FED UP! Idle & backfire problems

[Rangerdoc]

I've had it with this car! I'm ready to part-out this P.O.S. if I can't get it fixed soon....It's an 84GN...mostly stock. 90,000 miles. I bought several months ago from a "friend" (now an ex-friend) in Arizona. I live in Missouri now. It appeared to be in average condition for an 84. It didn't run too well, but I knew the turbo was bad. He said it just needed a new turbo and had run excellent before then.
I replaced the turbo late last summer right after I bought it... went with a stock turbo, except this one is water jacketed and has an adjustable wastegate. I noticed it didn't really idle any better & really ran like crap. I didn't mess with it much since I bought a new house. I decided a few months ago to tackle this project again. Now that you have the history, here's the symptoms:

Very rough idle, but doesn't die
Stumbles real bad off idle & often backfires (small) out the intake
Then it's OK at part throttle up to a point
The timing light shows it at 15deg @ idle. Jumps to 30deg once you rev it any.
Builds boost to 18# OK. Spools pretty quickly too.
Begins to misfire / light backfire (intake side) as RPM and throttle position increase.
I can go almost 100% throttle once past the off-idle stumble, but have to begin backing off the throttle fairly quickly as RPM's increase
Once up to 60+ MPH, I can't get it above 50% throttle or it misfires pretty bad.
I notice a puff of black smoke in the rear-view mirror when it misses.
Only one SES light ever. A few months ago I got a lean exhaust code, The car had been sitting at idle for 10 minutes or so. No other codes since.
Runs smooth only on cold starts when at high idle (2,000). Smooth for about 20 seconds, then the idle drops down to about 1,000 & it runs like crap from then on.

NOW... Here's what I've done:

New stock turbo.
New oil pump (cause of turbo failure)
New coil, wires, & plugs. (The old plugs read pretty rich to me) Gapped .040
Adjusted TPS (was way off), cleaned IAC
Checked fuel pressure - 35psi at idle & steady 40psi under load
Removed and cleaned injectors
New O2 sensor
New t-stat (had a 195deg in it)
New engine temp sensor
I was told the MAF was replaced just before I bought it (Geee... that shoulda been a clue... HUH?). I've tried unplugging it and the car will barely run. Then sets a MAF code OK.
Sprayed the hell out of it with starting fluid looking for vac leaks & luckily didn't burn the car to the ground. EGR not leaking.
Looked pretty hard under the dash for any broken vacuum lines
No noticeable exhaust leaks until after the catalytic converter (Shi@#y Midas exhaust job)
I don't have a scan tool
I've had this in to several shops. They all charge me 1/2 a week's paycheck to change some BS thing, say that's all it needed, but none have made it even slightly better. (One of them just cranked the idle up & called it good)

Any Suggestions?!?!? This car is really close to having an "unfortunate accident" and becoming an insurance claim. Heck! I'm ready to go buy a ricer I'm so P.O.'d

I guess I need to do a compression test to see if the cam is screwed. & get a vac guage hooked up. My gut feeling is a bad vacuum leak or an ignition problem. I'm just sick of spending money. I've already got almost twice what this car is worth into it.

 

[TurboBuickSix]

While your at it take a look at the timing chain,pop off the cam sensor cover and rotate the motor back and forth watching how many degrees before cam sensor changes direction.

 

[WFO]

well first i'd gap those plugs down to .035".what kind are they?

it sounds like a maf problem.if it's a parts store cheapy they're pretty hit and miss.


do you have a scantool or is there someone in your area you can borrow one from?

 

[Geoff87]

How did you clean the injectors?

Also, i agree with Sean regarding the plug gap.

 

[Buick From Hell]

Have you checked anything with the ECM? Chip loose, bad connections, bad ECM, etc..??

Go to the "Basic Hotair Info" thread at the top of the page, and click on the "ECM connector plug" link---it shows ALL the connections to the ECM, and also lists what ALL the voltage values of each connection should be with key-on-engine-off, key on-engine-running, etc...a little voltmeter testing might turn up something?

