jdm engine installed but running poorly!

So I just spent the last five days taking out my old engine and installing a jdm. I got everything back together today. Filled all fluids and started it up. Here is what it does. Starts right up, revs kind of high and then immediately dies. I did that a bunch of times then I started using my hand to operate the gas pedal. With a little throttle it will run rough however if I give it some throttle it hesitates and then revs up and runs pretty smooth. If I let go it drops back down and shuts off again. I used the whole harness off my old engine but retained the manifold and injectors that came on the jdm. The fuel pressure regulator turns into a plastic tube that I broke so I just ran some rubber hose to connect it, dies that matter. Oh I left the distributor that came in the jdm as well. Could it be timing? Engine seems pretty good once its reved up. What do I do or check. Its a 94 sc alltrac.

When it comes to replacing an engine there are a multitude of possible mistakes even the best mechanics can make. Vacuum lines and the possibility of mixing some up or leaving one disconnected is the 1st thing that comes to mind. Perhaps an injector plug was damaged or a temp sensor was left disconnected. maybe a wire or a chunk of dirt got pinched between a critical seal surface. Maybe the intake manifold or gasket was damaged during shipping (and no longer seals properly). Maybe a bolt, fitting, or some other component was left loose. Any and all of these things can and do happen on major projects. And these are only a few out of many (and yes, I've made most of these mistakes at one time or another). To make matters worse, the Previa is a bit unusual and can sometimes confuse the most seasoned techs. If I had one come in with a complaint like yours I would start with all the basics (check for oil inside the distributor, check ignition timing, etc). I would also compare against a vacuum hose diagram and double check all the wires and connectors. If all that looks good, I would check for vacuum leaks around the intake manifold and verify all nuts, bolts, and fittings were properly tightened. Quite often it's the simple stuff that gets you. Good luck and I hope you get it figured out. Tim

PS: You purchased the engine with the valve cover on and everything intact.............right?

sounds like a vacuum leak to me
I hope you got an S/C engine too as they're quite different from the N/A ones

There are a lot of vacumm lines how do I track it down if it is that. Also I ordered a s/c engine how do I confirm that it really is? It had the same letters on the block and everything seemed the same. The only things that were really different were one missing sensor in the manifold and the oil tube to the sump did not have the little injection tube so I swapped that.

My invoice says 2tzfe supercharged so hopefully its the right one.if not I will completely give up. So you are leaning towards vacuum leaks. Like I mentioned the little plastic hose that goes into the harness and connects to the fuel pressure regulator broke so I just connected it with some rubber hose. Is that OK. I have to keep my hand on the pedal to keep it running g so how do I find these leaks??

There are so many things disturbed when replacing an engine that it almost requires hands-on to chase things down. Based on your description I think the FPR tube you're talking about is the just the small vacuum tube from the "pressure-up" VSV. Assuming that's it, as long as it's attached and not leaking vacuum, then you're good. Even if it were disconnected and open, a vacuum leak of that size would not be enough to make the engine run that bad.

Did you check the basic stuff yet? When I say vacuum leaks I'm talking about a big and hopefully obvious one...............like a bigger port that's open someplace (brake booster source comes to mind). But sadly I have absolutely no experience with supercharged Previas and don't have a clue how they're set up regarding the vacuum system (or lack there-of). The newest service manual I have is 93, and that's no help, so I can not offer any (sorry). The best I can offer is advising you to do a thorough visual check of all your work..........hopefully something obvious will reveal itself. If you don't already have one, you need to get a factory service manual for your specific year & model, then compare the vacuum diagrams to your system. One by one check each end of each hose to make sure it's in the correct spot. Physically there is only one way (due to length & diameter) many of the hoses will go, so this reduces possibilities.

The good news is you know it runs, and there's no big blue clouds of smoke or knocks.........right? So you're almost there. Tim

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Originally Posted by chugach

My invoice says 2tzfe supercharged so hopefully its the right one.if not I will completely give up. So you are leaning towards vacuum leaks. Like I mentioned the little plastic hose that goes into the harness and connects to the fuel pressure regulator broke so I just connected it with some rubber hose. Is that OK. I have to keep my hand on the pedal to keep it running g so how do I find these leaks??

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2TZFE is NA

2TZ-FZE is SC

Are you kidding me? Is there a way to tell sc or na by looking at the block? I'm away from home for three weeks working so I can't recheck my invoice until I get home. I ordered it from engine world in California. I live in Alaska so it was expensive to ship. If its the wrong engine Im not sure what to do. Hopefully the mislabeled it.

Yes, those are the different model engine codes. I do not know what the differences are between them nor how to ID the JDM engine they sent you. Could be JDM sets up the NA to be used for SC, I don't know. That is says "supercharged" hopefully means it is equivalent of 2TZ-FZE

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Originally Posted by mountainhick

Yes, those are the different model engine codes. I do not know what the differences are between them nor how to ID the JDM engine they sent you. Could be JDM sets up the NA to be used for SC, I don't know. That is says "supercharged" hopefully means it is equivalent of 2TZ-FZE

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Greeting good people,

FYI on Previa engine:
2TZ-FE = non supercharge engine (91-'95)
2TZ-FZE= supercharge engine('94-'97), '94-95 SC was optional, '96-'97, all have SC

The easiest way to tell the different between the two engines are:

1) SC engine have smaller distributor plug
2) SC engine have crank sensor where as non sc do not
3) SC engine fuel injectors plugs are brown instead of grey like non sc
4) SC engine have different intake and exhaust manifold.
5) SC engine compressions are less than non sc (.5 psi)

There's more, but this should clear up a lot of confusion

Cheers :)

hey thanks for the info... I didn't know of the other specific differences other than the manifolds and lower compression :)
crankshaft sensor is obviously going to be at where the SADS bolts up to the engine right?

