redskinman

I recently bought a 1991 Toyota Winnebago,its a RV on a 91 Toyota chassis.Check engine light was on when I bought it,was hoping it would be simple but having problem locating the problem.Engine{V-6 3.0} has a misfire.Its throwing code 71,egr malfunction and code 25 for lean condition.I cannot find a vacuum leak anywhere.I replaced plugs,wires and distributor cap.Cylinders all have compression between 140-150.I did a vacuum test on EGR valve as instructed in youtube video and it held pressure.Changed fuel filter and it was full of rust so I suspected clogged fuel injector.Checked timing,it was good.
Now I am not mechanically inclined,I am learning as I go.I took it to a shop and this was their diagnosis:

Tech found only trouble code 71 egr temp sensor fault.Tech found cylinder 1 misfiring at this time.Tech found bad egr temp sensor and restricted egr valve.Concerning cylinder 1 misfire,tech found spark plug,plug cable,and distributor providing spark within specification.Tech found fuel inj resistance within spec and good signal to inj from pcm.Tech found good compression and no compression leaks on cylinder 1.Tech recommends replacement of egr valve and temp sensor."

So they said to replace EGR valve and sensor,which I did,ran worse and didnt fix misfire.I ended up removing EGR system and installing block kit.It ran better but still have misfire.I saw a video on youtube on how to check to see where misfire is coming from by removing plug wires one at a time from distrib cap and see if it runs worse.Well I tried that and cylinder 4 there is no change in how engine runs,so I dont know why shop thought misfire was on cylinder 1.So I bought the flamethrower injs off ebay.I thought this would be a bigger job then I could handle but I managed to do it.After new injs installed,still cyl 4 no change when doing spark plug wire test.
I emailed the owner of a local repair shop who has a "car doctor"radio show.Told him the symptoms.He said it could be broken valve spring or crack in valve seat.He said hook up vacuum gauge to direct vacuum outlet and see if gauge is erratic or holds steady,if it holds steady everything is good.So I rented vacuum pump and hooked it up to vacuum line coming out of brake booster.Gauge held steady at 18.
Just to back up a little bit,after putting on block kit no longer getting egr code,but was getting code for "lean condition" After installing fuel injs,have not had CEL come back on yet,but have only put about 25 miles on it since then.
So I moved on to the next thing that was suggested,replacing the actual distributor itself,which I did last night,no change.Did plug wire test again,cyl 4 still the only cyl with no change in how its running when pulling wire off cap.
I screwed up not checking fuel injs with multimeter before I installed them because i'm a newbie and didnt think about it.I feel the chances are very slim that if one of them was bad,what are the odds I would stick that one in cylinder I was having problems with? I just dont know what else to do at this point.
This is video I took this morning of exhaust,you can hear it doesnt sound right,it sputters,and its been this way since I bought it and nothing has helped.

redskinman

So it just occurred to me,to check the injs on engine now is major pain in as,have to take plenum off to gain access.But I do have old injs I took off that I have never tested and since I had problem with cyl 4 with old injs that it would be a good idea to check old injs and see if one was bad and it might have been the one that was on cyl 4.Well they all tested at 14.2,so it's still possible that the old one I took off 4 is so clogged it wasnt working,and it's still possible the new one I put on 4 is bad,but the chances seem highly unlikely.

atcfixer

iTrader: (1)

Odds of putting in 6 injectors, which which is bad into cyl 4 is 1 in 6 chance. That's not counting the fact likely all are good.

I assume it's the 3.0L right? It could be possible spark plugs could be mixed up, one being cyl 4. It kind of sounds like it could be running on 4 instead of 6, but kind of hard to tell (I'm not around the 3.0s much).

Since you've diag it as cyl 4 instead of cyl 1, it would be a good idea to check for injector pulse while cranking... which requires the fun of taking the top intake off again. That would tell us that the wiring is good, and the ecu is sending the signal to fire the injector. With some back probing at the ECU, and a engine wire diagram, you could hook up the injector test light w\o removing the intake parts, but it doesn't show if the injector is receiving the signal. Being a motor home, they sit a lot, and for some reason critters like to chew on wires. I have a 86 pickup with 67k miles that had the harness wire to the coil ate in half and a couple of the wires going to the carb.

Another thing that might sound a little silly, but is a good check is to swap spark plugs from another cylinder to 4 and repeat the spark plug wire pulling test to see if the problem moved. If it did, bad spark plug.

The compression test should rule out head gasket.

