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1991 Pickup, 22RE, 198k miles, new timing chain + tensioner at 195k miles.
So I recently did both a vacuum and leakdown test on my truck to chase a potential oil consumption issue. I took the distributor cap off to check where the rotor was pointing to check TDC for the leakdown and, of course, as I was putting it back on, I snapped the little bolt that hold the cap to the distributor. I have a new one on order from Toyota, but I ended up having to remove the distributor in order to drill out the other half of the broken bolt. I found a bolt laying around in my garage of the same thread pitch, so I put that in until the new ones arrive and the truck seemed fine for a few days.
Recently, the truck has started sputtering / bogging down under load. This is especially present at low speed / higher load, like going up a steep hill. It seems to do it more if I go into vacuum (lift off) and then accelerate at anything more than half throttle. The whole truck sorta bogs and it seems like it's not getting any fuel at all or something. The truck surges at idle (I couldn't initially diagnose this because I do not have a tachometer). It will surge up before dropping down and almost stalling before sort of "catching itself" and re-stabilizing.
I tried doing some diagnostic today, but I can't seem to figure it out. I thought I may have thrown the ignition timing out of whack when I took the distributor out, so I checked that today and it was a bit off but I set it to the correct specs without improving the issue. I pulled all plugs (only 6k miles on them) and they all look good. All wires seem fine, they are blue NGKs that were on the truck when I bought it. I tried disconnecting the TPS (throttle position sensor) and driving without it on but that did not change the problem at all.
The only potential thing I can visibly see is that one of the vacuum lines I pulled to do the vacuum test is old and cracked. I've included a photo below. While there is a split on it, the area that fits over the metal nipple still covers it completely so I don't know if this could be it.
What should I look at to figure this out? I was very careful with the distributor when I was screwing out the old bolt, saved for a few minor scrapes on that outside metal ring, but nothing more than a nick. I doubt the lack of two proper bolts on the distributor cap could cause it, right? Timing chain + tensioner are new so I doubt it have anything to do with that. I'm pretty stumped here guys. Thanks for any advice you can offer.
Vacuum line -
Last edited by Luca Signore; Jan 14, 2021 at 04:52 PM.
That vac line looks typical for the age and would not cause what you are describing.
Does the truck have a catalytic converter? Is it original? If so, pound or shake it to see if anything inside is moving around and could be clogging it. Also check the cat and pipe ahead of it(“A” pipe) for elevated temp when the problem occurs. A harbor freight ir thermometer is good to have.
Not saying this is the case with your truck, but I once had a '72 Chevy pickup with a 350 and HEI ignition that did a similar thing. It'd start and idle fine, and even rev up fine. But put it under load, and it'd balk like an angry mule. Turned it out was a failed distributor cap or coil. Food for thought. Basically, it could generate good spark, but not under load.
That vac line looks typical for the age and would not cause what you are describing.
Does the truck have a catalytic converter? Is it original? If so, pound or shake it to see if anything inside is moving around and could be clogging it. Also check the cat and pipe ahead of it(“A” pipe) for elevated temp when the problem occurs. A harbor freight ir thermometer is good to have.
The truck is a CA model so unfortunately it does have the cat. I went under the truck and banged on the cat with a rubber mallet a few times and didn't hear anything clanging around. Visually, the cat looks OK, but the muffler is a very different story (photos below)... not sure if that would have anything to do with it, but it was already this bad when I bought the truck, so idk. What kind of temperature difference am I looking for?
I also don't know if this matters at all, but I'm getting a lot of CO2 from the exhaust on first start up. I have a pretty sensitive/accurate CO2 tester and I was getting upwards of 200-300 ppm on first start up before stabilizing around 15 ppm after about a minute or so.
Not saying this is the case with your truck, but I once had a '72 Chevy pickup with a 350 and HEI ignition that did a similar thing. It'd start and idle fine, and even rev up fine. But put it under load, and it'd balk like an angry mule. Turned it out was a failed distributor cap or coil. Food for thought. Basically, it could generate good spark, but not under load.
A new cap is pretty cheap so probably not the worst thing to replace just in case. Is there any way to test a distributor cap?
Quick edit: The truck DOES have a surging idle as well. I originally could not diagnose this as I do not have a tachometer and I usually have the radio going. The truck's RPM will surge up, drop and almost stall, before stabilizing again.
The truck is a CA model so unfortunately it does have the cat. I went under the truck and banged on the cat with a rubber mallet a few times and didn't hear anything clanging around. Visually, the cat looks OK, but the muffler is a very different story (photos below)... not sure if that would have anything to do with it, but it was already this bad when I bought the truck, so idk. What kind of temperature difference am I looking for?
