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Discussion Starter · #1 ·
Hey everybody, just got a 92 2.6l pick up (totally stock) and am trying to get it ready for a move out west but i cant get to run right. Heres the symptoms

"Engine running rough, engine lacks power and excessive fuel consumption" - Isuzu workshop manual diagnosis section

I would say that I am down power about 25%, Idles terrible once ECM kicks in (not idle scew or throttle cable adjustment) will fluctuate between 450-2500rpm....... will settle down for a bit than start all over again. When I bring rpm range up it calms down a bit but still not running how it should be. Gets around 21-24 MPG.

- all vacume hoses are fine
- intake is not loose
- gaskets are good and are'nt stopping air flow
- checked spark plugs (bosch platinumns) brand new but were dirty - cleaned and reinstalled - no change
- changed air cleaner
- new fuel filter and full tank of high test
- changed thermal valve
- cleaned air cleaner port sensor
- replaced EGR valve
- changed distributor body, rotor, and cap... original wires tested and fine
- changed ignition coil
- changed o2 sensor
- reset timing - now heres where i think the problem could be buried after i have it set up for time (12degrees/900rpm) it will stay on my mark sporatically. its jumping like crazy from retarded to advanced than back to 12degrees for a few revolutions than crazy again.... timing belt excellent condition with .5" of play
- adjusted valves 2mm intake and exhaust
- checked compression isuzu calls for a limit of 119.5 psi with a variance of no more than 8.5psi....after 5 rev roles and three try's per cylander I averaged : cyl1- 136 cyl2- 135 cyl3-143 cyl4 -136
- changed ECM AND COMPUTOR

Now i realize that anyone that has just read that list is running the figures and must be thinking I'm made of money.... I'm not i just have the another parts vehicle that ran perfect until a head gasket went.
The parts that i have taken off that vehicle are the fallowing
- Thermal valve
- EGR valve
- ECM and computor
- ignition coil
- distributor body

all the other parts are new.

The only thing left out of the Isuzu workshop manual I havent tried is disconnecting the EGR pipe from the manifold and test with pipe plugged and I havent checked the function of my BPT (back pressure transducer) .........where is it?

If there are any suggestions that lead to me correcting this problem and your along my route out west ........... f$%# a beer I'll buy you a case!

Cheers
 

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Tad said:
My 2.6s used to run horribly when the cap needed replacement. I learned (was taught?) that the ones that have Italy stamped on the inside are garbage and can be bad new out of the box.

-Tad
TAD IS MUCHO CORRECT ON THIS , MAKE CERTAIN YOU HAVE A GOOD CAP PREF, A FACTORY CAP , HOWEVER YOUR PROB, SOUNDS LIKE THE TPS SW IS EITHER BAD OR BADLY OUT OF ADJUSTMENT . JERRY
 

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did you replace the splug wires?
 

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sounds a bit like my '90 pup (2.6L)

did you replace the timing belt? is the tensioner any good?

double check the vacuum lines. make sure they're sealed and they are connected in the proper locations.
as others have said, a good gas cap is important.
check that the EGR valve doesn't stick. if it came from a parts vehicle, this could be bad; especially if the parts vehicle has been laying around.

i've been getting just over 20MPG when my truck is running fine (no load) and around 6MPG when it wasn't. i still have some work to do on mine.

rpm oscilation at idle: i get it now and then but seems to quite after awhile. it lessened after i replaced all my vacuum lines. i'm suspection i still have a vacuum leak in my throtle body and/or intake manifold.

for the EGR valve, my truck would run well then choke and die after 30min or so. i thought i fixed it by replacing the computer, but i didn't and had to cancel my trip to tellico this weekend because of it :( i replaced the EGR valve with a new one from napa and it seems to run fine (for now)

here's a link to a very good thread on 4x4wire.
http://www.4x4wire.com/forums/showflat. ... ber=591821
 

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Discussion Starter · #9 ·
Yeah my belt is fine and my tensioner is perfect to.... as for the other stuff you mentioned (EGR valve etc.) its all good as well. On Monday im running a diagnostics check, so Ill have a better idea than. Cheers bud and thanks for the response
 

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They are referring to a distributor cap not a gas cap. A bad cap will make one run like it's running on 2 cylinders, maybe because it is. :lol:

Joe
 
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