So, I had issues with my 89 305 TPI.. which turned out at least to be bad injectors. So I ended up doing a lot of work before getting injectors, one of the last things was Bosch platinum +2's. Well, the car isn't driven - just idled and run at around 1500 for a few minutes here and there. A lot of water is ejected from the exhaust in the process. IT has the dual cats which I believe to be functioning, AIR is removed and all plugged. New o2 sensor, wires, cap rotor, etc.. Coil is stock and iffy.

Well, I can take pictures if need be - but when the spark plugs are int he engine they always have the electrodes oriented straight-verticle (ie: | to the ground).

I put in a used set of 19LBs (yellow) Bosch Design III's and have idled and run at 1500-2000 for perhaps a combined 1 and a half hours. Checking the plugs the sides that face the Intake valves all have a large flat black spot on them. It doesn't wipe off with a paper towel and is probably 3/16 in size. It is shaped like a trapezoid - you would know why if you know the bosch tip style.

I only checked 3, they are like this - though one that was in a cylinder with a known leaky old injector had two silvery shiney areas on either side, though off-center.

The black spot also continues further down the insulator where it is tough to see, though there is about an 1/8 gap between the spot near the tip and the lower portion.

I have a scan tool. BLM was going towards 106-108 - but I noticed the PCV valve (which is basically new) fluttered a TON, so I put in one that was new for a 2.8/3.8 which seemed softer and would allow more air. Well, I don't know how but BLM is in the 120's now! YAY! Around idle it's about 125-128, about 1500 its about 120 and around 2000 it's back around 126.

But, when in closed loop around 1500 it starts to buck a bit, like a 200RPM fluctuation - but the BLM has been adjusting a little and seems like it's getting better... however, I still question it as the car has ALWAYS had like a bucking problem in that range. Kinda like timing is freaking out but it checks out okay.. I never see any knock detected through the scan tool, should I?

I'm mainly curious about the plugs - but I suppose thinking about it would a bad knock sensor read no knock? and if so, does it sound like a possible cause for some issues?

For some odd reason when I bought the car there were two of the knock modules, a 350 and a 305 and the 350 one was hooked up. However, I changed it back and didn't notice a difference.

Whoever can help me at all is awesome! I love this car and have worked my butt off on it, only to be "rewarded" with it acting as it does! lol

 

If the black spots face the intake valves, it's oil coming in with the mixture. Usually guides/seals. Always suspect on an engine that old.

 

Great thought - earlier today I was thinking guides but the motor doesn't smoke.. at all. But I need to find my vacuum gauge - I know it had about a 4 in/hg flutter. That's why I changed the PCV to one that was more "stable".

I'll look more closely into that.

 

Even a bad PCV shouldn't cause that much fluctuation in vacuum readings. As a diagnostic test you could just plug the valve temporarily and see if the fluctuations go away. Idle speed will be lower (becuase the PCV valve is basically just a calibrated vacuum leak) but it should also smooth out.

Definitely continue with the vacuum gague testing and see what you find.

Some valves do "buzz" at idle. It's a thing that just seems to plague some setups. Best valve I've found to cure it is for a 91 Camaro with the 3.1 V6. Don't know why it works better than the spec V8 valve but it's always cured the problem for me.

 

Yeah - I'm definitely going to do some detailed vacuum gauge analysis. (Today) Unfortunately the car lived a rough life for a short while before me, the previous owner beat the heck out of the car. Luckily they only had it for a couple years so a lot of stuff was able to be brought back to health or replaced. It's just unfortunate that the mess I stumbled upon getting the car made me lose focus of potentially more serious problems.

My guess on the PCV valve rattle is that the engine doesn't pull the kind of vacuum that the stock PCV valve was calibrated for. Of course the TPI top-end setup always makes on wonder if there's a vacuum leak somewhere..

 

Well, during warm up/open loop all vacuum readings check out. idle vacuum is about 22 inches. No fluttering, no nothing. I did a whole bunch of test and it's all good.

So I bring it up to "1500" RPMs, 0.76Volts TPS reading. Well, holding a steady 0.76 the whole time it was boucing from 1425 - 1575, slight variation of about .5 inches of vacuum centered on 23 inches/hg. BLM 132 (though is it used in open loop?) -- Closed loop kicks in. Engine shoots for a BLM of about 119, vacuum flutters randomly between 20in-23in in non-uniform manner, spark adv ref 17-19, TPS still 0.76, RPM 1500-1625.

It feels like a bunch of random misses, though it would even out semi smooth for about 2 seconds every minute or so.

Should I be watching fuel pressure through all this? hmm, maybe I should do that. But the FPR is Vacuum so it would make for weird readings anyhow.

EDIT: I've done compression testing before and all was well. But I'm wondering if I should do leakdown testing. Also, this is really like the third set of injectors. Fist set was bad on Hot-ohms and assumed leaky so I swapped in 6 (from a pontiac bonneville 1990 3.8) 19LBS Bosch-like injectors (Looked Bosch, said Rochester. Unlike the original Multecs), now I have a used set of 302 Bosch Design III injectors that cold-ohms dead on... though I should hot check them today. Injection seemed like the problem but now I guess it was simply a contributor.

BTW, when this last scenario occurs EGR is bouncing between 60-95+ Percent. Back and fourth - almost like the engine is fighting the emissions equipment. I think it hates emissions as much as I do!

