# Bogging Bogging Bogging



## Matt_240 (Apr 7, 2004)

well, i know i have a s-chassis but i need help. I have a 95 240sx and heres the symptoms:
1. When in neutral, if I hold rpms constant at 2000 and then rev up quickly, 
the car bogs. So the revs go up, bogs at a certain point, then goes up 
again. 
2. Spark plugs black with fuel - rich
3. Exhaust shoots out black smoke - rich
4. Car runs fine when cold for first 3 minutes or so. Then as the car warms 
up, it starts to bog. gets worse at it nears operating temp.
5. While driving the car bogs especially when applying low to mid 
throttle. Mostly low throttle. Right when it bogs, if I apply more throttle, 
the car seems to regain control and rpms rise smoothly again until it bogs 
again. it bogs randomly but around 1000k~3000k rpm. 

Heres what ive done so far:
1. Changed spark plugs
2. Switched out spark plug wires
3. Changed rotor and cap – distributor
4. Switched out air intake temp sensor
5. Switched out MAF (4 different ones)
6. Checked intake piping for leaks
7. Checked vacuum lines - ok
8. Tested continuity from sensors (tps,MAF,Intake air temp, coolant temp) to ecu – all ok
9. Changed tps - adjusted it to .5 volts at closed throttle
10. Changed o2 sensor on exhaust manifold
11. Switched out ecu
12. Changed fuel filter
13. Switched out coolant temp sensor
14. Switched out distributor – adjusted timing to 20btdc or last position with timing light. 
15. Switched out fuel injectors
16. fuel pressure was fine
17. fuel pump @ 40~45psi = great
18. Removed EGR system so its all gone and plugged up

Things i haven't done yet/worried about:
1. IACV clean
2. TB clean
3. o2 sensor might not be shielded properly? could this be possible? ive read somewhere that the reading could be affected if other signals from a/c or something interfered with it. 

What i need is more ideas...cause im running out. This problem popped out of the blue. some things i did before this happened(more clues): 
1. went drifting 3 days beforehand 
2. when this problem happened, i wasn't the one driving it. it was at a body shop and they wanted to move the car and it just started bogging they said. body work was done on the fenders w/ hood propped up.

please help me out!! just throw ideas out at me. the cars now at a shop but they cant seem to figure it out either..and its the second shop ive taken it to. thanks


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## chimmike (Oct 17, 2002)

if you have a 240, why did you post in the sentra, b14 section?


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## Matt_240 (Apr 7, 2004)

chimmike said:


> if you have a 240, why did you post in the sentra, b14 section?


i answered your question in my first sentence. thanks


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## Harris (Nov 11, 2002)

Sorry, but this belongs in the S14 section. Moving...



As for advice, replace your O2 sensor(s) and see what that does for you.


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## MoonShine (Apr 7, 2004)

double post! Should be deleted(mod)


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## ReVerm (Jan 13, 2003)

Matt_240 said:


> i answered your question in my first sentence. thanks


You could have posted in the Naturally Aspirated forum, but that doens't matter for now.

About your spark plugs being coated in black: Are you certain it's all fuel? As you probably know, if there is oil mixed in there, you may be looking at a slew of other problems. I also saw that you didn't have rear O2 sensor listed on there. You may want to check that out. It was causing my car to do all kinds of strange things last year.


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## Forced240 (Jan 13, 2004)

It sounds like the timing is off.


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## morepower2 (Apr 19, 2002)

Matt_240 said:


> well, i know i have a s-chassis but i need help. I have a 95 240sx and heres the symptoms:
> 1. When in neutral, if I hold rpms constant at 2000 and then rev up quickly,
> the car bogs. So the revs go up, bogs at a certain point, then goes up
> again.
> ...


Did you check the wiring between the maf and the ECU? The MAF ground, if its not the MAF, it is probably one of these. It sounds like a classic MAF issue.

Mike


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## Matt_240 (Apr 7, 2004)

morepower2 said:


> Did you check the wiring between the maf and the ECU? The MAF ground, if its not the MAF, it is probably one of these. It sounds like a classic MAF issue.
> 
> Mike


yea, voltage is correct between the MAF and ecu. 

timing has been checked and rechecked. 

sorry about posting in all different areas. just wanted as many inputs as possible.


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## 93blackSER (Feb 1, 2003)

just do a rebuild. you'll figure out then. i'd also have a lawsuit against the body shop as it was in their possession when this started.


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## morepower2 (Apr 19, 2002)

Matt_240 said:


> yea, voltage is correct between the MAF and ecu.
> 
> timing has been checked and rechecked.
> 
> sorry about posting in all different areas. just wanted as many inputs as possible.


Did you check the ground? Did you see if you have a bad groud by checking for voltage accross the ground? Should be less than 10 Mv.

Mike


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## Murph (Aug 8, 2002)

Could it possibly be the coolant tempurature sensor? I have no idea if it can have such a huge effect, but who knows what sorta values its returning. I think this can be checked very quickly via the OBD port.

If your all out of ideas and the MAF checks out OK, it couldnt hurt to check this. Notorious for going bad!


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## Matt_240 (Apr 7, 2004)

Murph said:


> Could it possibly be the coolant tempurature sensor? I have no idea if it can have such a huge effect, but who knows what sorta values its returning. I think this can be checked very quickly via the OBD port.
> 
> If your all out of ideas and the MAF checks out OK, it couldnt hurt to check this. Notorious for going bad!


well, shop i took it to is onto something. the fuel injectors were replaced with new ones to see what happens. it ran perfect! then, they called me up saying i should come pick it up. by the time i get there and try and drive the car around though, the bogging started again. this time, the guys shifted the wire harness right about the injectors and it ran better. Sooo, we think it might be a thinning out wire int he wireharness which can send signals to the ecu a-ok when idle or under no load, but when it gets hot, under load, the wire fails to send the signal to the ecu causing my a/f ratio to go haywire. i'll post to let you guys know what happens. thanks for the help!


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## OPIUM (Aug 18, 2002)

check and re-check the grounds as well.. it could contribute to that


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## Matt_240 (Apr 7, 2004)

OPIUM said:


> check and re-check the grounds as well.. it could contribute to that


thanks i'll tell them to add more ground for the maf as well as other areas.


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## Matt_240 (Apr 7, 2004)

well, my cars back to normal. the problem was the wire harness and the fuel injectors. changed the injectors and spliced new wires in and it runs perfect now. thanks for the help guys.


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