Ok, I’m pretty tired of trying to figure this out, so here’s the full story to make it easier on you guys!

So, 2&1/2 years ago I bought a totally stock ’94 Z28 A4 and within 3 weeks it started stumbling/ running rich, with black smoke coming out the tailpipes, then it would jump back to normal and run fine. This progressively got worse until one day it wouldn’t even turn over. While inspecting the engine, I noticed the oil had a lot of fuel in it. My friend came over and scanned for codes, and the only thing that came up was code 16 (lo-res opti). He also said that some cylinders filled up with gas on startup and that’s why it wouldn’t turn over. I had purchased a service plan with my financing, so he said to take (tow) it to the dealer and make use of it.
They replaced 3 injectors, the fuel pressure regulator, the spark plugs & the oil/ filter. In the process, they somehow destroyed my A/C. They said the warranty would only cover defective parts, so that’s why they didn’t replace all the injectors.

It seemed to run Ok except for a rough idle that wasn’t there before (and no A/C).

About 2 months later, the same symptoms started happening again, rapidly getting worse, until one day I started it in my garage and it had a fit, and died. I turned it over again (bad move), and it pretty much blew apart. So, I again had it towed to the dealer, and they said 4 more injectors blew and caused 2 bent rods, a cracked piston, a destroyed starter and some teeth ripped off the flywheel. Joy…

It sat at the dealer’s for about 6 months before they finally came to the conclusion that there was diesel floating around in the gas tank (?!). I sure as hell know I didn’t do it! So anyway, at this time a new service manager was there, and basically helped me to get the full $ coverage of the warranty and some insurance coverage. I still had to pay over $3,000, but over $15,000 of work was done to the car. At this point, they said that’s all they could do, and told me to take a hike.

So, the car basically ran Ok until about 3 months later, when the serpentine belt cut into a heater hose and dumped antifreeze on the opti! The bastards had routed the hoses wrong, and there was less than a ½ inch of clearance. Anyway, I patched the hose, but now the primary fan wouldn’t come on, even with the A/C on. I traced the wires all the way back to the PCM and they were Ok, so I tapped into the wire (used for manual fan control) and it worked. For some reason, the secondary fan works Ok, but the PCM won’t turn on the primary under any circumstances. I mention this in case this may help in a diagnosis.

It ran Ok for a while, and then started bouncing between running fine and then running rough/rich, kind of like before, but without the black smoke. It seemed to only occur in closed loop, but after a while, as it got worse and happened more often, it would occur even in open loop. So I tried to track it down (I hoped it wasn’t the opti). I tested the IAT, ECT, EGR, TPS, IAC & MAF, and replaced the MAP (finding it was defective). I replaced the driver’s side O2, but couldn’t remove the passenger’s side without pulling the Y-pipe. Anyway, it got worse and about 8 months later the opti finally gave out, so I replaced it (1st time) (I discovered at this point that Checker rented out scan tools, so I rented one and got a code 16 [opti]). I also noticed that the ground wires (near the coil) were almost torn off, so I repaired them.
Here’s a link to my topic at that time: http://web.camaross.com/forums/showt...hreadid=207677

Well, it seemed to run Ok, then 3 months after that, before I could get an opti vent hose kit (I modified the non-vented unit to accept it), there was some heavy rain/ flooding, and (I think) it dealt yet another death blow to the opti, as the symptoms occurred yet again. I took apart the opti and inspected it, but could not find any obvious water damage. So I put it back together, and looked for other causes. Here’s that topic: http://web.camaross.com/forums/showt...hreadid=246389

At this point I disconnected the MAF and restarted the engine and it ran, but the problem was still there. I cleaned the MAF as well, but of course that made no difference. The car then got to the point where it wouldn’t run (very bad missing/ knocking), so I replaced the opti yet again, and tried to start it up, and got nothing. No spark. At this point, I seriously started thinking the PCM or something else might be the cause (being that the opti was brand new), so I started tearing everything apart and re-testing components/wiring with a multitester. I replaced the Ignition Control Module at this point, and tested the resistance of the coil, which seemed Ok, but nothing made a difference. So I rented the scan tool from checker again, and got another code 16. What the hell’s going on!?!
This scan tool won’t give running data, only codes, because my car’s an OBD1, so I asked my friend, who is a master mechanic with a $3,000 scan tool (the dealers don’t even have one) to help me out. His health is in poor condition, so in the little time he had to look at the car, he could only confirm the lo-res signal from the opti was not there, so he said to replace that before doing anything else. Apparently, the new opti was defective…

So, I found a deal on eBay and purchased a new GM opti, complete w/cap (the others were from Carquest) and installed it last week. I started it up, and idle jumped around and then stuck at about 2000 rpm. I tried to get the PCM to learn the correct idle position, but nothing worked. So I decided to take it out on a test drive since, other than the high idle, it seemed to be running well. The first few minutes, it ran great with more power than it ever had, but then after about 15 minutes it started stumbling and running very rich. Then it popped back to normal and seemed Ok. Problem back…
There were no codes at all this time, so the next day I pull apart the IAC valve and it was pretty dirty/corroded so I replace it. This brought the idle to normal, and the car seemed to be Ok, but of course, yet again after some time, it would intermittently run rich/stumble.
Now I really start researching and testing all the sensors and tracing all the wires/connectors with wiring diagrams. Everything seems within spec, and the grounds to the PCM are good, etc. The condition persisted even though (one by one) I disconnected the MAF, MAP, IAT, EGR, and O2’s.
The odd thing is that the only codes the PCM threw during all of this were 48(MAF) and 27(EGR). What’s going on with my PCM? Shouldn’t it have thrown more codes?

