Dads truck

[dirtautoguy]

Some may have read my post a few years ago about my dads truck it’s a 1997 k2500 with 454 vortec 167000 miles. In summery it would randomly get a lean bank 2 code. And run really rough it was not consistent enough to track down so we left it alone. Before we tore it apart my dad had a mechanic take a quick (free) look at it and told him cylinder 5 was missfiring but other then that it wall looked good.

Finally it started running really terrible consistently. Still with no codes. We pulled the upper intake off and found that 4/8 injectors were leaking….. we also found the vacuum line from the pressure regulator was kinked and cracked. If I plugged one end and blew into the other it wouldn’t hold pressure and it smelled like gas. I also found one plug wire that had a bit of rust and corrosion in it on plug 6

So we fired the parts cannon at it with 8 new Delphi injectors, new cap+rotor, fuel pressure regulator, vacuum hose, and intake gaskets.

When we fired it up the first time
It ran smoother than it ever has since he has owned it. And it certainly does drive 100x better. However now it does feel as though it has a misfire. There are no codes and my scanner won’t tell me what cylinder is missing. Even so it drives a lot better but still has an obvious issue.

It idles down to 650rpm and doesn’t appear to have any kind of vacuum leak. Fuel trims are much better. It used to be in the -4 percent and 18 percent. Now it stays pretty close to 0 and stayed within 2-3 percent of each other on long term.

The other issue that has come up after putting it together is the radio keeps cutting in and out. Sometimes with sound sometimes no sound and sometimes the theftlock light stays solid sometimes it flashes. No matter what I did though the truck will always restart so it doesn’t seem to be a true theft lock issue. The radio has been doing weird things for quite some time now anyway.

For fun I did a voltage test and found that between battery negative and body ground there was a .08vlt And .01 from battery neg to the block.

Before he goes home tonight I’m going to take a big wire and just hook it from the battery to the body and see if something changes. It couldn’t hurt?

I’m leaning towards replacing the plug wires and maybe plugs but he doesn’t want to spend more money than he has to.

Thoughts? Things to check/ try

 

[Schurkey]

it would randomly get a lean bank 2 code. And run really rough it was not consistent enough to track down so we left it alone. Before we tore it apart my dad had a mechanic take a quick (free) look at it and told him cylinder 5 was missfiring but other then that it wall looked good.

Misfires can cause "false" lean signal from the O2 sensor.

So we fired the parts cannon at it with 8 new Delphi injectors, new cap+rotor, fuel pressure regulator, vacuum hose, and intake gaskets.

It ran smoother than it ever has since he has owned it. And it certainly does drive 100x better. However now it does feel as though it has a misfire. There are no codes and my scanner won’t tell me what cylinder is missing.

Is your scan tool capable of indicating cylinder-specific misfires? Not all scan tools can. Wastes a lot of diagnostic time when the scan tool lies about the actual code--displaying P0300 instead of the cylinder-specific code--P0301--P0308.

The other issue that has come up after putting it together is the radio keeps cutting in and out. Sometimes with sound sometimes no sound and sometimes the theftlock light stays solid sometimes it flashes. No matter what I did though the truck will always restart so it doesn’t seem to be a true theft lock issue. The radio has been doing weird things for quite some time now anyway.

Sorry. No real help except to look for bad connections where the various fuses plug into the fuseholders. Corroded wire ends, loose terminals, etc.

Maybe a plain ol' defective radio?

For fun I did a voltage test and found that between battery negative and body ground there was a .08vlt And .01 from battery neg to the block.

Before he goes home tonight I’m going to take a big wire and just hook it from the battery to the body and see if something changes. It couldn’t hurt?

Can't really hurt, but those are good readings as far as I'm concerned.

I’m leaning towards replacing the plug wires and maybe plugs but he doesn’t want to spend more money than he has to.

How old are the plugs/wires? Wires can be tested with an ohmmeter from end-to-end; should be under 4000 ohms per foot of wire. Less is better--typically 2000 ohms/foot for new carbon-rope (conventional radio-suppression wires.) The helically-wound wires have dramatically lower resistance--40--200 ohms per foot, but still reduce current flow and therefore radio static by other means--inductance vs. resistance. And the plug wires shouldn't glow in the dark when the engine is running in a truly dark environment. No cut or burnt insulation.

