Engine missing and backfiring

Tiny
SCOTTB10
  • MEMBER
  • 1991 BUICK PARK AVENUE
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
So I had it coded yesterday, Came up with 22 throttle position sensor, 33 Mass air flow sensor and 45 O2 sensor reading rich. Does anybody know what might cause this combination of codes? The car start good and idles fine, It starts missing when I put it under a load. Either giving it a lot of gas or going up a hill.
Thursday, March 5th, 2020 AT 4:01 PM

33 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Disconnect the MAF and see if the issue smooths out. If it does then the PCM is getting a faulty MAF signal. Either from wiring or the sensor.

I then attached the codes if this doesn't resolve it. I would start with the 22 code and move to what I suspect you meant was 34. 33 is a wheel speed sensor code.

Run through this info and let me know what you find. Thanks
Images (Click to make bigger)
Thumb
Thumb
Thumb
Thumb
Thumb
Thumb
Thumb
Thumb
Thumb
Was this
answer
helpful?
Yes
No
Thursday, March 5th, 2020 AT 4:51 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
I noticed when I'm reading your repair pages you posted that it refers a lot of times to shorts. That is something I should have mentioned in my statement. The car must have a short because the battery keeps going dead. Is it possible the 2 issues are related?
Was this
answer
helpful?
Yes
No
Tuesday, April 14th, 2020 AT 6:25 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
It is possible. So what I would do it run through the test and see if you have a short. If not, then you may have two issues. At that point we can get a new post started and figure out the battery draw issue.

However, if you do, we repair it and see if that fixed the draw issue.
Was this
answer
helpful?
Yes
No
+1
Tuesday, April 14th, 2020 AT 7:13 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
MAP sensor reads 0 whether key on or off. I also read that a the code 45 should make the car smoke and run rough at idle, But not the case here, No smoke or rough idle.
Was this
answer
helpful?
Yes
No
Thursday, April 16th, 2020 AT 1:41 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
I did notice when I try to rev it up it hesitates.
Was this
answer
helpful?
Yes
No
Thursday, April 16th, 2020 AT 1:44 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
When you say you are getting 0 for the MAF does that mean you are following these steps and getting to the circled step? If so, then you have an open circuit, shorted to ground, or a PCM issue. I would check resistance from the PCM to the MAF sensor pin A and then check pin A to pin B.

From PCM to pin A you should have less then a half ohm of resistance. From A to B you should have an open circuit which means it is not shorted to ground.

If this checks out then you most likely have a PCM issue.

As for the no smoke or running rough, that can happen but is not proof of not having an issue. However, this code will cause a hesitation so I would address the MAF issue and then move on and retest the operation once that is operating.
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
Thursday, April 16th, 2020 AT 5:52 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
Is it possible I don't have a MAP sensor?
Was this
answer
helpful?
Yes
No
Saturday, May 9th, 2020 AT 12:50 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Correct. You do not have a MAP (manifold absolute pressure) sensor. You have a MAF (Mass air flow) sensor. They are just two different ways of telling the PCM how much air is entering the engine. The MAP will measure the pressure in the manifold and based on this, it calculates how much air it is pulling in.

The MAF is actually an air flow meter that measures the amount of air that is passing by it so the PCM doesn't need to calculate air flow to determine how much fuel to mix with the air to achieve the proper mixture.
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
+1
Sunday, May 10th, 2020 AT 6:34 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
Well that narrows it down. I think i'll replace the MAF and see what happens. It's funny how some show the vehicle with a MAP and some don't. The parts store had one to sell me, but I didn't buy it. I tried to buy the MAF but they didn't have any. I'll order one online. Thanks again, I'll keep you posted.
Was this
answer
helpful?
Yes
No
Sunday, May 10th, 2020 AT 7:02 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Sounds great. Yeah. Parts catalogs are not always completely accurate. The MAP that they tried to sell you may have been the correct part, just not labeled correctly. Good idea with ordering it online.

