I started the car up fine this morning after not driving it for about a week and drove it about 15 miles to breakfast. After breakfast, it suddenly wouldn't start. It would fire up, but then would die right away... I tried several times. Finally, I gave it about 1/2 throttle and it started. It ran fine on the freeway, but when I came to a stop after that, it died. Again, I couldn't start it without applying throttle. I managed to get home by keeping my foot on the gas at stops. The check engine light did not stay on.

Another thing I noticed: I smelled fuel after trying several times to start it up.

Anyone else have this problem suddenly appear? Any ideas on what is causing this? I'm guessing it's a fuel supply or vacuum problem because it runs just fine when not at idle.

Thanks, in advance, for any help!

** Update ** I replaced the MAF and the relays and cleaned the throttle body on 9/23. However, the problem starting it reappeared the next morning after driving it a while, then shutting it off for about 20 minutes. Any other experiences with this problem?



[Modified by K87ZZ4, 11:27 AM 9/24/2002]

 

Indeed you might start by checking vacuum lines, especially those to/from the purge canister near the left headlight.

If not a vacuum problem I would suspect the IAC valve. In this case get some intake cleaner, clean the TB, the throttle plates and remove and clean the IAC pintel and it's bore under the TB. If still a problem replace the IAC.

It could be a stuck injector, like the cold-start, but I would start with the above measures.


[Modified by 65Z01, 4:11 PM 9/22/2002]

 

My car just had a similar problem, check my subject, "86 won't idle". There are several thing to check, according to mechanic friends, forum members and my shop manual. These are the things to check right off.
check all the vacuum lines
unlpug the MAF, the computer will compensate by using a preset voltage to judge the mixture and the car will run somewhat correctly. This is what was wrong with mine, and no codes were present until unplugged the maf
check the fuel pressure
unplug the tan wire that goes to the distributor, as you would when you adjust the timing. If the pickup coil(not the ignition coil) in the distributor is bad, the car will run ok like this.
Your problem sounds like the maf, especially since it smells rich, as mine did too.
Good luck

 

Thanks for the pointer to your post. All of the vacuum lines I could find (and trace!) looked OK (no obvious problems, anyway). So, I unplugged the MAF and it started right up.

I'm guessing that means my MAF is bad and needs to be replaced... is that true?

So, since you found that the MAF was the problem on yours, did you just replace it? Should I just get one from the dealer? Is there anything else I should be doing while messing around with that?

And I noticed your comment about smelling fuel vapor... do you still think there might be a leak somewhere? Or, do you attribute that to the messed-up MAF just running it to rich at start-up?

Thanks, again, for the help... who knows how long I would have spent trying to figure this one out on my own.

 

Okinawa86vette, I read your resolution post where you said it idled fine after you unplugged the MAF.

I went to pull mine out of the garage and it started up fine, but then after idling a bit, it would slow down to abuot 400 RPM, then stumble and jump up to about 1,200 RPM, then it would settle right down about 5-600 RPM for another 15 seconds, or so, then do it again.

When I put it in gear to back out of the garage, it was really idling rough and almost acted like it was going to die. I guess it's really not going to be very driveable with the MAF unplugged.

Just wondering if this is the kind of behavior to expect with the MAF unplugged? Or, if maybe something else is going on, as well, and unplugging the MAF is just making it possible to start the car? Anyone have any experience with this?

 

I'm glad I helped. It was a pretty miserable week of me trying to trace the problem. I think my MAF was killed by the motor backfiring when I had the fuel regulator problem, so once the fuel system was fixed, the maf kept the car from working properly.
As far as replacement, that is the only way to fix it. There are a couple of options, but it pretty much comes down to price and performance. A new stock one from various mail order places ranges in price from $275 to 325, rebuilt ones are around 180 with a 50 dollar core charge.

Performance ones are just stock ones with the screens removed and the aluminum fins ground off. I would just go with a stock one, since you can remove the screens and grind down the aluminum later. I wouldn't even bother with the aluminum since most of the flow gains are from the screen removal and it's very easy to damage the filament when your hacking away with a dremel. They have similar prices to a new stock one, or maybe a few bucks more.
I haven't replaced mine yet. I wouldn't worry too much about a gas leak. I had a leaking regulator and then a split o-ring when I installed the new fuel reg, and you'll know when you have a leak. There will be a strong odor of raw gas from the engine bay area. If it just smells like it's running rich, try the new maf and it should cure that, since the maf has a huge impact on the air/fuel mixture.
Good luck. I'm sending my dad to the dealership monday to pick one up. I'm also going to have him check autozone and see if they are a little bit better priced. Out here in Okinawa, there's only one GM dealership, and their prices aren't too good, so I usually end up having my dad get it for me and ship it here or order from one of the mail order companies.
Once again, your welcome for the help, I'm just glad I was able to help.

