I Give Up!

**Banshee1967** · 12-16-2007, 05:15 PM

Been dealing with a few issues with the Trans Am over the past few months. Threw P1410 P1416 and 418. Secondary air circuit, relay..etc. I didn't bother with it until my fuel milage (90% freeway) began to suffer to the tune of 17-18 mpg. Car has 125k, and has no other issues. Only mod is loudmouth exhaust. No other codes.

Replaced the wires, new Delco irridium gapped at .52, new air check valves both sides, new fuel filter, new pvc valve, tire pressures are on. Did everything in 4 hours a few days ago and still 17-18 mpg.

The air valves I pulled off the car flowed both ways if that helps anyone.

I have cleaned the MAF with MAF cleaner and made sure everything was tight.

Any thoughts?

**Banshee1967** · 12-16-2007, 05:17 PM

I do smell raw fuel from time to time when the heat or air is on....but no signs of wet fuel under hood. I smell it on cold starts and under heavy acceleration. The plugs I replaced looked great. The plugs were tan with no carbon build up and only one plug had a gap of .80.

**sunsetorangess** · 12-16-2007, 06:46 PM

Umm, you said u replaced the plugs, are u saying one of the new plugs was gapped at .080? Are you still throwing the codes?
J

**Banshee1967** · 12-16-2007, 07:18 PM

One of the old plugs electrode eroded to .80. The insulator's on all were tan and very clean.

Still throwing all the same codes. What makes me wonder is that all the reading here on the forums state for the most part, these codes have little or no impact on fuel milage. Quite possible I am dealing with a coincidental repercussion of the air valves being able to flow both ways and allowing freeflow back into the system.

My next guess would be a vacuum leak somewhere.

**0rion** · 12-16-2007, 09:02 PM

it would be really nice to be able to log the car so you can see exactly what's going on. I'm not exactly sure on the valves except they are called "check valves" which typically means they should only flow one direction. I could see them making the O2's see a false lean condition and the pcm is adding extra fuel to compensate. How good are you at fabrication? It's really easy to make your own block offs for the air tube to manifold connection just to test it and see if the car runs better.

**JL8Jeff** · 12-17-2007, 12:09 PM

Did you delete the codes and they came back after putting on new check valves? The P1410 is the gas tank pressure code which probably means your charcoal canister needs to be replaced or the purge valve needs to be replaced. The P1416 and P1418 are codes for the AIR system and it sounds like your AIR pump is going bad and drawing too many amps. When the check valve went bad on my 93, the hot exhaust air went back to the AIR pump and condensation built up. Then the AIR pump actually filled with water from all the condensation build up and froze solid in the winter. That caused it to blow a fuse when it couldn't turn the pump on. Sounds like you have 2 different problems. Check your AIR pump to see if you have condesation built up in it. And you'll probably need to replace the charcoal canister.

**Banshee1967** · 12-17-2007, 07:50 PM

I deleted the codes today with the fuse removal tip I found here. I have yet to drive it yet, but from the past two times I borrowed an OBD II scanner and deleted them, the codes popped up after a few miles.

I surmise the charcoal canister is near the tank and the air pump around the front core support?

**0rion** · 12-17-2007, 08:38 PM

the canister is in the drivers rear quarter panel ( at least on my 98). The air pump is behind the drivers side headlight. Drop the access panel down that you'd use to change your drivers side foglight and look up in there.

**LETHALxLS1** · 12-17-2007, 09:14 PM

Originally Posted by JL8Jeff

Did you delete the codes and they came back after putting on new check valves? The P1410 is the gas tank pressure code which probably means your charcoal canister needs to be replaced or the purge valve needs to be replaced. The P1416 and P1418 are codes for the AIR system and it sounds like your AIR pump is going bad and drawing too many amps. When the check valve went bad on my 93, the hot exhaust air went back to the AIR pump and condensation built up. Then the AIR pump actually filled with water from all the condensation build up and froze solid in the winter. That caused it to blow a fuse when it couldn't turn the pump on. Sounds like you have 2 different problems. Check your AIR pump to see if you have condesation built up in it. And you'll probably need to replace the charcoal canister.

**Banshee1967** · 12-19-2007, 08:23 AM

I deleted the codes on Monday and drove it about a mile and SES light came back on. When I parked, I hear a high pitch intermittant "rotating scratch/squeal". I thought it was a tensioner pulley, but maybe it is the air pump.

Forgive me for being naieve. I am an old school builder and own two 68 Firebirds and a 67 Firebird...all 400's. This computer controlled stuff is nice, but complicated.

Is there a way to check the overall car by using the same port as the OBD II?

