Cutting Out

[VuickB6]

This car is gonna’ make me crazy.

I have an 87 GN mostly stock besides the general bolt ons, injectors, regulator, intake, exhaust, DP, chip, intercooler, etc.

This problem just started a few days ago, I have been working on the car for two solid days and can’t find it.

Problem: When I start the car it idles nice and clean and then it starts missing, then it will catch itself missing and smooth out and idle great and it will keep doing this. When I drive the car it will drive ok for a few minutes then it start sputtering real bad. Like its missing or the power has been turned off and on again. If you hit the gas hard it may take off or it may fall on its face. But nevertheless it is running real bad, then it may run great for a few minutes. This can happen with no boost or with boost or at idle. Sometimes it sputters so bad I dont think I am gonna make it to the driveway, then it dies. You may be able to shut it off and restart it and it runs great again, then it starts goofing within a few minutes.

Here is what I have done:

I changed: Crank Sensor, Ignition module, MAF, Coil Pack, TPS Sensor, ECM ( not chip ), that group of sensors on the passenger side fender wall, battery.

I unplugged the cam sensor while it was running and it ran the same, so I am guessing its not that. I check the battery ground and positive. I check the leads on the starter, alt. I checked for vacuum leaks. I checked the wire connections in the engine compartment. My fuel pressure is consistent during the episodes. Oil pressure is fine. Water temp is fine. It is throwing a rich code and a lean code (44 and 45 I think). About a month ago I changed the oil and fuel filter. I also ran injector cleaner a month ago also.

Help! If anybody has and ideas or suggestions please let me know.

Thanks

Kynan

 

[GNracerX]

I've had similar problems in the past . One event was an 02 sensor going bad. If you have a scanmaster check if your millivolt reading is updating regularly or slowly hovering in the .400 range at idle.

Another event was a spark plug wire. The metal jacket in the boot broke causing misfire. Sometimes it would drive smooth and others sputter. If I got on it the car would do fine until around 8-10 pounds of boost then sputter. But on both of the above mentioned the car never died.

My last encounter with same type of symptom was the IAC motor. It was sticking enough that I would get a partially good idle then die if I let off the gas abruptly, but it would drive good without sputter.

None of these situations is exactly what you are experiencing, but I hope some of this is useful. Keep us posted.

 

[RichX]

I've had the same exact problems with my car as you described it(87 Buick GN). My car is completely stock with only a K&N stock replacement filter. I've tried changing plugs & plug wires, fuel pump, fuel filter, replaced that baffle b/w the pump and the pickup(Is that thing important? still have it if I need it) with hose & clamps, cleaned fuel injectors, all wires & vacuum lines seem to be connected good, but still no go. I don't have all the fun stuff to check voltage, sensors, and for vacuum leaks (tried soapy water around seals & connections & didn't see anything goofy). Help on this would be great, suggestions on diagnostic equipment like the scanmaster (more tools - woopee! my wife will be very pleased...) would also help.

Thanks!

- Richard

 

[orion]

where is the fuel filter?

 

[nonosv6]

fuel filter is on the drivers side basicallly right in front of the rear lower control arm mount.....just follow the fuel lines on the drivers side back and you'll run right into it....joel

 

[humberto]

Could be a bad injector?

 

[RichX]

Just changed the O2 sensor & test drove... that didn't work. How do you test for a bad fuel injector? I don't know if this is a good test or not (works good on cars with multiple coils), but I hooked a timing light up to each one of the spark plug wires & revved up the engine to see if all cylinders are firing... held at several RPM ranges, bumped the throttle, etc. It appears that everything seems to be working on that end. That said, when holding at various RPM ranges, somtimes the motor misses. What is an IAC Motor & what does it do?

 

[VuickB6]

These are the things I still need to check. Some suggestions from friends.

Check the ground wires on the back of the block, the ones that connect below the coil.

Check the IAC.

Check Plug wires and Plugs

Replace fuel pump ( But I am getting good fuel pressure )

Also, I had a fellow say it could be the alternator.

The first time I had something like this happen, but not exactly the same, it did sputter but not as much it turned out to be a lose positive battery cable.

The problem this time is more prominent. I make it a block and the car jerks back and forth and almost seems like it is losing all spark or electrical, no lights flicker when the happens. The weird part is the car may start up and run as smooth as can be, drive for 3 blocks and then start screwing up. ERRRG

Thanks for the info you guys have gave, every bit helps.

 

[1NASTY6]

stumbling problem...

It sure sounds like your problem is related to the IAC....

Do you have the capability to check your IAC settings at all??

If not, just replace your IAC (pretty easy) and give it a try.

Sure sounds like that's the probnlem to me...

I thought maybe cam sensor, but you said that you ruled that out
already.

Good luck!

Tim

 

[RichX]

I hate to ask a potentially dumb question, but what is the IAC and where is it at on the car?

Thanks.

- Richard

 

[Eric Stage I]

Don't rule out the cam sensor. Unplugging it while its running bad won't necessarily change anything.

It sounds just like a cam sensor problem...

Take the cap off the cam sensor. Look inside the cap and see if the wheel has been cutting up into the plastic. Also pull up on the metal wheel and see how much up and down play there is. Also make sure the wheel is not spinning on the shaft.

Regards,
Eric

 

[wagon]

Originally posted by RichX
I hate to ask a potentially dumb question, but what is the IAC and where is it at on the car?

Thanks.

- Richard

IAC Idle Air Control
This is basically gives enough air so that the computer can adjust the idle. It is mounted on the throttle body, just below the up pipe. It has a four prong square electrical connector. gnttype.org has a procedure for setting it. You can't just replace it and go, it needs to be adjusted, the same time as the TPS.



Good Luck, and keep us posted with your progress.

Brian

 

[Intercooler]

Did this ever get resolved?

 

[RichX]

I haven't gotten it resolved yet. I am at the point of deciding what software package to buy to analyze the car's computer because I don't want to throw more parts at it at this point. I can't decide on Turbolink, Direct Scan, or Scanmaster. What do you recommend?

 

[Intercooler]

All of them I use DS and SM2