Chris

 

Sorry, I didn't read your second post. I didn't drive the car at all with the maf unplugged. I forgot to plug the maf in one time after cleaning out the engine bay a bit and it ran horrible with it unplugged. You should also get several MAF related codes, so just make sure to clear the computer after you install the new one so the old codes don't affect the car.
The dealerships usually have them in stock. To answer an earlier question, there's really not much else to do when you're fussing with the maf.
Let me know if there's anything else I can help with.
My email is csavaglio@hotmail.com
Chris

 

I am planning to pick up a reman MAF sensor and relays on the way home tonight (to be prepared) and also pick up some intake cleaner and give that a try first, as 65Z01 suggested.

From some old posts I read, some people found MAF sensors for about $140. Not around here! We don't have an Autozone, but the local Schmuck's has one for about $200 and Napa for about $250. Both have a 1 year warranty, so I guess I'll save $50 bucks. I guess I should keep in mind that a new one from the GM dealer would cost over $450... gee, what will I do with the $200 I saved? ;) :D

If this solves the problem then I'll be smilin' regardless.

 

My friend at that hotrod shop out here happened to have a used one, so I ended up buying it off of him. Put it on and the car ran well. I just need to clean the plugs since they're fouled up pretty bad. I still have to put my new tranny governor in so the car will shift out of first. I'm going out to do that stuff right now, so hopefully the car will be running the way it supposed to, maybe better.
Glad you found a good priced maf.

Chris

 

Well, my favorite kind of automotive problem reared it's ugly head -- the intermittent problem. I picked up all the parts on the way home, and decided to collect some ECM data with the start/idle problem to compare against. I plugged the MAF back in and presto! it started right up :( So, I became annoyed (what's new in auto mechanics ;) I thought about returning all the parts and then I figured I wasn't in the mood to deal with this again when it reared its ugly head... plus a new MAF might improve overall runability. That, and it seemed that several others had replaced the MAF to solve similar problems. So, I said "screw it" and cleaned the intake, replaced the relays and replaced the MAF. It started up and ran fine... and I took it out for a brief test drive to record some data... it seems to run fine.

Now, the true test will be if I encounter the start/idle problem again in the near future... I will be extremely annoyed if that happens, but I will have eliminated the MAF as the problem (hopefully!).

 

Well, I find myself annoyed :(

It started up fine this morning and ran normally. I drove it for about 15 minutes, then shut it off for about 20 minutes for an errand. When I went to start it, I had the same problem again, where it will fire up, but as soon as I let off the starter, it dies. So, maybe it's only acting up after it warms up?

It actually idled fairly well and didn't die in stop-and-go traffic on the way to work. I recorded data the whole way. When I got to work, I tried starting it several times and it was inconsistent: sometimes it wouldn't start, others it would. At one point, I actually TRIED to get it to die by putting my foot on the brake and hitting the accelerator, but it wouldn't die. So, it seems to act up worst after it has been shut off for a while.

Some of the data shows: Present IAC Steps are a constant 145; when the engine speed drops below 500 RPM, the Target IAC Steps will kick up from 0 to around 50; the MAF rate is 6.5 to 6.8 at idle; injector pulsewidth is ranging from 1.9 to 2.5; the 02 sensor is showing around 700 most of the time, but does bounce down to around 100 when there's a low idle speed.

Any help would be appreciated about what to do next to figure this out!

 

Do you have the original Multec fuel injectors (greenish-grey color body)? These are known for breaking down in resistance over time. Take a digital votmeter and check each one for a reading of 16-17 ohms. With the car off, unplug one at a time and put the voltmeter to the pins on the injector. You should be able to get to at least 6 of them without removing runners. my car had an intermiitent problem similar to yours and it turned out that one of my injectors was reading 2.9 ohms while the rest were at 16.2 ohms. I unplugged the one bad injector and the car ran great. I found a spare and installed it and the problem is cured.

 

I do have the original fuel injectors. I have been needing to get a multimeter for some time, so maybe I'll do that, then check the injectors out.

The part that has me confused is why, when I unplugged the MAF, it started right up and idled OK (except for a little oscillating every 15 seconds, or so), yet replacing the MAF doesn't seemed to have solved the problem? Maybe it was just a coincidence that it ran better when the MAF was unplugged.

