Please Help Inconsistant starting 2.5L

Rollin Smoke · #1 12-18-2006, 08:32 PM

Hello all. I hope someone on here can help my with my problem. I bought a 91 grand am( 2.5L TBI, auto) this past summer to communte to work. Great car until it started acting stupid. The car runs great once I've gotten it started.

Ok here is the scoop. Car would start and run great until one day it started having trouble starting. Sometime it will start right away and sometimes it just won't start if it has been sitting hour over 2 hours. If I go outside and start it every couple of hours it will fire right up everytime. However if I leave it sit for 3 hours it might now start. If it does start its after trying on and off for 10 mintues untill it finally decides to start. I've had morning that is just would not start, but it would start in the evening. I've also read the troubleshooting codes when it won't start. At times I get 33, 34, or 35 and sometimes no code what so ever. It just puzzles me to no end

...If someone could PLEASE help me get this care going 100% reiable it would be awesome

Below are my efforts in an attempt to resolve the mystery problem:

1. checked fuel pump, everything checked out
2. replaced the computer
3. tested MAP sensor @ autozone, ok
4. replaced IAC
5. visual inspection of vacuum hoses

crazy Jim · #2 12-19-2006, 07:27 AM

your engine may have an oil pressure sensor going bad. Also, does it crank strongly or does the battery seem weak? Make sure the air fiter is not plugged as well.

Scrapper · #3 12-19-2006, 07:51 AM

i dono if this is your problem but i got a 2.5 tbi in my s-10 and if it rains wont start unless i keep wire dry on it..i know another guy has same problem but his is ford ranger..but in 1 case it was module...good luck....

grfnkl · #4 12-19-2006, 09:09 AM

I have a 2.5 in my 88 and i think i know what you mean about the starting. When was the last tune up on the car? These engines are notorious for leaking oil out of the valve cover gasket down the front of the engine and onto the spark plugs. Eventually it makes it way down to them and fowls them up. Then you'll have intermittent problem with starting. Another possibility is the spark plug wires and ignition module. They too will cause a similiar effect. Scrapper is right about the wires being dry.... if it was a rainier day the car just wouldn't really wouldn't want to start. Some other basic possibilities, is your crankcase filter and air filter. As stong as these engines are they are very tempermental about everything. hopefully this gives you some direction or help.

xeroinfinity · #5 12-19-2006, 10:30 AM

Ok 33, 35 are MAF high/low freq.
The 34 was the map...

If you have NOT seen a 13 ,44 ,or 45 then I would say its the MAF.
Get it tested !

First check the wiring to the O2's and the MAF. Make sure the vacum lines are also not cracked that feed the MAP.

Intermittent problems can be challenging,
Good Luck

Rollin Smoke · #6 12-19-2006, 10:59 PM

Did it again. Didn't start it while at work after lunch and it didn't want to start when it was time to go home. After about 10 minutes of on and off attempts to start it it decided to fire for what ever reason.

Weather doesn't seem to be a factor. Car acts the same when when its 80 degrees or 30 degrees outside. Rain snow or sunshine same dang on thing.

Spark plugs are new, bout 3 months old. Wires are old b/c I wasn't sure I would be able to reach to change them. I'm gonna try and get that done this weekend.

What really bugs me is that if I start it every couple of hours you would never know there is a problem with it. What could possible change state after it hasn't been running for a couple of hours. Could ambient temperature be a factor? If so, what would let it finally start?

Air filter is only a week old.

Where/what is the ignition module?
Where/what is the MAF?
Where is the crankcase filter?

I've read about the crankcase sensor. could that be the problem? What does it do?

Sorry about all the questions. I'm just not used to working on such new engines. I prefer to work on my antique tractors instead, ah well.

Thanks

xeroinfinity · #7 12-20-2006, 08:56 AM

When you replaced the IAC did you set the pintal to 1/8" before installing it?
It is not set from the factory.

If you havent replaced the Ignition control modul,
then it is likely that this could be the intermmitant problem. Also the coils can cause this.

Heres a pic that can help you test the coils.
Testing the HEI ignition coil

The MAF sensor is in the air intake tube.
It mesures the amount of air moving into the engine.

Not sure on the CrankFilter location...
Heres another link that might help on this.
Crankcase Ventilation

Also a bad crank position sensor or maybe even a cam position sensor,
could cause these intermmitant experiances, giving a no start.
This link will help you find and test those.
troubleshootingThe links on the right will show you how to properly test these items in question.

Like I said before, intermittent problems can be hard to find.

grfnkl · #8 12-20-2006, 09:29 AM

the ignition module is located towards the back of the engine. Just follow the spark plug wires until you come to a box with the four spark plug wires. This would be your ignition module. I don't remember but i don't believe this engine actually has a MAF sensor, or if it does it's i've never noticed or located it. The crankcase filter, is in the same housing as your air filter. there's a small filter off to the right side in a plastic housing, which connects to a hose that goes into the valve cover. it may have some oil in the crankcase filter which is common.

Rollin Smoke · #9 12-20-2006, 10:02 PM

Well I read the directions for the IAC and it said to make sure it wasn't over 1 1/8 long, which it was not. BUT the starting problems were occuring long before I replaced it. No change when it was replaced.

On the matter of the MAF. There is not a sensor in the intake that I've noticed.

