2seater

Thank you for posting the fix. There seem to be more and more of the bad ECM's showing up, which appears to be more age, rather than mileage. You are right about the lack of codes for the ECM.

You should fix the thermostat as soon as you can. If it is really running that cool, it will probably be hard on mileage, and that is really too cool to effectively evaporate moisture and other bad stuff from the oil. Mine seems to go into closed loop operation at 130 degrees but there are apparently others that want 140 degrees plus to do so. Just my .02.

It's good to hear the trip went well, and you may have eliminated one item as the problem. A bad or lazy O2 sensor is usually the cause of poor mileage, but a misfire would tend to confuse the sensor also.

Essentially, the car has to reach closed loop operation before the torque converter clutch will operate, there is no transaxle temperature switch that I am aware of. When closed loop is reached, several things happen, in addition to the lockup enable. When cold/open loop, the engine runs on the preprogrammed information in the ECM, which is a fairly rich fuel/air ratio. When closed loop and the O2 sensor is modifying the mixture, is is no doubt a leaner mix. It takes more spark energy to fire a lean mixture than a rich one, so a weak ignition system may only show up when warmed up.

Good question on the cruise control. I do not know what the reaction would be but it should do no harm to try it. It may cause the cruise to surge as you toggle the lockup as the rpms should change some when the lockup goes away an vice-versa.

The TCC can be toggled on and off through diagnostics. You must be cruising in third or fourth gear for this to be active, although you can enter diagnostics and get to the proper area before starting to drive, as long as the engine is kept running. Enter diagnostics in the normal way, with the engine idling, by pressing "off" and temperature ^ (up) at the same time. Hold for a couple of seconds and the entire IPC should light up. Release the buttons. The odometer on the IPC will now go through any trouble codes that may be stored. When it is finished with this it should read "Ec?", press "fan up" on the climate control and the readout should change to "data Ec?", press "fan down" on the climate control and the readout should change to "Input Ec?", press "fan down" again and you should see "output Ec?", press "fan down" one more time and you should be at "or ide Ec?", press "fan up" to enter the overide section. At this point the odometer should read "ES00", press "fan up" one more time and you have arrived at "ES01" which is the torque converter overide. There should also be the number "0" below the ES01 on the display. This indicates the torque converter is unlocked. You should now drive the car and after reaching a speed where the converter will be locked, you press "temp. down" to turn the converter off and "temp.up" to turn it back on, and the number on the display should change to "99". You will need to maintain some pressure on the throttle as you are cruising, or the converter may unlock because you are coasting down, as the ECM will see the low voltage from the TPS as closed throttle. There is also an indicator on the climate control panel to indicate if the torque converter is locked. Observe the "medium" fan speed indicator on the climate control. If it is lit, the torque converter is being signaled to lock, if it is not, it is unlocked. The torque converter clutch circuit is always powered when the key is on, and the ECM turns the ground for the solenoid on and off to cause the lockup. If there is a wiring problem, where the lockup wire may be grounded, the converter may not respond to the lock-unlock signal, although if the converter remains locked as you come to a stop the engine should stall out. As a last resort, you can disconnect the transmission wiring harness at the top front of the transaxle housing. It is a round four or five wire connector and this will disable the converter lockup as well as the gear signals to the ECM. The car can be driven this way, although the check engine light may come on as the gear signals will be missing to the ECM, which are used to determine the correct EGR operation, among other things. Oh, one last thing, just press "bi-level" to exit diagnostics or turn the key off.

All the other posts have good suggestions, especially the rattling rear brakes, not harmful, but it is annoying. One other item may be the front anti-sway bar frame bushings or the ends that connect to the suspension. This is usually more of a clunk/thump type sound, rather than a rattle, and may be more evident when turning back and forth.

