My '87 dropped a code 32 while on the interstate yesterday. It runs perfectly and all seems fine but the code was set. I often have trouble fully seating the fuel cap. I did have trouble last time I filled up getting that cap to lock all the way down. I know a "32" is an EGR code but could the loose cap cause this? The vapors were really strong coming from the tank. I got the cap screwed down and drove back home and the light didn't reappear.

Is it coincidence or is there really something in the EGR circuit going haywire?

 

Replace the cap.

 

I honestly don't think the earlier OBDI cars care about a loose gas cap.

If the EGR threw a code, it will continue to do so. Test the circuit and go from there.

 

For what it's worth, TX emissions for pre-1996 cars includes an independent test of the fuel cap (they take it off the car and put it on their emissions machine)...my guess is a one-way valve in the gas cap that lets air into the tank, but not out.

Don't know anything about a code that would set because of a faulty cap; perhaps our more enlightened members will chime in!

 

OBDII cars have pressure sensors inside the tank... or something like that. OBDI cars do NOT.

There is no code related to a bad gas cap. That's why they are tested.

 

http://members.shaw.ca/corvette86/Code%2032.pdf

 

Yes the early cars can be triggered by loose gas caps. Mine used to do it.

 

Excellent read that will settle all of the dispute => http://www.canadiandriver.com/articles/jk/020116.htm

OBDI and older cars DO NOT have onboard ECM, CCM testing for vacuum leaks in the gas tank. The OBDII have EIGHT system checks to proceed through concerning the evaporative emissions testing. (Read the article to learn about them all)

Perhaps you had another problem, maybe with the fuel evaporation canister on your Vette, or another problem. From experience, I was with a friend who bought an '86, that among a lot of things (what do you expect for $3400) was missing a gas cap and drove home (about 25 miles with just a rag stuffed in the filler neck). Also, I drove to my house (about a mile) with no gas cap at all (after my locking one broke) without a single code on an LT1.

I would investage what AGENT 86 posted, and get your hands on a set of shop manuals for your car, they are essential if you own a Vette. My LT1 did the same thing, code 34 I believe on an LT1 (I'm trying to remember from 2 years ago) It would go on for about 30 seconds (during warmup driving) and shut off. Ended up being a small leak on the hose between the EGR and the intake. 5 minutes and a little wrenching and no more code; it had nothing to do with my gas cap.

Take Care!

 

No. This was the only issue.

Now that the cap is tightened until it clicks, I dont have the EGR popup.

 

Well, I just performed a field experiement at my college. I went out, took off my gas cap, started my Vette, let it idle, drove it around the parking garage (for about 30 seconds), parked it, idle for another 5 minutes, and shut it off. No Service Engine Soon light and putting the computer into diagnostic mode showed no stored codes, 12...12...12.

My buddy has a '99 Z28, I called him and met him at his car. Took the cap off, and started it. About 30 seconds passed and I hear a, "What did you do to my car?" Bingo! Check Engine Soon light...While the car is still running I put the cap back on loosely, and let it idle for about 5 minutes. The SES light is still on, so we turn off the car, I tighten the cap, wait 10 seconds, start it and no more light.

He said his younger brother has a '88 Iroc with the 350. We give me a call, he is at work but says he has time to spare. Long story short, he takes off his cap, starts it, no lights for a 3 minutes of idling, I hear him revving it pretty hard, moves the car (sloshing the gas) and still no light.

Point of all this? My previous point, OBDI systems do not check for fuel tank vacuum leaks, hence no "gas cap code." Take a look at the Service Manual pages AGENT 86 posted, do you see a "Make sure your gas cap is on tight" anywhere on that diagram? Of course not.

The reason you get a code 32 is because of the reasons listed in the manual:
The EGR switch was closed at start-up
The EGR switch was open when coolant temperatures greater than 176 degrees
The EGR switch was open when duty command by the ECM was greater than 48%
The EGR switch was open when the TPS was less than WOT but not at idle
All these conditions above are met for 4 minutes
No codes 21, 22, 33, 34

If you get a code 32 and turn off the car to tighten your gas cap, the EGR system has a chance to reset itself: The EGR solenoid has a chance to de-energize and energize, The EGR valve is close during cranking from negative back pressure on the valve, and thus has a chance to reopen during possitive intake/crankcase pressure (your PCV system) and finally, the EGR system has a chance to reset and due to the ECM's new input from coolant temperature sensors, MAP, and a whole bunch o' stuff.

I had the same problem, code 32, but for an LT1. It wasn't my gas cap, it was a mechanical problem that was a vacuum check in the diagram provided by the manual.

