Topic: Code 51, high nox at 15mph, looking for a leak upstream from 02 sensor...

[chrisfranklin]

https://www.youtube.com/watch?v=Ya8cZwhQ2ts&feature=youtube_gdata_player

Didn't install the intake manifold myself.  What's that look like to you guys? Bad angle, but that' s a hole for a manifold bolt, right?
Or am I way off? ...Need to look at the pdf's here for the Yj shop manuals and see what intake manifold diagram looks like

[sharpxmen]

that's not a bolt, it's a dowel pin and its purpose is to center the manifold (and for reference an intake vac leak on 91-95 YJ does not result in lean mixture but just high idle since it's using MAP and not MAF)

if you get code 51 look for low fuel pressure, clogged fuel filter, bad pump or bad O2 sensor (or less likely the IAT or collant temp sensor)

nice intake/exhaust gasket btw, the ones i've seen didn't have the metal on them.

- not sure if i remember correctly but i think i recall you having a MAP voltage modifier installed (if that's not the case disregard) - might want to check that as well.

[chrisfranklin]

About 20 minutes after I left the shop with this new intake manifold installed,  I see a CEL .   Checked the codes and got the Code 51.

It's been years probably since the last time I've checked the codes.  Didn't have cause until I got this CEL  post the recent intake-manifold installl work.

Put in a new O2 sensor a few days ago.    

Low fuel pressure, clogged fuel filter,  bad pump, or maybe IAT or CTS.  Changing the sensors and fuel filter are probably doable in short-order.  Haven't detected any new "feedback" from the fuel pump (however, wouldn't be surprised if the unit is the one my Jeep came with from the factory;  so pushing 20 years old and around 100k miles.

Did have an adjustable MAP sensor deal from Turbo City installed for a couple of days a while back (Art probably remembers all that  ).  I pulled it, though.  IIRC plastic adjustment screws on the thing yielded voltage adjustability that was a long way from precise.  Voltage readout on the MAP adjuster display would spike up/down if you even thought about messing with the screws...

[sharpxmen]

what exhaust manifold did you put on? my pacesetter had stepped washers as the "lip" thickness is different between that and the intake manifold. I'd say reset the 'puter first and see if it comes back.

EDIT: since you just had some work done it is probably related to that (the obvious "most likely"), so i would check all the vac hoses and check valves, make sure there's none on the MAP sensor line. How does it run anyway, maybe should start with that (any problems?)

[grumpygy]

what exhaust manifold did you put on? my pacesetter had stepped washers as the "lip" thickness is different between that and the intake manifold. I'd say reset the 'puter first and see if it comes back.

EDIT: since you just had some work done it is probably related to that (the obvious "most likely"), so i would check all the vac hoses and check valves, make sure there's none on the MAP sensor line. How does it run anyway, maybe should start with that (any problems?)

From the Video it looks like they did not use the steped washers and it looks like he needs to.

[sharpxmen]

they should come in the kit

but it should also high idle if not sealing properly unless they did something to compensate for that (like blocking the line coming from the valve cover).

[Jeffy]

Sharp is right, if there is a leak issue with the header you'll get an immediate high idle.  I highly doubt the shop did anything other then bolt it up like in the instructions.

Did you check the basics?  Did they reconnect all of the connections?  How about the IAT sensor?

[chrisfranklin]

http://i250.photobucket.com/albums/gg271/leeiaccoca/EmissionsTestResults9-21-12_zpsdd66b5a0.png

Emissions test results. 

No high idle.  As far as performance,  not noticing stumble, but can't say engine is running 100% either. 

When get a chance may "force flash" things  http://www.jeepsunlimited.com/forums/showthread.php?t=379374.  But not expecting that to fix anything. 

[sharpxmen]

that's for TJ, in your case just disconnect the battery like it's been covered here before.

[chrisfranklin]

that's for TJ, in your case just disconnect the battery like it's been covered here before.

Even more reason for me to not expect it to fix anything    Thanks for pointing that out, Sharp.

[aw12345]

Make sure the EGR valve works and the ports are clean, run some seafoam or some other engine top end cleaner through the engine and try again

[sharpxmen]

91-95 MPFI don't have EGR, tbi does.

[chrisfranklin]

Realizing today, I've got what's probably a high idle -- 1500rpm -- on startup.  It ultimately seems to settle back down to 700-800rpm or so.  It's been that way for a while; replaced the IAC valve awhile back, but the high idle is still there. 

[chrisfranklin]

This is still an outstanding issue...

Ordered and received delivery of a set of 5,10, 15" socket extensions http://www.amazon.com/gp/product/B000NI93M0/ref=oh_details_o01_s02_i00.  Going to see if I can find a lose bolt on the intake, header myself.