2seater

I installed a little bigger set a few weeks ago, 24# light blue, and noticed an instant difference in smoothness, even running the stock chip designed for about 19#. I thought I got a good deal @ $65 for six so even if adapters are needed, it is still a great deal. I am sure they will work equally as well as your 'Vette experience. Unfortunately I had to move up to old style 30# injectors, temporarily, until I get a chip programmed for the 24#. The turbo programmed chips I have were done for 30# and I noticed they feel much more coarse than the type 3's. I almost forgot, I also had a set of Multecs and one of them is starting to short internally. It still works, but current draw is way high, so it is on the way out. They have a reputation for breaking down internally. I think you made a good move.

The Bosch 3 are nice injectors. Did they include the EV6 to EV1 connector adapters? Helluva deal if they work.

Good call Ronnie I was theorizing prior to this by looking at the construction of the disconnected parts that the stepper motor spins on a threaded shaft which has the actual pintle on the end. I don't see any issue with electrically powering it back in, but if true, I could see where it may "unscrew" in the extended direction. I have the broken one, which may actually have just over-extended, although I don't know how that could have happened since it was installed at the time? I suspect the shaft may have a broken end and somehow that caused a loss of reference position? I agree it isn't likely the IAC, but I started down that path to see if it was giving any indication that the ECM saw a fault and was perhaps trying to keep the rpms up. Upon reflection, the ECM probably wouldn't care as the engine is running at elevated rpm and the IAC would have little effect? I noticed a previous post that mentioned the EPROM and /or possibly the ECM causing this. Could be. I have witnessed this behavior on extended coast down but it shouldn't engage immediately. I'll sneak back to my cave now.

Whoa boys. I got a couple of things wrong in what I said previously, (imagine that). The spark timing map has 255 cells, which I should have known (doh!) and the Y axis is rpm with the X being LV8. Doesn't make much difference I guess. I have always seen the IAC counts follow the throttle upwards with increased throttle, never have seen it static. My ASSumption is it increases to let the engine slow down under a semblance of control, for many reasons. Sort of like the dashpot used on carbs to keep the throttle from slamming shut. The IAC bypass air is still measured by the MAF as it is downstream. The throttle blade really only limits the air flow rate, nothing else. Everything else is calculated. I posted a few weeks ago about finding a broken IAC pintle. It may have been my fault from pressing too hard although have done that before? My idle IAC counts were over 100 so I knew something was wrong. I found it easier, and perhaps safer, to remove it, connect the wiring and run it in and out with the override controls. Pretty easy to see it if propped where visible through the windshield. Leave it fully retracted before installation and it will adjust.

Padgett could probably explain better, but there is a MAT chart in the program that will modify timing based on rather large steps in the incoming air temperature. Really cold, say -20F will add a few degrees, really hot, say 230F, will pull a little timing, also has an rpm relationship, but it really is just a modifier of the actual timing map. It does have an effect, but is not the main timing control. I have heard, or read, somewhere that the MAT information is used by the MAF for a baseline temperature reference, but I do not know this for sure. The MAF uses a heated wire and a thermistor to measure the temperature. The ECM uses a frequency to measure the amount of energy needed to maintain that target temperature and infers the actual air mass with this information. The actual timing map has a lot of cells, over 100 but I don't have it in front of me, so don't quote me on that. The X axis is rpm and the Y is engine load (LV8), which is a calculated value based on several factors. There are many maps, or charts that all interact. One that may be of interest is the BLM map, which has 16 cells, 0-15, which contain information on fueling, one axis is MAF and the other is rpm. IF you are at a point just over the line in one cell, and then drop rpm or air flow, to switch to a different cell, it may be wanting to add or subtract fuel based on the last number in that cell (this changes with the interaction of the integrator and block learn). I can't imagine that this is the case with yours as it apparently does it at different points in rpm or air flow and probably shouldn't have mentioned it. I am an absolute neophyte when it comes to the information in the chip, but am trying to learn and burn a few of my own.

It sounds pretty much like mine. IAC counts are stable at any steady throttle opening, but will drop to a new stable reading on coast. Something like 92 counts running steady 60'ish mph, let off throttle to coast, IAC counts decrease rapidly and steady out at 68. Just for reference, my IAC counts are in the forties at warm idle in gear, but they do move around a bit trying to maintain idle speed. If your IAC counts are stable, the ECM doesn't see a problem with the rpm fluctuation so it isn't trying to compensate? Not sure what that means? Mine will do the rpm drop cycle on extended coast down, but there is a time and speed delay for the DFCO in the chip to prevent it going into that mode immediately upon releasing the throttle, or at least there is supposed to be.

I make the assumption the decimal is in the wrong place on that tps setting? Is it .38? The IAC counts can be any number really, but as long as they keep the rpm where needed, and increase with increased throttle, that all sounds normal. I am not certain the lack of O2 signal would prevent closed loop but it would be logical that it would, since the fuel mixture reference active in closed loop would be missing. So is that surging still present when in open loop? Do the IAC counts wobble around when the surging is happening? I need to take mine out for a spin after relocating the IAT sensor and some shrouding for the air filter, so I can see what mine does.

It sounds very similar to my experience with a failing crankshaft position sensor. It did not fail in the classic manner but it seemingly healed itself. Does the engine stop dead like the key is turned off? The first thing I would check is the ICM below the coils for signs of overheating, aka green slime. The two items are intimately related. Neither will set a code, nor the fuel pressure as mentioned above.

