I found my vacuum leak... 1988 pontiac fiero gt. I took off the bottom part of the egr tube first and the whole thing just cam right out with the top of the egr tube flange still intact to the intake plenum. Everything came out and apart fine. This EGR tube although looks almost identical to Rodneys EGR tube maybe and earlier version? Im assuming since Rodney makes very high quality products that if this is in fact his EGR tube it probably plugged up with who knows what increasing the temperature exponentially and breaking the top of his tube. I although dont understand how that much carbon build up could get in there is it possibly a bad cat causing this maybe because of the restricted gasket getting clogged but with what?

any ideas on the carbon build up could it be caused by a failed catalytic converter?

The cat doesnt glow although it does rattle and has been changed before because it is aftermarket but has atleast 70k miles on it if not more. i havent checked pressure and it doesnt smell like rotten eggs but it was running extremely rich at low rpms could be due to the vacuum leak though.












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1988 Pontiac Fiero Gt (fully optioned, factory leather, 5-speed, CJB T-Tops: Black w/ gray interior and blk wheels)
1992 GMC Typhoon #0203
1971Chevorlet Corvette 454cu/ LS5/ 4-speed/ convertible
1993 BMW 850 Ci 6-speed V-12

[This message has been edited by gmctyphoon1992 (edited 08-30-2016).]

EDIT to ADD: I just finished the new Rodney Dickman EGR Tube installation and now my car is running really bogged down sounds like a freight train with a huge cam. It was running a lot better before almost fine with the EGR tube broken does that mean a clogged Catalytic converter with a new sealed exhaust causing this bogging down?

quote Originally posted by gmctyphoon1992: I although dont understand how that much carbon build up could get in there is it possibly a bad cat causing this maybe because of the restricted gasket getting clogged but with what? any ideas on the carbon build up could it be caused by a failed catalytic converter?

I've had the same experience with a plugged and broken EGR tube on my '88 Formula. In my situation, the carbon build-up had nothing to do with a plugged cat, as I still have the original cat on the car... and the engine runs very well.

quote Originally posted by Patrick Here: I'm poking around the top end of my Formula's 2.8 as discussed HERE, and among other things I've discovered that my EGR tube was completely plugged with "tar" where it connected to the underside of the upper plenum. Although this angle doesn't show it very well, the tar ball was protruding out of the plenum at least a quarter inch into the EGR tube. As you can see, the EGR tube is also cracked...

That makes sense maybe age then I am sure that EGR tube is atleast 7 or 8 years old. Thank you for the input Patrick!

As far as the new issue arised I started the car again and it would barely idol and it is hesitating really bad but as soon as i could get the RPMS up it would run a little more consistent.

When I am underneath the car from the end of the exhaust side to the CAT I literally can grab the exhaust and hold it and its warm almost cool to the touch. The exhaust (coming from the engine to the Cat) however is extremely hot I can only touch it for a split second

[This message has been edited by gmctyphoon1992 (edited 08-31-2016).]

quote Originally posted by gmctyphoon1992: As far as the new issue arised I started the car again and it would barely idol and it is hesitating really bad but as soon as i could get the RPMS up it would run a little more consistent.

I had a plugged cat on a different Fiero... an '86 GT. The symptoms of a plugged cat are the opposite of what you're experiencing. With a plugged cat, the engine would idle just fine, but because of the highly restricted exhaust, it could barely rev above 2500 or so RPM.

I suspect your issue is elsewhere, possibly caused by something you did when you replaced the EGR tube. Did you have the spark plug wires off the plugs?

[This message has been edited by Patrick (edited 08-31-2016).]

quote Originally posted by Patrick: I had a plugged cat on a different Fiero... an '86 GT. The symptoms of a plugged cat are the opposite of what you're experiencing. With a plugged cat, the engine would idle just fine, but because of the highly restricted exhaust, it could barely rev above 2500 or so RPM. I suspect your issue is elsewhere, possibly caused by something you did when you replaced the EGR tube. Did you have the spark plug wires off the plugs?

interesting I was leaning all over the open distributor maybe I bent a prong I'll check that out first!

quote Originally posted by gmctyphoon1992: I was leaning all over the open distributor maybe I bent a prong I'll check that out first!

...and make sure both banks of injectors are firing.

