1986 LeSabre 3.8 vin 3 Power Loss and Fuel Economy poor

[MattStrike]

I am having fuel economy loss and power loss issues - but first a little history

Got the car from my parents - sat for 4 years on a bad tranny. After rebuilding the trans, we had issues with wiring and a plugged cat causing a no-start issues and dieing issues. In the process of troubleshooting we replaced all the sensors with new Delco parts. After we got it running, we noticed a lack of top-end power and poor fuel economy (which we thought due to a bad TCC and fuel injectors). This condition has persisted despite replacing the computer, PROM, a second trans (4t60 swap) with new TCC, and a full engine rebuild. At this time there are no intermitant conditions present. I reconditioned all the wiring connections, tested wiring for shorts, have tested generator output...

Previous to the first trans being driven into having only reverse, the car would average 30 mpg driving locally and 32 mpg freeway consistantly. The 0-60 was between 8-9 seconds, and the motor had really good response and power. The original nylon timing gear had broken and been replaced, as well as the computer and ICM. Shortly thereafter the trans lost 2nd then 3rd then 4th then sat.

So, when I rebuilt the motor I checked everything with the wiring. I found a series of programs that allow you to read serial data off the ALDL connector. Unfortunately it only updates every 1.25 seconds because the computer only transmits serial data on a 160 baud rate. I plan to work around this by adapting the 86-87 riviera/toronado computer (8192 baud) later.

I found that the O2 sensor voltage jumps from rich to lean a lot, as opposed to the O2 sensor on my 89 PA that only fluctuates when the operating conditions change (fairly steady most of the time). The knock retard jumps to 26 degrees at 5300 RPM. The Spark Adv. gets up to 45 degrees when going downhill but usually around 20-32 during cruising conditions. I found using induction timing light and LEDs that the fuel injecters are firing sequentially at the right times thought the base pulse width isn't in the serial output. The balancer timing mark at idle bounces around all over the place, but is mostly steady under throttle and does advance normally with increased RPM. The ICM is a type 2 setup (has the normal 3 coil setup). I have tested with original GM ICM and aftermarket Borg-Warner ICM. All new ignition parts (AC Delco plugs).
The car always, indepenant of weather and operationg conditions, gets 21 mpg. There are no alignment issues and the car will coast down the road for from 55 mph a good 5 miles in neutral so I don't think there are any wheel bearing/tire issues. One of the other symptoms is the power output. From stop until about 2600 RPM it feels like 80% of what it should get, but the power decreases as the RPM goes up, and gives a hard jerking shift out of first (the trans doesn't do it behind the vin c 3800 it came from) and the older 440-t4 would do that too, but the 440-t4 in my 89 PA doesn't. Non-WOT accelerations don't make the trans shift hard. Shift points are all good, and TCC lockup is firm. 0-60 is 10-12 seconds.

Car voltage is 12.2 off and 13.7 at idle.
Idle is unsteady randomly varying from 550-800 RPM
In gear, idle occationally does not drop below 1100 unless throttle is pulsed to about 20%.
TPS resistance is clean and linear and the voltage output is the same, no spikes or skips
Temp sensors (coolant, air) resistance matches the book values
Cam and crank sensors and interupts are working
Computer is overriding the ICM to control timing
Computer is operating in Closed Loop
I am using stock 1987 fuel injectors (better spray than the original 1986 injectors).
I use a 192 degree thermostat
Engine feels a little rough during accel. when car is loaded down with 6 big people...
Car needs a bit of a runway to pass at freeway speeds
Duct between MAS and throttle body does not leak
There are no vacuum leaks
The EGR soleniod occationally passes very light vacuum to the valve setting code 32 when coasting and does cause cold-start issues though diconnecting the EGR has no effect on the problem.
Cold start misfires, but clears up after 5-10 seconds
Good throttle response from stop

I have put the original intake and cat on just to check if the high-flow stuff is causing the problems but they don't even effect anything (cold air sounds more aggressive). The motor was bored .030 over. Heads are stock with the stock headers, but heads and intake manifold passages are polished.
I have the 3 different computers used on that engine and 8 different PROMs. I do not have the original computer as it was turned in for a core on the reman. one that my parents had put in. (1227148, 1227783, 1227057)

I rode in my friends car that has the same motor from the same year and it doesn't have the power issues and he gets 28 mpg despite a broken MAS.

