[MikeyS]

hi i have an 98 jimny the car is struggling to get up to speed kinda like when you get the coil packs wet i have just replaced th coil packs and the spark plugs and on the spark plug closest to the gear box it had oil on it!!!

oh and it also seems like there is not much back up pressure.( i do have a 2" exhaust but its never been that badd)

Does anyone know what this could mean?? or if there related??

[joel]

how many kms on the engine?
is it running rough?

i would suggest you get the compression tested and go from there, could be just old and tired.

[joel]

is it running rough?

how many kms?

may be the engine is down on compression, old and tired.

i would suggest a compression test and go from there.

[MikeyS]

where do you get compression test from ??

and its only got 157XXX k's on her didnt think that was much?

[Gwagensteve]

MikeyS wrote:

oh and it also seems like there is not much back up pressure.( i do have a 2" exhaust but its never been that badd)

Does anyone know what this could mean??

No, I have no idea what that means.

Any mechanic should be able to do a compression test. Regardless of Km, the engine is over 15 years old. It's quite possible that it's down on compression.

Otherwise, collapsed/fouled catalytic converter, blocked fuel filter… normal stuff.

Steve.

[Marko_SJ]

MikeyS wrote:

oh and it also seems like there is not much back up pressure.( i do have a 2" exhaust but its never been that badd)

Does anyone know what this could mean?? or if there related??

I'd say its unrelated.

"Required" back pressure is a myth, if back pressure was required do you think drag cars would run a short section of pipe, or older planes running plain stubs out of the cylinder?

Somebody smarter than me can explain it, but the larger the exhaust the slower it will flow, if you go too large. This does not aid power.

2" is slightly large but not too large.

[Jezza86]

MikeyS wrote:

oh and it also seems like there is not much back up pressure.( i do have a 2" exhaust but its never been that badd)

back pressure?
are you saying there's no noticeable pluses coming out the exhaust tip whereas normally you would feel individual pulses?

[Jezza86]

Marko_SJ wrote:

MikeyS wrote:

oh and it also seems like there is not much back up pressure.( i do have a 2" exhaust but its never been that badd)

Does anyone know what this could mean?? or if there related??

I'd say its unrelated.

"Required" back pressure is a myth, if back pressure was required do you think drag cars would run a short section of pipe, or older planes running plain stubs out of the cylinder?

Somebody smarter than me can explain it, but the larger the exhaust the slower it will flow, if you go too large. This does not aid power.

2" is slightly large but not too large.

drag cars, and the old p51 mustang fighters ran superchargers which evacuate the cylinders on the valve overlap, leaving a headers scavenging effects redundant.
on the p51 the exhaust outlets additionally provided thrust. but i agree 2" is not big enough to limit peak power at 6k rpm. it may restrict torque margionally lower down the rev range.

[Marko_SJ]

Jezza86 wrote:

Marko_SJ wrote:

MikeyS wrote:

oh and it also seems like there is not much back up pressure.( i do have a 2" exhaust but its never been that badd)

Does anyone know what this could mean?? or if there related??

I'd say its unrelated.

"Required" back pressure is a myth, if back pressure was required do you think drag cars would run a short section of pipe, or older planes running plain stubs out of the cylinder?

Somebody smarter than me can explain it, but the larger the exhaust the slower it will flow, if you go too large. This does not aid power.

2" is slightly large but not too large.

drag cars, and the old p51 mustang fighters ran superchargers which evacuate the cylinders on the valve overlap, leaving a headers scavenging effects redundant.
on the p51 the exhaust outlets additionally provided thrust. but i agree 2" is not big enough to limit peak power at 6k rpm. it may restrict torque margionally lower down the rev range.

Its not a two stroke, it does not use sound or anything else to push the charge back into the cylinder. But yeah after re-reading, I see you are talking about the scavenging effect of the cylinders. This is what I was referring to. Nothing to do with "back pressure"


In anycase, none of this wanking is helping the OP.

I'll be quiet now.

[johnmath]

MikeyS, it is very difficult to remotely diagnose engine underperformance from verbalised qualitative observations. What do you mean by: "there is not much back up pressure"?

The first thing to do is to get a tune-up, which should not cost a great deal, but should pick up 90%+ of common performance problems.

[Rhinoman]

If there is little pressure at the end of the exhaust then a collapsed cat is quite possible.

[MikeyS]

Johnmath i dont know how to explain exactly but ill try explaining it again when i try to take of in 1st gear full throttle the cars pickup takes about 3mintues to even get to 20kph it pretty much stays at less then 10kph till you at like 5 or more rpm. The only thing i could compare it in my mind is to either when i get more coil packs wet or when i went from stock to 2" exhaust in both case made my car slow off take off sorry about the weird answer still learning names of parts and the feel of the jimny.

[MikeyS]

Rhinoman thank you ill check that today .

[Jezza86]

will the car rev freely when its in neutral?
if it does mabie its a transmission issue

[MikeyS]

i did the pressure test today cylinder:
1#150 psi
2#155 psi
3#120 psi
4#150 psi

does anyone know what the normal rating is??

[Rhinoman]

It should be 170+

[MikeyS]

my battery wasn't fully charged would that make much difference??


also my car is making some weird noises http://www.youtube.com/watch?v=t1gkaXB9 ... Rsdq9N30DQ

[jimny_timmy]

That sounds head gasket like.... My guess is that's why the compression is so low on #3

[B1GBOAR]

Nearly bet my testicles you have a slightly bent valve or similar. I had a Mitsubishi come in the other day with that and sounded Nearly exactly like that. Pull the head off and have a look. have a look on how to do a leak test to, that will tell you if you have a bent valve without pulling the head itself apart