Can't really think of much more to try off hand, good luck diag the problem.

redskinman

Yes its the v-6.I've already tried switching plugs.Are you talking about using a noid light to see if inj is getting signal?
Thanks

atcfixer

iTrader: (1)

Yea, I wasn't sure of the spelling and was on my other computer so the keyboard is kind of hard to reach (media computer). I tried to cheat to describe it a little different .

Anyway, I have wire diagrams for the 91 pickups with the 3.0L, I'd expect them to match the motor homes too.

The two pins for injector #4 would be located at the igniter pin 3 black with red stripe and ecu pin C25 (photo of connector below) which is white. The wiring is kind of weird, 2, 4, and 6 are on the white wire, and 1,3,5 are on the white with red stripe wire (C12).

Injector specs are 13.4-14.2 ohms.

redskinman

Thanks
Forgive my ignorance but I dont know exactly what you want me to check or where it is,I'm assuming it's under the plenum somewhere.Everything I've done to this truck is my first time{except for changing plugs and wires}which I've learned how to do watching YouTube videos.
Does the motor need to be running to do this test? The injs are not accessible without removing plenum.
I was watching some youtube videos of people using noid light and in those videos all the motors were being started to check injs.My engine runs,but once I remove connecting hose from throttle body it wont start,and to remove plenum I have to disconnect fuel lines and coolant lines and theres definitely no starting it after that.

atcfixer

iTrader: (1)

It doesn't need to run, it's purely to see if the injectors are getting a signal. Normally the noid light is held on the injector wire plug at the injector. Since you have to disconnect a fuel line, you'd want to also pull out the COR (Circuit opening relay, or basically the fuel pump relay). Pretty sure the COR is located behind the glove box area on your truck and is a bit of a pain to get to. Not sure what to do about the coolant, I think the best you could do is block it off as good as possible. The test doesn't take long, just need to see if it flashes or not.

The second option is to hook up wires from their source (where the wire at the injector comes from) and hook the noid light there so you can avoid taking the intake off. It takes a bit if messing around with wires and adding a length of wire to do the test, but I'd think it would be the easier route atleast for myself. I'm not sure if there would be problems with the test this way though with the injector still plugged in.

I'm basically targeting the ignitor and wiring with the test above. Slim chance it would be a bad computer but that's generally the last thing to try to replace (expensive new, used might not be too bad).

You could check for spark on plug wire 4, but you said you replaced plugs, wires, cap (and rotor?) so any problems for a single cylinder relating to the ignition should have been taken care of.

The very basics needed for a cyl to fire is compression, fuel, air, and spark. I'm thinking it's the fuel side of things. Actually describing it that way reminded me, pull cyl 4 spark plug and look at it. Since that cylinder isn't firing, it should be wet with gas if that injector is working. Anyway, a couple things to add the the list of requirements is also timing of spark, and correct air/fuel ratio, but generally all cylinders are effected equally on those items.

redskinman

I cannot get to injs or wiring without removing plenum.Forget about hooking up the noid lights,lets go back to the test you mentioned above{with wiring diagram}.That did not involve using noid light,is that correct?That's how I understood it anyway,that those would be tested with multimeter?
Yes I have replaced plugs,wires,rotor,cap,and distributor itself.I have then replaced plug on cyl 4 for a second time to make sure it wasnt plug..When I pulled plug out of 4 {when I replaced 1st new plug with 2nd new plug}it was wet,I didnt think of it at the time whether to check if it was oil or gas.
When I check plug again should I start it up and run it again some before checking?
Thanks

atcfixer

iTrader: (1)

The wiring run about was for the noid light test, just not sure if it would light up with the injector also drawing power.

You could also use a multi meter (disconnect ignitor and ecu and probe the terminals like normal, might have to flatten a paper clip for the ecu to get a connection on the pin). The multimeter won't read the correct ohms like at the injector because the wire itself has resistance. I've heard 1 ohm per foot but that might be way off. The multi meter test could validate the wiring isn't at fault as long as it shows a resistance, and it isn't super high (say 500+ ohms), but the wire diagram shows 3 injectors hooked together per side so I'm not super sure how that system works. I'm used to the 3.4L which has each injector wired separately on one pin, and the other is a shared signal power (black/red). In the 3.4L system, each of the separate wires can be grounded to fire the injector and hooks to the ecu.

