87 PUP 1.9 running rich

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ckh
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Posts: 7
Joined: Sat Sep 17, 2011 4:49 pm
Location: Las Vegas, NV

87 PUP 1.9 running rich

Postby ckh » Sun Sep 18, 2011 2:08 pm

I own an 87 PUP 1.9 w/4 speed and original carb (#8941230280). Failed smog test as it is running rich at all speeds, especially at idle.Popping in exhaust upon deceleration. I have done a compression test, pressure tested cooling system, checked timing. All are ok. Checked intake for tightness and replaced all questionable vacume lines. I then rebuilt carb with new needle & seat, new gaskets, set the float level, cleaned it thouroughly etc. Throttle shaft wear doesn't seem excessive. Reinstalled carb, no change. Attempted to adjust idle mixture, no change. Disassembled the carb again and noticed something that doesn't look right. Just below the choke plate there is a threaded hole approx. 1/4" dia. on the inside of the air horn. I think something might be missing from this hole (a check valve maybe?) as the hole runs to a vacume passage to what I would call an air jet,then down a tube thru the carb body to the carb base and exits at some small holes in the primary throttle bore just above the butterfly.I think something is missing from the above mentioned hole or it seems to me there would be a constant vacume leak. I would be grateful if someone out there that has an 87 with this carb, or just the carb itself,(the # is on the float bowl cover) could open the choke plate and let me know if mine is missing something. Using the front center of carb as a reference point, 12 o'clock, the hole or part is between 3&4 o'clock and 1 1/2" down from top of carb. I know nothing about emission controls. Could something in any of the emission control systems cause it to run overly rich? It runs smooth at speed but the rpm varies a little at idle. Any suggestions would be appreciated.
Thanks,
Colin

ckh
Regular Member
Posts: 7
Joined: Sat Sep 17, 2011 4:49 pm
Location: Las Vegas, NV

Re: 87 PUP 1.9 running rich

Postby ckh » Tue Oct 11, 2011 12:06 pm

Any ideas Jerry or 1badluv?

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JoeIsuzu
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Posts: 19583
Joined: Thu Aug 19, 2004 9:11 am
Location: Germantown (next to Elvistown), TN
Isuzu vehicle(s): Original owner, '83 LS Diesel, 5-spd, 2wd, Long Bed, restoration in progress!

Re: 87 PUP 1.9 running rich

Postby JoeIsuzu » Tue Oct 11, 2011 1:27 pm

ckh wrote:Any ideas Jerry or 1badluv?

Wow, I see what you mean. It's been weeks since you posted this. Yeah, I don't blame you for using the PM. Wish I could help.

Jack

lost_banjo
Regular Member
Posts: 14
Joined: Wed Jun 24, 2015 3:01 pm
Location: Louisiana
Isuzu vehicle(s): '86 P'up 4 speed Gas

Re: 87 PUP 1.9 running rich

Postby lost_banjo » Thu Oct 12, 2017 11:49 am

I have the same problem. Same pup, same carb.
Just found this post looking for a rebuild kit.
Ever find out the problem?

isuzuesque
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Posts: 170
Joined: Wed Jul 23, 2008 3:57 pm
Location: Sunnyvale, CA

Re: 87 PUP 1.9 running rich

Postby isuzuesque » Fri Oct 13, 2017 12:02 pm

I had this problem and for me it was that the mixture control solenoid had failed. I dint know if your truck has one of these. Does your truck have an ECM (computer)? The solenoid is inside of the carburetor and has two wires running into the top of the carburetor just beside where the needle valve is. This can be tested by disconnecting the oxygen sensor and disconnecting the WOT and IDLE switches and turning the ignition to on but with engine stopped. You will hear a clicking noise, this is the solenoid working properly.

John
1984 GMC S-15 Short Bed Pickup 2wd with Stock Isuzu 1.9L Gas Engine
manual 4 speed, manual steering, manual brakes, original owner, awesome!


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