2seater

Curious about the MAF sensor? Did the MAF come with the 1995 engine? Isn't the intake to the L67 an integrated MAF and throttle body (one piece)? If so, the actual MAF sensor is a different configuration. The LN3 sensor will bolt right in place, but the L67 won't fit the LN3 . If it is what I think it is, the L67 has a plastic extension that wraps around the sensor wires and forms part of the passageway through the MAF. Externally, the flat black plastic exterior is identical. The frequency range for both style sensors is the same, so the ECM should be able to read the L67 just fine.

Thanks guys. My car has been dormant for going on two years now and I finally intend to get it back on the road. The reason for the question has to do with getting a clean recording of sensors for tuning of the turbo engine. I have had some success in the past with my Auto X-ray but it has limited capability and sometimes difficulty connecting for recording a run. It was suggested I try disconnecting the BCM to cleanup the interference. I am going to try TunerPro RT for recording and it may work better than what I have tried in the past? Reading any individual parameter available isn't a problem, and the stock diagnostic works fine for that, or a scanner plugged into the ALDL. The problem I have seen in the past has been a recording of several sensors at the same time has sometimes shown an offset or delay from one sensor to the next, like something slows down the data access? I do appreciate the input.

I know this is a strange question, but does anyone know if the engine will operate and drive with the BCM disconnected? In addition, is the ALDL port still active with the BCM disconnected? My car is still in storage some miles away so I cannot find my own answer at this time.

There are two 1.5" core plugs (frost plugs) inside the bellhousing as well as the visible ones on the sides of the engine and are the same size. There are also two larger pressed in metal plugs in the bellhousing area, one each for the camshaft and balance shaft tunnels. Oil gallery plugs in the bellhousing area are threaded pipe plugs. You may be able to see up inside the bellhousing area if you remove the plastic cover on the bottom of that area, although I have never tried this.

Small gear reduction starter isn't needed but it does offer a lower amperage draw. Cost will be considerably higher if similar to what we used on my sons off road car. Helped header clearance too although not a factor here either.

My 1990 FSM recommends the 5W-30 but the only real difference is the cold weather performance as mentioned. It is similarly illustrated in the FSM. I confess, I have no idea why the recommendation would change. It probably makes little difference if a summer only car. Usually there is a label under the hood as well. I presently have four difference vehicles, the oldest being my '90 Reatta and the newest is an '05 Chrysler, with a Ford truck and Saturn in between. All list 5W-30 as the recommended oil? Curious situation.

That seems odd? The trend is to lighter weight oils with tighter internal engine clearances for efficiency and emissions. The two engines are essentially identical, at least the early "L" engines are exactly the same, except for how the cam is retained. What is the source for the information?

Have you flushed the cooling system prior to changing the pumps? Have had a similar problem myself.

Battery side only on my '90. Air cleaner side is flattened for clearance.

Sorry, I just noticed the readings are with key on and engine off so I deleted some of the stuff I had written.. Can't really tell much unless the engine is running to get useful readings. Yes, the EGR can cause very poor running if one or more pintle valves are stuck open. I had something like that happen to a couple of vehicles, one had an extremely rough idle, the other idled okay but was almost undriveable as the throttle was open. Both were vacuum operated systems, different than our system, but similar symptoms. If the valves are stuck, disconnecting the EGR will have no effect, but removing the EGR to check is fairly easy. The pintles are solenoid operated and you should be able to move them easily and they should snap back closed. I didn't think of that before :-(( If I remember right, you replaced the ECM? Have your tried a replacement PROM in the ECM. Some of the open loop programming is hardwired and some is in the PROM, and Padgett could probably shed some light on that. Have you checked the (2) main engine harness connectors at the top rear passengers side of the engine? There is also a main ground stud at the same approximate location, on the engine valley side of the head. Sorta near the PCV and probably buried under the rear plug wires.

I did a search and could not find an answer: Is there a paint code for the gray paint used on the valve covers and intake manifold?