A miss under load sounds more like a secondary ignition problem than anything else. A cam sensor problem will usually show up at lower speeds rather than at highway speed, as the injector timing may be incorrect, but this is less critical at elevated engine rpm. If the TCC is locking and unlocking, it will manifest itself as a jerkiness, and a misfire will be more evident when the converter is locked. The EGR should be operating while cruising at highway speed, but if it is stuck partially "on" while idling, it may cause the idle to be rough or even die. The O2 sensor may have an effect on driveability but usually shows up as poor mileage. A misfire will tend to confuse the O2 sensor also. The EGR can be removed and cleaned, plus the three pintle valves can be cycled with 12 volts to see if they are operating freely. The one item that is common to most of these items is the ECM, which has been showing up more and more as these cars age, not really a mileage thing, just age. The cam sensor could be wiring, or the sensor, but the most common is the magnet in the cam sprocket falls out. You can check the magnet (interupter) by removing the sensor at the rear of the timing cover, just below the water pump. Remove the one retaining bolt and rotate the engine until the magnet lines up with the hole in the cover. It is best to remove the accessory belt and the magnet will pull on a steel tool fairly strongly if it is there, or look with a mirror. You didn't mention the mileage, but if very high, a new timing chain will help restore lost power if you go after the cam sensor magnet the long way.

The drivers seat does look wrong for a '90. Are those suede inserts in the side and rear bolsters? I don't remember what the early leather/suede seats looked like, but maybe from an earlier car? Floormat doesn't look original either. All things considered, it looks pretty good for $6k.

Unfortunately, I cannot help with the spline size or count on the transaxle. I looked at Barney's figures for the tire rpm vs engine rpm and there is one clarification that needs to be made. The tire revolutions per mile are constant, at about 775 for the stock 215/65-15 tire. The tire revolutions per minute are what changes for a change in gear ratio. More tire revolutions per minute with the numerically lower ratio, or less engine speed for the same road speed.

It is normal for the fuel pump to run continuously. The fuel system is designed to circulate fuel at all times the engine is running. The fuel pressure is controlled by the pressure regulator at the engine which simply returns excess fuel to the tank, the pump does not turn on and off to control pressure. As for the noise, some amount of humming is normal, but if it is louder than before the original went bad, it may be possible they have one of the rubber isolators misplaced, which are supposed to be located where the fuel tank contacts the underside of the body.

Could you add any detail as to the suspected problem? The injectors themselves are generally pretty reliable, although they can be subject to deposit buildup over time. Most modern fuels, from the major makers, are pretty good at keeping deposit buildup down, especially on the intake valves. The injectors are operated by drivers inside the ECM, so that is part of the operating system as well.

Padgett is absolutely right, the ECM does not control the alternator. The BCM does provide the power to start the alternator, but the regulator is inside the alternator itself, and does the voltage regulation.

If you watch your knock numbers, and particularly the spark retard, you will know if you are losing performance. It is not unusual to see a few knock counts right after a shift during wide open throttle acceleration, with the stock chip and regular fuel. To me that means it is optimized for the fuel type being used and typically will turn in the best economy also. I have said this before but I will repeat this suggestion. Try a full throttle start with the fuel you are using now. A good running car should spin the tires for several feet. The next time you fill up, use the highest octane available, preferably from the same vendor. Try the test again. My observation is the car may be less responsive and wheelspin, if any, will be reduced. I have tested this pretty extensively, and higher octane is only useful if you have knock problems, or have other modifications to take advantage of it. Padgett has done a good job of putting this is numbers, and I suspect the additional time to peak cylinder pressure, (with hi octane), reduces the power making potential. It may feel smoother, but overall performance does not seem to increase.

Thanks, I have talked with Dave Buckshaw in the past. He had older stuff for the Series I engine (like my Reatta) but unfortunately we couldn't do an ECM for my car without losing the built in diagnostics. The quality of the work at that website does look first rate, but it doesn't all interchange with the older cars. I am intriqued, but something that extreme is outside of the budget. I didn't see any mentioned of that damned bottle, so I am glad to see the "wooosh" Buicks are alive. My purpose was about 8 psi of boost, 250-275 hp or so and I have reached that goal. Still have that programming to work out as knock retard is a bit of a problem. Thanks again for the tip and I will pursue this further.

It should be a 4T60, aka 440-T4. Turbocharger installation will be a cut and try, as there are no "kits" available to my knowledge. Turbo installation in my signature is on a '90 Reatta. Right click on the photo, then click on "add to favorites", click on the "favorites" at the top of the browser screen. In the favorites list, click on the image and it should blow up to full size.

