Hey guys,

First time poster, long time reader. This has been a great site for me, thanks to everyone.

Let me start out by saying that I have been reading this site for the last few months and I have found a wealth of information. Unfortunately, none of it has solved my problem.

Background: I have a 1998 4.3 in my toyota rockcrawler that has been in the truck for the past four years. The computer has been re-worked in the truck and this was prior to me purchasing the engine. But, the truck ran like a scalded dog for over three year. Recently the truck has started to act up and I don't know what the issue is.

Problem: The truck will start up and idle just fine and take gas slowly just fine to half throttle. If I jump on the gas, the motor will bog down, almost shut off and then backfire through the intake and exhaust then return to idle just fine. To me, the motor acts as if the timing isn't advancing as the throttle input increases.

I have tried to scan the computer and I cannot find any codes other than the trans codes that have always existed in it due to the fact that I have a 700r4 that is not computer controlled. But, these codes have been there since day one but this problem is very recent.

I have read many things on this site (yes, I used the search function many times).

I replaced the spider injectors since I was told that was an upgrade anyway and that acted like it wanted to fix the problem where it would take more gas but not all the way and since then the problem has come back as bad as it has ever been.

I have replaced/tried the following:
-spider injectors
-map sensor
-maf sensor
-tps sensor
-plugs
-wires
-rotor
-cap
-distributor
-pulled the O2 sensors with no differnce in performance
-fuel pump
-fuel filter

I have tried to test as many of these parts as my motor manual explains how to and the only one that failed was the map sensor and when that was replaced it made no difference.

I do not have cats on the truck and only the front two O2 sensors.

I have had two ASE master techs look at the truck and neither of them can figure it out.

I know and understand that this motor is far from stock but what drives me crazy about it is that is ran so well for so long and then decided to crap the bed without warning and I don't know how to fix it.

Does anyone have any ideas of things to try? I'm at a loss and I hesitated for a long time to post up here but I don't know what else to do. Any advice is much appreciated and feel free to flame on, I've got my suit on...

Thanks so much for any help you might be able to provide.

 

Check your ignition coil if it's starting to go bad you'll have a hot enough spark to start and run the engine but when colder temperatures or the demand for a hotter spark (WOT) things go screwy.

 

could you poss have gotten a bad tank of gas! disconnect the fuel filter and put a jar under the fuel line and turn the key on if ya have an elec pump still to see if you can get sum gas to see if it has water in it... if it ran like a scolded dog, it may have tapeworm, hehe sorry hadda add that in there.. lol u said the mototr isnt stock, what was done to it? maybe the cam is going on it or the crankshaft sensor..Is that stuff the eng still has?