[This message has been edited by Patrick (edited 08-31-2016).]

briefly looked at all the plug wires to make sure they were on tight, no bent fingers on the distributor as far as i know. I checked both injector bank injector fuses and they look good. I did disconnect the battery and the IAC wire as well as TPS wire for an hour or so while working on it so maybe the lack of idol at first start up is because of that. I did check however to make sure the IAC and TPS were in the right position and snug firmly with no kinked or frayed wires. The car will idol and run on its own after a couple seconds and a few taps on the gas pedal and starts to run alittle better once it warms up but is still chugging like a train. There is a little black smoke (rich condition looks like) and what looks like water vapor coming out of the exhaust and when the car is off the exhaust somewhat smokes like a just burnt out match.

The car ran almost near perfect (a little rich) with a miss only at low RPMS before I installed this EGR Tube. as soon as the EGR tube was fixed and sealed the car is now chugging and sounds like its idling with a heavy cam.

The picture below shows the cap with only one area of interest at cylinder no. 1 point on the cap and looks like it has a white halo around it at the bottom of the picture like it was firing really lean. checked the plug wire on it and seemed fine maybe check to see if the plug is bad?




here is a video of the car running for the second time . The car only ran for 30 seconds the first time before I shut it off. (Yes I know i have a recently discovered broken exhaust hanger lol)

https://youtu.be/eWen1NiXfuE

If nothing else, it definitely sounds like you have an exhaust leak. Cracked front exhaust manifold?

In regards to possible ignition problems... it's really easy to at least remove the three rear plugs and have a look. They should be absolutely clean.

Yeah I definitely do have an exhaust leak on the front side of the engine unfortunately.

i just pulled the plugs on 1-3-5 and they all dont look too bad plug 3 looks a little lean but the gapping doesnt look off nor were any of the plugs wet or considerably different than the other. 1 and 5 look almost exactly the same.

The plugs, wires, cap, and rotor were just changed less than 5k miles ago

[This message has been edited by gmctyphoon1992 (edited 08-31-2016).]

quote Originally posted by gmctyphoon1992: The plugs, wires, cap, and rotor were just changed less than 5k miles ago

The ground electrode on the center plug does look a little different... but I don't know whether it's significant or not.


Is the indicated terminal what you use for plug #1? You can use whatever terminal you wish, but normally that terminal would be for plug #4.

quote Originally posted by gmctyphoon1992: The picture below shows the cap with only one area of interest at cylinder no. 1 point on the cap and looks like it has a white halo around it at the bottom of the picture like it was firing really lean. checked the plug wire on it and seemed fine maybe check to see if the plug is bad?

[This message has been edited by Patrick (edited 08-31-2016).]

my apologies I am mistaken the arrow points to cylinder number 5 not 1. When the cap is on its the top left terminal on the cap. I also just went ahead and did an arc test real quick anyways just to rule it out. No arcing anywhere.

quote Originally posted by gmctyphoon1992: ...the arrow points to cylinder number 5 not 1

Okay, so I guess that means that normally what is terminal #1 is actually #2 with your setup... which is fine.

quote Originally posted by Patrick: Okay, so I guess that means that normally what is terminal #1 is actually #2 with your setup... which is fine.

Yeah with a little research and second guessing myself I found the Haynes manual states the firing rotation of cylinder #1 to be clockwise over by 1 from my setup.. and I'm currently set up to factory setup? counter clockwise by 1 from the haynes manual... so 6 is the top and top right is 1 and top left is 5

[This message has been edited by gmctyphoon1992 (edited 08-31-2016).]

quote Originally posted by gmctyphoon1992: Yeah with a little research and second guessing myself I found the Haynes manual states the firing rotation of cylinder #1 to be clockwise over by 1.. I'm currently set up to factory? counter clockwise by 1... so 6 is the top and top right is 1 and top left is 5

That's confusing as hell.

This makes it easier to see where #1 normally is...

tell me about it

my setup is currently counter clockwise by one terminal from that picture you posted.. which is ok i presume?

btw do you know exactly by chance what kind of pressure gauge I would need to get to check back pressure from the O2 sensor hole in the exhaust

[This message has been edited by gmctyphoon1992 (edited 08-31-2016).]

quote Originally posted by gmctyphoon1992: my setup is currently counter clockwise by one terminal from that picture you posted.. which is ok i presume?