Given the money spent on injectors, gaskets, some "tune-up" parts...new plugs and perhaps plug wires seems very minor.

 

[kolgeirr]

Seconding doing the plugs and wires. You said you found one with a rusted lead on 6 and that's just what was visible with the eye. Wires and plugs are wear items, just like the cap and rotor, on these Vortecs. The first thing I do when I'm having a potential ignition system issue is plugs and wires...

I had a Cyl 5 misfire on my Suburban when I got it which was logging misfire events but not tripping a CEL. It's a 350, so there might be some differences in the fix compared to the 454, but we did all of the things you did - injectors, lower and upper intake gaskets, cap/rotor (entire aluminum body distributor actually, was only $10 more than a good cap/rotor combo and you gotta pull it to do the lower intake gaskets) - plus plugs and wires, and it went away.

 

[dirtautoguy]

Thanks guys. I told him it might just be the radio crapping out…. It is from 1997.

The plugs and wires don’t have very many miles on them I think maybe 30000 on the high side but I’m the one that put them in probably 5-6 years ago. Considering the way terminal 6 looked I wondered what the inside of the wire looks like. Im not sure why I didn’t think of doing a resistance test I even had my voltmeter out doh!

When I get the chance I’ll check it or just see if he’ll spring for some new wires at a minimum and inspect the plugs.

The scanner I’m using is called blue driver. Unfortunatly it will not give me a misfire counter in mode 6. The engine light is not on so there’s no codes to read either

 

[dirtautoguy]

I got my hands on my dads truck again for a short time. The truck does run even better than it did when we finished the job. I’m wondering if maybe it had a fouled plug or something that maybe is clearing up on its own?

My dad had the oil changed and the shop scanned it for him and he had a misfire on cylinders 2 and 4but they only had counts of 2 and 8 misfires

I measured the resistance on #1 wire because that’s the only one that would come off without breaking. On auto range my meter read .536 which I think is really good.

For fun I did take a can of carb cleaner and checked for leaks while watching fuel trims and couldn’t find anything.

I still think new wires would be a good idea but ultimately it’s not my truck or money. I told him if he doesn’t want to do wires right now the. drive it for a while and see if it changes and we can always do plug wires later.

 

[Schurkey]

I measured the resistance on #1 wire because that’s the only one that would come off without breaking. On auto range my meter read .536 which I think is really good.

Depends on which "range" the meter used.

0.536 megohm would be 53,600 ohms, enormously too high.
0.536 kohm would be 536 ohms, unrealistically low for carbon-rope wires, yet somewhat high for helical-wound wires.

 

[dirtautoguy]

Update on this. My dad chose to replace his distributor shaft. He had a shop do it. We asked for the old parts though.

The nice thing is the shop said the one plug wire that was corroded was bad and just replaced all 8. So new distributor and new wires this time around.

The old distributer didn’t have any play in it that was really notable however the gear teeth had some wear. The best I could measure with a caliper is about 2 thousandths difference from the unworn part to the wear marks. Also when spun slowly it felt a little clunky like a dry or bad bearing. So I really don’t think it hurt anything replacing it and I do think it made a noticeable difference but the plug wires could have done that too.

So this is where is at now. The truck is light years better than it was especially in the torque and acceleration department.

I played with it a little tonight and it runs very smooth under load. Whether it’s stopped in gear or accelerating it’s runs great. When it’s in park or neutral it has a bit of a stumble or shake a lot like a miss but only at idle in park or nuetral. Under load it’s great.

My dads a little frustrated about it still. I told him it’s a 26 year old truck it’s gonna have to have repairs and it’s still wayyyy cheaper than a new truck. And quite frankly it’s a minor shake/miss but again it’s a 26 year old truck…..

 

[HotWheelsBurban]

I have heard on here, from several owners of '97 trucks, that there's something in the original tune that if the truck is at idle for more than like a minute or two, that the PCM changes the idle spec to make it run more efficiently and cleanly. My crew cab does this, after replacing the cap, rotor, plugs and fuel filter.
I probably will replace the plug wires; I have the set I bought for the Burb less the coil wire(all I ever got installed). I have added several more wire separators but some of them have moved.
I've also heard that O2 sensors beginning to fail will do this....