The MAF probably isn't the problem, but if they act up, it can cause all sorts of driveability issues. The purpose for disconnecting it is simply take it out of the equation. The engine will run in a default mode. It will run with MAF, TPS, O2 and Cam sensor disconnected and perhaps others, although I have only tried the ones mentioned. Sometimes a bad signal is worse than no signal. Your MAF air flow reading looked within reason. I understand what Padgett mentioned about cold enrichment, and I haven't watched injector pulse width during warm up, but that's about 20% duty cycle @ a moderate idle. Is the engine rpm reading a typo? I just noticed it is 20??

You mentioned pulling the hose from the throttle control. Was this the one connected to the fuel pressure regulator? Is the pcv valve in position and the rubber grommets in place? Do you have a vacuum gauge to connect to the intake? I know the engine doesn't run well, but should have around 18" Hg vacuum at warm idle. The standard rating for the fuel pressure regulator is 3 bar or 43.5 psi and should drop approximately one psi for every two inches Hg of manifold vacuum with engine running. The coolant temperature @ 25 deg.C will have the O2 sensor locked out and it won't be close to running closed loop. Can you get it warm enough to go closed loop so the O2 starts controlling the fuel system? I know you mentioned replacing the MAF but you might try disconnecting it and start the engine. In a good running system, the engine will start and idle okay with it disconnected, although it will set a code. It will generally die if disconnected while running. That injector pulse width looks very, very high. That looks like what I have seen at WOT and high rpm. IAC reading is high too, probably trying to keep the engine running. For some reason the spark advance is pinned at the max. value? Should be in the low 20's for warm idle. That all points to a control system problem or it is trying to cover for a vacuum leak or mechanical problem. The comment about the Central Power Supply causing odd problems was something I had not seen or heard of before, but our cars certainly have one.

The following is what I found on a gas spring/strut website. I originally thought that one of the reasons the rod would be down is to keep as grit or contamination from building up in the area where the rod enters the body. They are primarily a high pressure gas but apparently there must be a small amount of lubricant for the seal. In our particular application the strut is normally horizontal, and retracted, so I doubt that it makes a lot of difference. My car is in storage but I believe it is cylinder down and I am not certain if it will even fit the other way. I formerly worked in an industry that used lots of gas struts and we always mounted them rod down where packaging permitted it. DO'S • Do use standard gas springs rod down. • If springs are to be stored prior to use, the spring should be stored rod down to lubricate the seal. • Do try to use ball joints to help avoid side load forces. If eye (clevises) are used ensure a sloppy fit to allow lateral movement. • Do ensure that the end fittings are in line so that side load forces are not applied as a result of misalignment. • Do try to use shorter springs close to the hinge rather than long stroke springs away from the hinge. • Do provide physical stops to limit the spring’s extremes. i.e. ensure that undue force is not applied to over compress or over extend the spring. • Ensure the gas spring’s end fittings are fully screwed tight. • Where ball joints are used ensure the ball stud is flush with the surface and tightened. DON'Ts • Do not scratch, dent, chip, bend or paint the rod. • Do not puncture or incinerate. IGS provides a disposal service at minimal cost. • Do not lubricate the gas spring. • Do not cycle more than 15 times per minute. • Under no circumstances attempt to regas a spring. This is an extremely hazardous

It sure sounds like a fuel delivery problem. Easy to check with a gauge attached. Is the soot in the throttle body a dry powdery substance or a dark gummy buildup? Plug wires are on the correct cylinders, right? The timing chain being sloppy is a little harder to check on these engines since the tensioner (if operational) may skew the results a little, but there is no doubt the valve timing does retard a little with a worn chain. Certainly a useful test that costs nothing. I don't know if it is possible to jump a tooth, but it would make a huge difference if it did. If the tensioner is non-functional, there will be a small amount of slop, even in a new chain. I had one experience on a severely worn chain. In this case it was a 302 Ford in a pickup truck. No tensioner on this engine and I had over 30 degrees of crank rotation before the distributor would move, which is connected to the camshaft. The symptoms were: very hard to start and would sometimes flood itself (port fuel injected), very bad idle or it could stall, and severe lack of power. A new timing set did cure the problem in this case.