Ahh, anyhow I drop it back to idle and it surges then dies. Restart a few seconds later - high rev, die. Restart a few seconds later 1/4 throttle - high rev, 24 in vacuum, drop to 21 in/vacuum, let off pedal and it drops to around 20 then dies.

I had the issue with the old injectors as well where it would do the surging idle once it was hot so I turn the "idle speed" screw out a little and it still idled around 650. I turned it in a little yesterday and I think it made matters worse though the idle speed did not change. I wanted to clean the IAC passages when the plenum was off but it didn't want to come out so I just gave it a lot of FI cleaner.

I'm at a bit of a loss. I have gone through most sensors and such. The O2 system puts out 450mV and has decent cross counts most of the time, bouncing from Lean/Rich normally.

I think my car just sucks perhaps. I took it to a shop thats really good last year, they wouldnt touch it because it has an 89 305 Auto chip and the car is a stick. The previous owner must have swapped in a J/Y ECM or perhaps, a buddy's failed and I got the failed box? The yellow speed module was missing too and like I said the Knock module was swapped for a 350 one. Motor is definitely a 305 though, assumed original and looks to be.

EDIT: I've done compression testing before and all was well. But I'm wondering if I should do leakdown testing. Also, this is really like the third set of injectors. Fist set was bad on Hot-ohms and assumed leaky so I swapped in 6 (from a pontiac bonneville 1990 3.8) 19LBS Bosch-like injectors (Looked Bosch, said Rochester. Unlike the original Multecs), now I have a used set of 302 Bosch Design III injectors that cold-ohms dead on... though I should hot check them today. Injection seemed like the problem but now I guess it was simply a contributor.

EDIT: I was thinking about how the ECM really only has control over Spark Adv/Ret, Injector pulse width, EGR, and IAC. I need to find a copy of my BIN but looking at APYP at 1400-1600 I should have more like 24-32 spark advance. Though that might be a bit more aggressive of a table, plus its for a 350. Oddly the spark advance looks like what would be for if it was around 1000 RPMs, which is what the tach reads (though the scan tool is reading right from the ECM around 1500). The tach worked when I bought the car but now it reads a little low at idle and about 500-1000 off above idle. hmm..

 

So, it seems that this issue may have been caused by an oversight on my part. It appears that the exhaust may be leaking air inward which is being picked up by the O2 sensor. Although this is the second O2 sensor I have put on the car, as I assumed the number from the last one were incorrect, this one which is only a few months old did not change matters. The issue is that often when the car is around 1500RPMs it thinks it is going lean - I think this is when the exhaust heats up and leaks air. With the O2 connected and TPS at 0.76 volts the engine rotates just over 2000 RPMs, thats a big difference from 1500 based on the same amount of air.

Th O2 sensor will get below .100 sometimes to .010 or so when the problem occurs. Basically, the car has a rich exhaust when this happens... In Open Loop the exhaust is generally okay, though a bit rich (just not crazy rich). So, I think the issue is the ECM sees all-out-lean and dumps everything it can into the cylinders, I will check out the pulse width next time. So now I will be looking for leaks in the exhaust - I am just surprised at what an issue a potential leak could have caused. (I'm basing that statement on if there is a leak and if it is the cause.)

 

As recent as last week, I found spots on the porcelin part of all my plugs. I believe my plug gap was too wide at .050. Recommended gap is .035. I think because my gap was too wide, my car was not burning fuel completely. This resulted in unburned fuel going out my tail pipe. The O2 sensor was reading the unburnt fuel, and thought it was running to rich, therefore leaned our the mixture, which in turn caused some backfiring. Part of this was backed up by a borderling high HC's on an emission pre-test. I wouldn't consider this fact yet as I'm still trying to get to do another emission pre-test as soon as the rains stops.

There may be some relationship between your spark plug spots and mine if in fact you have an exhuast leak. Although I think if you had an exhaust leak and the 2 senor picked that up it would read it as to much fuel and infact have the opposite effect and lean out the fuel mixture instead. How do you know your running lean though? My scanner reads a fixed 15%, but I think that's just what the ECM thinks it is, not nesecarily what it is. I don't think BLM's mean that the car is neceserily running lean or rich, only what the ECM is trying to due based on what the O2 sensor sees. But I could be wrong.

I just remembered you mentioned that your BLM,s we're about 106-108. I'm pretty sure that means your ECM is trying to richen the mixture quite a bit. If so, that must mean that you are in fact running lean and not rich. Someone else will have to correct me if I'm wrong, just trying to help.

 

I'm sorry - sometimes my thoughts aren't as clear in text. However, what I meant was that the actual exhaust is quite rich and the CATs are throwing water out the tailpipe from unburnt fuel. the Bosch +2's are factory gapped to spec so I'm guessing they are good. I had the unburnt fuel issue with the old injectors and Autolites but - opposite the black side of the plug the porcelain is gleaming-white.

So, I think that the mixture is igniting but that it is so rich from the O2 thinking it is lean that there isn't enough time to burn the rich mixture. In essence it is like the timing isn't advanced enough for the mixture.. but the mixture is too rich to burn fully anyhow. I know that the coil is questionable but, I tested with a nice new MSD about a year back and it was essentially unchanged. So I ruled it out as I don't want to invest in external coil HEI parts. I wish I could put a regular coil in cap HEI dizzy on it, I have a new one on hand.

I'm gonna inspect the exhaust Sunday.