3/4 to WOT Skip/Surge.

[HighMileage]

Well,I've had this '87 GN for 2 weeks now,and am trying to get everything worked out.

One important issue is a skip/surge issue at about 3/4 to wide open throttle.

The prev owner said he put new plugs in. I also see new "Bad to the bone" wires. But something tells me this is not an ign issue.

One thing I noticed is that the wastegate solenoid <?> has the port nearest the drivers side open. The other port has a hose to the turbo.

I did some archive searching here and found that someone else also has that port open,but was waiting to see the results.

I looked for where that port would route to. But,it is not in the underhood vac diagram.

Maybe that open port is not my skip/surge issue..

Any suggestions?

Thanks.

Steve from Upstate NY. '87 GN. Mostly stock. ...an 8 1/2 out of 10. But can't represent up here in NY with a skip/surge.

 

[TurboBuRick]

Need a Powerlogger bro.

With the car running, unplug the cam sensor and take it for a ride. See if the miss goes away.

 

[DoubleD]

pretty sure the top port of the wastegate solenoid is always left open to atm. usually they have a little foam filter over em though, which yours has probably disappeared or disintegrated.

Not sure what the problem is for ya though... sorry. I know mine was breaking up from going way too rich after some adjustments in the MAFT. backed it off and it is better now...

 

[HighMileage]

Need a Powerlogger bro.

With the car running, unplug the cam sensor and take it for a ride. See if the miss goes away.

I unplugged the cam sensor while running,then got on the hiway. The surge/skip and sometimes backfire thru the exh still occurs at 3/4 to wot.

The car does pull strong to that point,building boost well.

It really seems like a fuel starvation issue,but I may be wrong.

I did buy a new NAPA Wix fuel filter. I don't know how long the filter that is on there has been there.

Any more suggestions?

Thanks

Steve from Upstate NY. '87 GN. Mostly stock. Getting new front Billsteins now.

 

[TurboBuRick]

Do you have a boost gauge? How much boost are you running? Have you checked your wastegate lines lately? Almost sounds like your over boosting.

Fuel pump, fuel regulator and mass air flow sensor could all be other possibility.

Where bouts in upstate N.Y.?

 

[HighMileage]

Wouldn't a bad MAF throw a code?

The only boost gauge I have is the led one on the cluster. It maxxes out at wot.

It also sends an occasional pop out of the exh when the skip/surge occurs.

You mention fuel pump... Mine has a low grumble sound unlike the whizz of my other '87-'90 GM cars.

I read alot here about hot-wiring pumps. Maybe I'm the next candidate. But I'd really like to properly diagnose this skip issue before I start throwing $$ at it.

I'm in Albany.

Steve. '87 GN. T-tops. 80k mi.

 

[Steve V]

Few ideas.

1 coil/module

2 whats' the plug gap?

3 maf(already mentioned)

4 get a fuel press guage and verify at idle and WOT.

5 crank sensor tight,what's the gap

6 could be a flat cam.

 

[83ttypecooled]

Hi,
I would cut to the chase and check fuel pressure under this load and at the time the supposed misfire occurs. That's what I think you are describing; a misfire at the high end. My car used to do this, until I replaced the pump. Our cars need fuel badly,and will regurgitate if they are not given a proper,steady flow of it. Check it out, let us know.

 

[grape of wrath]

Tps sensor could be bad it may have a bad spot at 3/4 throttle.

 

[TurboBuRick]

Wouldn't a bad MAF throw a code?

The only boost gauge I have is the led one on the cluster. It maxxes out at wot.

It also sends an occasional pop out of the exh when the skip/surge occurs.

You mention fuel pump... Mine has a low grumble sound unlike the whizz of my other '87-'90 GM cars.

I read alot here about hot-wiring pumps. Maybe I'm the next candidate. But I'd really like to properly diagnose this skip issue before I start throwing $$ at it.

I'm in Albany.

Steve. '87 GN. T-tops. 80k mi.

Bad maf may not set a code just have low readings.

Really should check the fuel pressure. Make sure it rises and holds with boost. You may very well have a weak pump.

Also check the vacuum lines on the wastegate. If they have are leaking, you will over boost.

Make sure no leaks in the maf pipe or intercooler couplings.

TPS is another possibility. Need a scantool to check it. Time for a scanmaster.

My mom is in Troy. I need to get up there for a visit.

 

[HighMileage]

(Update below)
Let me know when you'll be in the area,and I'll make sure I have no plans. It would be really nice to have someone who really knows about these cars to give it a good look over and let me know what I need. As we know,there are many specific things to these cars.

There are 3 or 4 GN's that race weekly over at Lebanon Valley Speedway on Wed nites. My little brother is the one with the bright red '08 Charger SRT-8 that runs consistent low 13's. They put quite a hurtin' on him.

I just got a call from him: "So,are you bringing that *thing* over on Wednesday so I can run ya?" <sigh> ...I can't. I can't go over there and run a skip-surge 15 or whatever in front of everyone. I just told him no,I'm busy.


**Update: I changed the fuel filter. It was a Hastings that had been on there since..??? (only had the car a month) Rusty liquid poured out of the end onto a white paper towel from the inlet end.
Stuck in the outlet end of the fuel line was a 2inch long piece of cigarette pack cellophane. That filter must have been breaking down internally. I wonder how much more of it made it's way forward to the engine.

Now I really should check further,to the injectors for more of it.

On there now is a NAPA Wix filter.

One bummer is... I can't find my fuel pressure tester. Which one of my 'friends' did I loan it to?

Steve from Albany,NY '87 GN ..mostly stock. Tomorow,a test-drive is planned to see if the skip-surge is gone.

 

[HighMileage]

Bad maf may not set a code just have low readings.