Let us know what happens. Thanks for the update.
Was this
answer
helpful?
Yes
No
Sunday, May 10th, 2020 AT 8:08 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
I tested the MAF sensor again, with the key on, engine off. I tested from terminal (A) to ground and got a reading of 2.20V. So if I follow the chart it say's ckt492 open shorted to ground or faulty PCM. How do I test the shorted ckt 492 or PCM?
Was this
answer
helpful?
Yes
No
Wednesday, May 13th, 2020 AT 3:16 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
Sorry, but I can't find a diagram that shows the ckt 492.
Was this
answer
helpful?
Yes
No
Wednesday, May 13th, 2020 AT 3:17 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
I'm not sure if I mentioned it, but my battery keep going dead, like I have a short.
Was this
answer
helpful?
Yes
No
Wednesday, May 13th, 2020 AT 3:19 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. The way to test for a short to ground is you put one of your meter leads in terminal A and then touch the other to a good ground location like the negative battery terminal. You need to have your meter on ohms and you should have an open circuit. If you have resistance from terminal A to ground then that means they are making contact which is a short to ground. To test for an open circuit, you need to unhook it from both ends and put one lead in each end of the circuit and check ohms. You should have less then a half ohm of resistance. If you have an high resistance or an open then that is the issue. If neither of these, they say to replace the PCM.

If your battery drains as well, we will need to get a new post started for that because that would not be related to this issue. So let's figure this issue out first and then move to the battery issue.
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
+1
Wednesday, May 13th, 2020 AT 7:36 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
Now I went into town and came back. But when I tried to start it an hour later it won't even turn over. Battery is at 100 percent. Doesn't even turn over and it's like every light on the dash lights up. So I down loaded the repair manual for the car and it said try to reset the security system using the door locks and I think it worked cause when I was done the horn honked. But the car still won't crank.
Was this
answer
helpful?
Yes
No
Sunday, May 17th, 2020 AT 4:44 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. If the car won't crank but the dash comes on shows that the ignition switch is at least functioning in the on position so let's move on to the control wire on the starter. Crank the engine and test for voltage on the purple wire at the starter. It is safe to say there is nothing there because this is the control wire. If nothing is there, go to the trans position switch and test it for voltage on the yellow wire when cranking.

If you have it then the position switch is the issue. If not, go before the relay and see if you have voltage.

Let me know these points and we can go from there. Thanks
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
+1
Sunday, May 17th, 2020 AT 7:18 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
Thanks again Kenny. I'll have to try this in the morning. Just as I think I'm getting close to the mass sensor problem. This has to happen. I know this car can run good, If I can just get it figured out. I found a part that's right next to the alternator where the plug wires run through. It had 3 nuts holding it on. So I took if off. Turned out to be something with a spring in it. But the gasket was all messed up. I don't know what it is. But it could be part or all of the problem.
It looked like it had a opening or a reservoir.
Was this
answer
helpful?
Yes
No
Sunday, May 17th, 2020 AT 7:54 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Can you get a picture of this? I am not exactly sure that would be off the top of my head. Thanks
Was this
answer
helpful?
Yes
No
+1
Monday, May 18th, 2020 AT 7:20 PM
Tiny
SCOTTB10
  • MEMBER
  • 36 POSTS
Yes, it's a mystery.
Was this
answer
helpful?
Yes
No
Tuesday, May 19th, 2020 AT 7:45 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
I like mysteries so let's figure this out. If you get a picture of it I am sure we can identify it. There are not too many parts on cars that stump me once we can see them. Thanks
Was this
answer
helpful?
Yes
No
Tuesday, May 19th, 2020 AT 5:40 PM

Please login or register to post a reply.

Related Engine Misfire Content

Intermittent Misfire
VIDEO
Intermittent Misfire
In­struc­tional re­pair video
Misfire Random Code P0300
GUIDE
Misfire Random Code P0300
The world of au­to­mo­tive di­ag­nos­tics can be com­plex, with nu­mer­ous codes and po­ten­tial is­sues to keep track of. One of the more com­mon en­gine di­ag­nos­tic codes is P0300, which...
VIEW MORE