprit - she's tip top after a new Walbro replaced what I suspect was the original pump. Thanks, all.

 

Glad to read this, Im having the exact same issue. My car will not rev over 3k in any mode.