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Buckling, Hesitation, and backfiring on new rebuild. HELP!
Well i just got my motor in the other night and it wouldn't start. So i tow started it and got it running and burned off most of the assembly fluids. During this time i had to keep it at at least 2500 rpm's or above otherwise it would stall. Well now i have about 100 miles on it (mostly freeway). When i am driving the engines acts really funny anywhere between 2200 and 3000 rpm's. It backfires or buckles and seems like it is about to stall but it's not. The engine makes a sounds like it's i giant bridge port and does a brap brap brap noise at this hesitation time. as soon as the car gets to 3,000 rpms the turbos kickin about 3-4 psi and the engine runs strong. Also if I step on the gas the car hesittates then boosts all of a sudden as soon as it hits 3k and then runs strong and takes off.
I'm almost positive that my compression is good so i think a bad apex seal is out of the question.
I can only think of a couple of things here so if any of you guys have any other ideas feel free to throw me a frickin bone here!
1. I am not getting any readings on my air fuel guage. I know it is wired correctly. When i put my rebuild in i just put a generic bosch one wire 02 sensor in. Ya know the type of thing you would just go to the local checkers and buy. ------Maybe this sensor has a different voltage output or something than what the stock one should have and the computer doesn't know the mixture ratios and is mis mixing. Or maybe it's not gettting any readings at all. This could maybe explain why my engine stalls if you dont hold the gas below 1500 rpms. running rich maybe? Or maybe i need to break in the seals longer so they seat better and get better compression in the lower rpms? Or maybe the assembly lube smoke fouled the sensor up who knows?
2. My manifold air temp sensor connector on the wiring harness broke so I am currently running without it. Could this affect my idling or aceleration between 2 and 3 thousand rpms. Does this sensor coincide with the o2 sensor?
3. Something about my turbos may be goofy. The hesitation starts when they start to spool up (like if you push on the gas between these rpm's) it sputters for a second then when it gets to 3,000 rpm's everything seems to run strong again.
4. Maybe something in my ignition is bad. Bad wires or something. The spark plugs are fairly new and should be pretty good but i dunno how old the wires are.
5. Maybe my ignition timing is off due to the streetport. I did it myself so there could be an error but i used the same template as my friend did on his rebuild and his is running fine now.
Im really stumped here and can't figure this out. I really need some help on this one. My mods are as follows if they have anything to do with it.
streetport, intake, downpipe, catback.
yeah it's on there. I took the black check valve off a really old parts car. can these go bad over time? considering they blow both ways when not as old even though there is a arrow pointing one way i doubt they can go bad. That still wouldn't explain the nof AFR's on my guage.
my bad yeah it's just the filter not a check valve (use of wrong terms). Im not really boosting it i have a manual controller open all the way and im seeing 1-4 psi depending on they way i'm driving. It's not like im flooring it it's just part of the driving sequential twins i can't help it unless i undid the intercooler hoses.
I'll have to look into the TPS. It's one of the few things on my car i don't know much about. That still wouldnt explain the no AFR readings though. I'm also getting alot of backfiring which is kinda leaning me toward the sensor problem because the backfiring means i'm peobably running rich.
And yes im running a streetported motor on the stock ecu. I know some people wouldnt do it but i'll think it'll be fine if i baby the car and keep it at 10 psi after the break in.
The O2 sensor is used for emissions and fuel economy when you're cruising. In this mode or closed loop mode it monitors the a/f ratio and it tries to keep it at stoich. At under acceleration it goes into open loop mode and ignores the a/f ratio and runs on the rich side to prevent detonation.
I believe the intake manifold temp sensor does affect the fuel maps and if it isn't plugged in I believe the computer will think the air temp is 0 degrees or something like that and will make your car run rich. If you have a PFC and a commander you can tell what the computer thinks the air temp is.
On second thought a disconnected o2 sensor that could probably cause problems too. My guess is that will also make the car run rich when cruising since the computer won't be able to go into closed loop mode if it can't read any voltage of the o2 sensor. The o2 sensor and the air temp sensor are unrelated but both can cause the car to run rich if they're not working right.
if it turns out to be the 02 sensor what can i fix here. It's brand new and it's wired as follows. 1. single wire coming from o2 sensor spliced to wire for A/F guage.
2. This line runs along the firewall then i have a wire splitter that splits the signal into the stock wire also.
3. Then near the steering grommet i have a thicker guage wire spliced into the wire that ran along the firewall.
Can all these connections be doing something funny. I used to have it wired like this with the stock one and it worked fine then. If i remember physics right then switches and that kind of stuff doesn't effect voltage. But that's only a certain type of connection (series maybe? any physics geniuses) and what kind of switch would a splitter be.
Am I correct that you just put a rebuilt motor in and you're boosting? You should double check all your hoses, connectors and your TPS. Also make sure all your ground wires are attached to where they need to be. You should also drive softly and notive these problems... not drive hard(IF you are...) and notice them. The engine should be in its break-in stage right now and not be boosted.
nope. I'm asuming my check engine light is on becuase the disconnected air temp senosr or the fact that right now the i don't think my 02 sensor is working.
Im really starting to get ed off here. I think from research It's either a grounding issue or my o2 sensor isn't working. I don't know why it wouldn't. It does have a small dent in it but i don't think this would effect it. I put a new grounding wire on the begining of my downpipe near the o2, it's really thick guage could this be fouling it up
I rebuilt it myself. ome on people i really need help here any more ideas? IF noone somes up with any soon i'm just gonna have to start eliminating problems by buying new stuff which i don't wanna do i wanna locate the problem and fix it.
What are some more symptoms? Is it back firing? Shooting flame *****? Smell funny? smoke? You've got like at least 3 things wrong that you havent fixed to see if it makes anything better... o2 sensor, intake temp sensor... fix those, they are their for a reason. What ECU are you running ? It could just be bogged down stinky rich in that rpm range because you have a crappy o2 sensor and you broke your intake temp sensor...
UPDATE- ok i checked my engine codes and im getting one for 02 sensor, air temp sensor, and one for knock sensor.
So here is my conclusion
1. a combination of the air temp sensor not reading and the 02 sensor not reading is combining for reallu bad fuel ratios and thus, the car bogs down.
2. The computer says reading the knock sensor isn't reading but i know it's plugged in i might have to go through and theck to make sure no wires are grounding out or anything.
This also might have put my car into limp mode with the knock sensor not reading which also might account for the bogging down. I'll get all this stuff taken care of saturday and post o follow up on how it went
Check these items:
Secondary injector connector (loose?)
TPS range (voltage)
EGR & control solenoid (voltage/operation)
Double throttle and solenoid (voltage/operation/proper vacuum routing)
Check all solenoids voltage and proper vacuum routing
check-valve operation and proper direction for turbo & charge control and charge relief
fuel pump relay
Read the repair manual (section F)-troubleshooting
it's a process of elimination otherwise, good luck!