Vehicle: 86 Toyota Pick Up 4wd EFI.

Problem: First off, I blew head gasket. I pulled head, resurfaced head new head gasket, put better cam in since I was in there, as well as new timing chain and steel rails. After all back together it is missing real real bad. Timing is on the money though. Seems to be slightly better (missing) as the vacume hose is pulled from fuel regulator. New regulator and still missing. New oem plugs and wires. Still missing but not nearly as bad. Change out TPS and now here's where I need the help. I am only missing or bogging down at around 2000 rpms. Before the new TPS it would, at idle, sparatically miss and also at slightest throttle movement would really bog down. The new TPS definatley made a difference, so then I started to look at the AFM.

No vac leaks anywhere, and the cam timing seems to be correct.

I have a buddy with an 85 so we started pulling stuff off his like the AFM and it made no difference. We pulled the igniter coil and made no difference. Even thought about the computer, so swapped it out and still made no difference.

So to reitterate what it does: Starts fine and idles. Pull on throttle cable to get engine at about 2000 rpms and it drops to 1200 rpm then back up then back down very repeditively in about 3 second intervals. Drop it to about 1800 rpm and it bogs and feels like it is missing bad, but it's not actually missing. All cylinders are firing during this. I want to say it's fuel related, but I'm holding fuel pressure at about 32ish psi. When it goes down as mentioned above the fuel pressure slightly joggs the needle to the positive.

The only thing I can think of besides the slight possibility that my TPS is not adjusted correctly is fuel and by the way where is the fuel filter?

I'm at a real loss here and have no idea what the deal is.

-Steven

 

no one?

 

sure the timing is perfect? have you set the crank and the cam to 0 timing? jsut one tooth off up top can cause the symptoms you decribe... my chain guides are shot, and sometimes my chain will jump a tooth, when it starts making more noise than usual, i am like crap, now i gotta put the chain back a tooth....

 

Check the TPS setting again. It sounds like you have it off a little bit.

 

sounds like TPS to me.

 

I'm gonna have to take it to a pro I think. There's a guy not too far from me that is pretty much strictly Yotas of the very offroad nature. Hopefully he can figure it out. I haven't touched the thing in over a week now.

By the way, I've tweaked that TPS to death.

Thanks all,
-Steven

 

Just FYI: The fuel filter is located under the intake manifold. Real adventure to get to, althogh there's an access panel located in teh passenger's side wheel wll that actually makes it a lot easier to get to. Took me 4.5 hours and LOTs of sweat the first time I changed it. Second time, I had the head et'c off, and that was a lot easier

 

The TPS is either set properly or it is not: http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

Check the AFM: http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml