Bucking during acceleration after engine swap

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Potiusmori
Posts: 7
Joined: Mon May 22, 2017 8:27 pm
Car: 2001 Nissan Sentra 1.8

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Hello everyone. So I just completed a engine and transmission swap on my 2001 sentra 1.8. Got engine and tranny from local jdm shop (JDM FLORIDA). Tranny shifts fine and the engine had alot of different parts on it so had to reuse intake manifold and everything attached, headers, egr and thermostat housing, PS pump, alternator, condenser and the plate on the engine head that has the valve timing sensor and camshaft position sensor on it ( new engine only had camshaft sensor no valve timing sensor. So anyway started it up and it idled fine with no cel's. When I put it in reverse and started to drive it drove fine until I pushed the gas a little harder and it started to buck and lost power but didn't stall. Got a cel so drove it very gently to auto parts store and scanned it. Entire drive had to baby gas pedal cause if I pressed too hard it would buck and had no power so let off gas and pressed again gently etc. After scanning it had the following codes: p1130,p1140,p0505,p0403 and p1171.
My question is what is causing the bucking during acceleration (over 2500rpms about). I looked into the codes and I can't figure out were to start looking. I would like to get rid of the bucking before chasing the other codes.


Potiusmori
Posts: 7
Joined: Mon May 22, 2017 8:27 pm
Car: 2001 Nissan Sentra 1.8

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This is old engine
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This is new engine
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This is old head plate with sensors
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This is plate on new engine which I took off and put old one on
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Potiusmori
Posts: 7
Joined: Mon May 22, 2017 8:27 pm
Car: 2001 Nissan Sentra 1.8

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I just had a thought. The old engine had cvtc as is evident from having the 2 sensors on side of head. If the engine I put into the car did not have cvtc then just changing the head plate on the side of the head with the sensors wouldn't give the new engine all the necessary components needed for computer to read cvtc right? I'm confused cause I'm an old scool chevy mechanic and vvt confuses me

zfollette
Posts: 2
Joined: Tue Jun 13, 2017 3:19 pm
Car: 2007 Nissan Sentra S 2.0

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Not that it's the best solution, but also coming from a sbc background, I'd say swap the head off the old engine to the new one. That is, if the head on the old engine is still good. My assumption is that there is definitely a vvt problem. I'm no expert at all, but perhaps the ECU is defaulting because there is no vvt sensor connection, sort of like unplugging a MAF sensor. Because of this, it could be modifying ignition timing to fit a factory valve timing change based on RPM or something. Without VVT, the valve timing is not going to change with it. My point is, the ignition timing might not be synced with the valve timing. That could definitely cause bucking and would make your engine fall flat on it's face. I'd say the cleanest solution would be to swap the head. Hopefully everything would still fit together.

candahar
Posts: 2
Joined: Thu Jun 22, 2017 2:05 pm
Car: 2002 sentra

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Looks like U need to swap intake manifold andn use the stuff to make the new one like the old one

amc49
Posts: 1183
Joined: Mon Jun 19, 2017 7:24 pm
Car: '11 Nissan Versa
'17 Nissan Altima

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I'm an SBC guy too among other things and you do NOT ignore codes to simply try to 'fix the bucking'. The computer there is screaming what it finds wrong and ignoring that is how you go nuts. Essentially you are saying you are smarter than the computer and well, you already see how well that is working. A $2000+ computer on every car now only to have us ignore it, that is A MISTAKE. You got egr, lean and valve timing codes and at least one of them drops the vehicle into limp mode to then run like crap. ANY of those codes can make for your bucking/no power issues. A switch from non-vvt to vvt is a mistake, wrong engine bought there.

The computer there expects exactly the same features on the engine it had before, don't do that and you may NEVER get it running right, the computer has no way to dump part of its' software instructions.


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