The only reason why that particular terminal is normally used as #1 is that it's the "best" location in regards to the harness being connected and plug wires reaching etc. Any terminal will do for #1 as long as the distributor rotor and harmonic balancer are lined up correctly, and the proper firing-order sequence is followed.

quote Originally posted by gmctyphoon1992: btw do you know exactly by chance what kind of pressure gauge I would need to get to check back pressure from the O2 sensor hole in the exhaust

I've seen mention made of using a gauge to check for back-pressure, but no, I'm not familiar with it. Apparently you can temporarily remove the O2 sensor (to reduce back-pressure) and see if the engine will idle/run any better, but I've never tried that.

[This message has been edited by Patrick (edited 08-31-2016).]

quote Originally posted by Patrick: I've seen mention made of using a gauge to check for back-pressure, but no, I'm not familiar with it. Apparently you can temporarily remove the O2 sensor (to reduce back-pressure) and see if the engine will idle/run any better, but I've never tried that.

Its no problem ! I am going to pull the o2 sensor tomorrow and see if it starts and idles better. If so ill see if I can disconnect the aftermarket Catalytic converter with the rusty clamps they attached it too and order a rodney CAT... did I also say there has been rattling coming from that CAT I have on now ?

[This message has been edited by gmctyphoon1992 (edited 08-31-2016).]

quote Originally posted by gmctyphoon1992: This EGR tube although looks almost identical to Rodneys EGR tube maybe and earlier version? ]

Your old broken EGR tube is a GM factory original. I can tell because the heat shield tube has a steel ring around the end. That is a factory original GM EGR tube. My tubes do not have that steel ring on the end of the heat tube. I believe they only had that steel ring on one end of the heat shield tube?

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Rodney Dickman

Fiero Parts And Acc's Web Page:
All new web page!:www.rodneydickman.com
Rodney Dickman's Fiero accessories
7604 Treeview Drive
Caledonia, WI 53108
Phone/Fax (262) 835-9575

quote Originally posted by Rodney: Also to note: EGR tubes fail from work hardening. Every time you start the engine the exhaust system heats up and moves a small amount flexing the ERG tube a tiny amount. Same thing when you shut off the engine. The exhaust system cools and moves a small amount. The exhaust system is mounted with springs. As you drive it the exhaust system moves a small mount as the car hits bumps etc. The exhaust system also moves as you accelerate and decelerate. The engine rotates some back and forth. The amount is determined my the strength of the dog bone. OEM GM dog bones are very soft and allow a large amount of engine movement. So EGR tubes by nature have a limited service life. They do not last forever.

Thanks for the input Rodney! That makes much more sense now and completely understand they have a limited service life. Btw your new EGR tube and gasket fits like a glove and went on with ease thank you again for that.

Update: So i pulled the o2 sensor and started the car and it ran 20% better a little hesitation but it would idle on its own. I put the o2 sensor back in and started the car for reference and the car wouldn't even idle it would just choke and die.

So that would mean that there is a blockage in exhaust aka bad or clogged catalytic converter?

The fact that your engine appears to run better with a hole opened up for the exhaust, and that your cat rattles... yeah, it's probably your cat that's blocking the exhaust.

Here's what the inside of the cat from my '86 GT looked like a few years ago...

quote Originally posted by Patrick: The fact that your engine appears to run better with a hole opened up for the exhaust, and that your cat rattles... yeah, it's probably your cat that's blocking the exhaust. Here's what the inside of the cat from my '86 GT looked like a few years ago...

So i pulled off the catalytic converter today and just ran it straight piped just to see if i still had the same problem or if it fixed it and the car runs pretty good although its super annoying and loud and I hate it. Im going to have to put a repair pipe or another cat back on there ASAP. The converter when looking in it didn't look bad but both of the honey combs were no longer stationary they were loose and moving all around inside the catalytic converter so I am going to change it anyways.

The car although it ran good wouldn't idle at all it kept dying every time I pushed the clutch in?

I did see although that the tps sensor was reading a -7% at idol? 0.25 volts. I know its supposed to read 0.5 volts can that be adjusted?

I also took a quick snap of my Winaldl readings

[This message has been edited by gmctyphoon1992 (edited 09-01-2016).]

quote Originally posted by gmctyphoon1992: I did see although that the tps sensor was reading a -7% at idol? 0.25 volts. I know its supposed to read 0.5 volts can that be adjusted?

It's been quite a while since I've done this, but the little arm thing on the TPS can be carefully bent to change the idle voltage reading.

