Endless P0171- some new hope - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 09-26-2009, 01:39 AM   #11
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Well, I'm at the point where no system on the car works properly. It'* amazing that the car runs at all, let alone all of the time.

The EGR pipe didn't change anything. Put the TB back on, and to eliminate any possibility, I put a bead of the GM red gasket maker on the gasket. It'* airtight for sure. That stuff has never failed me.

For laughs, let'* go through this and see how skewed I am....

Original issue - my boost gage was jiggling and the MAF to MAP readings were inconsistent. This appears at idle, and particularly during warming up. P0171 (lean burn) occurs upon occasion, usually at ignition or shortly thereafter.

Now the rest...

Fuel system- A fired up fuel pump, showed 40psi (short about 8psi), so it was recommended I replace the pump. Did so and the powered up pump showed 44psi. But found out that the fuel pump did fire to 52-54psi, except there simultaneously made a hissing sound, coming from the EVAP purge valve area, and it would drop to 44psi. It will do it repeatedly, no matter how many tries you bunch together.

Air system - Over the months, have basically replaced 75% of the vacuum lines and connectors, Also during that time, have a completely clean engine from spraying carb cleaner on all vacuum lines trying to find a leak. Putting aside that weird fuel pressure thing, on learned suggestion I focused on the EGR and its components the past few days. spraying brake cleaner on the EGR and its 2 pipes (1 to LIM, one to exhaust) it was clear that some was making its way to combustion. Last night, replaced EGR/manifold pipe, to no apparent avail.

Fuel/Air EVAP system - Today, on the way home from work, was rewarded with a P0440 EVAP System failure code. This is completely new. It is possibly the new gas cap i put on last week... or any part of the pump assembly which includes the new pump, pulsator, senders, lines and the installation itself. Also anything adversely effecting fuel tank pressure. Included with this is, of course, the EVAP canister, solenoid, and the vapor/vacuum lines from the gas tank to the canister, from the canister and TB to the purge unit.

Note: In a glorious event today, post P0440 DTC, on the way home from work, the boost gage behaved like it should. It was only one hour in endless months, but it was great. It was nice to look at the scan tool and see air and fuel trims in discernible patterns, instead of the usual frighteningly unexplainable mash. I was certain this was a random event like a broken clock is correct twice a day.When i arrived home I shut off the engine. Of course when i kicked it back over, it was back to bizzaro .

Electrical system - To show how much this is stressing the systems - if you turn on an accessory, or even press the power window button, the MAP and boost gage move up a good bit. I have the cleanest and virtually new battery cables. New highest cranking battery. Clean, tested ICM and coils. The only thing was that the old battery was really bad, and although the charging circuit tests out, I have an alternator on the way. For some odd reason our batteries and alts seem to go at the same time. So just in case.

I know this like some Facebook entry or blog ,but i wanted to put it all out there. I have been taking care of 3 Bonnevilles for a number of years, but this has me running around in circles. It would be dumb to just start replacing parts in hopes of finding the answer.

I have brainfreeze and a ton of frustration goin' on, and need any suggestions for the best approach here. Even better would be another set of eyeballs to take a look at it, there is so much going on. If there is an experienced wrencher within a couple hundred miles of Phila, I would happy to travel and make it mutually beneficial to turn this situation around.

I really enjoy learning and working on our Bonnevilles. I'd rather ask for help than let it start to be unfun.
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Old 10-10-2009, 06:10 PM   #12
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OK. I'm done whining.

The EVAP P0440 was the gas cap. FWIW, guys who have '95-'97s... your earlier issued gas caps might work, but the '98 (and probably '99") use one that is quite different in design. The part that screws into filler pipe is black and has an odd shaped triangular catch on its surface. Most every other year, that part of the cap is white and is threaded. Those white ones may or may not be cooperating with EVAP venting and fuel tank pressure. One that I picked up at the yard didn't. It was a real nice tight close, and apparently that isn't good.

-Either a leak in the EGR pipe or the TB was causing the P0171. Although, the boost gage/MAP reading is showing unaccounted air when comparing to the MAF sensor, that problem appears charging system/current draw related.

Die P0171.

- It also appears that I have a pressure leak where the main fuel line connects to the fuel rail. When I power up the fuel pump, the pressure goes to 50+psi, and immediately I hear a hissing sound and it drops and holds at around 44psi. I thought it was coming from the EVAP purge valve which is a few inches away, but it is coming out of the connector. When powered, the fuel pressure should go to 50+ and stay there. When I go further and actually turn it over, then it should fall back to the mid-40s for normal operation.

So I DID have a bunch of things going on. Freakin' plague of small problems. Gonna take care of them separately on the board, as i have questions.

One down, two to go.
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Old 10-10-2009, 06:14 PM   #13
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Most of the time it'* better to step back and look at all the small problems and fix them one at a time instead of looking at it as a huge problem and fixing it all at once. Keep at it, you will get them all.
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Old 10-10-2009, 06:42 PM   #14
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Quote:
Originally Posted by Danthurs View Post
Most of the time it'* better to step back and look at all the small problems and fix them one at a time instead of looking at it as a huge problem and fixing it all at once. Keep at it, you will get them all.
Exactly the truth. I got sucked in by symptoms stepping on each other.

I'm posting to Electrical. Just used your write up to multi-meter my charging system. Good piece, and I have somethiing going on electrically. Also I need some info on the fuel line/rail connection.

one at a time, and I'll be back on-line to start mods..
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