If it's a problem with the IAC system, then why did unplugging the MAF make a difference?


[Modified by K87ZZ4, 2:49 AM 9/25/2002]

 

Well, the car has started and idled fine every single time today (I was all set up with the computer to record data each time, too... go figure). So, rather than thinking some fairies snuck into the garage in the middle of the night and sprinkled magic dust on the intake system of my car, I think I may take the more thorough approach to cleaning the Throttle Body and take it apart and clean all the parts, separately. I haven't done that before.

Anyone have any tips on removing and cleaning the Throttle Body? It seems like I will have to remove the IAC pintel which, I presume, is what sets the idle speed. After I do that, I will have to set the idle speed, right? I don't want to mess with that if I don't have to... but if I need to take it all apart to get it good and clean, I will. Can I mark it so that I put it back exactly as it was?

I guess I should get the real shop manual for stuff like this, but I just haven't picked one up yet. Any help would be appreciated!

Thanks!


[Modified by K87ZZ4, 7:54 PM 9/25/2002]

 

If it were'nt for the fact that you had recently worked on the MAF I would say it sounds like a fuel pump going out.
They act like that, running around 25 pounds pressure instead of 40.
Have you checked fuel pressure?
:chevy

 

I haven't checked the fuel pressure recently, since I don't yet own a pressure gauge. I had it checked a few weeks ago when it was at the shop and it was in the high 30's.

 

Borrow one & tape it to your windshield & go for a drive .If it'll run that long.

 

What code are you getting?

 

That's the fun part, it's not setting a code :(

After I posted last night, I went to start it up and the problem appeared again. It barely started, idled really rough, then died. I started it again, and it again idled really rough; once I got going, it ran fine. I was prepared and was recording data... there are a lot of parameters, of course, but here are the key differences I've noticed between it starting normally and starting hard and idling rough:

When it starts and idles normally:
During the first 7 seconds after the engine starts:
The engine speed goes to 1,500 RPM and then comes down to about 1,000 RPM
The BLM (Coarse Fuel Correction) is 125 and BLM Cell Number is 6
The Idle Target is 900 RPM
The IAC Target is 130
The Present IAC position goes from 73 to 32

During the next 25-30 seconds:
The engine speed hovers around 900-1,000 RPM for about 15 seconds, and then comes down to about 600 RPM
The BLM (Coarse Fuel Correction) is at 125 for about 20 seconds, and then goes to 133 and BLM Cell Number is 1 for about 20 seconds, then goes to 0
The Idle Target is 900 RPM for about 15 seconds, then goes to 550
The IAC Target is 0, except for a couple of spikes to 128 (at about 20 and 25 seconds out)
The Present IAC position stays at 32 for about 10 seconds, jumps up to about 40 for 10 seconds, then drops to 25


When it it idles poorly and dies, the data shows:
During the 6-7 seconds after the engine started, it idled very rough, then died:
The engine speed ranges from 200 to 700 RPM
The BLM (Coarse Fuel Correction) is 133 and BLM Cell Number is 0
The Idle Target is 950 RPM
The IAC Target ranges from 0 to 2
The Present IAC position is static at 145

After starting it again, over a 30 second window, the idle continues rough:
The engine speed ranges from 450 to 600 RPM
The BLM (Coarse Fuel Correction) is 133 and BLM Cell Number is 0
The Idle Target is 925 RPM for about 15 seconds, then goes to about 900
The IAC Target ranges from 0 to 2
The Present IAC position stays at 145

So, the way I'm reading this is that when it starts and idles normally, the Present IAC Position is in the 30-70 range and the IAC Target is 130 for several seconds, then the target goes to 0.

When it won't start, or starts and dies, and idles rough, the Present IAC Position seems to be "stuck" at 145 and the IAC Target is 0-2.

So, I'm guessing, here, but I'm wondering if the IAC is stuck wide open when I have trouble starting it and it has a rough idle. I'm thinking it's stuck wide open because I can smell raw fuel sometimes at startup.

Does this make sense to anyone else? Does this indicate a problem with the IAC motor? Is it likely that cleaning the Throttle body and the IAC Valve will help? Or, do you think I will have to replace the IAC motor to solve this problem?

Anyone else have "normal" startup and idle data that they can compare to what I'm seeing? Is my "normal" startup really normal?

Thanks again for all the help.

 

I was having the same problem with my 92. They replaced the idle speed motor and everything is running great.

Lorna : )