Engine Performance problem
1998 Chevy Suburban V8 Four Wheel Drive Automatic 155610 miles
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I have 1998 Suburban that is missfiring.

We have replaced the intakemanifold gaskets, and that started to take care of the problem. I have also installed a JET Mass air flow sensor. When I put in the sensor I started to get bank one, bank two rich codes, and random missfire codes, when the check engine light came on.

The truck tends to sputter/missfire more in the morning until it get going, also if I hold the pedal constant and start to go up a hill it will sputter.

Just wondering if anyone had any insite.

Thanks

Monitor the fuel pressure when the problems are happening, critical that they are in spec.

Only misfire codes listed?

I am also getting bank 1 and bank 2 rich codes, as well as the random misfire. 172, 175, and 300, I think were the codes.

I changed the intake manifold in my 95 suburban and had the same problem recheck the spark plug wires and found 5 and 7 were backwards

Update,

They checked the fuel pressure and that seemed good.

I sent the Jet MAF sensor back, and they said it was a bad unit as far as the rich codes (I put the old one back in and the codes went away). So they sent me a new one that I got yesterday.

I came up with a list of things for them to check, and they all came back neg:

1. Charcoal canister
2. Fuel contaminated oli
3. Fuel pressure regulator
4. LEaking fuel injector
5. Sticking EGR valvle
6. Oxygen sensors
7. Manifold Absolute pressure sensor

I am wondering if there might be anything else that I am missing ie cap and rotor etc

Thanks for the help

Eric

The test are being done when the problem is happening correct?


Just multiple misfires codes now?


HAve they looked at the freeze frame data when the problem are happening?

THe funny thing with that is, WHen I go to drop it off I take them for a ride in it so that I can show them the problem. I think it continues to do it when they are working on it.

One thing that makes me think it may be somewhere in the ignition also is that it is worse when it rains.
We have put new wires on it but still get the same thing. When it is raining it sputters kind of hard on take off for a while until the truck get going, and warms up.

As far as the misfire codes, The engine light is not on.

Thanks,

Eric

IF they are looking at this when it is happening and have the scope on it, it should show what cylinders are dropping out or weak. Regardless of the CEL being on, codes may still be in it.

I agree on the ignition based on the dampness.

This style of cap and rotor are often problem child parts and do cause symptoms like you have.

http://www.autopartswarehouse.com/search/?N=9926+1588+4294967265+9288

I prefer Delphi brand.

I pulled up some old reports, and it is the 1,3, and 4
cylenders that were causing the problem then. The #4 has always been an issue, but that is due to oil fouling every once and a while(due to the rings on the piston?).

As far as the cap is the Delphi equivalent to the AC Delco, or should I be looking somewhere else for the cap.

As far as parts are concerned, which brand cap, rotor, plugs, and wires would be the best to put in?

I am also thinking about revamping the fuel system as far as the puel pressure regulator. The injector were changed a while ago, and just cleaned about 2 months ago.

Thanks again,

Eric

Brand wise, I generally use autolite plugs, but both delco and ngk are good too. Wires I like belden from napa or standard. Cap and rotor I prefer Delphi although delco is fine too. I stay away from the cheap ignition stuff.

How much oil do you go through between oil changes? Might want to jump up a heat range.