Sam hain

This all started about 3wks ago, went to leave for work and truck wouldn't start. Threw CEL P1300, so I replaced the coil and got it running and thought I had it fixed. But it has an hard miss about 2000 rpms, almost like its losing spark or something. This time no CEL's so I'm lost on what to check. I've had a few guys mention the MAF sensor and fuel pump. Right now the truck will start and idle fine, while sitting I can blip the throttle and it will rev up. If I hold the throttle at the est 2000rpms you can feel the truck knock like its losing spark or something. While driving it is when the miss is worse, it will buck and jerk more so when going up hill.

In the last 5 months I've replaced the following:

-muffler
-spark plugs
-plug wires
-coil
-battery
-distributor cap and rotor button
-throttle position sensor
-fuel filter
-knock sensor


95.5 2.7 Tacoma

vasinvictor

iTrader: (3)

I had the same nasty miss but at 3200. Wasn't remedied until I replaced the crank sensor. It even tested out fine with a DVM, but swapped with my brother's and it was fixed. Start with testing though. (900-1500ohms IIRC but look it up yourself)

TACOJO

I have a 2002 DLX with 2.4l. Have same symptom as your truck. I replaced crank sensor. It did not solve the problem. Still bucks and jerks,power loss,etc. It is an electrical issue affecting the TPS circuit,but Nobody can pinpoint the solution to this common Toyota defect. You can replace everything like I did and it will not solve the problem. Need to find a tech that is sharp on electrical troubleshooting. It's an electrical issue in TPS circuit. I bet my left shoe on this.

vasinvictor

iTrader: (3)

It's not a "common" problem. However the time you hear of it is when somebody has a problem. Wonder how many millions of Tacomas there are without this problem.... Anyway, to find a truly good mechanic that will troubleshoot and diagnose without shotgunning parts at a truck is truly rare. When you find him, please report to the rest of us lol

You need to get yourself a FSM and start going through the troubleshooting section. It's very complete and thorough. There is a problem, and it can be found and remedied. There are no ghosts.

Sam hain

Replaced crank shaft position sensor tonight and truck still has the miss. Father in-law and I did some simple troubleshooting and determined the plugs and wires are good because the miss got worse as we unplugged each plug wire while one of us rev'd the motor. Is it possible the igniter is bad?

vasinvictor

iTrader: (3)

Sorry I wasn't suggesting throwing parts at a truck without testing! The factory service manual has complete diagnostic testing including the tests for your igniter. It has flow chart of symptoms and diagnostic tests. You can usually find a copy of that floating around the internet.

TACOJO

I knew replacing crank sensor would not solve the problem. I'm sorry to hear that. We get excited with the expectation of thinking we have solved the problem sometimes and it's a big let down when the issue still persists. I'm going on six years with the same issue as your truck. As far as the ignitor, it may be ,but I do not know how to check the operation on that part. My truck does not use an ignitor. ( 2002 )

vasinvictor

iTrader: (3)

The 1995.5 - 2004 5vz defintely all have ignitors.

Edit: oh geeze I just realized we're dealing with a 4 banger here. Dang.

TACOJO

No offense taken. This is a very frustrating problem. I am sure it is electrical affecting the TPS. I've even taken it to the Toyota dealer. They couldn't find what was causing symptoms. You are correct in that I need to try flow chart,etc.. My truck is not equipped with an ignitor though. ( 2002 )
There are lots of Toyotas without this issue,but there are lots of them with this problem. Type in Toyota power loss or Toyota bogging down in the internet and you will see what I mean. Six years with this issue and still trying to solve it. I do thank you for your input.

Sam hain

Hooked a scan tool up and cyls 2 and 4 had several mis-fires in just a few secs at 3000rpms. Cyl2 got up to 34 and cyl4 something like 20. Buddy hooked up some type of tool with a light on it connected to each plug wire and plug and we couldn't see where it was losing spark there. The little light was solid on all cyls. Another buddy swapped out the igniter and MAF sensor and truck continued to miss. We are all stumped now.

AKHeathen

It might be the wire or resistor for those 2 cylinders as they are tied together for the fuel injectors and act as one. the union is pressed together, rather than soldered or crimped afik. apparently a common problem.

Sam hain

Can you explain a little better what wires I need to check and where they are please?

vasinvictor

iTrader: (3)

So you've ruled out spark problems? Time to move on to fuel. Now you need to verify compression and fuel. Firstly check compression. Maybe you have low compression due to rings or valves. Do you have good fuel pressure? Check your injector wire pulse to verify you have a steady injection signal. If yes, check injectors for partial clog. If bad signal, then check wires to proper ECU plugs.

Sam hain

After talking to some more people I'm leaning towards fuel. About 2months ago I had the 20yr old factory fuel filter replaced, I'm wondering if that dislodged some trash and has clogged the injectors? The guy who is working on it is going to swap the injectors from 2&4 (the ones that are misfiring) and put them on 1&3 and see if the misfire follows. If that checks out he's going to check compression. I'll post in the morning what he finds. Thanks guys.

Sam hain

Got truck fixed, ended up being a bad ECM/computer whatever you want to call it. Buddy swapped one out of a 96 model and truck ran smooth as silk, no jerking or CEL.


Computer number is 89661-04050 for anyone that needs one from a junk yard.

vasinvictor

iTrader: (3)

Well color me surprised. Glad you got it.

wyoming9

iTrader: (1)

After reading through this thread I was leaning toward the ECM Glad you had one to swap.

Sam hain

Spoke to soon, it wasn't the computer it was the distributor. Swapped one from a wrecked 96 and the miss is gone using my computer. Now I got a space computer I need to sell!

vasinvictor

iTrader: (3)

I want a space computer!

Sam hain

Haha I don't know why that put space computer, I didn't type that. I meant I've got a engine computer I need to sell. Junkyard wouldn't take it back.