Now that the crankcase filter has been described to me I know exactly what it is, I put a new one in when I put a new air filter in as well. So thats new as well.

The only consistant out of this whole deal is that the car will start if it doesn't sit for more than a couple of hours without being ran. About every 2 hours I go outside and start the car up to make sure I'll get home from work. But if I don't start it and try to go home at the end of the day it more than likely won't start. I'll sit out there and try for awhile and then a miracle will happen and it starts right up. Wierd.

Everyone thanks for the help so far....sooner or later we'll eventually get this figure out. I hope its sooner

xeroinfinity · #10 12-20-2006, 10:36 PM

Hum, when you get a no start you should try and check for codes.

Could be a crank position sensor too causing the start when warm, no start when cold

Also on the IAC, was the port in went into clean or did you clean it out ?

Rollin Smoke · #11 12-21-2006, 04:45 PM

when I do get a no start I try and check for codes. 99% of the time I only get a code 12, which I believe only means that its in diagnostic mode. IF I do get any other codes its 33, 34,or 35.

This afternoon I went outside and tried starting the car up, no dice. Came back out about 10 minutes later to put to put some stuff in the car and it started right up. Makes no damn sense to me.

Can I test the crankcase sensor?

How does the vacuum system work? would the system lose vacuum immediately, or could it lose pressure right away?

The port appreared to be clean, but I'm not sure what I'm looking for either.

xeroinfinity · #12 12-21-2006, 07:30 PM

Well I dont think you would get a 33 or 35 if you have no MAF, so you might have one gone bad. It can make it not start or run realy crapy.

On testing the crank sensor ...

Its to replace but should be simple to test with a voltmeter.
It is located under the coil housing or DIS.
1989-91 2.5L Engine schematic

Looking at that diagram I dont see what color wires they are though.

So, thier should be a plug with 3 wires coming from under the DIS.
1 wire would be hot with key on(+), and 1 is grnd.
The other is a signal wire.
Connecting the volt meter to the + and grnd,
with the someone else turning the car over,
should give 5 volt increase-decrease as the engines turned over.

*Tip here,
pull the fuse for the ignition or the fuel injector fuse,
so it doesnt start

Hope that helps.

Rollin Smoke · #13 12-22-2006, 10:50 AM

This is from the thread with all the trouble codes.

33 ........... Manifold Absolute Pressure (MAP) sensor signal voltage high
33 ........... Mass Air Flow (MAP) sensor or circuit - excessive airflow indicated
34 ........... Manifold Absolute Pressure (MAP) sensor signal voltage low
34........... Mass Air Flow (MAF) sensor signal - low airflow indicated
35........... Idle Speed Control (ISC) switch or circuit (shorted) (carbureted models)
35 ........... Idle Air Control (IAC) valve or circuit

It appears to me that depending on the model a number 33 could be a map or maf sensor, unless they consider them one in the same when diagnosing the car.

I was lookin at for sensors on the car yesterday. There is one in the manifold(not sure if it's exhaust or intake but I think it's intake), one right under the baffle in the throttle body. Could one of those be the MAF?

Oh side note, its raining right now and for what ever reason the car started up on the first try. Grrrrrrrr!

thanks again

grfnkl · #14 12-22-2006, 11:10 AM

Quote:

Originally Posted by Rollin Smoke

This is from the thread with all the trouble codes.

33 ........... Manifold Absolute Pressure (MAP) sensor signal voltage high
33 ........... Mass Air Flow (MAP) sensor or circuit - excessive airflow indicated
34 ........... Manifold Absolute Pressure (MAP) sensor signal voltage low
34........... Mass Air Flow (MAF) sensor signal - low airflow indicated
35........... Idle Speed Control (ISC) switch or circuit (shorted) (carbureted models)
35 ........... Idle Air Control (IAC) valve or circuit

It appears to me that depending on the model a number 33 could be a map or maf sensor, unless they consider them one in the same when diagnosing the car.

I was lookin at for sensors on the car yesterday. There is one in the manifold(not sure if it's exhaust or intake but I think it's intake), one right under the baffle in the throttle body. Could one of those be the MAF?

Oh side note, its raining right now and for what ever reason the car started up on the first try. Grrrrrrrr!

thanks again

It does depends on the car. Some of the older engines didn't have a MAF sensor in them. You more then likely have a MAP sensor though. I have to double check myself on this though. As far as the vaccuum lines. If they were the culprit they would have shown prior to this. You would have gotten a check engine light while driving especially after accelerating. You would also hear a somewhat noticable hissing noise from under the hood, plus the car would stumble a lot on acceleration. You could lose the vaccum after the car is turned off, but would gain it right back after the car is started. Hope this helps.....

xeroinfinity · #15 12-22-2006, 04:11 PM

So was this problem the same before the ECM change?

Those codes kinda make more sense now.

Replace the MAP, and double check the wires and if it has a vavum line check those.
THis would be on or close to the intake manifold.

And check the wires to the O2 sensors, could have broken wires.
Also a bad TPS can keep you from starting all thie time(as would a MAF if you have one).
This is on the side or bottom of the TB.
Here is a pic....
yours is a round with a rectangle coming off where the wires plug in.

Shorted TB injector wires can cause intermmitant starting too. Looks like you need to do some electrical testing,
how wonderful

Good Luck and Happy Holidays!

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