Running REAL rough again....

Hey all,

Last October I had a problem with the Spider/regulater assembly, and replaced it.. all was good.... Also - as a side-note.. I dunno if it's relevant or not.. but our county (Dallas County, Texas) just recently changed over to the 10% Ethanol blend of gasoline... I'm on about my 3rd-4th tank of gas on this new blend.

More recently, as in - last week... the Blazer ('95 S10 4dr/2WD) started running REAL rough and shaking almost violently when I'd stop at a stop sign. While driving, I feel a surge every couple of seconds. If I take my foot off the accelerator at - say about 40 MPH, it'll slow down for a sec... then the surge will kick in for a second, and net result is that I stay around 40MPH because of the surge... Much different feeling from when I had the REAL leaky spider/regulator last year. I'm also smelling a "rotten egg" smell - Dunno if that's simply from unburned fuel going though to the catalytic converter.. or if maybe my cat. converter is failing.. would a cat. converter failure cause these symtoms? (Hope not - that catalytic converter was changed about 4-5 years ago)

Just for grins, I opened up the manifold cover again tonight - just to see if the spider assy. was leaking again - and sure enough - there WAS some fluid in there.. but not much (maybe about 1-2 teaspoons worth on each side - passenger and drivers side of the manifold) - and it was kinda thick.. maybe like it's only recently started to leak, and is mixing with the carbon deposits under there for an oily-like sludgy liquid. I'll double check all the fuel supply connections/o-rings (nut assy.) when I have daylight tomorrow to make sure that those aren't what's leaking (I'm hoping so - as that spider assy ran about $308 for the spider/nut kit/regulator)

Anyway - I'm wondering if there's a way to test the fuel pump to see if I've got a problem with it and need to change it? Would a slight spider assy. or regulator leak cause those symtoms? Would a bad/failing fuel pump be more in line with these problems? If not - please shoot some more ideas for me to take a looksee at...

Thanks in advance,
Rex S.

ShadowHawk,

You maybe one of the "lucky" customers of the new ethanol blended requirement fuels. On older vehicles especially older hondas the ethanol would "eat" the rubber components of the fuel system. If you have to replace any parts of the spider and nut kit make sure that they are ethanol ready or this will happen again.

Check with the Chevy dealer's parts department in your area for parts that may need to be replaced due to this new EPA additive to reduce emissions.

Great... Okay...

I just sent off an email to the Chevy dealer that I got the spider kit/nut kit/gasket from. We'll see if/how long it takes for an answer. IF I don't hear from them by tomorrow afternoon, I'll give them a ring to see what they say. Geez.. the parts have only been on there 7 months...

I'll also change my fuel filter - just for grins.... Ya never know....

Thanks,
Rex

Just FYI for everyone, any vehicle produced after '91-'92 will have the fuel system components (viton o-rings) to handle up to a 20% ethanol blend. Beyond that, fuel and timing maps must be modified as to not decrease performance. 4-5 tank fulls wouldn't even begin to be enough time for a 10% ethanol blend to do any harm what so ever.

I for one LOVE how my vehicles run on 10% ethanol and wish that all of the gas stations around me would switch over already! The first few tank fulls will always be the clean out stage where your entire fuel system gets wiped clean of all of the varnish and deposits regular gasoline lays down. After that (in my experience), I have gotten better fuel mileage in my Bonneville and Bravada without any change in the way I drive. I have since moved and do not have a gas station that carries 10% blend anymore.

The rotten egg smell is typical of a clogging cat, but the rest of your symptoms don't sound like that is the problem. Any rich condition will severely shorten the life of the cat. Your fuel system problems prior to now, if the engine was allowed to run for long in that state, could have lead to the current demise of the cat. Additional fuel would be cause for some hesitation and run-on as you described. Try to pressurize the system and see if there are any leak points. Is it possible that an o-ring was damaged during the reinstallation of the new components?