 

I didnt say it checked for vacuum leaks in the tank, I said it threw a code. I'm not arguing, nor am I providing rationale for it.

It happened on nearly every highway trip before, and now it does not.

I already know what the manual says thank you. I've read the entire thing before.

 

Tried it on my 86. Drove about 45 minutes and 20+ miles. No code set. I don't see any reason it would, there are no sensors on the gas tank.

 

This will be my last post, I guess reading links to information pertinent to topics has fallen out of style for some...

I know you didn't say that, you didn't read the link I provided, that's all. What I'm telling you is that you don't have to argue for or against it; it's impossible because ODBI systems don't use solenoid sensors in the gas tank to detect emission vapor leaks. Read my post again, and click on the link...

http://www.canadiandriver.com/articles/jk/020116.htm

It explains the difference between the OBDI and OBDII systems relating to EGR and emission systems. FEDERAL STANDARDS implemented tighter laws on emissions, including regulations about vapor emissions. Our cars use timing and air/fuel ratios to just fudge the fuel emission inconsistencies hoping to provide a more acceptable emission output. The link explains everything.

Obviously, you haven't. I just looked through my whole shop manual for my 1992 and no where, and I mean no where, is it mentioned about the gas cap being related to any EGR problem....because it isn't! Don't you think if what you tried is an actual solution to an EGR problem (for a OBDI system) the manual would state, "Before anything, ensure the gas cap is properly fastened down and tight"? RWDsmoke did the best thing, he field tested it. No matter what manuals, spec sheets, etc say, the best is to field test it as I did this afternoon. I even did it again to my '92 Lumina, '97 Explorer, and '04 Intrepid. The '97 and '04, just by idling with the caps off threw codes while the Lumina idled like nothing was wrong.

The reason you had an SES light with a EGR code was due to an EGR system problem...this does not include the gas tank filler cap, period. Do a simple experiment, start the car, make sure it is at operating temperature and unscrew the cap. Check for a light whenever. It won't be there, I promise. I used to fill up my Vette, with the engine running (I know, a but that was when my starter was flaky and I didn't want to be left stranded 50 miles from home) The car will be fine with no codes. Whatever problem you had on the highway, I could take a guess and tell you that it was ambient related; meaning that it had something to do with outside temperature or speed or something else that was causing the EGR system to malfunction. Like I stated before, it happened to me. But the only think common to everything was that it was a cold morning (40's) and I got on the highway right away without my coolant reaching more than 100 degrees. Back when I tried to fix the problem on the fly, I waited and let the car idle for 5-10 minutes and it never happened.

I even checked the shop manual for my sister's 1997 Explorer...and what do you know? Her '97 Explorer uses an OBDII system and look at this under "OBDII Reference Code List:"

P0455- “Evaporative Emission Control Gross Leak”

Right next to it, what are causes?

A loose or improperly affixed gas cap
A non-conforming gas cap (i.e. not factory/original brand)
Other leak or damaged piece in EVAP system

I didn't mean for this to be a personal attack. I never said anything about what YOU did to YOUR gas cap. I was stating for the purpose of information to others, OBDI systems are NOT effected by loose gas caps. I am just stating what I tested, knew, and found out from website and now two mechanics. Cars before OBDII DO NOT have sensors or EVAP systems effected by loose gas caps.

 

I love it when people start jumping to conclusions about every f'king post I make. You tell them it cant work this way, I tell them from experience it can, fine, let it go. You dont offer an explanation for why it happened in this instance, you just post the same thing again. Everybody sees the criteria for EGR code activation, and I know them by heart already.

First of all, READ what I'm saying. I'm not arguing with you, I don't see how it happened, but it did and now it doesnt. I never changed the solenoid/switch or anything else.

I know the shop manual better than about 99% of the people here, so dont sit there and insult my intelligence by telling me I cant fking read.

Of course, we also know that GMs Engineers never ever ever make a mistake and that the Helm is the book that sits beside the Bible in Heaven.

I can go out and field test it on I-10 again tonight and report back to you if you like.

 

Okay, so I lied, :o my previous post isn't my last post, but this answers (just more directly and bluntly) the original question, "What code for loose fuel cap?" and more specifically the observation:

My answer: Coincidence

My reason: There are no sensors, solenoids, wires, probes, vacuum monitoring lines present in the fuel tank to report any code, including a code 32, since it is an OBDI system and not an OBDII system.

My suggestion: Look for leaks, vacuum or line leaks, or electrical inconsistencies in the EGR system. I did, and found the source of my problem. It might just be a flaky valve. It doesn't have to work all the time, every second, and when it fails, it doesn't have to fail forever. They are susceptible to carbon build up and heat fatigue. Shutting the car off (which de-energizes and energizes the system) might be enough to reset it to proper operation.