If I am having problems with an active system as the secondary air system (throwing codes) would a passive system like a charcoal canister or fuel regulator/pump being bad necessarily throw a code?

Thanks again! Learning alot from the archives..

**0rion** · 12-19-2007, 04:53 PM

actually, before I went and started changing canisters I would make sure the seal around the gas cap isn't bad. That's very cheap and very easy to replace. Secondly, pulling that air pump is a pretty easy job. If yours is screwed up you can probably find someone on here that'll sell you theirs pretty cheap because it's a popular item to take off. Pull your pump and inspect it and I'd almost guarantee it's jacked up.

To answer your question you can throw codes from any of the obd2 systems at the same time. Normally you'll find that they're related but I'm not sure that's the case here. I'm not sure how these 2 can be related.

**Banshee1967** · 12-21-2007, 10:20 AM

Update..

Removed air pump and works off of jumpers and 12v battery. All relays work. I have no power to the air pump or solenoid at the fuse box. All other circuits within that fuse panel check fine. Been working all day to trace..Anyone have any ideas?

**0rion** · 12-21-2007, 11:00 AM

wish I could be of more help but looking at the schematic I'm not sure what to tell you. There's an air injection bypass valve and an air injection bleed valve solenoid. Not sure where to tell you to look for those. The air pump relay control is fed straight from the pcm and there's a 25 amp fuse for the pump but you say you're not getting power to the fuse right? That fuse is fed from the bypass valve. The feed going into the bypass valve is pnk/blk and comes out orange. Hope maybe some of that helps you. Later this evening I'll scan the schematics and post them if that'd help you.

**Banshee1967** · 12-21-2007, 11:17 AM

Correct.

I am not getting power to the 25a air pump fuse...nor to either relays. Vacuum is 21' at the TB port at idle, decreases to 15 then bounces back up to 21 under hard acceleration. Fuel pressure is 59 with engine on and 49 with engine off, key on. Still having trouble pinpointing where 8 mpg went over 3 months...any thoughts?

Thanks!

**WARP211** · 12-21-2007, 02:16 PM

if you don't have power to the fuse for the AIR system then the next step would be to trace it down(The wires) to the PCM.. And make sure that the PCM is turing on the pump.. if you have a scanner then I would try and see if you can activate the solenoid with it. To see that the solenoids are operating. If the PCM is not turning on the AIIR system.. Then you need a NEW PCM.. If you have power at the PCM and its activating the AIR system. Then you would have to check the RELAY or the Wiring. To confirm your repairs were succesfull.. earse the codes drive it.. If the SES light doesn't come back on then you fix.. if it does then the problem still exist.

Now about the canister I would first replace the fuel cap.. Like 0rion said..

**Banshee1967** · 12-21-2007, 03:09 PM

New gas cap is on as of today...Did the Seafoam flush, fresh tank of 93, new plugs, wires, clean MAF, clean TB, tire pressures good, cleaned air filter...we'll see in about 300 miles, hopefully more.

**WARP211** · 12-21-2007, 06:16 PM

just to let you know that seafoam is for cars that have heavy build up of carbon on the valves.. it cleans off all the carbon on the valves.. Good stuff for cars that have High HC's.. when they fail smog..

**Banshee1967** · 12-22-2007, 07:44 AM

Even though my plugs looked great, no carbon whatsoever, my pvc looked bad and replaced it after the foam/rubber fitting disintegrated leaving the bottom (check valve open air and not pulling anything from the 3/8" tube that goes to the rear of the engine. That is why I decided to Seafoam the motor and do a complete tune up. Just trying to weed out where 8 mpg went and doing a complete range of maintenance while there.

Is there anything PCM-wise that I can accomplish by taking her in and checked that will improve anything? That is after I fix the power problem to the air circuit and replace the charcoal canister?

**WARP211** · 12-22-2007, 08:54 AM

Not to my knowledge.. if everthing check's out and PCM is working and operating fine.. then it is what it is..

**JL8Jeff** · 12-22-2007, 09:13 AM

Don't forget, you will drop gas mileage in the winter due to the colder weather and fuel differences. I'm down about 1.5-2 mpg from the summer. Every car I've ever had would drop about the same amount going from warm to cold weather. Except my old 1991 454SS pickup! That went from 11.5 mpg down to 11 mpg!

You might also have an issue with the stock cats starting to go bad if they are still the originals on the car. I think there was some form of service bulletin on some of the LT1 cars for the AIR pump wiring harness. You might want to search around for information to see if it extended to the LS1 cars as well. The AIR pump usually only runs at cold startup so if you were looking for voltage at the pump/fuse/relay after it was warmed up it was too late to check for it. Check it again on a cold start to verify there is or isn't power getting to the pump.