Thanks for the note on the ethanol blend. Yes - I had noticed an initial boost in my MPG as well. On my first tank of 10% blend, I went from 20MPG (highway miles) to 22MPG (hiway miles) for my 120 mile round-trip daily commute to my 2nd job. While I DID notice a marked increase in my MPG, with that first tank, I also felt a lack of power from the engine in that first tank-full.. maybe a trade-off to getting better MPG.

Last year - when I had posted my initial problems with the rough idle, I had driven for appx 1-1/2 years with it in that condition - with the OE regulator dumping fuel into the upper manifold, and running rich, rough idle, etc... It's entirely possible that during that period of time that the beginnings of catalytic converter cloggings began...

Now that I've had my morning coffee, I'll get out and see what's up with the 'ole Blazer...

Rex

Hmm.. Never did notice any decrease in performance with my Bravada on 10% blend...

Anyway, yeah, running rich for that long could very well have ruined/clogged your cat. Typically symptoms of a clogged cat will be sluggish acceleration through the rpm band or resistance to higher rpms for obvious reasons. The faster the rpm, the more flow is required of the exhaust. If the cat is getting clogged, it'll be worse the higher the rpm.

Most exhaust shops can do a simple back pressure test by removing one upstream O2 sensor and the downstream O2 sensor and checking the difference in back pressure. Also, if there is a VERY noticable temperature difference before and after the cat (significantly higher before), that is a good sign that things are not right.

Ah.... Just got a reply form the Caddy dealership that sold me the replacement parts (spider kit, etc) last October.. here's verbatim what they said in their email to me:

quote:

YOU SHOULD NOT USE ANY ETHANOL AT ALL. EVEN THOUGH THEY SAY A 10 % MIX IS OKAY. THERE SIMPLY IS NOT ENOUGH EVIDENCE THAT IT WILL NOT CAUSE ALL KINDS OF FUEL RELATED PROBLEMS ON OLDER VEHICLES. INCLUDING DAMAGE TO INJECTORS, PRESSURE REGULATORS, AND FUEL MODULES. IF YOU STILL HAVE YOUR RECEIPT YOU CAN WARRANTY THE PART AT A GM DEALER. BUT I WOULD SKIP THE ETHANOL STORY. LET US KNOW IF WE CAN HELP YOU FURTHER


THANK YOU

Scratching my greying head.....
Rex

There are many states that no longer have anything BUT 10% ethanol blends and you are telling me that their older vehicles are just SOL. Don't think so... The o-rings are about the only part of a fuel system that ethanol will affect and viton has been used as the fuel system o-ring material since the early '90s. But this is quickly becoming a topic for a different thread.

Sounds like you should be able to get replacement parts to try it again. Good luck to you!

Yep - I explained to him that it was an EPA mandated fuel change - not a *choice* that I made to use the gas.. oh well.. the o-rings are fine.. I just inspected them. Maybe the connection from the nut-kit was bad or something. I'm gonna put it all back together, button it up, and keep looking for my receipt for the parts.

Thanks for the direction and assistance. I'm still a bit concerned about the fuel pump possibility (tested the relays - they're okay) - but I'll let that be another session... and I'll change the fuel filter this afternoon, anyway, to see if that helps.... Maybe the ethanol cleaned up the tank, and it's got the filter clogged, etc. etc... and causing problems...

We'll see.
Rex S.

That is a possibility, but the fuel in the plenum is not a good sign. Replacing the fuel filter is never a bad thing. For the price, it's good preventative maintenance.

Check your EGR Valve, carbon that builds up can flake off and cause the EGR valve to stick open, causing the symptoms youre describing. Spray some intake/carb cleaner in it. This problem is mostly on 95 CPI Blazers. Advance Auto has a EGR valve gasket with a screen to block the carbon. I went through 5 EGR valves before realizing what it was (dealership "couldnt" just clean it, had to replace it). If you look below your throttle body and back in a little, you can see the EGR valve. It only has two bolts, and one electrical connector, you can wiggle it out of the tight spot its in.

