Just started to stumble/backfire...why?

R

Renthorin

Lone Wolf
Joined
May 24, 2001
Parked the car 7 weeks ago with a fresh tank of gas. It ran great.
Today I take her out for a car cruise and as soon as I start to build boost she begins to stumble. If I push it I get a backfire under the hood and loss of power.

I let up and can cruise all day until I build boost.
Stock turbo, injectors, turbotweak chip, hotwired fuel pump...nothing radical.

No knock on the sensor.

I hooked up my turbolink and there are no error codes. I want to check what each of the number ranges should be but can't for the life of me find my manual with "this should be in this range.." etc.

I did notice that the MAF was reading around 5 at idle. In park, I stepped on the gas to get her up to about 2500 rpm and the MAF went to 15. I think it should have moved more than that but not sure.

It is NOT the stock MAF. That went bad years ago and I have the corvette one with the MAF translator.

Just wonding if someone can point me to a doc or page where I can get the range for my readings.

Oh, and if anyone has any suggestions I'd welcome them too : - )

thanks,

Will
 
Could be moisture in the gas from sitting that long, double check your translator settings, make sure nothing came loose under the hood and you don't have a vac leak somewhere even if you say it shows no knock.
Maybe put some fuel treatment in if you haven't tried that, something to take the moisture out of the gas. Might be a fuel issue where it aint getting enough fuel under boost so need to see if fuel pressure is stable and the correct range. I would look into checking the fuel pressure, check under the hood for vac line leaks, verify translator settings.
Run some injector and fuel cleaner through it to see if it clears up after checking things out. Could be an injector going or just dirty injectors, but sounds like a fuel delivery issue from what you are describing.
Until you fix the issue, wouldnt recommend getting into too much boost with the car.


Posted from the TurboBuick.Com mobile app
 
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Sounds like a possible cam sensor issue.
 
Any members or TR owners that are nearby that have extra parts for you to test different things to rule where the issue is?


Posted from the TurboBuick.Com mobile app
 
Not sure who is in my area these days. Our local club disbanded a few years ago.

Not sure this matters but the fuel I've run for the last few years and what's in there now is 110. I just love the smell too much to go back to 94 : - )

Question - if I'm just sitting in the driveway and get on the gas to about 3k rpm what should my MAF reading be?

I have a small vac leack somewhere, had it for years. I say that as my BLM will slowly climb up at idle and then the car will stumble and they drop down...only to start climbing up.

The car idles great and runs fine until a few pounds of boost show up.

I'll check my FP to make sure that's fine. I don't remember for certain but do I want 43 lbs at idle? Is that with the vac line on or off for the FP reg?
 
Need to trace where that vac leak is and get it fixed so you can figure out what exactly is wrong. But i have a feeling the small leak has turned into something bigger and that is contributing to now running rougher.
Have you ever let it sit a long time and then tried to drive it without any issues prior to the last time it sat for 7 weeks?
What octane is the TurboTweak chip burned for along with what injector and boost? is it a version 5.6, version 5.7 chip or newer version than either of those?
It's possible you might of fouled up the O2 sensor running race gas through it for awhile.

It's line off 43 and about 40 with it on. + or - a psi
 
Pretty sure the vac leack is coming from the throttle body. When I put a power plate in I cranked too hard on a bolt and it stripped the threads. That was about 8 years ago and it's had the vac leak problem since then. I need to fix that but I have a feeling that isn't this problem.

I let it sit for 4-5 months every winter and it never has this problem.
The chip is a strip/street 100 octane chip but I've always run 110 or 111 octane with no issues.

It is possible the O2 sensor could be fouled. It's done that to me before. In those cases the check engine light came on and it isn't on now.

I'll have to check the FP tomorrow and report back.

thanks for the suggestions.

How can I verify the MAF is working correctly?
 
It would be nice if someone who knew the answer to your questions would post in this thread. But all you have is me :D

Posted from the TurboBuick.Com mobile app
 
52690d1356664741-first-turbo-buick-engine-purchase-advice-welcome-3.8-rebuild-2.jpg

You see the black plastic round cap with a rectangle shape that is a greenish color, that's where your Cam sensor is bud. In the event it wasn't sarcasm, have a feeling it was sarcasm though.
 
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Thanks. No, it wasn't sarcasm. I honestly don't know where it is :) Well...I didn't know. Now I do.

I'll check the turbo Y hose too. Just have to wait for the weekend

Thanks again gents for all the help.

Will
 
You're welcome, i hunted around google to find a pic that was clear enough to show you where it was and got lucky that the one i found happen to be of one a member posted of an ideal view.
 
OK....after not doing a damn thing to the poor car last year I'm ready to try to fix this problem.

I have a 3.5" MAF. Checked the translator settings and they were set for a 3" MAF but have been since day one so not sure that is the problem. I measured 3.5 as the outer diameter of the MAF inlet.

I haven’t taken it out for a test run yet to try unplugging the cam sensor but I will shortly.

One thing I find odd is at idle my MAF readings are .32 or so at idle and dont' really ever go up much. I put it in drive..stand on the brake…build some boost..and they barely climb to .4 on both turbolink and my real-time O2 meter.

That seems wrong???

Is there a way to test either the MAF or the translator without swapping in a different one?

Oh yeah...just checked O2 readings and I have to swap that puppy out too I think.
On my Turbolink: O2x was at zero and mv was around 233 or something.
 
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