Running on 7

[karitoki]

I knew it! In the month I've had my 89 2500 2wd Suburban I've felt something just wasn't right. It sounded like there was an exhaust leak and the power/economy (ha!) wasn't what I thought a 454 would have. I just got done replacing hoses and I took it over to my neighbor who knows a lot more than I do about GM engines. I asked him if he would go for a ride with me and see what he thought. He walked up to the truck and said, "Hold on, let me listen to the exhaust". He basically bent over and stood up and said, "Yep, your only running on 7", and walked back to his garage. I wish I had figured this out BEFORE pulling a trailer on a 800 mile vacation. Crap. From what I've read on other forums I'm lucky I didn't light the catalytic converter on fire or worse. Judging from the sound, I'm pretty sure it's on the battery side of the engine. There is no valve knock. I'm gonna hope its just plugs, wires, cap, or a rotor and not a valve or a cam. We'll see Monday.

 

[Chaz]

My 5.7 sounds like its runnin on 7 when its cold and in park, I think its the non heated oxygen sensor,,

 

[Driver4r]

Welcome to the party. My 355 is Firing on all 8, but #7 is so low on compression that its pretty much considered dead. I have yet to put air into the cylinder to determine if it is rings or a valve hanging up a little bit(99% sure its rings). But atleast i know mines firing on all 8 cause i have 0 gas coming out the back. Its all condensation.

 

[karitoki]

Thanks for the replies. I don't see any type of smoke coming out of the back of mine either. Doesn't smell of gas either. I plan on pulling the plugs and checking them first (while the engines cold), then checking the spark on all the plugs on the suspect side. I really hope it's not anything serious, but it is what it is and we'll deal with it. Thanks again. Please keep the ideas coming.

 

[karitoki]

I have yet to put air into the cylinder to determine if it is rings or a valve hanging up a little bit(99% sure its rings).

Is this a complicated test proceedure?

 

[89Suburban]

K.I.S.S

Keep
It
Simple
Stupid

Start with the basics.

Pull the plugs and check their condition.

 

[Jims86]

K.I.S.S

Keep
It
Simple
Stupid

Start with the basics.

Pull the plugs and check their condition.

Keep it even simpler...hook a test lead to ground, and probe each plug wire at the distributor while its running, when you hit the dead cylinder, the rpm wont go down like on the other 7 cylinders.

 

[89Suburban]

I'd be scared to do that, I had enough shocks from that last **** I went through lol! Still feeling those zaps...

 

[Jims86]

I'd be scared to do that, I had enough shocks from that last **** I went through lol! Still feeling those zaps...

Nah, it will go directly down the lead...shortest path, and it takes less that a minute to find the offending cylinder.

 

[karitoki]

I have a test probe (a HF model with the big aligator clip) so I'll give it a try. Do I just stick the spark plug wire where it enters it's distributor jack?

 

[89Suburban]

It's just a straight run of wire right? No lamp or meter?

I wish I was there to watch lol.

 

[Jims86]

I have a test probe (a HF model with the big aligator clip) so I'll give it a try. Do I just stick the spark plug wire where it enters it's distributor jack?

Yup, just poke the top of the boot, you can seal it back up with a little spot of black RTV when your done. I never sealed mine up, come to think of it.

 

[karitoki]

What the heck is going on?

I found the bad plug wire. The number four wire had been resting against a tube coming off the exhaust manifold. After I had located the bad plug using the probe, I latched on the the plug hood, and when I pulled the wire snapped in half. Great, right? I go and buy all new wires, plugs, cap, and rotor. I triple check that I have the plug wires on the right plugs and cap locations. Start it up and it runs worse than it did before! And to top it off, the "Service Engine Soon" light comes on! The only thing I can think I did wrong was maybe gapping the plugs at the wrong gap. I have them at .045. Any ideas?

Also, I'm using ACDelco Rapidfire Plugs. It had ACDelco CR43TS plugs in it before

 

[Jims86]

I found the bad plug wire. The number four wire had been resting against a tube coming off the exhaust manifold. After I had located the bad plug using the probe, I latched on the the plug hood, and when I pulled the wire snapped in half. Great, right? I go and buy all new wires, plugs, cap, and rotor. I triple check that I have the plug wires on the right plugs and cap locations. Start it up and it runs worse than it did before! And to top it off, the "Service Engine Soon" light comes on! The only thing I can think I did wrong was maybe gapping the plugs at the wrong gap. I have them at .045. Any ideas?

Also, I'm using ACDelco Rapidfire Plugs. It had ACDelco CR43TS plugs in it before

Go back over the plug routing...look at 5-7, if everything is correctly routed, and it still runs like ****,, take em back, and get another set.

 

[karitoki]

Thanks Jims86

I pulled the plugs (all stunk of gas) and put the originals back in. Still runs like poop. The plugs and the wires are going back tomorrow. Wasted a whole afternoon and evening because of the darn O'Reily's junk. No more. They have lost a customer. On a positive note, the original problem was found. Now if I can get some decent plugs and wires I think we'll be off to the races.