2seater

The throttle body and associated sensors can stay right where they are when removing the intake manifold. The one bolt that attaches the throttle cable bracket to the rear head can be a bit of a PITA, but nothing else need to be removed. The tube for the EGR must be disconnected as well as all wiring connected to the sensors. The bypass hose and heater tubes on the passengers side must be disconnected and disengaged. There are a bunch of spark plug and wiring cables that must be pulled back for clearance. The fuel rail can stay in plkace but the fuel lines need to be disconnected. Remove the alternator for better access to the wiring and hoses on the pass. side of the engine. Don't forget to disconnect the battery first.

'90 is the same. Actual coolant temperature is available in diagnostics and can be accessed on the move.

Mc, I know what you mean about the meters ability to see the signal but the only reason I tried it was the FSM recommends this test. The spare engine w/sensor doesn't show anything either, so I am pretty sure the chip is the problem. It runs perfectly in all other respects. Dave, what a generous offer. I do not have a spare ECM and I have considered getting one for another reason as well. I use it to power MAF sensors to test on the flowbench. I know about Gibby's too. I'm sure it's a mud bath right now. No need for extraordinary meaures yet.

Thanks Dave. Is that the EEPROM, alias MEMCAL, APTN that's available? I did check the wiring and knock sensor. The harness voltage to the connection at the sensor is 4.92 volts, which is correct and the sensor resistance @ 3800 ohms is also correct. The only thing I cannot confirm is the voltage output of the sensor when knocking on the engine. My digital VOM does not show any voltage generated when knocking on the engine. Perhaps it is too slow to respond? I think I have an old analog meter somewhere and I will give that a try. Failing that, I will try a different knock sensor. All tests so far point to a bad "chip".

Uh no, it isn't stock, it's something else. It's the actual chip portion of the MEMCAL, mounted in a socket that allows it to be removed and swapped without replacing the entire assembly. It is supposed to be the copy of the stock ANWU. I have several "chips", but all have programming for larger injectors and reduced timing for the turbo installation. I also have a complete memcal, however it is also programmed for the turbo, version 1.0. So I don't have an unmolested memcal to try.

It does it both cold and hot. Takes a few seconds for it to come on and then approx. one minute to go out. The knock counts do not increment upwards while this is happening but I retested and the sensor does indicate knock when the engine is tapped lightly. The reason I mention the chip is one of the iterations of the turbo programmed chips had an error that did not read knock, so I am guessing there could be an error in the chip. The FSM diagnostic tree also mentions the MEMCAL. I do need to check the sensor and wiring at the sensor for proper voltage and resistance when the engine is cooler.

Interesting observation on the fenders and water deflection. I suspect the lack of vertical flange is due to the composite material used for the fenders. The lack of drip rails on the roof look nice but no fun in the actual rain. Operation is still normal except the service engine light will come on for one to two minutes when started after sitting a while. Of course now is the time the climate control decided to stop operation of the temp. up button so diagnostics could not be accessed. I have repaired this once before and a thorough cleaning of the buttons has restored proper operation again. In any case, I get a code 043, knock sensor, both current and history. I watched the knock indicator when the engine was started and it does indeed show 4 degrees of timing is being pulled and the spark timing indicator confirms the same reduction in timing. The actual knock indicator does not indicate any knock is present and I know it is registering properly. After a short time, a minute or so, the knock retard stops and timing returns to normal. The service engine light goes out as well. I will investigate further but I suspect the Memcal may be at fault. This is the modified memcal with the ZIF socket for chip changes (turbo project) and the only stock programming chip I have fits this socket. Need to find a stock '90 Memcal to eliminate this possible gremlin. Stock program was ANWU.

Thanks everyone, and I appreciate the detailed reply Mc. I do not find a smoking gun in any of the power and ground connections in the area of the battery. I get no voltage drop in any connection on the hot side and no more than a .1-.2 ohms for any negative connection. Of course the problem has disappeared after reseating the battery connections previously, so there may be noting to find. The power to the starter has never been a problem so it may have only been a ground fault as suggested. So far, so good. Thganks all.

