knock sensor? map sensor? both should set a code, but i'm assuming that the mil probabbly isn't hooked up right. where you said it only happens when it's cold, try unplugging the O2 sensor, also try unplugging the coolant temperature sensor. it will force the ecu in limp mode. if the engine coolant temperature sensor sets high, it makes the ecu think the engines is 300* if it fails near open it'll set to -50 when you unplug it, the computer thinks it's broken and ignores the input.
tbi frustration
- Thread starter lewis
- Start date
It sounds like it is a closed loop problem which indicated a sensor problem, programing problem or wiring problem to me.
As I think back, you know some cars (Jeeps, Trucks, Vans, whatever) have issues when the VSS isn't plugged in or wrong. My friends jeep would not run at all (Chevy small block with TBI) until he put in a special adapter (or something) from Painless Wiring on the Spedo sensor. Ran terrible without it. Just a thought.
Also are your plug wires new or old, and you just might try changing spark plug brands, sometimes it matters and sometimes it doesn't.
Maybe it is time to try Diagnostic software.
Second time: try unplugging the O2 sensor and see what happens...
As I think back, you know some cars (Jeeps, Trucks, Vans, whatever) have issues when the VSS isn't plugged in or wrong. My friends jeep would not run at all (Chevy small block with TBI) until he put in a special adapter (or something) from Painless Wiring on the Spedo sensor. Ran terrible without it. Just a thought.
Also are your plug wires new or old, and you just might try changing spark plug brands, sometimes it matters and sometimes it doesn't.
Maybe it is time to try Diagnostic software.
Second time: try unplugging the O2 sensor and see what happens...
also caused by running lean( if you don't believe me I can show you)
i know. a computer controlled system running that lean will throw (emissions related) codes. you stated there is no codes (did you put a scantool on it? some codes wont throw a light).
put a scantool on it
check o2 sensors
temp as the computer sees it. the computer will activate a fuel cut when overheating is observed (ie a faulty sensor) .this sensor does not run the gauge, that is a different sensor.not sure if they can be mixed up.
ignition advance (as the computer sees it, not your timing light). does it jump around? is it excessive? esp when a load is put on it.
does it have the under cap ignitor? these are a relatively common failure as well (due to vibration/poor heat sink, esp as they get older).most parts stores can check the ignitor.
i know. a computer controlled system running that lean will throw (emissions related) codes. you stated there is no codes (did you put a scantool on it? some codes wont throw a light).
put a scantool on it
check o2 sensors
temp as the computer sees it. the computer will activate a fuel cut when overheating is observed (ie a faulty sensor) .this sensor does not run the gauge, that is a different sensor.not sure if they can be mixed up.
ignition advance (as the computer sees it, not your timing light). does it jump around? is it excessive? esp when a load is put on it.
does it have the under cap ignitor? these are a relatively common failure as well (due to vibration/poor heat sink, esp as they get older).most parts stores can check the ignitor.
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ROCKRUNNER
Active Member
- Location
- SLC
I have seen this problem first hand I belive the water temp sensor on top of the intake is a good place to check. Good Luck!
Hellois from Norway...
I have had the same problem as you.. no codes, good fuelpressure, good timing and so on....
The problem on my chit was the distributor.. I just tried one from another running engine and the missfiring was gone...
And of course.. you have to take battery+ after adjusting timing but that you already knew..
I have had the same problem as you.. no codes, good fuelpressure, good timing and so on....
The problem on my chit was the distributor.. I just tried one from another running engine and the missfiring was gone...
And of course.. you have to take battery+ after adjusting timing but that you already knew..
I haven't put a scantool on it yet because everyone that I know that has one is just the one that read codes and there is no codes. When I unplugged the temp sensor it seemed to smell like it was running richer but still same problems. timing stays somewhat steady just around a little but dot excessive. but haven't checked when there is a load cause that is impossible by yourself. The part under the cap I switched out with one I know works.wr250 said:
I messed with it a little tonight and what makes me confused is that I can unplug the temp sensor and it smells like its running richer but still have the problems so I think it must be something with the ignition.So then I can squirt a shot of starting fluid in the tbi when its acting up and its runs just fine for a few seconds so this would make it not be ignition. Maybe fuel but I can put a different chip in and it still has the same problem until it floods out and dies.
have you read your tps with a meter? should read between .650 and 5 (closed to wot) if you have a partial short, it could be telling the engine that the throttle plate is either more or less open then it is, which should adjust the timing fuel everything, also you say it's running lean try pulling out the iac valve cleaning it extending it all the way( so it's closed and leaving it unplugged) see if the problem is still present. They occasionally get stuck.
you say you have 15lbs of fuel pressure, how much in volume?
i ask because a pump may put out sufficient pressure, but not enough volume (8 ounces or more in ten seconds).
usually due to a clogged intank filter, or obstructed pickup. also is there water in the tank? (wild guess, saw a van recently with your symptoms, had a small amount of water in the tank).
i ask because a pump may put out sufficient pressure, but not enough volume (8 ounces or more in ten seconds).
usually due to a clogged intank filter, or obstructed pickup. also is there water in the tank? (wild guess, saw a van recently with your symptoms, had a small amount of water in the tank).
I've been watching your problem with interest. because I've been having a similar problem with a 4.3 tbi. One thing I did to drive it was set the timing with about 6 to 8 deg of advance instead of unpluging the brown or tan wire and timing at tdc. can't figure out why this works. Run into a guy in moab one week-end that had to do the same thing to make his rig also run.
fergusor
Registered User
- Location
- Clearfield, ut
lewis said:
my 4.3 tbi does this so I jumped the 2 wires on the temp sensor on the front of the engine so that it will stay in closed or open loop. (I cant remeber what one it is) but, I was going through the same thing and I replace all the sensors and nothing worked. It would run great until it would hit 120 and then at temp it would pop and sounded like it was missing real bad. The only thing Ive found with jumping the wires is it takes a min till the motor runs 100% when I first start it up after it sits awhile.
This might be the willy wonka golden ticket. I have unplugged it many times with no change and even changed out the sensor. Maybe I have it in a bad spot( its in the heater hose port) but when I stuck a wire in the plug and jumped it the problem went away, although I haven't gotten to drive it yet, but it didn't do what it normally did just sitting there and it through the code of temp sensor high. I plugged it back in to the sensor and it shot some flames that ignited some gas that spilled out from taking the fuel meter cover off and so I had a fire, not bad, got it out quick. So hopefully this is the end to the problem and I appreciate everyones input, interest and help.fergusor said:
usually means it's failed to an open state, which is causing the problem, you probabbly have the wrong sensor plugged into the wrong port or bought the wrong sensor. there are 2 sensors one is for an idiot light and one is for the computer, the take the same wiring. or it's just bad, easiest way is to read it with a meter, unplug the wire and see what kind of resistance you get as the engine starts to warm up.
fergusor
Registered User
- Location
- Clearfield, ut
to me I would think the sensor is working. When it hit the correct temp it sends a signal to the computer. Something else isnt working. On mine I replaced every thing and even tried different computers. I decided to stop wasting money and jump it so I could go and wheel, but mines also on a buggy and so no emissions.
so what else could not be working because by jumping it it will drive but it often floods out cause its running too rich now. I have tried 2 different sensors and no change. This is also on a buggy so no emissions either.