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Intake Replaced, Still Running Lean

grandamle91

grandamle91

New member
I just got done replacing my UIM and its still running lean. When I take the oil cap off the idle changes and you can hear alot of air being sucked in.

98 Pontiac Grand Prix Running Lean - YouTube
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1998 Pontiac Grand Prix GT 3.8
Lowered 3 Inches
Cat, EGR, U-Bend Delete, 3" Exhaust All The Way Back Into Duals
Aluminium Sub-Frame
Power Steering, Trans Cooler, Soon Oil Cooler
K&N Custom Made Cold Air
Denso IT16 Plugs, MSD Coils, MSD Wires
12k HID
LEDS
 


IIRC that code states that bank 1 is lean. May indicate an O2 sensor issue.

When you replaced the PCV did you make sure it had 2 orings on it, one on the PCV itself and the larger one that rests in the UIM? I think there should also be a sping on top of it as well. You may still have a slight vac. leak throwing the lean code.
 


I have never seen an O2 be a lean bank issue. Please read this link
GearChatter.com :: View topic - DTC P0171 or P0174

That should give us a good understanding of how/why the code sets.

From my experience I have found this code to typically be:

The metal tube under the throttle body from the EGR to the LIM. These crack at the lim where the piece holds it.

Vacuum lines cracked/broken: specifially on the NA at the throttle body. Look at those silly goofy connections and ask yourself..how can they not split and leak.

UIM to LIM gasket. It's not all that common. But when the bolts go in with 89in lbs of torque (hand tight if that) and you are worried about breaking the plastic manifold (97-03), it's understandable.

TB to UIM gasket: It happens..and it's pretty common.

PCV: Missing an o-ring top (cap) or bottom (under/on pcv) is quite common and would cause this.

Battery cables: Yes..the cables being corroded not only at the battery but inside the cable itself can screw with voltage etc just enough to throw P0171 and send you on a 3-4 month journey that lands you swapping on new cables because you have no hair left. Pull the cables off the battery, remove the bolt and then pull the plastic boot off. Take a good look. Any corrosion is bad.

FalconJohn has a thread going and I took a look at his car. The only thing I could remotely find were a bad vacuum line at the TB and his battery cables were questionable. He's still fighting the code, replaced the positive cable..and I'm awaiting him to replace the negative cable... FWIW I shotgunned a good used O2 on the car and there was no change.
 
FordMan77 said:
IIRC that code states that bank 1 is lean. May indicate an O2 sensor issue.

When you replaced the PCV did you make sure it had 2 orings on it, one on the PCV itself and the larger one that rests in the UIM? I think there should also be a sping on top of it as well. You may still have a slight vac. leak throwing the lean code.
Click to expand...


The pcv didn't, I'll throw one on and clear the code

I've changed the o2 couple months back

I swapped out the plastic vac lines with rubber back when I did the o2

I know my batt cables do need to be replaced

I'll try these tips and report back
 
Does your HVAC routing system work? In other words, if you select "defrost," does the air route to the windshield area, and does it blow out the driver and passenger vents if you select them? I ask because I had the same code once, and it turns out the vacuum line that supplied vacuum to the HVAC control was disconnected; It's the line that runs along the firewall, to the passenger fender well. If disconnected and leaking, the HVAC controls will not function properly and you will get a bank 1 lean code.
 
Yea they work. i put the o-ring on the pcv value, cleared the code and drove it about 10 miles today and its back. When I stop and go to hit the gas it almost dies but catches and takes off, and some times when it driving around 35mph and chokes
 
Sorry to hear that. Have you tried spraying starter fluid near where vacuum leaks may be present, listening for a change in idle?
 


I just did that, i did find a little leak by the brake vac line. the o ring didnt seat right. it just seems loose. I just did the big 3 with 0\1 gauge wireing. So i'm keeping my fingers crossed
 
The new UIM, the brake booster hose didn't go back in right and the o ring popped out of it groove when i went to put it back.
 


Sorry i don't mean to butt in, except i recently had the same problem i replaced the LIM gasket and the UIM gaskets got it all back together started it and instantly could hear a vacuum leak i ignored it and eventually the SES light came on i took it to a shop a buddy of mine works at and they put it on a scanner and it indicated a lean condition. So I went home took it all back apart to find out what was causing it. Turns out the LIM had a small piece of old UIM gasket still stuck on it that i had missed that was preventing it from sealing and allowing air to leak in. Moral of the story make sure everything is VERY, VERY clean before you put it all back together. Hope this helps.
 
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