z4csl428

im trying to find out whats wrong with my car. ive been set on it being in limp mode but im not sure. it pulls a knock sensor engine code. whenever you go past 1/4 throttle it will rest at atmospheric and backfire constantly. i thought limp mode would just cause it to fuel cut and it wouldnt do anything but it seems like its struggling, does this sound like it could be limp mode or something else like in the fuel (injector, clogged fuel filter) or spark (plug, wire)? i got it out of limp mode and running for one weekend but it went back to this, i found an injector plug came off so i plugged it back up thinking it would be fine but its still like this...

Kevin T. Wyum

Sounds like hose off the MAP sensor.

Kevin T. Wyum

Or check for spark.

POS7

If you're backfiring, you're running rich. Likely culprits are MAP sensor disconnected or spark (bad ignition coil, SP wires, spark plugs, etc)

z4csl428

map sensor is connected. so this doesnt sound like limp mode? how can i check what is making bad spark...

POS7

try resetting the ecu. I believe shops have tools to test the spark. You should be able to use a voltometer to test the ignition coils.

I had a similar problem as yours before. I changed stuff until I fixed it, not the most high tech solution.

I changed:

1. spark plugs, then
2. spark plug wire, then
3. ignition coil (fixed the problem)

rynberg

Sure sounds like limp home mode to me. Didn't you post about this before? A knock sensor code will put the stock ecu in limp home mode. The knock sensor, its installation, or its wiring is the problem. Until you fix it, you're not going anywhere...

POS7

try resetting the ecu. I believe shops have tools to test the spark. You should be able to use a voltometer to test the ignition coils.

I had a similar problem as yours before. I changed stuff until I fixed it, not the most high tech solution.

I changed:

1. spark plugs, then
2. spark plug wire, then
3. ignition coil (fixed the problem)

z4csl428

im planning on fixing the knock sensor problem one way or another by replacing it if i have to or just letting a PFC do it since im looking for one anyway. the car ran great though this past weekend while it was still pulling a knock sensor code. i am also running premix would running too much stop up an injector or just make it run way too rich and create this problem?...

Houdini

iTrader: (3)

well, I believe if you have a bad knock sensor reading, it may think there's high knock all the time and retard the timing. If you retard the timing enough, you'll probably get backifiring. Fix the sensor, should fix the problem.

z4csl428

well i know its hooked up from the sensor to the harness that it goes to. could it be disconnected farther back? since i know its connected what do i do next...

z4csl428

bump

z4csl428

i mean i dont see how the sensor could be bad it was fine on the old block, i simply unscrewed it and put it on the new block. but whats next since im pretty sure its connected (unless theres a connection beyond where it goes into the harness)? new sensor?....

z4csl428

^^^

tiger18

iTrader: (1)

its in limp mode,,,,stop beating round the bush,,,,replace the knock sensor,,,and reset the ECU
limp mode does exactly what you saying,,,wont let you boost,,,only part throttle

z4csl428

i replaced the sensor and reset the ecu today. still having the problem...bump

bdennis

Make sure that the power steering connection is not connected to the knock sensor. They are the same type of plug and they are in the exact same area. I know it sounds stupid but I did it when I rebuilt my engine. If you turn your steering wheel does your engine light go out for a second? Check the wiring diagram and make sure you have the right connector on the knock sensor then reset the ecu.

z4csl428

thats where ive had it plugged up, even when the car ran great. but i found where it was supposed to go and plugged it up there last friday and it still pulls a code. i dont think its my knock sensor anymore because 1) we unplugged my friends and drove it around and it never went in limp nor had any side effects. 2) the car ran great for one weekend and it was still pulling a knock sensor code and a thermosensor code (fixed the thermosensor code) the car only pulls a knock sensor code other than the solenoid codes it pulls because of the non. seq. mod so i am wondering if its something else. would a bad coil or wire or something else in the fire cause it not to boost or go past 1/4 throttle? if not what else would?...

z4csl428

plugged my friends stock ECU up and its running fine for the moment. keep in mind it did the same thing when i put the new harness on it but only ran good for 3 days. so is there something in the harness that would fry a comp?...