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Originally Posted by TheMAN

hey thanks for the info... I didn't know of the other specific differences other than the manifolds and lower compression :)
crankshaft sensor is obviously going to be at where the SADS bolts up to the engine right?

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Actually, it's on the top of the engine near the oil filter cap. It's very long and extended down toward the crankshaft.

ok for now im assuming that i truly have an s/c engine. when i get home im going to replace all the vacuum lines. does anyone know the sizes of these lines. im ordering rolls of vacuum line from a company that has 4mm 6mm 8mm and 10mm. i guess all the small lines are 4mm and what other size? according to garage tuner if i had a non s/c engine i wouldnt get it running at all which makes me feel a lot better.

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Actually, it's on the top of the engine near the oil filter cap. It's very long and extended down toward the crankshaft.

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Could someone post a photo of this thing? It would be nice to use for a quick spot check when buying a used engine.

There was some question about whether I got a S/C engine by mistake when I installed mine. I don't have any running issues, though. Still, it's surprising to me that the difference between the engines is as subtle as this. And it's entirely reasonable to expect the people in the JDM business to mix them up and sell whatever they have in stock as being "close enough".
Perhaps someone has a record of the ranges of engine serial numbers stamped into the blocks that were assigned to the non-S/C engines and the S/C engines? The numbers are very easy to find on an engine out of the van, and not impossible on one still in. Maybe someone with access to some Toyota Rosetta Stone?

OK I made a short video clip of what the new engine is doinghttp:// https://www.youtube.com/watc...e_gdata_player. If that does not work try searching previa jdm install

Doesn't come up for me & can't find it using search. When you're on the page just copy the address bar and paste it here. What's your youtube username?

My user name is Jason wilsin . Clip is called previa jdm install need advice
http://m.youtube.com/watch?v=ShiAEKLFexE

That link works. Try disconnecting the TPS, then see what happens.

Disconnected tps and nothing changed.

On the plus side, it sounds good (no knocks or other bad noises). Just something that will probably seem stupid when you find it. Since I have no experience with SC engines I don't know what else to tell you.........as much as I want to help, I should probably just leave this thread to the SC guys. I hope somebody chimes in soon with a solution. Good luck. Tim

Sounds like a big vacuum leak possibly, and the MAF is not switching the C/O relay for the fuel pump because it's not seeing much airflow. If you hold the throttle down a bit, will it stay running? Did the air inlet tube get a crack in it, past the MAF? Possibly a huge leak from the manifold gasket, but it seems it would still run if that were the case.

The engine sounds great though! As Tim stated, no knocks or strange sounds.

did you try to run the engine while holding the throttle open? I would like to see a video of that!

I get home in a week and I will post another video of it running while I hold down the throttle. If I hold it down it will stutter and then catch up at higher rpm but as soon as I let go it will die again.
How do I test the MAF? And what is the c/o relay?
Someone suggested I unplug the tps and try it. I did and that had no effect.

The C/O relay is essentially the Fuel Pump relay, it is in the main relay box under the cover, upper center of the dash. While cranking the engine, the computer closes the relay to allow the fuel pump to run. Then once the engine starts and you turn the key from start to run, the mass airflow takes over fuel pump control. It does this by an internal switch which will close the C/O relay and allow the fuel pump to continue running.

If you have a huge vacuum leak, the mass airflow sensor may not close the C/O relay due to not seeing enough airflow. Also the MAF could be bad. One thing you could possibly try is to jump the two wire terminals for the fuel pump tester, it is located under the driver seat near the OBD1 test port on pre-96 models. On the OBD2 equipped (96 and newer), I am not sure where it is. By jumping this wire you are overriding the C/O relay. If it keeps running, likely it would be really rough or super high idle, then your issue lies with the MAF. Possible huge vacuum leak, possible bad MAF, cracked or loose inlet from the MAF to the throttle body.

the 96 uses a real hot wire MAF, not a VAF like the 91-93... I'm very sure how the COR works is very different on the 94-97
diagnosis connector should still be under the driver's seat.... there is an OBD2 connector that is inside the fuse box also where the 91 only dashboard speakers would go... it might be useful if you have a good scantool that will allow you to display live ECU data

Really? OK, that's good to know, my friend has a 96 and I always thought most parts would be interchangeable. So how does the C/O work on the 95-96? I would be interested in knowing that.

I would love to tell you if I had a 94+ shop manual

So I gave up trying to figure it out on my own and took it to a mechanic. He has only put two hours into it but says there is no vac leak. He had it running on propane and said it ran fine and that the injectors just shut off on their own. He is going to track down why this happens. He said my install looked good though! Anyone know what would cause the injectors to just shut off on their own?

I forgot to follow up on this since its been a long time but the problem was a cracked super charger. from water getting into it and freezing.

Wow. How on earth did you figure that one out? I would have never guessed that one.