OBDII Vehicle Identification:
http://www.obd-codes.com/faq/do-i-ha...ii-vehicle.php

OBDII Background and System Description:
http://www.obdii.com/background.html

OBDI & OBDII Differences and Characteristics: (VERY COMPREHENSIVE)
http://www.autoshop101.com/forms/h46.pdf

OBDII EVAP System:
http://www.motorage.com/motorage/dat...06/article.pdf

This last link is the key. The reason why OBDII cars have the potential to throw a SES light for a loose gas cap is due to the EVAP (Evaporative Control Monitor) System. OBDI cars do not have an EVAP system, nor anything relating to it. In conclusion, I stated, there are no sensors, solenoids, or anything else that would permit a "loose gas cap" code. PERIOD.

O'Shark, I take it that when this happened (I read your post, but it's a little unclear) that when you finally got the cap down, your Vette was off? Did you shut it off, retightened the cap and, started the car? If that's the case, I would suggest what I stated a few posts before, that you "reset" the EGR system as it is always resets when you start the car. They are such things as intermittent problems. Everyone has experienced them. I would call this a coincidence. Like I suggested wait until your car is at operating temperature and then unscrew the cap and let the car idle; there will be no SES light.

My question: Wouldn't you think, of all the possibilities of unscrewing and screwing down your gas cap, you might have not screwed it down all the way before? Ever seen a 1996 and newer gas cap. The 1994,1995, and 1996 gas caps are threaded and "click" caps rather than screw down all the way. This helps prevent cross threading or side threading (which would cause a leak) since the caps don't click if they aren't seated correctly. 1996 and newer vehicles (with OBDII systems requiring OBDII compliant caps [they sell them specifically advertised as such]) first push in through a groove guide in the filler neck, and then click to lock position.

And just because I have to:

I simply disputed this statement by inferring they can not be triggered by loose gas caps because there is no system to monitor a problem effected by a loose gas cap. As far as an OBDI system in concerned, there is no cap, actually, there is no tank. Plain and simple.

You're right, I do post the same thing again and again...that his gas cap has nothing to do with it. PERIOD. I don't offer an explanation for why it happened because I'm not the car, nor clairvoyant. I stated exactly:

INVESTIGATE the EGR SYSTEM relating to electrical and vacuum leaks in proximity to the EGR system. That was my suggestion. Am I suppose to give an exact answer to every problem? That is the forum; a collection of answers to certain problems and suggestions for problems involving a lot of components. But I guess that concept never sunk in, since knowing the shop manual better than 99% of the people here (which I find to be a tad bit wild over-exaggeration) must be a delight. But next time, I will be sure to not only know exactly what the problem is, but I can telekinetically fix it for a forum member. High enough standards?

Well, I can't resist. Please read what I said about your "reading abilities":

Yeah, I never said you couldn't read. The word "haven't" refers to your statement:
So if you push both sentences together you get the following dialogue:

You: "I've read the entire thing before."
Me: "Obviously, you haven't."

I never refered to anything about your reading ability. I just said you didn't read the manual if you believe an OBDI system uses gas tank vacuum checks which includes the gas cap as an integral part of the system. I could NOW state the obvious, but I won't....

I'm not sure, but do I sense sarcasm? I don't know; I could be completely wrong about that as well. I never said anything of the sort at all. You don't need to preach to me about the fallibility of GM engineers (cough, Opti-Spark location) I am just telling you, for the 3rd (at least) time, that OBDI computers do not monitor gas tank vacuum pressure, effected by loose caps.

By all means field test it, I know people like RWDsmoke has tested it with results in my favor. I have talked to 2 C4 owners and 2 C5 owners who all performed by experiment with results all in my favor. I expect your result to follow suit...

I'm in attempt to provide accurate information and correct other's to the best of my knowledge. Members do it to me, and I am grateful; as to not pass on false knowledge to other members. You stated that, you offered input on your experience. Simply, your experience, as far as you detailed, has been with your car only. I have tested my "answer" with over 15 cars now; all follow my stand. I am just suggesting: check to see if your results match anyone else's before you speak the definitive. No hostility, just a suggestion.

 

FWIW, I reset the computer and the problem has not reappeared. Just for a little background, the car had not been driven for over a week and has 99K miles on it. The SES light didn't appear until approx. 40 miles into the trip. It ran perfectly during the whole thing and got excellent fuel economy both driving down and back....nearly 200 miles.

It appears to have cured itself for the time being.