i have an 88 toyota with the 4 cyl fuel inj. motor. it runs fine at an idle or when cold(maybe a little rich). as the motor warms up, when you stand on it, it cuts out like it is starving for fuel. if you let off just a little bit, it smooths back out. if you go up a hill on the highway and push the accelerator down to climb the hill it starts loseing power and cutting out until you let off then it smooths back out.
the fuel filter is new, it shows no codes on the computer. it has new plugs, all vacuum hoses are tight,the mass air flow senser connections are tight.
what has me puzzled is that it smells like it is running rich, but yet acts like it is starving for fuel when you stand on it.

any help is appreciated. thank you, rusty.

 

forgot 2 things.

1st: it did show code 51
2nd:it runs like this when the timing is set to factory specs.

if you adjust it, it will have more power and not cut out, the only problem is that it runs rich and doesnt idle very good when you do that. im lost......thanks.

one last thing....when it does finally get up there in rpms while driving, if you let off the accelerator it will back fire a time or to sometimes.

 

Is the vacuum reaching the fuel pressure regulator?
- http://www.4crawler.com/4x4/CheapTri...ine_Pix/8.html

 

thank you for the picture! i will check that.

 

o.k.....i unpluged the tps, cold sv, and the water temp sensor while running and it still ran the same.
ran rich,mash it to the floor and it all but dies, let off just a little and it smooths right out. i can rev it up if i give it gas slowly. but dam its running rich. my question is, how can nothing change on how it runs when all of the above items are unplugged while running, doesnt make any sense to me?? thanks

 

Could be the ECU is running in open loop mode due to one or more of those sensors not working right (have you pulled trouble codes?). Disconnecting sensors/devices in open loop mode does nothing, since all that does is put the ECU into open loop mode (which you are already in). Have you checked for vacuum at the fuel pressure regulator?

And why is that important? Well, it is vacuum at the top of the FPR that adjusts the fuel pressure for the engine load. Low pressure at low load (like idle) and higher pressure at higher loads. Why is this done? To keep the engine from running too rich at low loads. Without vacuum there, you get full pressure all the time and too much fuel flows through the injectors, loading up the engine and making it run rich, until you hit around 2500RPM or so.

 

This is just my 2 cents worth but I have an 85 4wd sr5 efi pickup and was having a problem like yours. At cold engine temps it would rine fine after it warmed up it would stumble and hesitate at around 2400 rpm and above. I was going crazy with this problem. I unplugged the vacuum line to the egr valve and the hesitation went away, pluggede it back in and hesitation came back. Currently running with the vacuum line plugged. Vacuum modulator seems to be working ok. Not sure if the egr valve is bad or if I have a different problem. I too could use some help.

 

the only trouble code was 51. i pulled the hoses off the fpr, it would idle up a little smoother when i took them off. one of them made no difference when taken off. will check them closer tonight. thank you both for your help. the search continues....

 

i have the same problem. have you found the problem?

 

does your tuck act up like after you run it for a while then cut it off and when you start it back up when engine is warm does it wanna cut out? mine does all the same things your truck is doing. i can not figure it out. but when the moter is cold it runs fine but when you stand on it it cuts out like starving for fuel

 

any luck on solving it? i have tried all i know to do