I also don't know if this matters at all, but I'm getting a lot of CO2 from the exhaust on first start up. I have a pretty sensitive/accurate CO2 tester and I was getting upwards of 200-300 ppm on first start up before stabilizing around 15 ppm after about a minute or so.
That muffler's fine.
Not really your problem, but it likely doesn't "muffle" very well anymore.
When I researched this last, I was thinking the Walker option with some stainless steel would be the best replacement given that the Toyota part is made of unobtainium now.
Haha yeah the truck is definitely a "waker upper" for my neighbors in the morning. Muffler is on my "to-buy" list once I get this annoying problem figured out.
I tried to test the distributor cap as well with one lead on the little springy center contact and then the other on the contacts for each plug, but I keep getting OL on all of them. I'm not sure if I'm testing them correctly, but I can't imagine my cap is completely shot on all 4 if it still turns on and runs, right? Picture of the cap below - how does this look?
You'd really need to do a high-voltage test to check out the wires and the cap. I've seen caps crack and fail, but you'd not pick that up with your DMM. In a cap, there isn't any continuity other than from the inside contact to its corresponding outside contact.
It's also possible that a coil can fail to deliver a powerful enough spark. There might be a DC-resistance check you do on the coil -- not sure. I'd check the FSM.
Is there any chance in all your work on the distributor that you tried to clean the inside of the cap with something? It needs to be dry in there, with no chemical residue.
I've always had backfire with moisture in the dizzy cap and normally clears itself once it's good and hot. You can spray WD-40 in it then wipe out the excess.
Last edited by 87-4runner; Jan 15, 2021 at 04:28 AM.
Use some fine emery cloth, and clean the contacts inside the distributor cap. On my screen, the contacts look burnt, and they need to be cleaned. Better yet just buy a new cap and rotor. Cap could have hairline crack.
When I replaced my cap about four years ago, I bought the Echlin premium from NAPA. It has brass contacts. Costs more yes!
I've always had backfire with moisture in the dizzy cap and normally clears itself once it's good and hot. You can spray WD-40 in it then wipe out the excess.
Spark plugs were replaced 6k miles ago with NGKs, so I doubt they're bad already. I pulled them and they're a bit ashy but nothing crazy.
I'll pull the TPS today and see if it is working mechanically and then also do the testing with the multimeter.
How would I diagnose the FPR?
I'll probably just get a new distributor cap and rotor at this point. AFAIK, they are original to the truck which has 199k miles and 30 years of existence.
Use some fine emery cloth, and clean the contacts inside the distributor cap. On my screen, the contacts look burnt, and they need to be cleaned. Better yet just buy a new cap and rotor. Cap could have hairline crack.
When I replaced my cap about four years ago, I bought the Echlin premium from NAPA. It has brass contacts. Costs more yes!
You'd really need to do a high-voltage test to check out the wires and the cap. I've seen caps crack and fail, but you'd not pick that up with your DMM. In a cap, there isn't any continuity other than from the inside contact to its corresponding outside contact.
It's also possible that a coil can fail to deliver a powerful enough spark. There might be a DC-resistance check you do on the coil -- not sure. I'd check the FSM.
Is there any chance in all your work on the distributor that you tried to clean the inside of the cap with something? It needs to be dry in there, with no chemical residue.
Yep, just found a test for the coil in the FSM - I'll do that one today after work. I'm pretty sure I left the cap in the engine bay while I was drilling out the screw from the distributor itself, so I doubt. It looks pretty clean to me, but I'll give it a quick cleaning to see if that could be it. I'll probably just order a new cap and rotor anyway.
UPDATE: So I replaced the fuel filter today since I had a new one laying around that I had never installed (what a major PITA btw. holy lord) and it seems to have done the trick. I don't know 1000% if this solved it, but my idle seems smoother and I did a couple loops around the block on some hills and I did not get any bogging at all - the truck pulled nice and strong. I'll have to go on a longer drive to really fully prove it, but yesterday I was getting the bogging even on the flat roads and I did 2 loops this time so maybe, just maybe, its fixed. The old fuel filter was realllly nasty - below is a phot of the fuel that was coming out of it - if the fuel was this dirty, should I assume my injectors need cleaning / replacing as well?
If the problem persists when I do another test drive tomorrow, I'll tackle the TPS adjustment as well.
Glad you found a problem to fix.
I'd run can of sea foam in my fuel to clean injectors.
Just bought some Marvel Mystery Oil - seems like that has gotten comparable reviews to SF. Would it be prudent to change the fuel filter again after a few tanks of gas? I've heard the MMO/SF will loosen up the gunk but it'll then get into the filter.
Jan 14, 2021 | 02:30 PM