Before you do that, has the throttle-plate stop screw been messed with... or is the cap still covering the screw? Hopefully nobody has touched it.

[This message has been edited by Patrick (edited 09-01-2016).]

It doesn't look like any tampering of any kind. I re adjusted the tps sensor to read 0.5 volts or so or just close to that and now that is correct. I checked for dead spots on the tps sensor from idle to full throttle and that checked out good.

I pulled the egr valve because reading on the forum that sometimes that could cause weird issues to arise and it holds vacuum but there is something rattling inside the valve? does that mean its bad? also can i clean the egr valve pintle with throttle body cleaner or should i stay away from any cleaner and just tap the pintle to remove deposits ? There is also a loose washer just sitting on the bottom where the pintle is should that be there and should it be loose like that?

[This message has been edited by gmctyphoon1992 (edited 09-01-2016).]

quote Originally posted by gmctyphoon1992: I pulled the egr valve because reading on the forum that sometimes that could cause weird issues to arise and it holds vacuum but there is something rattling inside the valve?

Being able to hold vacuum is good, but of course that doesn't help determine whether or not the pintle is sealing. It's been so long since I've looked at a pintle valve that I forget what they look like. Can you see carbon build-up? Any chance that the "rattle" you hear is simply a chunk of carbon loose inside a passageway? Other than that, I don't know what would produce a rattle.

quote Originally posted by Patrick: Being able to hold vacuum is good, but of course that doesn't help determine whether or not the pintle is sealing. It's been so long since I've looked at a pintle valve that I forget what they look like. Can you see carbon build-up? Any chance that the "rattle" you hear is simply a chunk of carbon loose inside a passageway? Other than that, I don't know what would produce a rattle.

I see the rattle. its some kind of washer looking thing attached to the pintle that is rattling around loose and doesnt matter if there is vacuum applied or not it stays loose

so I bought a new EGR valve and judging by the look of the old and new one clearly the seal on the old one was bad and longer properly working which means at 100% of the time the car was getting 100% exhaust gas through the bad valve into the tube (which probably caused it to clog up like that and fail) into the intake which probably caused the car to want to have such low INT (95) and BLM (120) numbers to enrich the mixture in order to balance air/fuel mix from the open bad valve.

I now have the correct orifice washer to put on a new AC Delco EGR valve 214-1415. I although am a little hesitant on punching a notch into the bottom of the valve to keep the washer in place. Is there some sort of exhaust glue that I can apply to keep the washer there instead? I have a Thermosteel exhaust repair glue that hardens to a permanent compound would that work?

I doesn't take much to peen the washer in. Just take a small punch or chisel and hammer and peen a small tit over the washer

Yeah, just use a small center-punch and make four or five little dents that push against the washer.

I notched the washer in place as you both above me said and it worked perfectly despite my uneasiness in taking a hammer and punch to a new EGR valve. I installed a straight pipe where the cat was and attached to the rest of the exhaust.

I also bent the little tab up on the TPS sensor and it now reads .55 volts 1% idle which is about spot on I am not really going to keep messing with it so I don't break it.

So the car now has a new EGR valve, EGR tube, fixed TPS sensor and Removed CAT and it runs and idles now almost perfect!

I re read my sensor values after the work done and the BLM is now 130 and more importantly the INT is at 128 and not 95 like it was.

So to take away from this for others to diagnose the car had a bad EGR valve with a disconnected orifice washer which let the hot exhaust gases to flow 100% of the time through the EGR tube into the intake plenum which gummed up the tube with rich exhaust gases. This caused more than likely caused the demise of the EGR tube which was completely broken off. I am assuming the huge vacuum leak from this caused a high idle condition in which a mechanic or the previous owner decided it was ok to tamper with the TPS sensor to get the idle down rather than fix the problem so that had to be adjusted back to its original position. With the tube fixed and the valve still bad the car basically had a penny sized vacuum leak causing the ECM to try to drastically increase fuel hince INT was 95 to make up for the excess air into the motor. With the car in this overly rich condition from a broken tube for so long basically killed my CAT clogging it up with soot and fuel which was making the car idle like a diesel with no power which wasn't noticeable originally when the car had a broken Valve and tube. With the new valve and EGR tube the car runs the way it should much better than it has in awhile.

Thanks again for the help and information Patrick a +1 for you !