- This topic has 14 replies, 6 voices, and was last updated 11 years, 2 months ago by
.
-
Topic
-
So here is the scoop.
I replaced the fuel injectors on my 1998 Chevy Cavalier with remanufactured ones. It ran great for a couple days but then (to my displeasure) one of the injectors went out (It was defective). The company sent me another one and when I got it I put it in right away.
This is where the problem comes in. The fuel trim readings were out of this world. It would start at 0.0 and then steadily decrease until it hit about -35%, then it floats up and down between -35% and around -25%. Randomly it will shoot back up to 0.0% and I can hear a change in the engine idle when this happens.
So immediately I thought “Wow these injectors are trash!” And I put my old ones back in. (The old ones were not shot, I was just replacing them because I was trying to smooth out my idle (when cold) and I felt like I tried everything else)
The weird part is the car is doing the SAME thing with the old injectors in!
If I rev the engine hard, a LOT of white smoke comes out the tail pipe. When I put my hand in it, I can feel definite moisture and it looks as if the muffler is spitting water out. (Not the normal water leakage through the weep hole.)
So I immediately think “coolant in combustion chambers” and do a compression test. Well it passed with flying colors, around 180 PSI on each cylinder. I know that sometimes a head gasket problem does not always show up on a compression test, so I plan on doing a leak down test next.
It is just weird to me why the fuel trim is so awful, and then will randomly shoot up to 0.0%. And why all of a sudden white smoke? Maybe the head gasket was on its last limb and running on 3 cylinders with misfires was enough to push it over the edge.
Any ideas?
EDIT:
Oh I just realized that cylinder 4 had a reading of 165ish, while the rest were up toward 180. I don’t know if this is concrete evidence considering 165 is still a good reading!
-
Replies
-
What is the air temp at your location when you see the steam out of the tail pipe? Are you having to add coolant to it? Do you have something to read the upstream O2 sensor?
Id be looking for consistency of all cylinders during a compression test. If 4 is standing out then thats where I would do the leakdown. The reading on 4 may be within specs vis manufacturer, but still inconsistent with other 3 cylinders. ..that would point me towards that cylinder. Either its seals in the valve cover (did you replace all the seals in the valve cover?) Or just inspect and assume all where good?
But if coolant levels arent dropping then your not leaking/burning. Sometimes an old schoold vacuum gauge speaks louder than all else. Couldn’t white smoke be carbon? I may have a sticking valve on my project so thats kind of on my mind in this response. …but I am by no means a professional when it comes to ways/methods to isolate a problem in this area. The temp of the area its tested in intrigues me.
The ambient temperature is around 40 degrees Fahrenheit.
I don’t seem to be losing any coolant, but I haven’t ran it long enough to be confident about that. What’s funny is, it doesn’t seem to do it the first few minutes the car is started up. Only after a certain amount of time does the white smoke appear.
The 02 sensor readings all indicated an excessively rich condition. Getting up to 0.930 volts for O2S11 and 0.735 volts for O2S12. When I looked at the graphical representation, the readings would fluctuate from very rich to very lean. The computer is not throwing any codes except for the IAT sensor (I have the air snorkel off and the sensor is disconnected).
The white smoke doesn’t smell like gas or anything that would indicate a rich condition. It definitely seems like steam, it has definite moisture to it.
it could be that after it warms up, coolant leaks on cylinder no.4. Do a block test to see if you have any hydrocarbons in your coolant system.
I’m sure your exhaust steam is just condensation. You need to test the fuel pressure and hook up a scan tool that reads data from all the sensors to see if the data is correct.
Make sure the coolant is full and bled properly.Is that the design where the injectors sit almost all the way down in the rail?
If it is they are FAMOUS for tearing small nicks in the sealing o rings leading to injectors leaking straight into the cylinder. Pull the injectors again and go over the orings very carefully. I would almost bet you have a torn oring.
Remember negative trim numbers mean the computer is subtracting fuel pulse widths to attempt to correct a overly rich condition. And believe it or not in some cases a rich condition can actually produce white smoke.
I really don’t think the exhaust steam is condensation. I am talking about a big white cloud here, not just “some white smoke.” (Should have been more descriptive about that!)
I will check the O-rings next time I am working on it. Maybe I will even get new ones just to rule out the possibility. The thing is, is that it doesn’t smell at ALL like a rich condition. It very much seams like steam coming out the tail pipe.
I had a scan tool on the car, and I CAN read all the live data, but I only chose to look at the ST fuel trim s and the two O2 sensor readings.
I will keep you guys updated. If you have any more insights let me know for sure! 🙂
EDIT:
Also, this car does not have a schrader valve so it makes it very difficult to measure the fuel pressure. I do not have a T fitting.[quote=”Xyius” post=76744]I really don’t think the exhaust steam is condensation. I am talking about a big white cloud here, not just “some white smoke.” (Should have been more descriptive about that!)
I will check the O-rings next time I am working on it. Maybe I will even get new ones just to rule out the possibility. The thing is, is that it doesn’t smell at ALL like a rich condition. It very much seams like steam coming out the tail pipe.
I had a scan tool on the car, and I CAN read all the live data, but I only chose to look at the ST fuel trim s and the two O2 sensor readings.
I will keep you guys updated. If you have any more insights let me know for sure! 🙂
EDIT:
Also, this car does not have a schrader valve so it makes it very difficult to measure the fuel pressure. I do not have a T fitting.[/quote]You have the same set up I do on my S-10. The reason I suspect O’rings is because :blush: when I did my engine rebuild I damaged a Oring putting the injectors in and had almost the same trim numbers and weird white smoke. Pulled the injectors (another set of new orings) and vasolined them up well and no more problems.
So I got a new set of O-rings and inspected the old ones. They did seem to be scratched up so I put the new ones in and lubed them up real good with vaseline.
The problem has definitely gotten a LOT better, but it is still there unfortunately. 🙁
Before the engine is up to temp it will reach fuel trims of about -23 (less than before) but hover around -15. When the engine is warmed up it hovers at around -7. When I rev the engine there is still white smoke. (Less than before though!)
I am glad that the O-rings helped but I am confused as to what could be causing this 🙁
Well I figured out the problem. When the faulty injector leaked raw fuel into the engine and through the exhaust stream, it fouled both O2 sensors. I replaced the upstream sensor and the fuel trims dropped from -35% to -1% through-10%. Still need to do the other one! Will keep you posted!
[quote=”Xyius” post=77609]Well I figured out the problem. When the faulty injector leaked raw fuel into the engine and through the exhaust stream, it fouled both O2 sensors. I replaced the upstream sensor and the fuel trims dropped from -35% to -1% through-10%. Still need to do the other one! Will keep you posted![/quote]
Excellent, got to love progress.
- You must be logged in to reply to this topic.