brief engine cutout on throttle

[Fred Spruill]

Hey guys! New to the site and have a tech question about my GN's engine performance. On hard acceleration, as the turbo starts to spool, the engine starts cutting out like it is miss firing. If I give more throttle, it gets worse. The exhaust smells too rich with unspent fuel, so I thought it had to be ignition related. I have replaced the ignition control module along with the coil pack. It did seem to get somewhat better, but it still has the problem. I went to the parts store and was going to get a set of plug wires, but on the advice of the parts counter guy, tried some Lucas injector cleaner. That did not seem to make a difference. I do have the performance plug wires on it which are some pretty thick wires and they are only about a year old. I am starting to think maybe the fuel filter or even the fuel pump. Some technical stuff - my car is chipped and has the large front mount inter cooler and a BstC boost controller. Other than that it is stock. Any suggestions or advice would be greatly appreciated. Thanks!

 

[dragrazor]

Scanmaster?

 

[trixdout]

^this and boost gauge?

Sent from my iPhone using Turbo Buick

 

[Fred Spruill]

No scan master. Hopefully in the future. What about the boost gauge?

 

[Fred Spruill]

Yes. I have a boost gauge.

 

[dragrazor]

I know money may be tight for some of us but a scanmaster would be my next purchase if I were you before you throw money at it and not know what your car is doing. I was able to fix a few issues just from the numbers i was getting from my scanmaster. I am by no means an expert on these cars. I am still learning. You have very knowledgeable people on these forums and just about all of them will tell you that you need an engine monitoring system before throwing money at the problem. I see your message count is 3. Welcome to the site.

 

[pacecarta]

lets see if im following

you think its ignition , you replaced the coil and module , but then think it could be wires but then didnt try another set
what plugs and what do they look like , while they're out ..how's the compression?

if you suspect fuel delivery hook a fuel pressure gauge to the rail and see what you have,,,
a scanmaster would have given you an o2 reading and from there you would have data to base a move on.
sometimes just swapping parts will do it , but easier if you hook up with someone with a known working part to borrow for a test rather than to drop hundreds on parts that didnt need replacing, and there are tests and testers for some of the sensors including the ignition module/coilpack and the wires

you could guess all day . it could be maf sensor , crank sensor , coolant sensor , regulator , regulator hose , cam lobe (lifter pushrod rocker shaft) , bad plugs or wires or stupid stuff that needs a look over to find ..like crossed ign wires ,regulator hose popped off , battery cable on the exhaust manifold, chaffed wiring , bad connector on oil switch (not kidding its more common than you would think )
...even the cam sensor has caused what you describe.... you need data and then a knowledgeable course of action based on what data you have
the scanmaster would give you some of that data , you would see coolant temp sensor/maf air flo/tps voltage/o2 volts/battery volts/iac count/o2 cross count/ and knock.
and temporarily get a fuel gauge hooked to it that you can see while you drive

case in point
you say its rich but you suspect fuel delivery is low??? so i guess its new filter and pump time or will you see what the pressure is

 

[earlbrown]

You need to park that car and take care of a laundry list of preventative maintenance and mandatory upgrades.

...or you can keep driving it and be forced to park it due to blown head gasket(s), lack of preventative maintenance and mandatory upgrades.

 

[Fred Spruill]

I am definitely still learning about these cars. I bought mine just over a year ago. It spends most of the time under cover in the garage as it is an investment/enjoyment car and has only been driven 2000 miles in the last year. This problem came on gradually over the last 100 miles. But I now understand that I have been looking at the symptoms and treating it like it was any other 25+ year old car. I will for sure be buying a scanmaster now so I can have all the information I need. I didn't realize there were so many things that could affect the engine performance like this. Thank you all for chiming in. I will update when I know more.

 

[earlbrown]

A chain is only as strong as it's weakest link..... and these damn cars have a chitload of links!

 

[klmnla]

I have bee chasing the same problem for 5 years. I have been through an extensive list of possibilities twice with no luck. My scan master numbers are spot on perfect. I just did a compression test today, which you should do also. My only option now is to remove the valve covers and look for a worn cam lobe. If replacing the cam fixes it, I guess I should have started there first.

 

[Fred Spruill]

Update: I bought a scanmaster and got it installed tonight. At idle everything looked normal according to the documentation except for the O2 mv reading. It jumps all over the place between 180 and 800. I believe I have bad O2 sensors. I also tried tapping the MAF while idling and it did studder slightly. My next step will be to get O2 sensors and a MAF.

 

[pacecarta]

o2 jumping doesnt indicate bed o2 , it should jump rich lean if the car is in closed loop
and you should see the o2 cc (cross counts) cycle at least 255 time in 90 seconds

in open loop it should be steady at idle and with throttle it should hold a steady (rich) O2 reading

 

[bogies87]

You need to check for a wiped cam lobe. I learned the hard way.

Sent from my SCH-I535 using Tapatalk 2

 

[Joeld]

funny how as a rank amateur myself i a sitting here wondering what your scanmastet numbers are

i really have no idea how you can accurately tune /diagnose without one.

i also have a low mile car that previous owner (original owner) bought as an investment. here we are almost thirty years later and i changed the airfilter for the first time a month or so ago.

i wouldve hurt my car bad without this forum and scanmaster.

think of this car as having been designed from the beginning to require a scantool just like the car cant function without the ecm it really wont function for long without a scan tool

much more fun and rewarding with scan tool

joel

 

[Dave Dunbar]

A bad MAF will feel like a plugged fuel filter. When it's idling tap the sensor, if it stumbles and misses that's it.

 

[GNONYX]

Welcome to a great site, you will find many, many guys who are very knowledgeable in these cars as well as many mentors who sleep and dreams about these cars. Since this is your first GN you might need to start with what you have and don't know what is in the engine, and a good start is to do a spring maintenance cleaning. http://www.gnttype.org/maint/basics.html
Baby steps needed to be taking as earlbrown mention if you keep driving you could blown a head gasket.
Now that you installed the ScanMaster list the numbers from the first to last and in column formation so members can see where to guild you with.

 

[GullsGN]

Update: I bought a scanmaster and got it installed tonight. At idle everything looked normal according to the documentation except for the O2 mv reading. It jumps all over the place between 180 and 800. I believe I have bad O2 sensors. I also tried tapping the MAF while idling and it did studder slightly. My next step will be to get O2 sensors and a MAF.

You tapped the MAF and it stumbles. You found it. Just replace the MAF and you are good to go. I recommend a Translator and a LS1 MAF. The stock MAFs you can buy for the GN are remans and 75% do not work well on our cars.
Steve

 

[Bescurred]

Update: I bought a scanmaster and got it installed tonight. At idle everything looked normal according to the documentation except for the O2 mv reading. It jumps all over the place between 180 and 800. I believe I have bad O2 sensors. I also tried tapping the MAF while idling and it did studder slightly. My next step will be to get O2 sensors and a MAF.

There is only 1 o2 sensor. Do you have a friend local with a known good MAF?

I'm not sure what your plans are with the car but if the MAF turns out to be bad I'd go with the MAF translator and a LS1/LT1 style.

 

[GullsGN]

Update: I bought a scanmaster and got it installed tonight. At idle everything looked normal according to the documentation except for the O2 mv reading. It jumps all over the place between 180 and 800. I believe I have bad O2 sensors. I also tried tapping the MAF while idling and it did studder slightly. My next step will be to get O2 sensors and a MAF.

Why do you believe you have a bad o2 sensor (there is only one)? Numbers jumping all over the place is normal at idle. Should be around 800 at WOT.

Steve