Missing while cold
Missing while cold I have a miss while cold. It runs great when warm. It usually takes two minutes or so before running smooth. There are no codes and I sprayed the intake manifold at start up to check for vacuum leaks. I am leaning toward a dirty AIC and not defective since there are no codes. Any thoughts??
Don't know about AFRs, meaning I do not know if the motor is running too rich or lean. My scanner only does codes and I do not have HP tuners,so I have no way to check the trims. But, spraying the manifold tells me it is not sucking air and so it is not lean.
I saw an interesting vid on you tube.The guy was having the same problem. It turned out to be a dirty AIC.
I saw an interesting vid on you tube.The guy was having the same problem. It turned out to be a dirty AIC.
Leaking injector possibly. You could always pull the rails/injectors up and place a paper towel under them. If they drip any fuel with the key on or off, you know they are leaking. Or very possible it is the intake gasket even though carb cleaner doesn't make a difference or set any codes.
Nice tip about the injectors. I suppose the manifold could suck air from underneath where the spray wouldn't go.I am going to clean the AIC first and then go from there. Thanks to both of you for the input.
TECH Addict
Joined: Aug 2005
Posts: 2,305
Likes: 126
From: Monroe,NY
Take a temp gun and check all the exhaust primaries and if one is a lot lower that is the cylinder with the miss. I had a coil that would miss when cold at idle and at part throttle but was fine wot.
Thats a good point. I suspected a coil earlier but moved on from there after I checked the spark while running. This was on # 1, and it was good but the motor was hot. Besides, I was thinking about a temp reader. So, going to Harbor Freight this week is in the cards.
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Inspect the plugs for excessive gap too. I've had that problem a few times with worn plugs. Fuel lights off much easier once the engine warms up. Could also be lean.
As chevymec said, could be intake gaskets leaking too. Had many that leaked that didn't respond to spraying with brake clean.
As chevymec said, could be intake gaskets leaking too. Had many that leaked that didn't respond to spraying with brake clean.
To bad you don't have a way to scan it...I've had a bunch come through the shop that didn't change the idle with a shot of carb clean...but, with monitoring the O2 sensor voltage, would drive them pig rich after the shot without changing the idle...
Agree, after seeing it hardly ever work after 20 years of being a tech I've pretty much given up on spraying to find vacuum leaks. It works for me about 1 out of 20+ times or maybe even less.
I use a stethoscope to find vacuum leaks. I pulled the end off and attached a length of vacuum line to the end of the rubber hose with a vac line coupler. Then I stuck a piece of brake line up in the vacuum hose so I could also run the tip across exhaust looking for leaks, it works really well on vacuum leaks, exh leaks, I even use it for evap leaks sometimes.
Agree, after seeing it hardly ever work after 20 years of being a tech I've pretty much given up on spraying to find vacuum leaks. It works for me about 1 out of 20+ times or maybe even less.
I use a stethoscope to find vacuum leaks. I pulled the end off and attached a length of vacuum line to the end of the rubber hose with a vac line coupler. Then I stuck a piece of brake line up in the vacuum hose so I could also run the tip across exhaust looking for leaks, it works really well on vacuum leaks, exh leaks, I even use it for evap leaks sometimes.
I use a stethoscope to find vacuum leaks. I pulled the end off and attached a length of vacuum line to the end of the rubber hose with a vac line coupler. Then I stuck a piece of brake line up in the vacuum hose so I could also run the tip across exhaust looking for leaks, it works really well on vacuum leaks, exh leaks, I even use it for evap leaks sometimes.
Trying to find a vacuum leak with something with 02 sensors is pointless unless you are watching the 02 voltage and STFT. The PCM will immediately pull fuel out and you will not get the increase in RPM's like you will trying to find a leak with a carb engine.
You can also use a water bottle, drill an 1/8 hole in the cap, point and shoot. If you do have a leak, it will suck with water in and no you won't hydrolock your engine.
You can also use a water bottle, drill an 1/8 hole in the cap, point and shoot. If you do have a leak, it will suck with water in and no you won't hydrolock your engine.
Trying to find a vacuum leak with something with 02 sensors is pointless unless you are watching the 02 voltage and STFT. The PCM will immediately pull fuel out and you will not get the increase in RPM's like you will trying to find a leak with a carb engine.
You can also use a water bottle, drill an 1/8 hole in the cap, point and shoot. If you do have a leak, it will suck with water in and no you won't hydrolock your engine.
You can also use a water bottle, drill an 1/8 hole in the cap, point and shoot. If you do have a leak, it will suck with water in and no you won't hydrolock your engine.
That works too. I start by watching STFT and LTFT, if I see overly positive number I know I likely have a leak.
Che70velle, this thing is wonderful for pin pointing, and I mean pin size hole pin pointing, leaks. Here's a pic of how I arranged it. I recently found a intermittently leaking bypass actuator on a whipple blower with this after the truck went to a couple shops and they couldn't find it. Some people like smoke machines but if it's a small leak it won't smoke enough to see the leak, but you'll hear it like a heavy wind noise through the stethoscope.
I’m gonna build one of those. I like the hard line at the end for heat, but better yet accuracy. Sometimes plastic will rub and it makes its own noises. The metal line wouldn’t do that...I wouldn’t think.