In any case, I ordered a cable from WOT Electronics and downloaded Freescan, so I might have a better chance at tracking something down, as I’m on my own at this point. I’m waiting for the cable, but, in the meantime, I’m wondering if any of you guys have any ideas.
This is driving me absolutely insane!

The other day, I started thinking that perhaps the injectors might be messing up, being that the 3 the dealer replaced were exposed to the ‘diesel’ or whatever condition that caused the catastrophic failure. To my knowledge they didn’t re-replace those 3 when they replaced the others.
So, I hooked up a fuel gauge to the rail and took some measurements:

Key on/engine off: 42psi, solid. I then turned off the key and watched the pressure bleed down. Here’s the time/psi: 5:26 PM/42psi, 5:28/40, 5:32/35, 5:34/30, 5:40/23, 5:44/20. Is this normal (bleeding down from 42-20psi in 18 minutes)?

Engine on: 36 psi solid, with slight variations in response to throttle movement (due to vacuum). Pressure remained stable even when the symptoms re-occurred and it started running very rich.

I then tested the resistance of each of the injector coils, and they are all within a range of 12.4 to 12.8 Ohms. Ok… I checked for voltage at the connectors with the key on, and got 12.06 volts. Ok… Then I checked the wires from the injector plugs to the corresponding PCM connector pins. The (-) wires showed .03ohms (all the wires in the car that I tested for resistance showed below .05 ohms, which I assume is pretty good) and most of the (+) wires showed .05, but # 2 showed 1.8ohms and #3 showed 1.3ohms. Is this a problem?

Then I pull the fuel rail and place some brown paper under the injectors and turn on the key to see if there are any leaks. #8 and #3 seem to leak a very small amount. I’m only really sure there was gas there by the smell, because it evaporated so fast. All the others had no smell of fresh gas. At this point I put some cardboard under the injectors, disconnect the Ignition Control connector, and crank the motor. All injectors spray some amount of gas, but nothing excessive. I can’t find the paperwork for the dealer’s repairs, so I’m not sure which injectors were first changed, although I think #3 was one of them.


So, for reference…


NEW:

Long Block
Trans (A4)
Fuel- Pump, Filter, Pressure regulator, Injectors, drained/cleaned tank, lines
Opti cap/rotor (1x by dealer)
Opti unit & cap/rotor(3x !!!)
Ignition Control Module
IAT
IAC
MAP
PCV
Alternator
Water Pump
Plugs/Wires (plugs 2x)
O2- Driver’s side (can’t get the passenger’s side out yet)
A/C Evaporator

TESTED (w/ multimeter, using Chilton’s and Haynes Manuals as reference):

TPS
EGR
ECT
Coil
Vacuum
Injectors

Tested wiring (from connectors to PCM connector pins) for continuity/resistance grounds, etc, for all of the above including MAF. Unplugged (Independently) IAT, MAF, EGR, O2’s. Symptoms remained.
Tested resistance on injectors (12.4-12.8 Ohms)


I really hope someone can help me out here. I really don't want to build a new car part by part!

Thanks,
Tom.

P.S. What should I look for when I get the Freescan hooked up?

 

EGR? I dunno? Sounds like some sort of closed loop thing.

Wait, that's a no But it should have thrown more than a 48 and 27, it should have also thrown a code for the IAT and MAP I believe.

Have you checked the ground lug on the passenger side strut tower? It may be corroded or loose. Tried swapping pcm's?

 

I didn't see anywhere where either someone removed or replaced the cat. If you were running rich enough to hydro-lock the engine then it is totally shot. That is, it is plugged solid. Try disconnecting it and running without it or remove an O2 and screw in an expensive back pressure tester. May not be your your only problem but I know it's one of them.

 

Hi!

Chicken, yeah, I checked the ground all over the place (including the engine mount, the coil mount and the PCM ground to the block) and with one lead of the multimeter on the neg battery post, and the other on the ground lug, I get a pretty consistent .03ohms, which I think is pretty good...
And no, I don't have another PCM to swap out. If I did, I would at least have known right away if it was the PCM causing these problems!

Slopok, I wondered about the cat, but I thought that if it were plugged, the problem would be more consistent. when the car runs good, it hauls ***! I spun (not just chirped) the tires hitting 3rd gear at 80MPH- not bad for an automatic! But then it will run like crap and barely move, When it's running good, the exhaust smells very clean, but when it's bad, it"s very rich smelling. There seems to be decent flow out the exhaust either way (as far as I can tell)... I might just yank the cat out, however, to see what's in there in any case...

Thanks...

This is driving me crazy!

 

I just thought of another thing...

I hadn't noticed this before the problems started happening, but when I rev the engine, the 'check gauges' light will blink very rapidly (kind of in synch with the RPM) at around 4-5000 RPM. Is this some sort of factory redline warning (even though it's not near the redline)?

And, also, when I rev the engine to any RPM and let it drop down to idle again, I notice a voltage drop of ~1.5 volts, then it immediately jumps back up to where it's supposed to be. Is this normal for the alternator to do this (it, too is new)?

These things seem to happen whether the problem is occurring or not.


Very strange, very strange..... maybe I should have the car exorcized!

 

Hi.

Here's an update on the situation, and a few more questions...

http://web.camaross.com/forums/showt...64#post2303664


Thanks.