In case you don't remember my story, here's a quick recap. I have an '89 2.8 that wouldn't pass the CA emissions testing. It has a miss from idle to about 3k rpm. I replaced cap/rotor/plugs/wires and that didn't quite get the job done. I went to a mechanic who charged me $40 to look at the car for 10 minutes and tell me that I needed new injectors.

I pulled the injectors and had them cleaned and blueprinted by Rich at Cruzin Performance (I highly recommend him, excellent customer service) and I just finished installing them tonight. Well, the car runs about the same and I think I've got the problem narrowed down somewhat. When I pull the #3 plug wire while the car is idling, it makes absolutely no difference in the way the car idles. The car is also running very rich. I haven't done a compression check yet, but I'm thinking that I either have a leaking valve or a blown head gasket causing low compression and its not burning the fuel, which would explain why its running rich. Does this sound reasonable? Its not burning oil, so I'm pretty sure its not rings. The engine has 106k miles BTW. Also, how can I tell if its a valve or if its a head gasket? I haven't noticed oil in the water, or vice versa, but there have been a couple times when I've had my water reserve tank bubble over when the car was nowhere close to overheating. I suppose that could be from engine compression getting into the water system. Any thoughts? Sorry for the long post.

Thanks,
Brandon

 

An '89 running rich? The computer should lean the crap out of the engine if the O2 sniffs raw fuel. Anyway the comp check will help out on the diagnosis. I don't want to venture a guess without a few more facts.

 

Compression test that one cylinder first, the same location, opposite side, then the rest same opposite side.
You may know, quickest, that way.

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Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

I have a 89 Bonneville doing the same thing.I replaced the wires,plugs,coil pack and injector.Didn't help a damn thing!
I still need to check the compression,which I have had the guage for about 2 months now and still haven't done it
I,like you,figure it is a gasket or a burnt valve.If you find anything out PLEASE let me know!

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[This message has been edited by Kevin S (edited March 21, 2001).]

 

I always meant to ask this- What's a burnt valve? Is that like a burnt piston- it's melted (or blown) away in the center?


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

I'll try to borrow a friend's compression guage this weekend and I'll let you all know what comes up.

As far as what a burnt valve is, honestly, I'm not totally sure. I just know that a burnt valve doesn't seal well against the seat and you lose compression. I'd like to hear a more elaborate answer too, if anyone knows.

Brandon

 

A burnt valve will usually have a small area that is burned away on the seating surface of the valve. It will make the seat surface no longer round, so it won't fit into the seat to form a good seal.

The bigger the burned area, the worse they run.

Do a compression check.

For what its worth, usually when a head gasket is blown between 2 cylinders, it has 2 low firing holes.

It really doesn't matter if its a head gasket or a burnt valve, if the compression isn't there, the heads got to come off anyway and then it gets gaskets and a valve job.

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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

R.I.P. #3
My favorite quote about D.E. "He can see air"

 

how does plug #3 look like? maybe there is the answer, wet? black?

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www.marion-becker-nidda.de
91 Firebird 3.1
Modsynomax ultra flow stainless steel

 

What is the compression supposed to be at?

 

On my Pontiac it's the #1 cylider that has the miss and the plug looks like the rest.The plug is firing.My guess is the compression is so low,what fuel is igniting just isn't burning fast enough to go BOOM

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[This message has been edited by Kevin S (edited March 23, 2001).]

 

Thanks for the clarification, Engineboy!

Luke, last I checked compression on my 2.8, I had 5 cylinders between 160-180 PSI, with one "dog" cylinder at either 145 or 150.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Hey Tom that isn't good to have more than a 10% variance in any one cylinder when you do a compression check. Your numbers make mine look weak. I had 140-145 psi in all 6 of my cylinders.

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- Mike Harvey -
1986 Firebird S/E

 

I have a feeling my numbers (being out of that 10%) are because of mileage. The one cylinder that's a dog is because of the over-advanced timing I had- the spark plug's center electrode blew into little pieces, and must've screwed up my rings somehow. You should've seen my face when I pulled that plug out! My distributor hold-down bolt had loosened up, and my timing was so advanced it was off the scale!


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

On my 3.4 engine swap, I had to compression check to adjust the valves.
I had 175 to 200 compression in my block.
That's a 40K mile block.

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Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

That's pretty good KED. My 1500 mile 4.3 was 150 on 5 and 145 on the other.

The actual PSI you'll get will vary depending on CR and miles on the shortblock. It's not really fair to compare the #'s of different engines.