 

[Rangerdoc]

OK...
I regapped to .035, AC R44TS. I checked the slop in the chain by observing the cam sensor. As I slightly rock the crank back & forth, the cam sensor rotates almost instantly. I don't have the equipment to measure how many degrees of play, but like I said, the cam sensor rotates almost instantly. There's more play in my breaker bar than there is in the chain. I pulled the MAF and It's an AC, so it's not an off-brand. That & if I unplug the MAF, the car dies.

I took the injectors into a local shop who cleaned them on a bench.

I did get a vacuum gauge on it today. When I first start it cold, it runs about 15" at 1,800 rpm. Runs smooth - no misses. After about 20 seconds the idle drops down to about 1,200 & the vacuum drops to only10". I only have about 9" when in drive at 1,000 rpm. The vacuum drops to zero momentarily as I open the throttle.

I checked the PCV and all the under hood lines - no leaks.

The chip is good and tight, but I haven't checked the voltages. I'll post when I get a chance to do that.

Thanks... so far no luck.

 

[WFO]

i'm leaning towards ecm/chip here.for one,it should idle ~750-800 rpm,it's controlled by the chip,not the screw on the tb.

you should also have a bunch more vacuum.


i had a funky problem like this once and it turned out to be the ecm connector pins were corroded all to hell.you might want to pull your ecm out and have a look at it.


later,sean

 

[Rangerdoc]

Thanks, I'll check it out. I did just check the the ECM out. The chip is really tight and the main connector seems tight w/o any visible corrosion. I have yet to try the voltages from the ECM chart. Time is scarce these days. That's why I bought a stock car... because I wanted the reliability. I used to enjoy working on cars, but aside from maintenance, anymore I just want to turn the key and have it run.

Maybe in the next week or two I can get a little money together and look more closely at it. I'm just sick of throwing $100 bills at this car to find I might as well have burned my money - because nothing even makes a slight difference.
A co-worker did recommend a shop nearby who he claims is excellent with this kind of work. I can say from now on, I'm not paying a dime until I drive the car and decide it's fixed.

As far as the idle, I've closed the TB screw 100% trying to get the idle where it belongs & the IAC just opens up more, so you may be onto the right track. I can say if I got the idle down to 800 rpm's, the car would not keep running. It still act like a major vacuum leak. I read here once of somebody who pressurized his engine & used soap to look for bubbles. Maybe worth a shot.

 

[GNandGS]

hrmm...

Vacuum is kinda low isnt it? I dont have a HA... but higher idle will produce less vacuum.

Brainstorm:

* Network with semi local Buick guys. This should get you started - http://www.gnttype.org/members/name.html#MO

* While running, push up on the EGR diaphragm and see if the car dies or tries to. It should.

* PCV system. You want no leaks and a GM valve ONLY.

* "Checked fuel pressure - 35psi at idle & steady 40psi under load" Does under load mean with the hose attached?

* Vac block on TB. Cracked? Leaking?

* Vac leaks in general. Very difficult on the HA IMO to see/trace them all... might look again. Might be routed wrong.

* System voltage? Number of places to check - keep it simple and check at the batt with key OFF and with the car running. Do the other checks later if clues point that way.

Gotta go, thats a start. Maybe.

S

 

[Rangerdoc]

Thanks for the ideas. I've checked most, but not all of these. Gotta go to work for now, but I'll write when I've checked them all.

This was my daily driver, but it was getting so frustrating that I bought a new car yesterday. At least now I can not worry about re-assembling the car between each tech session. ( Of course I'm broke for the next 5 years now )

Thanks for the help guys

-Jason

 

[Rangerdoc]

* While running, push up on the EGR diaphragm and see if the car dies or tries to. It should. Tried it & it dies.