Really should check the fuel pressure. Make sure it rises and holds with boost. You may very well have a weak pump.

Also check the vacuum lines on the wastegate. If they have are leaking, you will over boost.

Make sure no leaks in the maf pipe or intercooler couplings.

TPS is another possibility. Need a scantool to check it. Time for a scanmaster.

A new fuel filter didn't solve the problem. Even tho there was a piece of cellophane stuck in the outlet.

I'm giving myself one more day to find my fuel press tester. Then I'll have to buy another.

Boost holds at 12 when the skip/surge occurs.

No leaks in MAF or intercooler. No probs with vac lines to wategate.

Can the TPS be checked with an ohm-meter? I doubt the MAF could be.

"Scanmaster". Can you point me to which is best? I'm used to checking OBDI GM's with a paper clip.

Thanks!

Steve from Albany,NY. '87 GN,t-tops. Got the "Nice car!" comment twice today. One guy actually knew what it was!

 

[TurboBuRick]

A new fuel filter didn't solve the problem. Even tho there was a piece of cellophane stuck in the outlet.

I'm giving myself one more day to find my fuel press tester. Then I'll have to buy another.

Boost holds at 12 when the skip/surge occurs.

No leaks in MAF or intercooler. No probs with vac lines to wategate.

Can the TPS be checked with an ohm-meter? I doubt the MAF could be.

"Scanmaster". Can you point me to which is best? I'm used to checking OBDI GM's with a paper clip.

Thanks!

Steve from Albany,NY. '87 GN,t-tops. Got the "Nice car!" comment twice today. One guy actually knew what it was!

Ya, you really need the fp gauge.

If the filter element broke, you might want to pull the fuel rail and check the inlets on the injectors.

TPS can be checked with a dvm. should be .42vdc tp closed and 4.0vdc wot with no drop outs durring the sweep. If you had a scanmaster you would just scroll to tps. :biggrin:

Hard to tell if the maf is the problem without data. Another way is try one thats working on another car.

Go here to get a scanmaster. FULL THROTTLE SPEED - All Brands

Keep us posted.

 

[jasjamz]

I'd stop going to WOT until you get a scanmaster. The powerlogger is a step up from that. Does the car have four plugs and a relay at the rear of the car for fuel pump connections or just the factory plug?

Pull a plug, what kind and number are they? What's the gap? What octane are you using?

 

[HighMileage]

I appreciate you guys bearing with me on this. If I can't find my FP tester,I'll get another this afternoon.

Q: After the engine has been off for 8hrs or so,shouldn't there be some kind of pressure at the fuel rail's schrader valve? I just got nothing out of it. Engine off,of course. After cycling the pump,I got a small squirt.

Found this: The PCV valve wasn't in it's grommet! It was next to it. I've been meaning to degrease the engine. Good thing I didn't! Ohhhh.

**Mcasteel2112.. I just have one elect-plug with 3 wires near the filler neck. Appears to be untouched. As far as spark plugs? No idea what is in there and what gap. The prev owner said he put AC Delco's in.

I've only had this car since July 18th.

I just took a small test-drive. No wot. At almost 3/4 the skip/surge started. But,by the time I looked at the boost gauge,it screamed from 50 to 85mph effortlessly. This thing is gonna be a rocket when fixed.

Looks like I have some checking to do this afternoon. Will check back after 7.

Steve from Upstate,NY. '87 GN,t-tops. Mostly stock. ??

 

[jasjamz]

Sounds like your car is lacking the fuel pump hotwire kit. Read up on them and get one. Decide which plug is the easiest to pull and get one out and check it. Fuel pressure after 8 hrs???? I know most will loose it fast after the key is off if the check valve in the pump goes out. Leaky injectors, that can vary. Keep us posted...

 

[HighMileage]

(Test findings below)
Rant: I would have had more time to diagnose the prob this afternoon,but on my way home from getting a new FP tester,some young chick driver tried the impossible in traffic and went down my drivers side rear fender. LUCKILY I had my '87 Buick Century errand-mobile with 293,000mi. Afterwards,her concern was HER car and had a bad attitude.

If I had the GN,it would have suffered a 'nasty' crease down it's flawless rear fender. If it was a guy and that happened,and he wasn't remorseful.... Well,you know how I'd feel,and I'll bet you'd feel the same way.

**A few test findings:

1) 43psi of FP at idle and when slightly revved. I have to figure out how to lengthen the hose so I can drive and check pressure.

2) TPS showed values of exactly what you guys mentioned. No dead spots either.

3) Took out a spark plug. ...which was a 1/2 turn too loose. It was a new AC Delco 41-803 with a .40 gap. Looks like they'll all have to be checked.

4) Ground strap on firewall near master cyl was loose.

More tomorrow..

Thank you very much for your support! lol

Steve from Upstate,NY '87 GN t-tops and 80k. Mostly stock.

 

[qwks6]

I bet with proper a/f monitoring you'll find your problem. Scanmaster will tell a lot.

fp should be tested vac line off, and adjusted as such. It should rise with boost.

I'd monitor for knock. Without a real boost gauge, and without a way to monitor knock, and without a way to monitor air/fuel ratio it's really hard to pinpoint what's wrong.

 

[TurboBuRick]

Platinum plugs? Thats a no-no.

Get some cr43ts gap at .030

 

[HighMileage]

I'm ordering a Powerlogger.

Thurs I'll be replacing the plugs and checking the crank sensor.
My guess is the prev owner replaced the plugs,chasing down this issue.

I'll be out of town this weekend. The GN is staying home in a secured area.

Hopefully the Powerlogger will be here early next week.

Btw,I only use Super Unleaded in this car.

Thanks.

Steve from Upstate,NY. '87 GN,t-tops. Mostly stock.