z0s0

Hi Fred (or anyone else that can help)

Little backstory: Car is basically stock motor-wise, k&n cai, magnaflow exhaust, trickflow intake elbow. Tune is stock tune that to my knowledge has never been altered or messed with. Last fall I finally got around to putting on a set of LT headers (pacesetter). While I was at it, due to the difficulty of getting the emissions-equipped version of these headers in, I physically removed the AIR, EGR and cat. Tune was not touched to deal with these items. Car ran somewhat rough after header install, had missing problem in midrange, that's really all I remember. While chasing that down and checking plugs, etc...I noticed I was losing coolant, no leaks anywhere, and realized I had a head gasket issue. Car was put away until spring. This spring I changed the head gaskets out, put new ngk tr55 iridium plugs in, new set of ac delco plug wires, new ac delco o2's in the headers, new 24lb cobra injectors, new off-brand opti. Car ran well for about 2 days, and went downhill quick. Scan found the opti death code, so I replaced it with a delphi unit.

Where I'm at now: Car starts fine, idles relatively well, fuel pressure in the low 40's measured at the fuel rail. The problems are with idle (intermittent surging of what sounds like a few hundred rpm but it's hardly reflected in the tach), and either a misfire or some sort of hesitation, again intermittent, throughout the driving range but mostly at cruising speed, when you're just maintaining your speed. I feel it's running rich but can't seem to figure out why. I say this because the plugs generally have a gas smell to them when I pull them and are generally blacker than they should be for how new they are. Plug wires are all connected, and routed correctly. ICM is new 2 years ago but considering running tests on that soon. Anyway, datalog is posted below, if you could take a look whenever you get a chance Fred, just need a gentle knudge or kick in the right direction

Car was started, idled for about 3 min, driven with a good WOT and a few good accel runs.

https://www.dropbox.com/s/pbfprvyg5l...P7S2209452.csv

Thanks!

Injuneer

Without looking at the data log, did you carefully block off the EGR connections on the intake manifold?

z0s0

Yep, block off plates installed and oversealed with rtv just in case. I buzzed the air/egr fittings off the headers and had them welded closed.

z0s0

Headers are tight as well, double checked bolt torque and none had backed out. Some other things...I checked the vacuum line coming from the fpr and although you can smell gas there is never any actually present. I do not appear to have any exhaust or vac leaks upstream of the o2s.

z0s0

I am no tuning guru by any means so one of the many things Ive been wondering is by eliminating air, egr and being catless and not having the tune altered to compensate for these deletions, could that be throwing things off enough to have these issues? I have read in multiple places that the stock tune is good enough unless you have internal mods, which I do not.

Injuneer

AIR: You can delete the system, and as long as there is a good fuse in the AIR pimp circuit, no code will set.

CAT: There are no after-cat O2 sensors on the OBD-1 cars, so there is no way for the PCM to know if the cat is there or not. No codes.

EGR: There are 2 codes for EGR. One is for the EGR vacuum solenoid. Put a 1 kOhm resistor across the harness connector pins = no code. Second code is for EGR flow, and the OBD-1 diagnostic is not very sensitive. The PCM cycles the EGR valve, and looks for an expected change in manifold absolute pressure (MAP). You might get DTC 32 for this. Impact on engine performance will be negligible.

[EDIT] Taking a quick look at the log, you have no codes set.

The key is how well you capped the connections for AIR and EGR. If the openings in the headers were cut off and welded up, there should be no exhaust leaks. Exhaust leaks in the connection locations can burn valves and cause the engine to run excessively rich. Next issue is the vacuum connection on the driver side of the intake manifold for the EGR solenoid. Has to be capped off. Don't forget the connection for the AIR pump suction hose on the intake air ducting. Needs to be capped. Won't set a code, or cause any change in engine performance, but will allow dirty air to enter the engine.

I'll look at the data log, but there are several other people in line in front of you.

Injuneer

Another quick look shows the problem is on Bank 1 (driver side). Long term fuel trim at idle is 141-144, meaning the PCM is adding 10% extra fuel to compensate for a perceived lean condition. Bank 2 (passenger side) is right on spec at 126-128 LTFT at idle. The Bank 1 O2 sensor seems to be switching very slowly. IAC counts are down to 7, indicating the engine may be getting air from some other source. Look for a vacuum leak on the driver side of the engine.

Is it possible you contaminated the driver side O2 sensor with anti-sieze, or by spraying it with rust penetrant while removing it from the old exhaust system? Did you buy extensions or make your own?

What did you do with the EGR vacuum solenoid? Is it still hooked up, with the vacuum line from the intake manifold connected, and no EGR valve?

z0s0

Fred, I was extra careful about sealing up the egr/air fittings on both the headers and manifold, I knew that upstream leaks cause issues with the function of the o2s. The headers are welded closed but I will certainly doublecheck the egr and egr pipe block offs on the rear of the manifold. The egr vacuum port is capped. One thing I did do...and I did it to eliminate the check engine light/egr code...when I eliminated egr I kept the plastic solenoid thingy connected to the wiring harness. Would that be cause for concern? Simply plugging that in keeps the code away.

z0s0

Fred, posted the above before seeing your last post. The egr solenoid is connected to the wiring harness only. The vacuum line was removed and plugged. Yes, its certainly possible I got antisieze on the o2's. I can try taking that one out and hitting it with brake cleaner? Or even switch them and see if the problem jumps to bank2. The o2 extensions I got on ebay as I heard that was the way to go instead of using the make-your-own kit pacesetter provides. I just tested both extensions the other day with a multimeter and they both showed continuity on all pins. Even tho this did seem o2-ish to me initially, I sort of ruled it out since I was having the surge issue at idle/open loop and I had thought o2's weren't used by the pcm until after the system went into closed loop. I'll have to really try and determine if I am getting any of these issues during open loop if that is true.

z0s0

Replaced driver side o2, no change to data. Really checked for vac leaks on and around intake, nothing found. Checked driver side plugs, looked ok, one was a little stained pink?, headers tight, no exhaust leaks shead of o2's, double checked ds plug wires all routed correctly. Ran vac test on manifold, not too sure what to make of it. Vac is at 19 at idle, needle has a quiver to it, not sure if that indicates anything. Did 2 throttle blips, one to 2000rpm and one to 2500rpm. Needle drops, then jumps inro 20's , not sure if thats normal either..heres the vid:

http://tinyurl.com/m35emfh

z0s0

When I say no change to data I guess I should have ckarified that the o2 is now switching quicker but the ltfc is still at 136-141. Wondering if the valves could be out of adjustment on that side? Could that cause this? Might check that today.

z0s0

Pulled injector harnesses off that side one at a time with engine running..noticeable difference in engine sound with each one pulled except for cyl5. Going to repeat test today and if same result test out the plug, wire and injector.

Injuneer

The vacuum results are normal. A bit of needle twitch is normal, but maybe just +/- 0.50" . In excess of that is not OK. If you look at the scanner, read the MAP. That's just about the "opposite" of vacuum. MAP minus Barometer = vacuum.

z0s0

Problem solved. #5 plug wire was fried an inch from the boot. Apparently those accel fiberglass heat sleeves need a little more R&D.

Injuneer

Well, at least we had it pinned to Bank 1.