Lost top end power in 88 Cherokee 4.0.
 

Ok, I am on a fishing expedition for likely things to check.

Our 88 Cherokee with the 4.0 has lost power above half throttle. It
goes fine up to that point, then just bogs, no matter what gear it is
in. It has been neglected for 4 years as far as tuning goes due to me
not being up to it.

I first changed out the 'very' dirty distributor cap and rotor which
made starting 'much' faster and smoother.

I then changed the gas filter because it was once again rusted to the
rot point after about 8 years.

Air filter is new.

I cleaned the connections on the TPS and IAC and verified the TPS
doesn't have any 'dead' spots with my meter.

I cleaned the CPS and coil connections also.

No joy on any of that.

I have been having some cold idle issues and have been thinking on
cleaning the IAC, but don't know if that will have a top end effect or not.

I am also thinking on unplugging the EGR just to make sure it isn't
blown vacuum wise because it only bogs under throttle when things like
the EGR are active.

Any other ideas?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Re: Lost top end power in 88 Cherokee 4.0.
 

> Any other ideas?
>

Did you open up the old fuel filter, or blow it backwards into a can to
inspect for dirt or sparkles that could indicate a pump dying?
I would run a fuel pressure test, and then a cat pressure test.
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

Re: Lost top end power in 88 Cherokee 4.0.
 

> Any other ideas?
>

Did you open up the old fuel filter, or blow it backwards into a can to
inspect for dirt or sparkles that could indicate a pump dying?
I would run a fuel pressure test, and then a cat pressure test.
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

Re: Lost top end power in 88 Cherokee 4.0.
 

> Any other ideas?
>

Did you open up the old fuel filter, or blow it backwards into a can to
inspect for dirt or sparkles that could indicate a pump dying?
I would run a fuel pressure test, and then a cat pressure test.
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

Re: Lost top end power in 88 Cherokee 4.0.
 

> Any other ideas?
>

Did you open up the old fuel filter, or blow it backwards into a can to
inspect for dirt or sparkles that could indicate a pump dying?
I would run a fuel pressure test, and then a cat pressure test.
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

Re: Lost top end power in 88 Cherokee 4.0.
 

Stupendous Man wrote:
>> Any other ideas?
>>
>
> Did you open up the old fuel filter, or blow it backwards into a can to
> inspect for dirt or sparkles that could indicate a pump dying?
> I would run a fuel pressure test, and then a cat pressure test.

Yes I did blow out the filter and besides being a bit hard to blow
through, it appeared ok. Rotted pretty bad though.

I have no cat to check, well there has been nothing 'in' the cat since
before I bought it and it still passed emissions great.

I have no real way to check for fuel pressure I don't think unless one
of my old compression testers could be converted??

The miss is pretty consistent.

Thanks,

Mike

Re: Lost top end power in 88 Cherokee 4.0.
 

Stupendous Man wrote:
>> Any other ideas?
>>
>
> Did you open up the old fuel filter, or blow it backwards into a can to
> inspect for dirt or sparkles that could indicate a pump dying?
> I would run a fuel pressure test, and then a cat pressure test.

Yes I did blow out the filter and besides being a bit hard to blow
through, it appeared ok. Rotted pretty bad though.

I have no cat to check, well there has been nothing 'in' the cat since
before I bought it and it still passed emissions great.

I have no real way to check for fuel pressure I don't think unless one
of my old compression testers could be converted??

The miss is pretty consistent.

Thanks,

Mike

Re: Lost top end power in 88 Cherokee 4.0.
 

Stupendous Man wrote:
>> Any other ideas?
>>
>
> Did you open up the old fuel filter, or blow it backwards into a can to
> inspect for dirt or sparkles that could indicate a pump dying?
> I would run a fuel pressure test, and then a cat pressure test.

Yes I did blow out the filter and besides being a bit hard to blow
through, it appeared ok. Rotted pretty bad though.

I have no cat to check, well there has been nothing 'in' the cat since
before I bought it and it still passed emissions great.

I have no real way to check for fuel pressure I don't think unless one
of my old compression testers could be converted??

The miss is pretty consistent.

Thanks,

Mike

Re: Lost top end power in 88 Cherokee 4.0.
 

Stupendous Man wrote:
>> Any other ideas?
>>
>
> Did you open up the old fuel filter, or blow it backwards into a can to
> inspect for dirt or sparkles that could indicate a pump dying?
> I would run a fuel pressure test, and then a cat pressure test.

Yes I did blow out the filter and besides being a bit hard to blow
through, it appeared ok. Rotted pretty bad though.

I have no cat to check, well there has been nothing 'in' the cat since
before I bought it and it still passed emissions great.

I have no real way to check for fuel pressure I don't think unless one
of my old compression testers could be converted??

The miss is pretty consistent.

Thanks,

Mike

Re: Lost top end power in 88 Cherokee 4.0.
 

Plug wires can do this, but they will usually give you some backfiring along
with the bogging down.

Earle

"Mike Romain" <romainm@sympatico.ca> wrote in message
news:4659a194$0$3020$9a6e19ea@unlimited.newshostin g.com...
> Ok, I am on a fishing expedition for likely things to check.
>
> Our 88 Cherokee with the 4.0 has lost power above half throttle. It
> goes fine up to that point, then just bogs, no matter what gear it is
> in. It has been neglected for 4 years as far as tuning goes due to me
> not being up to it.
>
> I first changed out the 'very' dirty distributor cap and rotor which
> made starting 'much' faster and smoother.
>
> I then changed the gas filter because it was once again rusted to the
> rot point after about 8 years.
>
> Air filter is new.
>
> I cleaned the connections on the TPS and IAC and verified the TPS
> doesn't have any 'dead' spots with my meter.
>
> I cleaned the CPS and coil connections also.
>
> No joy on any of that.
>
> I have been having some cold idle issues and have been thinking on
> cleaning the IAC, but don't know if that will have a top end effect or
not.
>
> I am also thinking on unplugging the EGR just to make sure it isn't
> blown vacuum wise because it only bogs under throttle when things like
> the EGR are active.
>
> Any other ideas?
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
> (More Off Road album links at bottom of the view page)