Engine Stumbles when accelerating

[Spartacus]

1986 Automatic

I'm trying to figure out what is causing my engine to stumble.

I have already replaced spark plugs, rotor, distributor cap, wires.

No codes are coming up, TPS, coil are both good. Cleaned throttle body.

I'll just describe how I have been able to recreate the problem:

I'll start the engine (hot or cold), then floor it until I get to about 30 mph (engine runs fine during this part) and then I let off accelerator. Anytime I try to accelerate after that, the engine stumbles and the idle speed is erratic, even stalls sometimes if stopped at a light.

Any help is greatly appreciated! Thank you!

[ochowdero]

might have water in the plug well,
or maf sensor i belive can cause this if its dirty..
anyone correct me if im wrong
lol

[Sonyps307]

Check for air/vacuum leaks

[Spartacus]

Originally Posted by Sonyps307

Check for air/vacuum leaks

I forgot to mention that I checked all hoses for leaks. As far as I can tell they are all good. And I had a mechanic verify that they were

They are very small stumbles most of the time. Almost like little 'hiccups' of the engine cutting out.

When it is really bad then it will actually cause it to shift late and hard in addition to the stumbles. The RPMs will just go up to about 4k or 5k before it shifts.

New transmission installed about 3 months ago, this problem has occurred before and after the transmission was replaced

[Sonyps307]

Does it happen more when cold or hot

[Spartacus]

Originally Posted by Sonyps307

Does it happen more when cold or hot

It seems to not matter.

I just read this thing about a problem for supras being the speed sensor and the solder points attached to the odometer. Something about it not sending the correct signals to the ecu.

Does that make sense?

[spunkenhimer]

there are a lot of factors that we may need to know about your car here. If its turbo then you may want to have that checked for cracks or leaks. also if its reg 7mge then could be a bhg or timing slip i'd check the timing if you can get a timing light on it. also i've heard that the 7mge gas pumps go out pretty easily sometimes.
if you can do a diagnostic check on the car this may help

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/

the diagnostic specs are in there somewhere.

[mof920]

My engine would stumble a lot until I realized it was a BHG. You might want to check that out. Check oil, steam in exhaust, etc. Could be the tranny as well though. When my W58 went out.... ooooh crap. It shredded in two.

[Spartacus]

Originally Posted by spunkenhimer

there are a lot of factors that we may need to know about your car here. If its turbo then you may want to have that checked for cracks or leaks. also if its reg 7mge then could be a bhg or timing slip i'd check the timing if you can get a timing light on it. also i've heard that the 7mge gas pumps go out pretty easily sometimes.
if you can do a diagnostic check on the car this may help

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/

the diagnostic specs are in there somewhere.

Thanks for your reply

The car is not turbo. I just had and engine tune-up last week so I dont think its a bhg or timing, I like the mechanic, I assume he would check those things.

Could be the gas pump, do you know how I could check for that?

The diagnostic isnt throwing any codes

[Spartacus]

Originally Posted by mof920

My engine would stumble a lot until I realized it was a BHG. You might want to check that out. Check oil, steam in exhaust, etc. Could be the tranny as well though. When my W58 went out.... ooooh crap. It shredded in two.

Thanks, I'll check those things but I dont think its a bhg.

The car has a new tranny, just put in a few months ago and the problem happened before and after it was put in