Thanks for the heads-up... I just finished buttoning it all up, and came in for a nice ice-cold iced tea to cool off with....

Anyway - Yes - I did check the EGR while I had it all open. All clear, and passages leading to the valve are clear (for now).

Rex

I wish I was so lucky. All we have is 10% and I don't like it. I don't have hard numbers, but I'm getting about 20 miles a tank less than I used to. I was driving a rental car for work and I was able to fill up with non ethanol gas and the mileage was noticably higher. Living in NY sucks.

quote:

ORIGINAL: swartlkk

Just FYI for everyone, any vehicle produced after '91-'92 will have the fuel system components (viton o-rings) to handle up to a 20% ethanol blend. Beyond that, fuel and timing maps must be modified as to not decrease performance. 4-5 tank fulls wouldn't even begin to be enough time for a 10% ethanol blend to do any harm what so ever.

I for one LOVE how my vehicles run on 10% ethanol and wish that all of the gas stations around me would switch over already! The first few tank fulls will always be the clean out stage where your entire fuel system gets wiped clean of all of the varnish and deposits regular gasoline lays down. After that (in my experience), I have gotten better fuel mileage in my Bonneville and Bravada without any change in the way I drive. I have since moved and do not have a gas station that carries 10% blend anymore.

The rotten egg smell is typical of a clogging cat, but the rest of your symptoms don't sound like that is the problem. Any rich condition will severely shorten the life of the cat. Your fuel system problems prior to now, if the engine was allowed to run for long in that state, could have lead to the current demise of the cat. Additional fuel would be cause for some hesitation and run-on as you described. Try to pressurize the system and see if there are any leak points. Is it possible that an o-ring was damaged during the reinstallation of the new components?

Well, things seems to be getting worse with my '95 Blazer.

I took it to my local muffler shop last week, suspecting a clogged catalytic converter. They used a gas cutting torch to make a small hole in the rear of the cat. converter to inspect it while the blazer was running, and the honeycomb insde was glowing red - they say this is a BIG indicator of lots of fuel being dumped into the converter, and the converter is burning it off - thus creating gthe rotton egg smell. The converter is well, and is performing it's job.

Blazer still has the shakes real bad when accelerating... And last night I notices that the freeze plug above the starter motor is seeping/leaking. I'm not nearly equipped enough to takle pulling the engine to do that myself - so it may be time to find a shop to do the work.

Is there a way of testing my MAP sensor / EGR Valve / and the other things that may be causing this running rough situation? I've not had a chance to open up the intake plenum again - but last time I opened it, there was a good spray of oil inside there, and a little accumulation of teaspoon - sized puddles in the lower portions.

Rex S. - who may be in the market for another vehicle soon.... (if I can't get this kicked)

I'll give ya $50 for it.

Couple of things.
Hogwash, older vehicles run just fine on 10% ethanol blend. Been running it in my '87 S10-Blazer for over 2 years now. The dealer is blowing smoke up yours. Mgiht be that way on highly tuned caddy engiens, bu the good old work horse 4.3L doesn't have that problem, especially on a '95. My '93 Astro van with a 4.3L only got feed 10% mix and I never changed the fuel filter. I had 286,000 miles on it before I totaled it one mornign on my way to work. Engine was as strong as the day I got it with 60,000 miles on it. Ethanol will clean out your fuel system, and yes it could be a partially plugged fuel filter. By the way, when was the last time you gave your truck a tune up? Air filter could be so plugged that your not getting a proper mix, it could also be a faulty O2 sensor. Defualt mode is to dump fuel, it runs, but like crap. PVC valve? Fuel pressure? spark plug gap, distriburator cap. Any and all of them combined will cuase all sorts of problems.

The best thing to do is check for any codes, and give it a tune up if it has been 3 years or more.