Sorry for such a long post. I wanted to describe as fully as possible the symptoms and what I've learned from my troubleshooting. My fuel pump started pumping air into the fuel lines yesterday and is making grinding noises so I have to replace that before doing any more data logging/testing.

[chemicall]

I find a high idle can sometimes be the intake manifold gaskets leaking, thus when the motor running air is sucked in around the gasket. Causing a higher idle - Did you replace intake gaskets when you rebuilt the motor?

If your fuel pump is making noises and it is bad, maybe it was part of the problem, had you tested fuel pressure before?

[MattStrike]

Update:

All gaskets are new, and do not leak. I probed all the gaskets with a small rubber hose to my ear, and no leaks heard.

Brand new fuel pump that is quiet and does not pump any air. New fuel filter, cleaned the tank, new strainer and pulsator thingy... the car runs like it did with air in the lines. It intermittently misfires under load or not, causing surges or dieing at idle. The coils are tested good in another car, the wires and plugs are new, I can hear each injector ticking even when the car misfires.

Then disaster strikes - somehow the bolt that holds the camshaft interrupt to the sprocket unscrewed itself and punched through the timing cover and the magnet went flying down the road behind me; smashing into a million billion pieces and setting code 41. Replaced the timing cover, water pump, sprocket bolts, magnet and cam sensor (thankfully I have a space motor sitting dead).

The car still misfires. I checked the crank sensor and interrupt and I see nothing wrong there. I have another crank sensor I can try though I doubt that it is the problem. I have disconnected everything not essential to the motor running (sensors, prom removed to run on calpak, etc.) and there is no change in how the car runs. The only thing I can think of is that the injectors are clogging, or the balancer interrupts are broken somehow though they look normal.

Fuel pressure is 30-34 psi at idle (high vacuum) and 40-44 during acceleration (low vacuum), but never drops. I don't recall that being normal and will change the regulator out when I check the injectors and see what it does.

It can never just be a bad coil or something with my car...

[MattStrike]

hmmph. The fuel rail was clean and no gunk in the injectors. There appears that there is air building up in the fuel lines still - not sure how a brand new fuel pump can be causing it. The regulator on my spare fuel rail does the same with the pressure as the original regulator. Trying to figure out how air is getting into the pressure side of the fuel lines.

[MattStrike]

The misfire issue seems to have magically fixed itself...I seriously can't figure out why it fixed itself, but it just suddenly went away for no reason today. I didn't drive any differently, the level in the gas tank hasn't changed significantly. No reason for any of it. Whatev's - my car hates me.

so back to the issue with the power and fuel economy.

Again, the computers I have are the 1227148, 1227783, 1227057. The first is the computer normally in the '86 LeSabre, the second was found in an '87 LeSabre though I've never seen another with the same number, and the last was pulled from an '86 Toronado (serial data transmitted at 8192 baud rather than 160 baud). I'm thinking that my car had a unique or uncommon ecm that controlled the timing differently than normal. I still have the original PROM. Too bad I can't trace the VIN at the dealer on any car built before 1990.

Does anybody know of any other computers used with the 86 vin 3 motor?

[MattStrike]

? Dead forum ?....

I'm going to try pulling fuel injectors off a newer 3800 motor and using those...I have reason to believe that the injectors on mine are screwed up, so I want to get ones with a better nozzle and a slightly higher flow rate. The newer misfire that developed right after I started posting here is present during open loop operation still, but it goes away in closed loop with the 8192 baud riviera computer. At least it only does it from idle stopped when trying to start now. However, the lesabre computer I was using for the last 3 years with no problems still misfires randomly continuously so can't use it anymore. still only get 21 mpg. My car hates me...and my buddy gloated to me the other day how he got 31mpg going from Detroit to Cedar Point with 4 people in the car (he has a century with the lg3 motor).

Then, my EFILive crashed while building a profile for the 8192 computer and it lost everything so I have to start over with that again :(

The stats I've found for the injectors so far:
Original injectors Q-stat: 141.8g/min @ 300kPa Q-dyn: 4.39g/min
1991 Regal 3800 Q-stat: 150.5g/min @ 300kPa Q-dyn: 4.55g/min
Either way, with the motor breathing better (CAI, cat, .030 bore over) the slight increase in fuel capacity may help the computer adjust the A/F ratio (or royally screw it up). Should be fun finding out!

[Jrs3800]

Interesting what you are doing...