Just a thought, but a leaking injector maybe? It will tolerate additional fuel when cool and my '90 will go closed loop at less than 130 deg.F, so that is not a hard and fast temperature. Have you tried going into the overides in the diagnostics? Go to the injector overides and you can toggle each one on and off to see if there is a difference in the effect on the engine as you do so. It may help isolate if this is confined to a single cylinder. I have never seen the fuel integrator or BLM go over 150, but if it is doing so, it is trying desperately to add fuel for some reason. What do ED19 and 20 read when, and if, it ever runs well? One other common reason for the fuel to go to the high range is a vacuum leak somewhere. If you run your fingers over the vacuum hoses, and they come away with a black residue like soot, they should be replaced. They can be porous even if they look to be intact. Pay particular attention to the hoses behind the throttle body area near the firewall. If you try disconnecting the lines from the plastic vacuum block on top of the throttle body adapter to the intake, be very careful as this is generally very brittle and can be broken easily. One other prime spot for a vacuum leak is the rubber grommets at the PCV valve connection. There have been reports of these getting hard and deteriorated.

I believe the 4.5-4.9 Caddy engines were pushrod style where the Northstar is overhead cam which is wider. It would certainly be a hoot if it could be made to fit. I think I saw where the Northstar is now being installed in one of Pontiac's high performance models to replace the S/C 3800 and they gained performance.

It would seem to me that the flow rate to flush the system would be too low if just left to dribble past the valves and small ports in the system. If the system is pretty clean to start with, it would probably work fine to change the fluid. Toy, no; tool, yes

There is essentially no difference between pressure bleeding and vacuum, they are both using positive pressure at the master cylinder to push fluid through the system. The pressure bleeder is easy to understand since you are adding to the existing atmospheric pressure to push the fluid through. Applying vacuum to the other end of the system, at the bleeder, allows atmospheric pressure to push the fluid through in the exact same manner. An approximation of the pressure generated at the master cylinder is one half of the amount of vacuum created at the bleeder. In other words, if you can pull about 29+ inches of vacuum at the bleeder, you will have approx. one atmosphere of pressure,(about 14.5 psi at sea level), differential acting on the master cylinder. I have used both with equal success, however the automatic refilling of the master cylinder with the pressure bleeder makes life a lot easier. I made my own pressure bleeder for not much money, with a two quart capacity. I hang the pressure bleeder higher than the master cylinder, and use the first quart without any pressure in the bleeder. I let the rear brakes bleed themselves using the onboard pump, and use about 1/2 of the fluid in the bleeder. I then pressurize the bleeder to 12-15psi and push the rest of the fluid out through the front brakes.

You would be right, the turbo installation looks nice. I would love to have that short exit for the exhaust! That is probably the toughest part, snaking the exhaust back out past all the stuff in the way. Kinda interesting that they consider the knock sensor to be part of the Stage 2 setup, I wouldn't be without it. I appreciate the link EDSO.

Poor fuel mileage is most commonly caused by a failing O2 sensor, although other things can cause that problem. If the transaxle is making strange noises, changing the fluid may help, and is a good place to start. Unlikely a trans. problem will cause poor mileage but if it is slipping, or does not lockup the torque converter, it is possible.

GM, where did you put the knock sensor? The oil pressure port could be tapped into the rear of the same passage the sender came from, that's where I get the oil for my turbo. I didn't realize, (until I looked after this post), that the knock sensor hole is not just a blind hole.

The amber NA bulbs should be the correct ones, as there is no amber filter inside the housing. The clear bulbs could be used but you will have a mix of clear and amber light to the front if you do.

Hey, thanks Padgett. My crude formula shows 170 gm/sec is good for about 224hp, although the only way to validate that would be a dyno run. I guess I shouldn't be surprised that they used the same scale which should cover even the Series II N/A engine. If he still has the bypass open, maybe the performance will pick up when it is fully operational? I wish he had a pressure gauge too. I estimate my turbo setup would need 1-2psi more boost to cancel the increased backpressure in the exhaust side, but then again I don't have the parasitic load of the S/C. If I understand point "E", the situation would get worse with the MAF air flow sensing unless you invent a new subroutine? I, for one, really appreciate the time and effort you and Greg put into this. The programming side of this is well over my head (see learning brain surgery ) and I appreciate putting this in laymens terms.