Anyway this test is kind of nulled out if the spark plug is wet with gas. (null is nothing in computer talk). Run the engine for a minute or so, and pull the spark plug. Don't take too long or the fuel might evaporate off. You could probably smell the gas on the tip of the plug if you can't see it since it's a little harder to see the wetness on a new plug. If it's wet, that pretty much validates the injector is working, atleast enough to get fuel in the cylinder. While the plug is out, find a place to set it so the threaded part can ground out (top of the engine probably) and crank it and watch for spark. It should be a nice white/blue spark. If no spark, try another plug, either one of the old ones or from another cylinder and test it on plug wire 4 again. If still no spark try swapping the spark plug wire with another spot on the distributor (keep note so you can reverse it) and test again. I suspect you would have spark at some point in this test, but if not, it's pointing at something electrical (distributor (probably not, but it also holds the "crank" sensor and rpm signals), igniter, coil, ecu), or the wiring between them which is unlikely since it runs.

Sorry I'm kind of all over the place, I'm probably not the best person for helping a person new to this out via typed messages, but I do have the patience for it so that's a good thing. I'm kind of shocked no one else has hopped on this and suggested anything else, or even confirmed my thoughts.

Oh for the "lean condition" thing in your first post, O2 sensor comes to mind, but should watch for that after fixing the running problem. Right now the engine is pumping extra oxygen in the exhaust system because of the misfire, so it's an error that makes sense for your situation.

Just to blurt a little bit, a good tech (computers, automotive, or anyone diagnosing issues) will target finding the "root of the problem" or the actual cause of the problem instead of fixing the symptoms. It isn't the easiest thing to do of course, but it's a good thing to strive for. I tried to find an inspirational quote or a witty joke to throw in with this, but didn't find anything right away. Not trying to be negative or anything, just something to do in life in general.

redskinman

Ok I will try the spark plug test.
Yes i'm tired of throwing money and parts at the problem,but at 125,000 miles I thought I would probably need to be replacing these parts in the near future anyway,luckily the total cost on parts is under 500 bucks.
Like you said "a good tech will target finding the root of the problem",well I took it to one shop that had good reviews online and came recommended who had " Toyota tech"on hand,and if i would have done what they said I would have been out 1100 bucks and I would still have the misfire.So I'm leary of taking it in to another shop to try and diagnose it,especially since it's being very difficult to pinpoint.I feel they would have came up with the same things I have done but charged me an arm and a leg to do it.But I'm pretty much at the end of what I can do.
I appreciate the help.

atcfixer

iTrader: (1)

The shop might not like it, but you can use them to diag the problem, then refuse to have the work done and do it your self. A dealership *should* be the most educated and have the best access to info relating to these trucks, but all shops have problems with some workers not being as good as others. My dad used to work as a tech and has seen so many people try to shortcut work on important parts (brakes etc), then wonder why they have come backs for warranty work. We have a lot of rust up here, and few people actually clean the brake slides and such.

Toyota computers rarely go bad, but so far all the bad computer trucks I've had, had a rust hole right by the computer in the passenger side fender. Might be a spot to take a peek at, even if the computer isn't bad, it's something that is needed to keep water out of the cab and the computer's electronics.

So far this has been a good mystery. I really hate to blindly throw parts at things, but I do have a couple in mind if it comes down to it. I've only done that once on a toyota, and I was actually right (computer in a 512k mile truck), last owner replaced like $500 worth of random electronics on it before selling it to me. The other time I kind of blindly replaced parts was on a grand am, and I was wrong, it had a miss only under load and figured it was the module (ignitor for a Toyota), long story short, it was one of the new spark plugs I put in it, must have been dropped before I got it or something since it pulled apart when I pulled the boot off (my dad's guess lol).

Anyway let me know how the spark plug mix up of things goes, and let me know if the way I explained it is confusing, I could probably lay out the details in a better format. If it gets us nowhere, I have a good ignitor and computer I could send, and if they fix the problem, pay me for whatever part fixed it, and if it doesn't work, you'd just be out just the shipping for both directions (~$20-30 I'd guess).

redskinman

You have been explaining things fine,I appreciate it.And thanks so much for the offer on the parts,very nice of you,I might have to take you up on it.Since you bring up igniter and computer I remembered I actually have a spare igniter I bought off ebay before I actually even purchased the Toyota,lol.A guy on the toyota motorhome forum bought one,it was only 5 bucks so I figured what the heck.I dont know where its at on the truck to switch them out

atcfixer

iTrader: (1)

Should be near the coil (center wire on the distributor cap that hops over the air intake tubing). Pretty positive it's on driver's side fender and has something like 6 wires hooked to it. Wires should go to the coil. Should look something like this:


Some connect directly on the coil like this one:


The parts I have are from a 91 or 92 pickup 2wd 3vz 3.0L v6. I'd suggest checking to make sure the part numbers match before plugging in the ignitor (if you find it). Same logic goes for the computer even if the plugs are the same. Nothing else electricl comes to mind that could make a single cylinder misfire, so hopefully it's just the ignitor.

scope103

Before I spent TOO much time on the injector pulse, I'd re-do the compression test. That's an easy cause of a single cylinder producing no output, and it requires only a $20 tool. Do all the cylinders if you can, to assure your technique is correct. Also, cylinder-cylinder comparison is important.

