When did you last change the fuel filter? A car running lean/starving for fuel will have symptoms like yours.

 

changed fuel filter, pump and surge tank filter in the past 2 months

 

It sounds like it could be an ignition problem if it can't hold 4500rpm

 

i can rev it past 4500 sitting in park...

 

Definitely sounds like fuel then. Even though you recently changed the filter, if there was rust in the tank it can still plug a filter quickly. Filters last until they are plugged, that could be one tankful or a thousand depending on the fuel.

 

if I get a chance I'll try and take it for a spin and see if it'll go past 4500 or shift

 

It could be the box playing up too. When they go home, they tend to restrict the revs

 

ha that's reassuring 😂

 

Took a quick vid. Got to about 5k and bam.. didn't shift either

https://streamable.com/nunib

 

if if it was the front ignition coil wouldn't it not even make it past like 3k rpm? I did new main coil, plugs, wires and cap. The only think I can think is that the centrifugal advance might be sticking and I know the vacuum advance is bad. Would that be the issue?

 

anyone have a chance to look at the vid... I took it for a spin the other day and it hit 4.5k and bucked like a bronco. On/off/on/off... I just have to let off the gas

 

I didn't get much from the video

BUT.....the 'bucked like a bronco' really rings a bell.

On my '88 XJS V12 (years ago) I had a severe case of bronco-itis. Under gentle acceleration it was fine. Under moderate or hard acceleration it would buck and carry on like crazy....almost violently.

Cutting to the chase it was in inlet (RH side) pressure regulator. I can't remember how I came to that determination but I remember a fair bit of hair pulling and I remember that eliminating it solved the problem!

Cheers
DD

 

hmm I'll have to look it all over. I wonder if it will do it at half throttle.

 

Went for a spin today and tried to basically 1/4-1/2 throttle past 4.5k rpms... it wouldn't. Just bucked like it's hitting a wall. Like I said feels like I hit a rev limiter. Would that be the trans governor?

 

I can't think of any trans problem that would cause the engine to buck and carry on as you mentioned. That sounds like a fuel or ignition problem....and the transmission wouldn't have anything to do with that.

However....

It seems plausible to me that there might be some sort of transmission failure scenario that drags the engine to the point where it can't develop higher RPM. Some sort of torque converter failure perhaps? I'd think you be feeling other symptoms as well; some sort of weirdness in the transmission behavior.

Fix the bucking-like-a-bronco condition and then see how the transmission behaves.

Cheers
DD

 

yeah it's a bizzare thing. Once up to temp the trans feels fine. If it's cold their can be some hunting and feels like the tq converter doesn't want to lock always. Like I said you can tell the trans was replaced with some used unit as the tq converter shield is gone and converter is baby blue and pan is as well. That's why I was wondering if the gov would act strange if it was out of something that had a low rpm use? At wot it's smooth and shifts at 4500-5000k.

oh one thing though the trans when cold has a hell of a time wanting to reverse!

 

If this is the original TH400 transmission, there is no converter lockup. I'm not aware of there being a locking converter for that transmission, I did look a while ago.

 

oh hmm well it feels more slipping in cold then gets crisper shifts...

 

The TH400 never came from the factory with a lockup converter, there was someone modifying them.

Is the oil level in the trans correct, if so then I would drop the pan and check for debris in the pan, there is a magnet there to attract the metal debris, when I dropped mine the pan was full of sludge.

 

i dropped the pan in spring and all was good