Zero is dead lean. In ordinary operation it should not get to that level. That said, I have seen momentary zero readings on my own, (primarily on coast down), although most of the chips I have been running are modified to some extent, so it may not be totally representative Are there any exhaust leaks anywhere near the O2 sensor, or upstream? It sounds like you are correct that it is reacting rather than the cause. By the way, Bosch developed and brought the first automotive O2 sensor to market a long time ago. Just my own personal experience but have found little difference in operation between good quality, name brand, sensors.

Padgett, Thanks for looking at this. I know very little about the actual effects of some of the programming in the chips. I have been trying to learn a bit about this for my different turbo installs so I hesitate to state any conclusions because almost all of the files I am working with have been modified to some extent by someone else. The reason I mentioned this is I have noticed some similar effects during some of the recording/driving regimes I have been doing to observe the operation of the various chips. The O2 will sometimes drop to zero on coast, cross counts also momentarily go to zero, sometimes there is a definite feeling of engine braking when lifting off throttle, even though TCC has been programmed to operate only above 55 mph.

I looked at the DFCO parameters in a 1990 chip program and I must admit some of it is beyond my present understanding. Perhaps Padgett could better define, but from what I saw, this system should not operate below about 145* engine temp. It also shows a 1275 rpm enable and 1000 rpm disable and a 1.6 second delay before activating, plus just 1.6% TPS should deactivate. If the BLM changes at the same time, it is likely changing to a different cell to read in the BLM chart.

This sounds like the normal Deceleration Fuel Cut Off but it may be activating at an unusual speed? I do not remember offhand what the speeds are for this to activate, but am pretty sure there are limits programmed in. If I get a chance I will check the parameters in the chip files I have. Does the injector pulse width drop off somewhat in sync with this feeling?

It is the same person, aka: Darth Fiero, GMTuners, and Sinister Performance. He has been very helpful to me in the past.

This may be related to your issue and it does have to do with the IAC. There is some history behind this discovery that I won't go into here, but it was an intermittent problem with low idle or stall. I have been recently reviewing a log file for a different reason and I noticed there were points where the idle rpm dropped to approx.400 rpm which confirmed there was something going on with the IAC. IAC counts were way high at idle, like over 100 and there was little response using the override to change idle speed. I removed the IAC and while wiping the pintle to clean, the shaft actually fell out. It had apparently failed internally? In any case, I retrieved another used one from my stock, plugged it in without installing it, and cycled it from one extreme to the other with the override while watching the movement. It worked smoothly, installed it, and idle issue disappeared. By the way, even with the IAC fully closed, you should have a warm idle speed in park of 450-500 rpm, which is likely too low to idle in gear. That is adjusted with the throttle stop screw at the linkage but unless it has been adjusted previously, that should be okay as is. Carbon buildup near the throttle blade will affect this baseline idle speed .

It's not only the pressure, but the fluid compatibility needs to be checked also. Petroleum based fluids will swell and destroy brake soft parts but I don't know about the reverse?

Pics of a fuel injector won't show much other than they are skinny and a blue-gray color (24#). Same for the cam, one looks much like another unless installed with a degree wheel and dial indicator in place. I guess the sig should say Re-lightly turbocharged, thanks for pointing that out. There is a continuing story behind that I won't go in to in this thread. Just for reference, I finally found another '88 cam replacement part number and that search turned up a new, in the box cam on ebay for a decent price. The Clevite number is 229-2211 and looks correct based on a quick visual and caliper check.

Installed Bosch Type III injectors today. Even though they are 26% oversized, the idle and low speed running is smoother than even before. Also found a Mahle-Clevite 1988 cam which came in the mail yesterday.

Thanks to your advice, I found the $5B4 .xdf decodes my .bins so I can read them. I looked into the details of the definition Robert created for me (2010 it turns out) and it was apparently based on $5B2 which no longer exists in T/P? I wonder why? No matter, it looks like you have a handle on it and much appreciate the guidance.

The ECM must relearn the new signal so it is best to disconnect the battery negative for a short time and start the ECM over to learn the new parameters from scratch. Have you looked at the MAF reading in the diagnostics to see if it is way out of whack?

Thanks Padgett, much appreciated.

Okay, thanks. Already have Tuner Pro RT and have been using it but is a pretty old version so I don't have that large of data display. Looks nice though. Edit: Sorry for a bit of hijack but a related topic. I looked at the TP site and I see the definition file is for a different ECM ( my1228253 isn't listed), but I am using the 1228253 datastream definition they did for me somewhere around 2010, maybe earlier? In any case will that DF .xdf let me edit my bins? I have a bunch of them from GMTuners from a long time ago. TIA

Hmmm, that looks pretty good. What are you using for that display?

Added two blue led "theater lights" in bottom outside corners of the rearview mirror, hot with ignition on.

Glad you found what you needed. I purchased mine along with some other parts but I know what you mean about shipping being out of line on some things, and it isn't just Rock Auto. I have taken issue with them on occasion about the lack of options for the shipping but to what effect? It does pay to shop around

I used a Sealed Power (Federal Mogul) set from Rock Auto #381-8073. I did not use the entire set as the engine I was working on had already been partially converted to brass and it also includes all the screw in oil passage plugs plus steel cam tunnel plug. I couldn't find my record of what I paid for it I imagine the plugs you want to replace are on the right side of the engine which faces toward the rear of the car? I don't know of a method to replace and the most common seems to be the rubber expansion plugs. You may be in ground breaking mode.