Trouble code and drive ability troubleshooting

[Spike555]

Just for poops and giggles try changing brands of gas and run a bottle of Marvel Mystery Oil through her.

Since the brake cleaner came up nil I'd look into the coils.
Spark plugs are cheap, so don't worry about fouling those.

 

[2001LC]

Disconnecting battery for 20 minutes after doing tune up work, is a good idea. This reset the ECM to factory default. Then ECM will then relearn with changes you made.

 

[Mauser]

I tried brake cleaner, ether, propane, and cigar smoke trying to find my vacuum leak. Never could find anything. I think the best way is to find a shop with a real smoke machine.

 

[Poncherelli]

Took the truck back to a local mechanic...not sure I trust their opinion after it took 15 minutes to figure out where the lift mount points were to get the truck off the ground...but here’s what they said...

A few codes are pending, not setting a check engine code. Two are for wheel speed sensors. Another is for AC.

And a fourth is regarding the brake system. I will post the actual code numbers in a few minutes.

Could the brake system be causing a vacuum leak? They didn’t have any insight into why the truck was roughly idling. Said it didn’t seem like a misfire because it went away under load but agreed it was running poorly at idle.

A third repair shop recommended changing all the coil packs instead of trying to find the bad one if it was coil related since there isn’t any sign of a misfire code. Not sure I want to go this route...sounds like throwing parts at the problem.

 

[Poncherelli]

Disconnecting battery for 20 minutes after doing tune up work, is a good idea. This reset the ECM to factory default. Then ECM will then relearn with changes you made.

Did this. Didn’t seem to help anything.

 

[2001LC]

You mentioned worst after spark plug change. Assume spark plugs installed to spec, but may be worth inspecting. A vacuum line may be off. The one left off the most comes up to front underside of air box from vane (power steering) pump.

Also those cracked vacuum lines at the end are often ok, not great but ok, if not disturb. But keep in mind, air box was pulled and vacuum lines were disturbed swapping plugs.

Have you tried a tank of gas with 44k or Chevron Techron added to it. These fuel system cleans can have very good results. Try and run it at high RPM on HWY as much as possible.

A full set of Denso/OEM coils are so sweet, but benefit is usually only incremental when no code or misfire detected. Your issues sounds like more is needed. I suspect your rig has been running with bad MAF, possible vacuum leaks and plugs with wide gaps, possible clogged air filter for very long time. Running poorly for long time can have bad effect on CATS, and cylinders get carboned up too.

 

[Poncherelli]

Ponied up for an engine diagnostic today. Live stream data showed cylinder 6 misfiring. Changing coil tomorrow w A denso coil off amazon ($55), hoping it resolves.

 

[Poncherelli]

Here’s the culprit. Spider crack in the boot. Amazed the technician who changed the plugs...knowing the truck was running roughly, wouldn’t look at the coil boots when they had them out.

Going to post in the thread re: coil issues as well with syptoms etc.

 

[Spike555]

That could very well allow spark to leak out and short to the valve cover.

 

[Poncherelli]

Curious...do they make replacement rubber boots? If the coil was working well enough...could it be “refurbished”??

 

[Spike555]

Liquid Tape.
Otherwise I am sure there is a replacement for that.

 

[PADDO]

Curious...do they make replacement rubber boots? If the coil was working well enough...could it be “refurbished”??

Denso part number 671-8184 coil on plug boot kit (8) for about $50. A cracked boot like that has no insulation integrity, you can see HV breakthrough marks (that small carbonized white spot) where it’s been shorting which will definitely give you rough running without throwing misfire DTCs.

 

[Poncherelli]

So then, something not often mentioned -- perhaps a middle ground for replacement of all coils is replacement of the boots at some point. I'm actually leaning towards it since I have a low mile, but 20 year old vehicle so I'm sure the rubber is breaking down on most of the coils.

 

[PADDO]

So then, something not often mentioned -- perhaps a middle ground for replacement of all coils is replacement of the boots at some point. I'm actually leaning towards it since I have a low mile, but 20 year old vehicle so I'm sure the rubber is breaking down on most of the coils.

Agreed it’s not often mentioned to replace boot insulators but those of us in the know do After year’s of heat cycling and ionizing gas exposure it’s not unexpected for the insulating properties of the boots to decline to the point the field strength produced by the COP overcomes the dielectric strength of the insulator.

 

[Poncherelli]

Still trying to figure out a workflow to solve this issue....truck is still occasionally idling rough. And when under load around 1800-2000rpm stumbles.

So far:

Changed MAF sensor. Drove better for 1 day, then back to rough idle/stumbling

Engine code o2 sensor. Changed. Code went way

changed spark plugs, issue got worse.

ran a bottle of Techron injector cleaner, issue better but still present

Then paid for an engine diag, tech said coil #6 was misfiring. Changed #6 (spider cracks in boot)

Drove better for 1 day, then, issue came back

“Refurbed” all coils w new boots, saw one coil tube was cracked (#8 coil). Changed coil. Ran better for 20miles the. Idle issue back.

Spoke w a tech who said I should change plugs out of misfiring coils. Changed plugs on #6 and #8. They looked alittle carbon burned/fouled...is that from a vacuum leak?

Issue better but stumbling still present.

Saw oil residue around oil fill and PCV , Chaves PCV and grommet.

Issue still persists.

Curious if anyone has an idea of what my work flow should be now...change vacuum hoses?

Another thing that confuses me, my evap and catalytic monitors won’t ready.

 

[Poncherelli]

Should I mention the stumble kinda feels like a transmission slip, or total power loss for a half second then recover.

 

[John Young]

Check the PVC valve and the grommet to see if any leak/dark spot around the PVC area. My grommet was cracking and gave me the P0171. I changed both the PCV and the grommet to fix the problem. Just be careful not to drop the grommet inside when try to remove it.

I had the same thing on my high-mileage 1998. The grommet and PVC valve were 29 bucks at the local Toyota dealer. But ultimately the cause of my PO171 was aged, cracked and brittle injector seals. Having those changed seems to have permanently addressed the PO171.

 

[Poncherelli]

If you only have P0171 and not P0174 (bank 2) then the issue is most likely from the O2 sensor.

If you have P0171 and P0174, i.e. bank 1 and 2, it could be a vacuum leak, fuel pressure, or injector contamination/blockage.

No misfires?

Correction, misfires...but changed coils and still running kinda rough.

 

[Poncherelli]

I had the same thing on my high-mileage 1998. The grommet and PVC valve were 29 bucks at the local Toyota dealer. But ultimately the cause of my PO171 was aged, cracked and brittle injector seals. Having those changed seems to have permanently addressed the PO171.

Hmm. Something to look into. Thanks for intel.

 

[Poncherelli]

I've gone through bringing back air and fuel to as like new as I possibly can. i.e. Filters, cleaning MAF & T-Body, vacuum lines & PCV, intake & fuel injector gaskets & seals, spark plugs, fuel injectors clean & rebuilt with all yielding very good results. To the point everything but coils done. But still have a little more fuel smell while idling in shop than I like, a slight rough idle only I'd notice and acceleration not as smooth as I'd like. Replace all coils and bam! like new again!

I've also had a coil that is going bad but not yet throwing a code. They'll tend to do this when hot. I've found them, by connecting to tech stream with mini VCI while engine hot. Then while engine running put in D with foot on brake and raise RPM. This puts engine under a load. Then watch "cylinder misfire count". When replacing coils avoid buying those cheap ebay coils. They are most likely counterfeit/knockoffs and don't work well or last long.

I think I’m needing to bite the bullet and get all coils. Thanks for your story...sounds familiar