The 3800 Vin C injectors may work for you... The Vin L may also work too, but I think the Vin C injectors will be closer to your originals.. The Vin C 3800 should be a Bosch injector( does not have the plastic tips ) The Vin L 3800( Tuned Port ) should be a rochester injector..

Let us know if that makes any difference

[MattStrike]

Injector.....Q-stat.....Q-dyn
vin C.........146.3......4.29
vin 3.........141.8......4.39
vin L.........150.5......4.55

I decided to use the vin L injectors because the dynamic flow rate (43.5 psi, 2.5ms pulse, g/1000 pulses) is higher than my vin 3 injectors and the vin C injectors are lower. The 4t60 trans I have is geared to redline at 5600 rpm where the original 440t4 redlines at 5200 rpm, plus having the better airflow in and out of the motor and being bored over I thought that decreasing the amount of fuel wasn't a good idea and might starve the engine when nearing red-line.

It seems like the new injectors solved the random constant misfire issue that was present. Seems to be running like it did before the fuel pump fiasco.

I tried to get the 1227057 ECM to transmit serial data, but EFILive was giving me a COM error: header byte undetected. It does this when the program is run without a serial connection normally, so it means the ECM isn't transmitting data. That, or it is some special GMP4 ECM and is not full-function (one-way data like the 160 baud ECM). Maybe the computer has some bad drivers or something, but I think I can get another one from the local junkyard.

I don't know how long the old injector(s) were not working, but it was only recently that they were causing a misfire. I'll check my gas mileage again - but even with the screwed up injectors it still got 20.88 mpg.

[wjcollier07]

Alright, so your original post was extremely informative, however, have any of the conditions changed since you added the new injectors? Has the KR gone down? Are there currently any codes besides random misfires? Have you tried swapping the engine wiring harness out with another LG3 harness just in case this one has a small short somewhere possibly causing the misfires, telling the ICM to fire incorrectly, or pulsing an injector at the wrong time?

There really aren't too many things left here. We're still just dealing with a simple internal combustion engine that just needs correct timing of fuel, air and spark, so...since you've got all those..and the timing is electronically controlled...its obviously the electronics involved...and since you're having some issues with the computers...I guess that's a pretty large factor.

[MattStrike]

I have been using the 1225057 computer since the cam sensor broke out. It only misfired when cold on that computer when I did the swap, and I needed to drive the car to work.

So I started the car cold again today, and it did the misfire thing again only once when starting from stop, but didn't do it again the rest of the time it was cold. Before it was dying whenever I went from park to reverse or to drive and whenever I tried to accelerate. I am going to check in the morning to see if the EGR is causing that particular occurence or maybe a weak coil, then try the 1227148 computer to get the ALDL data and hope it doesn't still miss.

I have been working on getting the ALDL data with the new computer. Apparently the 1227057 computer responds to a unique aldl poll that no existing PC programs use - bah. I hope to solve that because it transmits KR and SA at the same time and the injector BPW.

I don't have another LG3 wiring harness so haven't tried that yet. I can pick one up tomorrow from the junkyard if I find one.

[MattStrike]

So I put the 1227148 ecm back in to log data.

The knock retard is proportional to the throttle %, from 0-25 degrees all the time. The only time there is 0 KR is when there is 0% throttle.

When started cold, as always, the motor runs rough. It will die if the egr valve is connected to the vacuum, but after 10 seconds like throwing a switch the roughness goes away. As far as I can tell, this is the computer overriding the spark control. I forced the computer to run on the CALPAK and the motor runs rough and extremely rich, but it feels like the most primitive spark control isn't working. Same thing for when I disconnect the spark control override and force ICM to control timing. As far as I know the ICM should have the baseline spark timing to run the motor smoothly but without the spark advance. There is a gasoline smell coming from the car, but no fuel system leaks that I can find.

The BLM and INT show adjustments for the new injectors however insignificant that adjustment is.

Even though there aren't any codes being stored by the computer, the malfuction count increases from time to time.

With the 7148 computer the random misfire went away so it would seem as if one or more of the old '87 injectors were indeed going bad.

So that leaves how the ECM could be controlling the timing to be still not correct. I don't see how the crank sensor or interupts can be moved out of alignment with the crankshaft. The balancer doesn't have any rubber on it for this year motor, so that isn't cracked or separated. The only adjustment on the crank sensor is for the gap between the balancer vanes and the sensor. It acts like the reference signal is 10 degrees off of the actual position of the crank.