I installed my new Accel Superram intake, LTR's and 24# injectors last weekend. At the same time I replaced the passengers side header gasket with a Mr. Gasket copper one to fix a miniscule exhaust leak. What really pisses me off is that now it leaks worse than it did with the fiber gasket on there! What a waste of 2 hours!
Checked to make sure that the engine was at TDC, #1 at compression, reset the timing, etc. The car starts fine, will idle for a couple of minutes, then starts surging from 700 to about 550 RPM's If I drive it, I can feel a slight rpm variation when I am doing a steady speed. If I stop with the car still in drive, the surging is more pronounced, and the car will occasionally stall.

Since the exhaust leak is on the passenger side, will this set off the knock sensor? That would account for the slight drop in performance as well.
I borrowed Mike Davis's bin he modified for his ZZ4 project, and changed the spark advance tables to that of an 89 corvette (same aluminum heads), disabled the egr and set my injector flow rate to 24 pounds/hour. It doesn't help with the rough idle problem, but the performance is still good even if it is running crappy - it pulls well to 5800 rpm's!

Sprayed the engine with ether when it was running - no vacuum leaks. Fuel pressure is set at 50, remains steady at 43 except when the rpm's drop, then it rises to 48+ - this must be a clue, but I can't figure it out…
I replaced the pickup could on the distributor cause it was looking real tired too. No difference. Sprayed windex on the plug wires at night with the engine running, looking for the blue light show - nothing.

Right now, I am out of ideas. Anybody out there have any? I am going to R&R the passenger side header gasket tomorrow, but I doubt that it will make any difference.

I just took some pictures of the new installed manifold - you can see them at http://www.havemann.com/lee/firebird.html . Warning: they are BIG, and the format is rough - I didn't have time to design a web page.

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89 Firebird Formula
WS6 package,ZZ4 Crate engine
SLP 58MM TB, Edelbrock TES Headers
Random Tech 3" cat, SLP 3" stainless exhaust
9 bolt rear, Hotchiss swing arms, Lakewood panhard rod
Corvette 2/4 servo, kevlar band, full poly rear.
Centerline 16x8 rims, B.F Goodrich drag radials

 

Well, this probably won't help much but check and recheck all the connections. Don't assume anything is ok; that thing is probably the one that's giving you all the trouble.
-Check the terminals on the wires. Make sure they don't have any carbon buildup.
-Check the gear on the distributor. It might be worn and play with your head.
-Check firing sequence.Obvious but it happens
-Check your damper. Yes, if it's old and the outer ring has slipped, you will have a hell of a time setting the timing right (happened to me)
-Check idle speed and TPS
-check ignition module. You say the car starts going haywire when it warms up. It might be the module.

Hope this helps some
Rick

 

Any luck!


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'88 GTA 350 Full of Leprosy (rust)
Full Exhaust, Free mods, Xtreme Energy cam, Intake Pieces and 2100 RPM TQ
Check out my car here:
www.fortunecity.com/silverstone/brabham/42/

13.39@102.50 MPH
1.90 Sec ----- Best 60FT
104.23 MPH -- Best Trap Speed
AIM HIGH!

 

Any luck!


------------------
'88 GTA 350 Full of Leprosy (rust)
Full Exhaust, Free mods, Xtreme Energy cam, Intake Pieces and 2100 RPM TQ
Check out my car here:
www.fortunecity.com/silverstone/brabham/42/

13.39@102.50 MPH
1.90 Sec ----- Best 60FT
104.23 MPH -- Best Trap Speed
AIM HIGH!

 

Board was down all weekend - talk about withdrawal symptoms!

Well, on Sunday I replaced the gasket - that was an adventure all in itself - This time I unbolted the header from the Y pipe so I could set it up better, and of course one of the bolts sheared off. Pull the AC compressor, air pump, bracket, get the header out (breaking my temp sensor in the process), drill, tap, replace it.

