Rough idle and spudded under acceleration.

[mattcsn]

I'm having an issue that kinda sprang up from nowhere. Under heavy acceleration the car will spudded and miss. It only happens after about 5-10 minutes of driving. Before that the car runs just fine under wot.

After replacing the ignition coil and module the car seems to idle worse. It's better when I unplug the mat but only because it seems to run at a higher rpm.

Plugs are only a few months old and all vacuum lines are also newer and hooked up.

I was considering the crank sensor or cam sensor? But after idle leveling out which maf unplugged I'm confused.

Car is basically stock with hotwire, down pipe and fuel pump upgrades.

Thanks for the assistance.

I have attached scan at idle. BLM seems to be high on idle scan?

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[captndave737]

Did this happen after refuelling? I’ve had that happen a couple of times after getting bad gas. Went away with the next fill Up!

 

[captndave737]

BLM’s are way high.

 

[mattcsn]

Gas didn't change, but I also have changed gas since then.

What is the next step with such high BLM?

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[captndave737]

http://www.vortexbuicks-etc.com/blms.htm
The BLM’s are above the normal correction range. I’d suspect a vacuum leak or a leak in the intake system after the MAF Sensor. Bad fuel pump, clogged fuel filter possibly. Are you throwing any codes? Bad O2 sensor maybe.

 

[mattcsn]

http://www.vortexbuicks-etc.com/blms.htm
The BLM’s are above the normal correction range. I’d suspect a vacuum leak or a leak in the intake system after the MAF Sensor. Bad fuel pump, clogged fuel filter possibly. Are you throwing any codes? Bad O2 sensor maybe.

I'll take a look at the link. I do not have any vacuum leaks that I can determine. I've followed the lines all multiple times.

Fuel pump & filter are new within last 4-4 months.



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[mattcsn]

I'll take a look at the O2 sensor though. Looks like it could be related to the high blm.

The blms whip it shape thought when driving. It looks like it's just out of wack at idle. Also even during sputter/acceleration, I see no abnormalities on the scan.

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[626gn]

What new coil pack and module did you use? Sometimes even new stuff doesn't necessarily work if its not right.

 

[mattcsn]

I bought an ac Delco module and ac Delco coil pack. Then tried the standard motor parts ignition module. But was wondering if that was indeed the issue considering the idle got worse when changing the coil pack out.

I guess I can check the coil pack with a multimeter and see. I was just hesitant considering I tried 2 and figured my odds we're good at least one was working.

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[626gn]

I bought an ac Delco module and ac Delco coil pack. Then tried the standard motor parts ignition module. But was wondering if that was indeed the issue considering the idle got worse when changing the coil pack out.

I guess I can check the coil pack with a multimeter and see. I was just hesitant considering I tried 2 and figured my odds we're good at least one was working.

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Checking a coil pack with a multimeter won't be conclusive. It could ohm out ok but still be not.

 

[mattcsn]

Ugh it was vacuum related. I checked 10 times but missed one small hose with a hole in it. Thanks guys hopefully this is the fix.

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[earlbrown]

by ''basically stock'', do you mean outdated chip and injectors that are over 1/3rd of a century old?....

 

[mattcsn]

by ''basically stock'', do you mean outdated chip and injectors that are over 1/3rd of a century old?....

Injectors are newer but same as stock size. Chip is older.

Vacuum fix didn't fix it though. It still sputterrs under wot but idles a little better.

What is weird is it drives perfect the first five minutes until it warms up.

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[mattcsn]

Isn't iac high as well ?

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[captndave737]

Probably in open loop the first 5 minutes. To find a leak that isn’t obvious gat a propane torch. With the car running open the valve of the torch (not lit) and work you’re way around everything, hoses intake manifold etc. If there’s a leak the propane is sucked in and the car will stumble.

 

[Chuck Leeper]

Gas didn't change, but I also have changed gas since then.

What is the next step with such high BLM?

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Is this on your Yugo?
How about a description of the set up.
Not much for help, with no idea of the way the car is equipped.

 

[mattcsn]

Here is an updated scan. This is a brief idle at part at a stop light and then a medium press on the gas it sputters and misses bad after the 7mph mark and it looks like the O2 levels drop to 0?

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[Chuck Leeper]

Looks to me as tho the MAF readings are whacked...MAF Dropout.
The O2 readings do the same.
The IAC is opening.