Hi there everyone, I recently bought an 89 Toyota sr5 pickup that had two dead cylinders. The truck came with another 3.0 that I swapped in but I am having some issues. The truck idles at about 500 rpms, even though I have tried to adjust the idle speed. If I try to give it just a little bit of throttle it will die, however if I give it enough throttle it will rev up, but very slowly. Then when I let off the throttle it dies. So far I have replaced the spark plugs, fuel filter, and air filter, as well as a cracked intake hose. Any help on this problem would be appreciated!
Thanks,
Alex

 

Check for codes, put the idle screw back where it was originality and check TPS adjustment , check fuel pressure.

 

Thanks offroadnutz,
How do I check the TPS and the fuel pressure? I know that the fuel pressure regulator is under the air intake plenum, and is therefore impossible to get the without taking the plenum off, so is there a designated place to test the fuel pressure on the other fuel rail? And what should the fuel pressure be?

 

Did you have any codes?

Here is a link for the TPS adjustment
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

Here is a link for the fuel pressure check
https://www.yotatech.com/forums/f116...-tester-95019/

If it still does it after you have verified proper adjustment and function of the TPS, one quick simple check you can do is to spray carb cleaner in a vacuum port while your revving the engine. If it revs normal when you spray then you most likely have a fuel related problem.
Our trucks are notorious for eating fuel pumps. Especially if they are a brand other than Denso. I replaced 3 in one year on my truck before I saw the light.

 

Thanks again,
I will try to run those tests and see, I just barely replaced the old fuel pump as the truck had been sitting for a while and the old one was bad, so I wouldnt think it would be that. i will check back when I run the tests to tell if this one of those things is the problem.

 

I checked the codes and got 12 (engine speed sensor circuit) and 24 (intake air temp sensor) I also tried to test the mass air flow sensor as well but that just makes it unable to run completely. I still haven't checked the fuel pressure or the TPS, I'm not sure where the idle screw was at before?

 

Vacuum leak. Most likely the intake tube is cracked. r you have some hoses not connected, or connected wrong.

 

I would pull the EFI fuse to clear the codes and see if they come back. This way you will know if they are legitimate or not.

If you dont know where the idle adjustment screw was I would still check the TPS per the link I gave you and adjust it where the adjustment screw currently is. Have you been adjusting the idle screw or the throttle stop screw?

As Team420 says, check all vac hoses and throttle body hoses. I know you said you replaced one for cracking but did you check the entire assembly between the throttle body and AFM?

Let us know what you find...

 

I have checked all of the vacuum hoses, (it took quite a search to find the diagrams to do so) I'm pretty sure the rest of the intake hoses are good, it was just the one that was split on the end. I will try to do the TPS this weekend. I will also be sure to clear the codes and double check them.

 

It can be difficult to spot a crack on the intake tube... they usually crack between the ribs...

Just saying this cuz it sounds an aewful lot like a big vacuum leak...

 

Hi there everyone, sorry it's been so long.
So first off, I checked the vacuum hoses again and replaced a couple that were split on the ends. I also checked/adjusted the TPS, but I am still having the same issues as before.
At this point I'm not sure what to think, at this point I think I will have to trailer it to a mechanic.

 

Have you pulled the plugs to get an idea what your mixture looks like burnt? I had a similar problem on my 3.4 that would idle ok and run solid high rpm but everything in between was crap. After replacing coils, plugs, sensors, ect... she was still running rich at the tail pipe with one nasty black plug in cylinder 3. A $35 fuel injector later she ran perfect.

 

Thanks for the advice, but I have already replaced my plugs, and the old ones looked pretty worn out, but none were excessively black.

I messed around a bit this evening with my dad, we found if I turn my throttle stop screw in, (opening the throttle slightly) it runs much better, actually revs the way it should so long as you don't give it too much gas and it is above 1500 rpm, however doing this puts the TPS out of spec??? When I try putting the TPS back to spec it makes the thing run like it did before. Not sure if this means a problem with the TPS or something else throwing things out of whack, but the way it is now I may even be able to drive it to have mechanic I know look at it...

 

have you tested your vafm? 100% sure all vacuum hoses are connected to the correct ports?

 

I know my vacuum hoses are correct, but I have not tested the vafm? Do you mean the afm by that? I am on my way to check it right now... Will update on that

 

Afm readings are all normal but one, the e2-vc reading show 0ohms when it should be about 180? When I try to run the engine with it unplugged it makes it idle really rough, then dies. Those AFMs are expensive, so I don't want to buy a new one unless I'm absolutely sure it's the problem.

 

hmmm... I havent dealt with afm tesing in a bit... so I may be off... if.. according to the fsm the readings that you found were off, are for air temp sensor readins... then, no biggie... mine has been way off for years. if someting other than the air temp tho... its a concern....

 

I also forgot to mention here, I cleared my codes, and the old ones have disappeared, but now I have codes 51(a/c or ctp?) and 52(knock sensor circuit) not sure what to make of these, but maybe you guys have an idea?
Thanks
Alex

 

i would go back over the wiring. specifically common sensor grounds, and main grounds. rt ft. plenum to battery, battery to body, and main engine harness. thourougly cheack the variable air flow meter. it's quite similar to many fuel level senders, and prone to pcb contact wear, closed switch contact corrosion, and flap hinge corrosion, causing sticking. next, pull the hose from the valve cover to the intake boot and plug the opening to the intake boot to eliminate crank case vacuum leaks. to get to the internals of the afm, use a box cutter and cut the silicone directly against the aluminum body. you'll run into like 4 ribs, but nothing important, besides the terminal pins, which are more than 10mm below the top. also inspect the resonating, dampening, and oil collection chambers.

 

Ok, new update, I finally got the truck to a mechanic friend this week, and we have eliminated a bunch of options, we have a code 52 (knock sensor) the truck idles rough but when given a little gas runs better(but not too much gas) upon putting a timing light on the it, we have found that the timing changes, at an idle it is really retarded, like 10 degrees atdc, then when given a little gas, about 15 degrees btdc (so 25deg total change in timing). Has anybody dealt with this before? Is it the knock sensor or wiring? Or the ecu? Or is there something else causing my knock sensor to send that signal to the ecu?
I would greatly appreciate whatever help I can get here...