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car bogs down when its hits,(sees) boost

kleenf4i

Proven Member
261
0
Oct 30, 2012
tampa, Florida
the o2 is good.Its hard to tell if the maf is good but when i unplug the maf while the car is running it will die, so im pretty sure its working.

It may be that the ECM is seeing knock and retarding the timing, which would make it feel gutless. I had that problem with my rb25 skyline swapped 240. When it got up to tell it would start knocking and the ECM would back off timing. 14 psi felt like nothing.

So how did you resolve it?
I lived in lexington for 5 years. I see you live in Irmo.

so the car is ticking/knocking. it would come and go.Now it doesnt go away.Cant tell if its the head or bottom end.The oil pump is working fine. I think it may be a case of not catching a no oil condition early enough.
 
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1983gsp

Proven Member
288
2
Nov 27, 2007
Pascagoula, Mississippi
A bad o2 will not cause a dsm to not boost. When you apply 100% throttle, the ecu goes into open loop, disregards the o2, and runs a predetermined fuel and timing map. It monitors the knock sensor to pull timing when needed. The only time a car looks at the o2 is during closed loop operation which is Idle or part throttle.
 
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kleenf4i

Proven Member
261
0
Oct 30, 2012
tampa, Florida
That tick/knock is probably confusing the ECU. Get some Lucas synthetic oil stabilizer. Replace one quart of oil with it and see if it stops.

ill try this, but sounds like a bad valve tap, or a very early stage rod knock.
And whats weird, I went out again, and it will go away then come back. I KNOW a rod knock does not ever go away. This comes and goes. Im now thinking its starting to crankwalk. which is worse than a spun bearing or a rod knock.

A bad o2 will not cause a dsm to not boost. When you apply 100% throttle, the ecu goes into open loop, disregards the o2, and runs a predetermined fuel and timing map. It monitors the knock sensor to pull timing when needed. The only time a car looks at the o2 is during closed loop operation which is Idle or part throttle.


yeah the o2 is perfectly fine. and the maf is fine, so i think because it will idle fine, but if i unplug it, it dies. so that means the maf is online and working. Im agreeing that the the ecu is "hearing" theknock and retarding the timing to the point that it wants to shut down.
 

dsmornothing

Probationary Member
605
5
Jul 23, 2009
Ishpeming, Michigan
A bad o2 will not cause a dsm to not boost. When you apply 100% throttle, the ecu goes into open loop, disregards the o2, and runs a predetermined fuel and timing map. It monitors the knock sensor to pull timing when needed. The only time a car looks at the o2 is during closed loop operation which is Idle or part throttle.

I never said the O2 was the soul source of not being able to boost. What I did say is a bad O2 can foul your plugs out and cause blow out and boost. You still have not checked your plugs and reported back with how they look. We dont know if this car is a 1g or 2g 6 bolt or 7 bolt. Some of these things should be told BEFORE you ask for help. But if your knock sensor is bad they usually start leaking a sticky goo from them.

My bad it looks like this is a 2g. But is it a 7 bolt or is it 6 bolt swapped?
 
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Cdc1221

Proven Member
1,513
1
Feb 16, 2012
Jackson, Georgia
ill try this, but sounds like a bad valve tap, or a very early stage rod knock.
And whats weird, I went out again, and it will go away then come back. I KNOW a rod knock does not ever go away. This comes and goes. Im now thinking its starting to crankwalk. which is worse than a spun bearing or a rod knock.




yeah the o2 is perfectly fine. and the maf is fine, so i think because it will idle fine, but if i unplug it, it dies. so that means the maf is online and working. Im agreeing that the the ecu is "hearing" theknock and retarding the timing to the point that it wants to shut down.

Crankwalk does not make an audible sound. Besides, cw happens very rarely. But it does sound like you need to check out the rod bearings. Check it now before you ruin the crank.
 

kleenf4i

Proven Member
261
0
Oct 30, 2012
tampa, Florida
I never said the O2 was the soul source of not being able to boost. What I did say is a bad O2 can foul your plugs out and cause blow out and boost. You still have not checked your plugs and reported back with how they look. We dont know if this car is a 1g or 2g 6 bolt or 7 bolt. Some of these things should be told BEFORE you ask for help. But if your knock sensor is bad they usually start leaking a sticky goo from them.

My bad it looks like this is a 2g. But is it a 7 bolt or is it 6 bolt swapped?

7bolt. The 2nd p.o. rebuilt it. the p.o. i bought it from only had it for about a month.

Crankwalk does not make an audible sound. Besides, cw happens very rarely. But it does sound like you need to check out the rod bearings. Check it now before you ruin the crank.

yeah im going to have to drop the oil pan. and check it out. I can always replace the rod bearings if the crank didnt take a beeting. which I dont think it did yet.
 

bcracecar

Proven Member
94
0
Oct 29, 2012
Wichita, Kansas
Usually if you have rod knock, you are going to know it is rod knock LOL. Especially if you are driving it, because it WILL get louder. Lifter tick is always a common thing on these cars, I would still pull the plugs to see what kind of shape they are. Make sure the gapping is correct. Does it seem to be running rich? When my car was detecting "knock" and retarding the timing, it cut pretty furiously and made a nice little pop in boost. Does this sound familiar to you? The way you are describing the power loss though, sounds like you may have some loss in compression somewhere though... Start with the little painless things first and get them out of the way. No need to OVER think things before you eliminate the minor factors in the situation. I would recommend running one more BLT just to be completely sure.
 

kleenf4i

Proven Member
261
0
Oct 30, 2012
tampa, Florida
there is now a HEAVY KNOCK , seems from the top end though.I dont think its a rod knock. it seens the valves are bent and keep hitting the pistions at this point. Car stall, no power at all. and barely drives. It is now parked and woont be driven until its figured out.Through the valve cover I can feel the knock. when i go to the oil pan, theres no knock from it.new thread on knock will be started.

So it was a spun bearing. So now i sell this one and get another. I will be awhile before I can save up enough to buy what i want , but at least the problem has been found. It would stand, because of the rod knock the ecu would tell the timing to completely retard itself and thats why i had no power. At first i could barly hear the knock. then it got louder and i got it home( about 2 miles down the road and shut it off. The computer was hearing the slight rod knock as being bad enough to want to shut down the motor.
 

trillatl

Proven Member
98
0
Jul 3, 2011
Akron, Ohio
I didn't read all of to comments but I do know my car did the same thing when the cord to my MAF was not plugged all the way in. It acted like a huge boost leak. I was told to buy a new MAF and I was like I don't think thats the issue. I cleaned out the harness and plugged it back in and problem fixed. This also caused my car to jump timing one tooth... Hope you get it figured out.:banghead:
 

dsmornothing

Probationary Member
605
5
Jul 23, 2009
Ishpeming, Michigan
I didn't read all of to comments but I do know my car did the same thing when the cord to my MAF was not plugged all the way in. It acted like a huge boost leak. I was told to buy a new MAF and I was like I don't think thats the issue. I cleaned out the harness and plugged it back in and problem fixed. This also caused my car to jump timing one tooth... Hope you get it figured out.:banghead:

How does your MAF not functioning cause timing to jump a tooth?
 

trillatl

Proven Member
98
0
Jul 3, 2011
Akron, Ohio
How does your MAF not functioning cause timing to jump a tooth?

Un plug your MAF and try to drive the car... Let me know how that works out...::nono: it will jurk and buck like hell... I was on the highway then this happened to me... It feel the same way if one of your IC pipes comes loose...
 
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