When you pick up the compression tester, spend another $20 for a timing light. That's the easy way to check for spark; just put the inductive pickup on the lead, and if the light flashes, you're good to go.

As atcfixer suggested, checking for a wet plug is pretty easy (you have to remove the plugs for the compression test), and will rule out a missing injector pulse (though a dry plug does not conclusively show an injector pulse problem).

Good luck!

redskinman

Yes,when I get parts I tell them it's for a 91 toyota 2wd pickup with v-6 3vze.I will check the part#s to be sure but I'm pretty confident they are the same,that would be awesome if it fixed my problem.The only thing I've found different about my engine was that stupid EGR valve that the shop wanted to replace.I think I found the last one available in the USA,it was quite a search to find it let me tell you.It was special because it had an extra stem on it that a coolant line went to.
Thanks

redskinman

I just checked compression in that cylinder again a couple days ago,I didnt do all of them again,just cyl 4,and it was 140.I do have timing light,I have checked that wire with timing light,and just changed distributor and confirmed it was in time with timing light,but I appreciate the help.
Thanks

redskinman

Ok had a few minutes to check it when I got home from work before it got dark.Switched out ignition modules,they were not the same part number but when I google toyota igniter 89621-12010 its says its for a 89-92 toyota pickup or 4 runner with the v-6 so I took the chance,it ran the same.Only ran it about a minute and turned it off and switched them back.Then I started it back up and ran it a couple minutes then pulled the plug,it was dry,so I pulled plug next to it,it was dry also.So i put them back in and let truck cool off a few minutes while I put some wiper fluid in my truck.Tried again,this time running it for exactly 60 seconds,pulled both plugs,which i'm sure took me at most 3 minutes to do,both were dry again.It was plug 6 I was checking also,and cyl 6 passes the pulling the wire off cap test.
I then tried pulling plug 4 and laying it on engine for spark test,No one was home to help me so I had to crank it myself.I had it laying up near throttle body so I could see it from cab,when I turned engine over I saw a white spark on plug before plug fell from it's perch almost as soon as turning it over.I didnt try it again because engine sounded awful without plug in hole{and I had connector hose that attaches to throttle body off because its easier to get to plugs with it off}so it scared me wondering if I did something wrong.While plug is out and laying on engine and you crank it over will engine still start? I saw the plug get a white spark,no blue but like I said it fell as soon as turning it over.

atcfixer

iTrader: (1)

White is better than blue, it goes down the line yellow then orange, basically the heat ranges of metal in reverse, its a sign of how hot the spark is, and it makes sure it's a nice high voltage. It's sounding like spark/ignition is fine, and it's something todo with fuel delivery. Since you've swapped out injectors, the next thing I'd be after is to see if the injector is receiving a signal (pain to do). I'm back at pointing at wiring or ecu. It could be possible the fuel rail had some junk get past the filter, but it seems like it would have effected all, or most cylinders.

The cylinders it fires on should be dry, and in time should get a brownish colored build up or black if it's running rich.

When you swapped out the injectors, did it feel to have more power (with the miss of course)? If it seemed to run better, the fuel rail theory could be a logical thing, but it seems #2 would have even more problems being down the line further.

redskinman

Yes I thought it was running better after replacing injs,but that could be by mind playing tricks on me with wishful thinking.It did not feel like it had more power.I have no record of valves ever being adjusting on this rig and I dont know if that would have anything to do with the problem but I want to bring it up so you are completely informed.These motorhomes are always under a constant load so it's recommended valves are adjusted every 60,000 miles,unlike pickups or 4 runners that might be able to go 2 or 3 hundred thousand before requiring it.I'm attaching pic of what plug on 4 looked like tonight,didnt take a pic of 6 but it looked the same.

redskinman

Also heres pics of what fuel filter looked like when i emptied out the gas that was in it,after it dried you can see all the rust on the paper towel.Another reason I thought it would be a good idea to go ahead and replace injs even if that wasnt the problem but I was very hopeful it was at the time.