No codes being published... I check it every couple of days, now just to make sure.

Oil changed last in mid-March of this year, Air filter changed at same time...
Fuel filter - changed appx 3-4 weeks ago (about a week after the current condition started).

O2 Sensor - Changed in late March of 2005. (so about 15 months ago)

Plugs changed in October of last year (8 months ago) - along with the spider kit & nut kit.
Wires changed in March 2004.

On my first tank of 10% Ethanol blend, I got right at 22 MPG - so I can't complain about the initial mileage... But that's gone down the tubes for now.

Thanks,
Rex

Have you checked for a vacuum leak?
Look for a lose hose on the backside of the intake manifold. About where the distriburator cap is. Also check the air pump, and air pump valves. I haven't had to service them yet so I am unfamiliar with how to do it.

quote:

ORIGINAL: ShadowHawk

No codes being published... I check it every couple of days, now just to make sure.

Oil changed last in mid-March of this year, Air filter changed at same time...
Fuel filter - changed appx 3-4 weeks ago (about a week after the current condition started).

O2 Sensor - Changed in late March of 2005. (so about 15 months ago)

Plugs changed in October of last year (8 months ago) - along with the spider kit & nut kit.
Wires changed in March 2004.

On my first tank of 10% Ethanol blend, I got right at 22 MPG - so I can't complain about the initial mileage... But that's gone down the tubes for now.

Thanks,
Rex

Hey Rex...
How about the CAP, ROTOR, WIRES, COIL. How old are they? Sometimes the obvious slips right by us. have you checked for leaking wires at night?

Well, 2 days ago, I changed the PCV valve and the EGR valve. Still oily in the intake plenum... and the rough idle didn't change after I reset the computer (by disconnecting the battery for about an hour while performing the changeout of the EGR valve).

One thing I noticed, was that when I bought the EGR valve, Auto-Zone's computers had a note stating "LOCATE TEST CHART EGR1 IN WELLS TEST MANUAL" - Does anyone here have a copy or access to this manual? My Auto-Zone did not have it there for reference...

THis recirculation circuit has me a bit baffeled.. I understand how it works.. and what it does - on paper... but I'd like some direction on testing individual components without the expense of just buying new and replacing 'til it works.

quote:

Have you checked for a vacuum leak?
Look for a lose hose on the backside of the intake manifold. About where the distriburator cap is. Also check the air pump, and air pump valves. I haven't had to service them yet so I am unfamiliar with how to do it.

Hose to back of manifold is intact - and was replaced about 15 mos. ago. All hoses that I have access to appear to be intact. THere's one hose from the MAP sensor that also goes WAY down to the back of the engine, but I lose track of it before I can see where it terminates - so I can't fully say that it's leak-free. Air pump? Unfamiliar with that...

quote:

Hey Rex...
How about the CAP, ROTOR, WIRES, COIL. How old are they? Sometimes the obvious slips right by us. have you checked for leaking wires at night?

Cap, rotor, coils & wires were all replaced about 2 years ago IIRC. I have run it at night with the hood up, but have not noticed any light or arcing from wires.

Thanks,
Rex S

just last week i noticed some of the same things and i drove to the video store and it was sure dumb luck that i looked under the frund wheel well and notaced a small arc caused by my spark plug wire poping off(not all the way off but like half way off) i took it home and let it cool down cuz its the one behind the stering shaft(same blazer you have) i pushed it all the way on and that solved the problem.

my blazer ran like that for almost a hole week and i tried almost everythign but that seemed to fix it i went ahead and checked the rest of the wires to be sure

you mite want to try that.

its simple but it fixed my problem

I forgot to post my fix... as it's been fixed again...

Turns out that the Spider kit failed... so one cylinder was being flooded with fuel. If I had my receipt - I could have gotten the part covered by GM warranty... but couldn't find it - so had to open up my wallet at a stealership for parts + LABOR....

Rex S.