odd acceleration problem

[MA71_Static]

So this problem just happened out of nowhere, just started up one day and this is what started happening. The problem is, when the car accelerates it seems like someone is flipping an on/off switch before 2000 rpm but if it manages to get to 2k rpm under WOT it will accelerate without a problem. Some days it is manageable and I can get it on the freeway but somedays it just isn't happening. Idles great most of the time until it starts to act up then its alittle irratic but never stalls just bounces between 500-800 rpm but when its idling before it becomes a pain in my a** its a steady 650 rpm. I haven't been driving it much, just when I feel like attempting to tackle the problem lol. The car: 1989 Supra Turbo Automatic, 3000 miles on rebuilt engine, 123674miles total, no CEL, no stored codes. Any help will be greatly appreciated

 

[Nick M]

when the car accelerates it seems like someone is flipping an on/off switch before 2000 rpm

Understood. Is this with the pedal to the floor or part throttle?

but if it manages to get to 2k rpm under WOT it will accelerate without a problem.

Not understood. You mean if it gets over 2000 RPM?

Without having looked at it, the first thing I would do is ensure the OEM tune up parts are in good shape.

 

[MA71_Static]

Understood. Is this with the pedal to the floor or part throttle?.

Mostly part throttle but it will do it under WOT half the time.

Not understood. You mean if it gets over 2000 RPM?.

Oops I didn't word it correctly lol, while normally accelerating or anything under 50% throttle input it manages to get to 2000rpm the only way it will accelerate further is to give it WOT. Its an odd problem. The plugs and wires are new and only have 3500 miles, I switched MAF's but it didn't effect it.

 

[Nick M]

Toyota brand plugs and wires set to suggested gap? Even when they say plugs are gapped, they are often wrong. Boots on tight? Your description sounds like tune up parts. Could be something else though.

 

[MA71_Static]

Plugs are gapped correctly and the wires are new, its not like a misfire its more like the entire coilpack turning off then turning back on intermittenly.

 

[MA71_Static]

So I went to double check the plugs and wires and when I pulled the plug wires from cylinders 5 and 6 they were soaked in oil. I also found a coolant line going to the IAC had developed a leak. Not sure if any of those are causing the problem but I am in the process of repairing them. Might as well check the head olts while I'm there lol.

 

[Poodles]

yep, misfire would do it...

Check the oil galley plugs (the large socket head plugs that run down the center of the head) as they will leak if they third cam cover gasket (the thing that seals the plug wires to the sparkplug wells) is worn out...

 

[Nick M]

Plugs are gapped correctly and the wires are new, its not like a misfire its more like the entire coilpack turning off then turning back on intermittenly.

Well if a coil pack not firing isn't a misfire, what do you think is a misfire then?

 

[MA71_Static]

Well if a coil pack not firing isn't a misfire, what do you think is a misfire then?

Its not a misfire cause its not firing at all, there is no stumble or sputter. Its the whole engine dieing, not a single cylinder.

 

[Nick M]

Look for loose grounds and other loose wires.

Does the tack drop to zero or merely hesitate when this happens.

 

[92TealSupra]

I would serious look into the IAC, and check your spark plugs, even if they're gapped take them out and look at them and then tell us what is on them or what they look like, doesn't matter if they're new or not these things can still go wrong!

 

[PROJECT N00b]

check your TPS ^__^ mine used to do that and i found out it was the TPS.

 

[MA71_Static]

So today I pulled the plugs and removed the valve covers. The plugs are clean and still at the correct gap, I did find oil in the area between the valve covers on cylinders 5 and 6 so I tightened down the hex bolts some more. Tomorrow I will replace the TPS with a known working one off my 91 Turbo and see how things pan out. Thanks for the replies, hearing other input helps bring ideas to other possible issues