Here's a tip - don't put D port header gaskets on Edelbrock TES headers - they won't seal. I had to use square ports, even though my heads are D port...

Anyway, after I got the whole thing reassembled, it fires right up. Same sh*t, runs fine for a couple minutes then surges.
I'm gonna put the scanner on it tonight and see what's going on. It has a new symptom now - when you put it in drive, foot on the brake
the idle climbs up to ~900 then drops to 450, surges to 750 a couple of times, then climbs up to 900 again.

While I had it all apart, I checked the firing order, it was right on. Also swapped in a different coil and wire, no change.
I also changed out the dist rotor, cause the old one had a lot of wiggle on the shaft.

I have a spare balancer from a 305 TBI engine - if I have to I will swap them too. They are the same, right?

Thanks for the tips - I am going to go and try the ignition module now.

 

Hmmmm...

Sounds like the problems start when the engine goes into closed-loop.

Did you lose manfold vacuum in the swap? Could be that the larger plenum area, etc, are causing the ECM to (correctly) read a value out of its known tables and then it does something to try to correct it, causing the surge.

The ECM wouldn't care on cold start, because it works from pre-programmed values, but when it's gotta fend for itself, after it warms up, it get goes wiggy.

Things like the increase in fuel pressure would be consistent with an engine trying to correct itself and create a stronger vacuum signal.

This can be 'chipped' out with a reprogrammed PROM, I'd guess.

Free advice, and worth every penny.



------------------
Bob
'87 Formula TPI 5-speed

 

I recently put a 356 in my car, it has alot of the same up-down idling probs that you have. It did it with the all stock intake and still with the new superrram upper-but not as bad.
Hey, you said you have d-port TES headers for a f-body? I have vette heads with d-ports and am using my old square port ones from my 305. Where did you get them? I need a set cause i think my headers are restricting a little.
thanx.

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'88 RS (originally 2.8)
-350, .040 over, vette alum. L98s, stock tpi.
-305 injectors & chip
-TES headers & edelbrock cat back
-3.73 gears, 700r4.
Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
on a 2.050 60 ft.
(Damn the 2.8!)

 

Don't you think it might be the O2 sensor!?!
Check it with the scanner. Just a guess
Rick

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'88 GTA 350 Full of Leprosy (rust)

Check out my car here:
www.fortunecity.com/silverstone/brabham/42/

13.39@102.50 MPH
1.90 Sec ----- Best 60FT
104.23 MPH -- Best Trap Speed
AIM HIGH!

 

I was thinking vacuum - I am running out of other things to check. My O2 is new, so is the TPS. Just about the only ECM related part that isn't new is the IAC.
Unfortunately, John (He is my Snap on pal) lent his scanner out and won't get it back until Wednesday, so I am stuck until then. I think I will throw a vacuum gauge on it tomorrow morning and see what it looks like. If that's the case, I am going to have to go over to DIY PROM and get some suggestions as to how to correct it.

I did replace the electronic spark control module while I was at it, no diff.

87FAKE-IROC-Z: What I meant to say was that you can't use D port style gaskets with the Edelbrock TES headers. The headers are almost round, and the bottom of the gasket won't seal up. That's why I went back to the square gaskets.

I took my son to his baseball game, and it was such a nice day that I took the bird, even if it is running crappy. Man that thing is an animal! I wound it out to 6300 rpm and it would still give more if I wanted it. Snaps your neck back on the shifts too.

Had to modify my sig:


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1989 Firebird Formula, WS6 Package
ZZ4 Crate engine, Accel 24 pound injectors, Accel Superram intake, Accel Large tube runners
SLP 58 mm throttlebody, Edelbrock TES headers, SLP 3" SS exhaust, Random Tech 3" hi flow cat
700R4 trans w/ vette 2/4 shift servo, worked valve body, kevlar band, 2200 rpm stall converter
Borg Warner 9 bolt rear (full poly mounts) Hotchiss panhard rod, Lakewood LCA's, Spohn subframe connectors, self modified chip.