Thanks guys. Yes, the knock sensor seems to be a non-player and registers normally. The only thing I actually did, aside from wiggling everything in sight, was tighten the battery cables. The problem is gone. The connections appeared (felt) tight and clean, however the positive cable is suspect due to internal corrosion. I had removed the red insulator previously to clean it as best possible but not much can be done without physically taking the connections apart, shorten and recrimp/solder, but that doesn't look practical. I checked the resistance of the two accessible connections from the positive terminal and it shows .3 ohms from the battery + to the terminal box on the fender and to the alternator hot connection. While the engine is running, these same connections show in the 20-25 ohm range?? Is this indicative of normal operation or does it point up the high resistance present due to current flow. My gut feeling is that it is not normal and needs to be repaired/replaced?

I returned my car to essentially stock some time ago but have only driven it a few hundred miles since and it has worked flawlessly. I washed the car yesterday and it has decided not to run properly since. No washing was done under the hood, and it was just a quick rinse job. I have traced the bad behavior to this point. If you drop the hood with the engine idling, it will quit immediately. The same thing happens just popping the hood from the closed position. With the hood open and engine running, just a hand slap on the strut brace or either of the front diagonal braces will cause an instant stall also. Wiggling or tapping on the accessible sensors and wiring has no effect, including the MAF. A sharp rap on the engine at various points has no effect and continues to idle smoothly. I doubt it is fuel related as the engine stops immediately, no bumbling and dying, just dead in an instant. I will delve into it deeper after the engine cools and maybe change the knock sensor, as I would have expected a stumble when rapping on the engine. I checked its operation just a week or so ago and it registered on the knock counter normally when tapping the engine. I am sort of stumped as to what connection could be fragile enough to fail under the conditions described? Battery connection or the hot and ground boxes on the right fender? Ideas anyone?

Are we talking about the rubber bushings which connect the bar to the frame or the end links that connect to the suspension at either end? The end links on a '90 look like small tie rods, sort of. The earlier models are the common bolt and bushing that goes back for decades. For the frame bushings, measure the diameter of the bar at some straight area and convert to metric to get the correct parts. I think, the early models used a larger bar with more compliant end links and the later models a smaller bar with more rigid ends? Measure to be sure.

Are you thinking of the fwd version as used in the Monte SS? I would think you could pump up what you have to about those stock LS4 levels, of course, I "shoulda had a V8" would still lurk in the backgound

Update on a/c system charge. After making arrangements to have the system drained and recharged @ one service facility they called back later and asked if I was doing a 134A conversion, which was not an option. So, I took it to a second facility and spoke with the service tech there. He pretty much echoed the advice from MC and stated my numbers were not too far off, and was likely just a little low on charge. The catch is, they cannot add Freon without doing a full leak check and essentially doing what I originally requested. He suggested to just run it until such time as a conversion or replacement was necessary. I do have access to R12 so I simply topped off the system to get the low side at 30-31 psi minimum. The numbers look very good as related to temperature, high and low side, so I guess I have established my own baseline to keep an eye on the system over time. Now only time will tell and I greatly value the tutorial on error codes and the advice.

If you are only finding the type of MAF with the design on the right of photo, it is most likely the vin L variant. It probably has what Padgett colorfully, and accurately, calls the snakes manifold. The photo is of a sensor from an aluminum snakes style manifold, also called Tuned Port, and the later models are plastic. While the sensor has the same frequency range, the housing is different. The one I have is made by Hitachi, the same maker as the vin C MAF, but, it is a unified throttle body and MAF assembly, not two discreet parts bolted together. As a matter of fact, I have that exact unit installed on my intake and it works just fine, however, it required fabrication of an adapter plate due to the totally different mounting flange. I suspect the yard in your area doesn't have anything 20+ years old, but you may find something in things like a Buick Century with the 3300 engine, a little brother to the 3800. I know they were available up until at least 1993. I have tested air flow vs frequency on the flow bench and it is very close to the response of the sensor we are interested in and it works fine.

