Exhaust pops at idle, sounds like small explosions

[wingman65]

Just finished swapping out dead motor in 95 GP SE (3100) with a used donor. Got everything put back together and got it to start but it makes loud popping (explosion) sounds at the exhaust, mainly at idle. Any ideas on what to look for is appreciated.

Engine runs smooth otherwise, no CEL but occasionally the pop will kill the engine. The rear of the cat was glowing red but not the front. First thought was clogged cat, or exhaust leak, or dead cylinder, or leaking injector, or ....???

[pocket-rocket]

Welcome to the site!

Glowing cat and popping sounds leads me to believe it's running too rich. What year 3100 did you use? Did you use the entire donor or bolt on your intake, fuel rail, ect.? I would check your injectors to make sure one isn't stuck open. I wouldn't drive it until you find the problem since too much fuel can wash the oil layer off of the cylinder walls and kill your cat. When you find the problem I would also give the oil a sniff test to see if it smells like fuel. If it does, change it.

[wingman65]

The motor was an exact match from a 95 monte. It was complete so I do have another complete set of injectors, ignition egr, etc. I used my original injectors because they looked better. Is there a way of cleaning them and checking them on the bench?

[pocket-rocket]

There are a couple people on this board that can clean them out pretty good. One is 60dgrzbelow0 (click -> http://60degreev6.com/forum/member.p...0-60dgrzbelow0) and the other is Superdave (click -> http://60degreev6.com/forum/member.php/6686-Superdave). The reason I asked about the year of engine is later engines ran at a higher fuel pressure that is set by the fuel pressure regulator, and your PCM isn't programmed for that pressure which would make it run rich.

[wingman65]

Fixed the missfire (bad plug wire) and the exhaust leak. The car idles great but has no power when accelerating and makes a whistling sound in engine compartment when giving it gas under load. Does this sound like a clogged cat? What size pipe do I need to replace the cat on 95 GP, is it 2.25 OD?

[60dgrzbelow0]

Wingman65... Put a Fuel Pressure Gauge on the Fuel Rail/Manifold and eyeball the gauge as you cycle it through its paces... if you see sudden drops in pressure coincidental with the engine staggering and popping, then the Fuel Pump is your probable culprit.

To Improve Power, Performace and Gas Mileage...

Instead of trying any complicated EFI spray cleaning methods... you might be more satisfied with getting one of these Rochester Multec Fuel Injector Filter Basket Kits from ebay (around $20.00) and just follow the instructions on this video to R&R the old gunked up ones. After re-installing them, drop a large bottle of Chevron Techron into the gas tank and drive that baby around for a while to sort of wake the engine up at operating temperatures. Please look at the first two images on my photobucket link for the basket kit...and if you like, you can view the rest with videos at your leisure if you want to see the "Full Monty" of "The FrankInjector Machine" at work. Welcome Aboard...

eBay has the Rochester Multec Filter Basket Kits for only $20.00 with Free S&H

http://cgi.ebay.com/ebaymotors/Rochester-Multec-Fuel-Injector-Service-Kit-6-Cylinder-/200405725088?pt=Motors_Car_Truck_Parts_Accessories&hash=item2ea91cafa0

My Photobucket on this topic and "The FrankInjector Machine"

http://s557.photobucket.com/albums/ss19/60dgrzbelow0/HOMEMADEEFICLEANER/

The "How-To" video for replacing the Filter baskets on Rochester Multec Fuel Injectors

http://www.youtube.com/watch?v=V2sD5UsOnJs&feature=related