I just got done with install of cam, lifters, 1.6 RRs, headers, delteq, new O2 sensors, Autolite 104s gapped at .042, madz28 tune, emissions delete. Car ran great before. Now, about 80% of the time, my car won't start right up without touching the gas, perhaps 10%-20% throttle. If I don't touch the throttle, it'll sometimes start after maybe 10 seconds of cranking, sometimes not. Also, mainly when warmed up, it really doesn't like taking off from a stop. If I don't rev to 1500 or so and keep it there, it wants to buck and die. In 1st gear at idle it bucks pretty hard. Every once in a while at low RPMs and low speed it has a BIG stumble. I searched for vacuum leaks and exhaust leaks. I don't think there are any. Plug wires are new and have 8" heat shields and are away from headers. None are crossed or touching eachother. 99% sure they're not the problem. Fuel pressure at KOEO is about 48, at idle about 40, at throttle it's 40-44, under compression about 38. I left the pressure gauge overnight. The pressure was still 35. Pulled injectors, no leaks and all of them squirt. No fuel in the vacuum line. Unhooked MAF, no difference. Logs show TPS working fine. If anyone wants to take a look at the logs, let me know and I'll email them. I'm tempted to pull the plugs and try a different gap but I'm looking for some good interpretation of logs first.

 

Anyone???

 

Have you logged your knock, could be your stumble on take off.

 

Yes, it shows quite a bit of knock retard at times. I run 91 octane fuel and I added a bunch of octane boost. I have an LT4KM installed and the tune should have helped also. It also looks like the fuel trims are all messed up too, but I don't know. That's why I asked. I emailed Ion a few days ago but he must be out or busy. I have scans in spreadsheet format if anyone's interested in taking a look.

 

You can e-mail the logs to me, as long as they are in a format that can be used with Excel.

InjuneerZZ@aol.com

 

Email sent.

 

Got it - Quick question.... what it the approx. elevation where you live? MAP at WOT
(24-25"Hg) looks like you are at about 5,000-ft. O2's are way lean at 100% throttle..... Its gonna take a while to look it over. I'll get back to you, maybe tomorrow

 

Good guess. 5280'

 

Update: I unplugged the knock sensor and the car ran better so I did the knock sensor resistor mod and it seems to have cured 90% of its ills. Starts good, runs good with ZERO knock retard. I put a new starter on with all the other new goodies. It sounds different than the old starter. It must have been causing the KS to make starting hard. I also noticed that the left header collector is touching the bottom of the body under the passenger's feet. I don't know how to fix that one. I assume that's where the rest of the knock was coming from. Now the fuel trims are the only thing I see that need attention. Will run the car for a while and then send logs to Ion for review.

 

Your data log looks bad. The TPS sensor nosedives to "0" all over the place, and when it does, pulse widths go to "0",. O2's drop to lean, MAP suddenly drops from 17"Hg to 7"Hg.... possibly you were intentionally jerking the throttle around? In the same frames, your knock goes to "0", even though the previous frame it waqs 4.6degrees, and in the following frame it was 7.3degrees. Looks like you may have some bad connectors, or you have a faulty engine ground.

Look around line 60.... RPM goes 1423 - 1059 - 490..... yet the entire time the throttle position was 16% - 34% - 24%. None of these data points make any sense at all... probably the most screwed up log I have ever seen.

Look around line 20, when you were at 100% throttle... 6 frames in a row show 100% TPP, then there's a frame that shows 0% TPP, followed by the next frame that shows 100% TPP. Like the connector was shorting out or something. In the same frames, at 100% TPP, your O2's go

L - - - R
855 - 660
570 - 725
660 -110
85 - 85
75 - 65
100 - 75
900 - 885
65 - 60

And at the same time the PCM is operating in Cell 15, but in one frame at 100% thorttle, it suddenly changes to Cell 3.

The data log has no time stamp on it, so I can't tell what the scanning interval is. Maybe you just used such a long interval that I can't see all the data in the same relationship on the same line.

I think with the knock sensor desensitization, all you are doing is sort of masking your problems, which go much deeper than the knock sensor. If the engine is really running the way the log indicates, it must feel extremely rough. If it is, you run the risk of doing some damage to the engine.

 

Sent you the log with time index if that helps. Are the pulse widths supposed to go to 0 when the throttle is at 0 and you're decelerating?

 

I respect Injuneer's opinion enought that I decided to plug in the knock sensor and go about it another way. I pulled the KS and wrapped the threads with 3 or 4 wraps of teflon tape. That alone cut the knock retard by about 70%. I'll get some LT4 valve covers also. I also found this page: http://www.charm.net/~mchaney/f-tech.htm
It shows how to desensitize the KS in any percentage you want. I'll try maybe 50% and see what happens.