Thanks for letting us know what corrected your issue. This is a learning experience for all of us and it is something to file away in the memory banks. Odd about the sensor plug being different. I have never encountered that before? As a matter of fact, the plug is the same for the 3300 Buick engine (and the frequency response is close enough that it will work also), as well as the early model TPI style and the 3" MAF for the Chevy 3.4. The last two are not physically interchangeable for the vin C engine but the frequency range is the same as ours. Maybe I am misunderstanding and you meant the part that inserts into the MAF housing? Do they look like this? The one on the right is for a TPI style.

I have never checked one with a VOM to see if a good one reads anything of value or not? I think the FSM doesn't indicate any test readings and actually states it has a "special" output. I just tested a known good one and I get ~ 31.4 mOhm from B-A and C-A, the first letter connected to the red lead and .515 mOhm between B-C or C-B. I do not know if this actually means anything or not except to say that is does show something.

I have a few spare tested MAF's too if you get in a pinch. By the way, the MAF generates a frequency output that is read by the ECM. I am sure there is some voltage reading but it is not what GM uses for the air flow conversion. If you have a VOM with frequency capability the range is 2kHz @ 3.19 gr/sec to 10.4kHz @ 170 gr/sec. Running better with it disconnected is a good indicator it has problems. Fuel pressure and your ECM fueling numbers look good too. You could just take a look at the MAF reading and see what it does at different engine speeds or while driving. The closed loop threshold on my '90 seems to be about 130*F. but, to confirm that everything is good and hot and active, fully warmed would be a good double check.

Oops, I posted at the same time. The numbers look pretty normal but it doesn't appear to be fully warmed? Does it run better when cool before closed loop? It looks like it is right at the closed loop threshold temperature and idling in park.

What's the fuel pressure? This sounds sort of similar to the other thread just seems to have died without resolution. Padgetts suggestion of a snapshot, or recording sensor readings individually may be helpful here. Cam sensor shouldn't cause a real loss of power, just smoothness at idle and low speed. Was anything other than cam sensor replaced or modified recently?

The photo I posted is an air/air intercooler but I generally see air/water types used in the supercharged engines with the Roots style blowers?

This isn't the best photo but is of my project for my turbo reinstall:

The favored item for no spark @ startup is the Crank Position Sensor.

The air inlet tube should be replaced with the correct parts if at all possible. There is supposed to be a foam rubber adapter with a bell mouth in the radiator header and a gently tapered plastic tube that connects to the air box. I have flow tested the air box assembly and it flows the best with the correct parts (even though it looks restricted). For normal driving, it probably isn't a big deal, but for maximum flow in stock form, the correct parts work best.

Just by chance, I am working on a new project for my Reatta and today was the first day I fired it up, so it was a good opportunity to hear the intake sound. I turned the a/c on to check the operation and there is indeed a fairly dramatic difference in the sound of the intake as the IAC cycles to pick up the load of the a/c compressor. It sounds like what was described as "too much air" when the engine is loaded. Since the idle speed is approximately normal, it would seem the engine is under some sort of load, or, it is struggling to stay running and the IAC opens to compensate. Even without a fuel pressure gauge, checking the fuel integrator and block learn in diagnostics will give some idea if the ECM is trying to add or subtract fuel. If fuel supply is low, one or both should read way high, well above the target of 128.

Interesting, artificially limiting the air intake seems to have improved the operation? I do have a CAI of my own and there is a fair amount of intake sound, even at idle. It would still be interesting to see what the sensors say, particularly the MAF, TPS, O2 and the fuel Integrator and Block Learn, only after warmed up. When I connect or disconnect the MAF while running it usually causes a bad stumble or even a stall? You indicated no change, correct? The PCV should survive a visual examination or it should be replaced anyway. If you remove the rag, does the bad behavior return?