yzzerdd

I'm working on my brother's car(my old car) and am stumped, so I thought I'd come here. It is a 1990 Buick LeSabre with a 3800 series 1. 4-speed automatic. Ran GREAT when I sold it to him a year ago. When I sold the car, it read the following codes:

22--TPS signal low
41--Cam sensor circuit(probably missing magnet)

It ran great. Winter, spring, summer, fall. Drove reliably. Now, it has one extra code:

34--Mass airflow sensor

When in park, it idles pretty well. It responds throughout the throttle range. Has a slight miss, but not bad. When in gear, it idles rough. Sort of like it's in closed-loop and just going throughout the timing range. When driving, it misses, has little power. When I floor it, sometimes it just tries to go, kicks down, and has bad spark knock. Other times, it just backfires when the pedal hits the floor.

I've checked for spark on all cylinders. The plugs look fine. The wires are good. And whereas the vacuum lines are aging, they don't seem to be the cause.

Does anyone have experience with this motor? I'm going to try cleaning the mass airflow sensor, but am leery as to if that would cause this. I tried running it unplugged, and it did run, but a little worse.

I had an 87 Cutlass Ciera with a 3.8L 4spd. When it's mass airflow sensor went out, it would die if not on the gas, and ran just as bad. But this just seems a bit different than the Ciera.

Any ideas?

Rickman48

Fix the codes!
22 + 34 together are the problem!
Now that they're both up - one won't re-set unless both are fixed.
Clean MAS with carb cleaner - carefully, and replace the TPS.
Unplug battery for 30 seconds, start + drive!

yzzerdd

Yeah, I was trying to replace the TPS this afternoon. I have a new one, but it's damn near impossible to get to one of the two phillips screws. That is, without removing the throttle body, which would seem to be held on with two nuts, but it wouldn't budge with them removed. I'll get back at it tomorrow before work and see what I can do. Hopefully my check will be in so I can clean the mass airflow sensor. I've heard that you should only use electrical contact cleaner for the sensor, though?

DeltaPace77

Not aware of a cam sensor, But if it's a crank tigger problem under the harmonic balancer, you're really needing to take care of this, as is one to leave you stranded. Could be wrong not knowing about a cam sensor, as if the timing chain stretched, jumping a tooth, even more work. Either one with drop power way down, and cause backfiring.

Joe C

The cam sensor uses a magnet on the timing chain cams gear. You can remove the cam sensor and rotate the engine buy the crank pulley and look into the cam sensor hole to see if the magnet is missing. if the magnet is missing you will have to remove the tinging cover to remove the timing chain and gear to replace the magnet. Also check the wires to the MAF sensor to see if any are broken if not bad MAF sensor. To replace the TPS it is easier to remove the throttle body but you will need to adjust the sensor.

jackedolds

Rather than buy a can of carb clean - buy a can of Mass airflow sensor cleaner as it is made for this. make sure after cleaning that the element is completely dry before pluggin in and turning the key on. If you can see dirt on the element clean it. If there is no accumulation of dirt - cleaning it will likely do nothing for it, but I always clean them before condemning them unless the signal shows electrical problems (this can only be seen with an oscilloscope or very very very fast graphing meter - i.e. digital storage oscilloscope).

yzzerdd

I cleaned the mass airflow sensor, with significant improvement to the running of the engine. More power, and a bit less chug to it. Still doesn't run quite right. I've been trying to figure out how to take the throttle body off, so I can replace the TPS that way. I have a new sensor, and it is a non-adjustable type. I got one screw on the old TPS loose, but cannot get the other to budge. I only see two bolts holding the throttle body on, one to the left, one to the right. I removed both nuts, but there seems to be a third. Hopefully I can look in to it tomorrow.

yzzerdd

I replaced the TPS just now. I unplugged the battery, hooked it back up, and ran it for a minute. Code 34, mas airflow, is gone. Still have the TPS code. However, it may just need adjusting. I have two TPS sensors that were brand new laying around. Both for 3800's, one for the 90 LeSabre, and the other I had for an old car, a 94 Regal. After taking off the LeSabre's TPS, I found that it actually WAS adjustable, so I installed the TPS that I had that was adjustable. I have the screws just hand snugged so I can adjust by ear for now. I guess I'll adjust by volts tomorrow. If the code still doesn't clear, I will be swapping in the other TPS I have.

5V at idle, right?

--Jack
Vise grips saved my life, btw. Love 'em!

OLDSRALLYE350

uhhhhh no around .33 t0 .46 volt at idle. The computer sends a 5 volt signal to the tps which is modified from around .3 volt to about 4.5 volts when wide open.

yzzerdd

Ah, my memory failed me. Broke out the voltmeter today and got right down to probing. I have the TPS adjusted as perfect as I can with analog. I did several runs, and several code checks after reseting my ECM. I now only have code 41, cam sensor. And whereas the difference is phenomenal with the cleaned mass airflow, and the new TPS working together, I still have a miss. Hmmmmmm. I pulled three plugs closest to the front of the car. They all looked pretty good.

The reason I don't suggest that it is the cam magnet, is because it's been bad for at least a year without trouble. I do intend on replacing it eventually, but for now, I'm working 7 days a week, and would like to have wiggle room when I replace it.

yzzerdd

I replaced the plugs and wires this morning, and let me tell you, the car runs like it's brand new. In the year that I've had this LeSabre, it has NEVER ran this good. No more stalling, no misses. The plugs and wires weren't in terrible shape, but they were pretty old. Also, I did some reading, and some people had misses caused by the heat shields on the plugs closest to the firewall. I removed them, just in case, to make sure that's not an issue later. Thankyou all for your help.

EDIT: It's worth mentioning, it had ACDELCO plugs, and that's what I put back in it, gapped to spec. Duralast wires.