Engine is sputtering before secondaries

[anarchy04]

Hears the deal, about a week and a half ago I did some work to the SHO and now it really is a dog at low rpms right up untill the secondaries open, once the secondaries are open the thing screams like it always has in the past. The work I did consisted of putting in a new set a platinum motorcraft plugs, 5.5 quarts of Mobile 1 5w30 ( which has really impressed me, not a single puff of smoke not even when I first start it ), different intake manifold and valve covers, and an oil filter. I think it needs new plug wires personally cause it has always acted like it has had a miss at lower rpms but not near as bad as it is now, now when I floor it at 1500 it will actually buck a couple of times then spit and sputter its way to 4000 then it is like a whole different car, tons of power and no missing what so ever. I also get a check engine light after I drive it for like 10 minutes which I think are the O2 sensors cause they look like the original ones, luckily the parts car had newer ones that i got sitting in the trunk. The last thing that I'm concerned about is my mass airflow sensor, I can unplug it and the only difference is that as soon as I unplug it I get a CE light, runs the same though. My friend shoguy 92 is going to give me another mass airflow sensor, so I guess I'll see if that helps. Yeah let me know what you think of the sputtering though.

 

[mrclean]

That sounds similar to my car, it misses quite a lot, then as soon as you hit that power ban. Even after I replaced my plugs. Then I replaced the wires and then the car purred like it should, power all the way through,etc. so I'd replace those and see what happens.

 

[AutoSHO]

If it started when you swapped intake manifolds, then you can bet you've got a vacuum leak somewhere.

 

[projectSHO89]

Visually verify that the secondaries actually open and close when the car starts/stops.

Steve

 

[sdpatt]

Check engine light? CHECK THE CODES! (Yes, I am yelling).

Sputtering? Do we call that a misfire? If no EEC code indicates another likely cause, the plugs or plug wires are the source of a misfire. Probably plug wires since you just replaced the plugs.

I'll bet you either don't have a well seated intake or have left off a vacuum connection. Below is a excerpt from my valve gapping procedure in the disassembly section. The reinstallation requires that you reconnect each of those connections.

1. Disconnect all vacuum and coolant hoses from the intake manifold and throttle body.

· One 5/8" PCV hose and two 1/4" coolant hoses under the throttle body (the fourth 1/4" vacuum hose routes to the idle air control (IAC) valve and does not need to be removed, the hose clamp on one of the 1/4" coolant hoses is not easily accessible until the manifold is lifted a few inches)
· One 1/4" vacuum hose and one 3/8" crankcase breather hose on the top forward face of the throttle body
· One 3/16" vacuum hose on the fuel pressure regulator
· One 5/8" vacuum hose on the passenger side rear of the intake plenum
· One 3/16" vacuum hose to the secondary intake vacuum accumulator (optional)
· One 1/8" plastic vacuum hose on the exhaust gas recirculation (EGR) valve (3.2L)
· One 1/8" plastic vacuum hose on the EGR pressure sensor module (3.2L)

2. Disconnect the electrical connectors from the intake manifold and throttle body.

· Two to the distributorless ignition system (DIS) module on the intake crossover tube
· One to the idle air control (IAC) valve
· One to the throttle position sensor (TPS)
· One to the mass air flow (MAF) sensor
· One to the solenoid on the vacuum accumulator (black plastic canister)
· One to the EGR pressure sensor module (3.2L)

 

[anarchy04]

Secondaries open and close like they should, and I got all that stuff hooked up right. If the intake wasn't seated correctly then wouldn't it idle like crap? Right now it idles just fine, only acts weird when I'm on the gas.