* PCV system. You want no leaks and a GM valve ONLY. Checked the PCV.. OK

* "Checked fuel pressure - 35psi at idle & steady 40psi under load" Does under load mean with the hose attached? Under boost would be a better way to describe it. I dunno why it's higher at RPM's and boost than idle, but it is.

* Vac block on TB. Cracked? Leaking? I removed all hoses and capped the ports... no change. Removed teh block and inspected it. Tested around base-OK I actually created a small vac leak to test the effectiveness of the brakleen test - The engine immediately revs when a leak is sprayed even lightly. .

* Vac leaks in general. Very difficult on the HA IMO to see/trace them all... might look again. Might be routed wrong.

* System voltage? Number of places to check - keep it simple and check at the batt with key OFF and with the car running. Do the other checks later if clues point that way. runs about 14.2 volts at idle. Max 14.6 when revved up . Still haven't gotten a chance to check ECM stuff.

 

[GNandGS]

Originally posted by Rangerdoc
* While running, push up on the EGR diaphragm and see if the car dies or tries to. It should. Tried it & it dies.

We can PROBABLY skip that then.

* PCV system. You want no leaks and a GM valve ONLY. Checked the PCV.. OK

A GM part? Some folks have all sorts of trouble with others. If unsure replace it.

* "Checked fuel pressure - 35psi at idle & steady 40psi under load" Does under load mean with the hose attached? Under boost would be a better way to describe it. I dunno why it's higher at RPM's and boost than idle, but it is.

Skip this for now then

* Vac block on TB. Cracked? Leaking? I removed all hoses and capped the ports... no change. Removed teh block and inspected it. Tested around base-OK I actually created a small vac leak to test the effectiveness of the brakleen test - The engine immediately revs when a leak is sprayed even lightly. .

Ok.

* Vac leaks in general. Very difficult on the HA IMO to see/trace them all... might look again. Might be routed wrong.

How about these? Were you able to trace them all? Some are tough to see. Dont forget the Throttlebody.

* System voltage? Number of places to check - keep it simple and check at the batt with key OFF and with the car running. Do the other checks later if clues point that way. runs about 14.2 volts at idle. Max 14.6 when revved up . Still haven't gotten a chance to check ECM stuff.

OK

You MUST get with some locals. A lot of Buick guys are willing to travel if its not "too" far. Buy em lunch.

Shawn

 

[GNandGS]

http://www.gnttype.org/members/name.html#MO

With these guys you can verify some things like MAF and ECM parts - stuff quick but $$ to try.

Also, I didnt mean to say that the PCV will cause all your issues. Might explain some of them....

I could throw stuff out all day and never name the right thing. Lookup some folks within driving distance, let the car sit (save your sanity) til you have some help then get back with us.

Shawn

 

[FJM568]

Originally posted by Rangerdoc


* "Checked fuel pressure - 35psi at idle & steady 40psi under load" Does under load mean with the hose attached? Under boost would be a better way to describe it. I dunno why it's higher at RPM's and boost than idle, but it is.

Does this mean that you are showing 35psi at idle and 40psi when you are into more than 5# boost??? Is it 40 psi at 10# or 14# or whatever boost??? In other words, if your static FP is 35# and you are running X lbs of boost, is your fuel pressure now 35 + X??? Your fuel pressure should go up over your static idle fuel pressure 1lb for every 1 lb of boost you are running...If not, you either have a bad fuel pump or a bad fuel pressure regulator...

One of the first things you should change on these cars is the stock fuel pump...They were barely able to keep up when they were new, let alone 15-20 yrs later...

go to www.gnttype.org and take a couple of days and read through everything there, regardless if it is in the 86/7 section, or in the 84/5 section...The basics between the different years are the same...You will learn alot about these cars just by doing that...

Hope this helps some...

 

[Rangerdoc]

Well, I think I can hook up with a hotair owner nearby here. He has a scantool and plenty of parts. I'll post as soon as I have some answers.
Thanks.