Padgett, do you remember when I asked anyone willing to do a full throttle run to post their maximum airflow reading from the MAF? This has to be maybe ten years ago or so. If I recall correctly, you were one the kind people that responded. The reason I bring this up is your numbers were higher than expected. As a matter of fact, yours showed as much as my '90 after I had done manifold porting, cleaned up the heads, had the throttle body enlarged and a free flow cone air filter installed. I chalked this up to your living near sea level or the MAF sensors were just not accurate enough. I have several MAF sensors, and have flow tested them, so I know they have reasonable repeatabilty but now I wonder if yours was the only '88 in the few that responded??

I believe the stock rocker ratio is 1.6:1. Agree that both cams are pretty mild, but the '88 would seem less so. I have done airflow tests on an aluminum snakes style manifold and the throttle body by itself, and surprisingly, it flows the same as the vin C. It looks more efficient, but it isn't. The manifold itself flows less than the vin C at the same pressures. It would certainly tune differently with the very long runners curled around inside. The plastic version probably flows better if it has a larger throttle body. The aluminum version throttle body looks larger until you actually measure it. I don't know if this means anything or not, but the '88 cam has "J74" cast into the barrel near the end journal and the '90 cam is J55.

First item: Checked cam timing on an original 1990 engine with 92k mles and again with new timing set installed. Cam timing was retarded 1.5 to 2 degrees with the original chain vs the new set. Essentially the stretched chain removed much of the 2.5 degree advance built into the camshaft. Second item: Anecdotal stories have stated that the 1988 engines seem more responsive and/or powerful than '89 or '90. I have no personal comparison info. on a butt dyno. but I did compare an OEM 1988 camshaft to the '89 and '90 version by installing in my original engine on the stand in my garage. The '88 cam is larger in all respects. Plotted on a graph, the later cam lobe profiles fit almost completely inside the '88 version. 1988 cam has symetrical lobes, 192.5 degree duration @ .050", 112.5 degree lobe separation, set at 3.5 deg. advanced and .270"+ of lobe lift. 1989/1990 cam has asymetrical lobes, 187 intake and 189.5 exhaust duration @ .050", 115.5 degree lobe separation, set at 2.5 degrees advanced with about .251" intake and .255 exhaust lobe lift. At .200" lobe lift, the early cam has a 12.5 to 14.5 degree duration advantage. One last observation. The closing flank of the intake lobes of both cams are identical and overlay each other on a graph from .150" lift on down, which should make the dynamic compression of the engine very similar.

Don't forget the short bypass hose from the intake manifold to the top of the front cover at the water pump area.

Do you have any problems with the climate control? Do all functions operate in their full range?

IIRC the supercharger experiment on the Vin C engine actually worked fairly well and the transmission is what gave up, but this was a high mileage car to start with? From what I have seen published, the compression ratios for the Buick 3800 through the 90's, is the same, regardless if supercharged or not? This does appear to have changed circa 2000. I would bet the heads are exactly the same but generally the S/C engines use different pistons and sometimes rods, so it is possible they have a different dish in the piston, and possibly height, to change the total enclosed volume? History has shown lower compression and higher boost will produce more power than higher compression and lower boost. I never thought about the possible relationship to total volume?

I don't remember the exact dimensions, but when I rebuilt my engine with .050" taller pistons I checked it at that time. Valve lift is only in the low .400" range and if I remember correctly there is around .5" from the valve face to the piston (valve closed). It "should be" impossible for the valve to hit the piston.

Did this valve contact occur on a stock 3800 engine? Valve lift is only a little over .4" and with the dished pistons, interference shouldn't occur. If it is possible, it would be good to know.:confused:

Be a little careful using an electric vacuum inside the intake where there may be fuel vapors present. Probably not a big problem with an injected engine but??? That small piece of hard rubber shouldn't cause any harm. It's not directly over the #2 intake port but is very close, so it may have dropped down the port onto the intake valve, or if the valve was open, into the cylinder. The clearances inside the cylinder are not very tight (this is a not interference engine) so the valves don't even come close to the pistons

Bad crank sensor will not signal ECM to open injectors for priming shot, so plugs may very well stay dry. Fuel pump has nothing to do with crank sensor, but injectors won't work if the correct signal is not received from CPS.