Mark1260

How's everyone doing?

My 1990 pickup 3vze is acting a little funky. 229,000 miles on the body, engine rebuilt about 80,000 miles ago. It has new plugs and wires (about 2 months old), k&n air filter, Thrusher Exhaust (flowmaster knockoff). I have been searching around for a while now, but have only found somewhat similar, but not the same, types of problems.

First, when I start it, especially when its 40 degrees F or below, it both takes a few extra cranks, as well as usually stalling 2 or 3 times. I will either have to feather the throttle, or sometimes after it eventually starts it will idle at 1,500+ rpms for a few mins. Cold start injector?

Secondly, when it is a cold start and I start taking off (1st or reverse) it will bog down HEAVILY, and sometimes stall. I need to give it a substantial amount of throttle when taking off for a good 10 mins after starting.

Oh but wait, there is more

When I am accelerating from a stop, first gear is very slow especially below 3,200rpm. I could outrun the truck easily, and once it hits ~4,200 is stops accelerating. But i have to continue revving because if I don't second will be worthlessly slow. After shifting into second, between 2,200 and 3,300 rpms, it practically stops accelerating again. Once it hits ~3,300 rpms its like a turbo kicks in or something.

At highway speeds, 4th gear and 5th gear have zero torque. If I am going ~55-70 mph I have to downshift to 3rd gear to gain any speed, even then it is a minuscule amount. Also, to make it up any incline, even at 65mph, I have to downshift to third. Sometimes even 2nd after it slows down to ~40mph because 3rd, 4th, and 5th wont pull.

Is there something that could cause these types of problems? Or am I looking at a multitude of issues? The belt sequels really badly when it is first started, so I figure it needs a new belt, or at least tightened, but would that cause any of this?

Thanks for any help/ideas/suggestions!!

camo31_10.50

you're not in 4lo are you? lmao




clutch slipping at all?

Yotaguy0001

Is your cat plugged? I had similar issues with my 92, my problem was leaking exhaust valves. Maybe a compression check is in your future?

Mark1260

Haha, no, my 4Lo is way fast! It makes me feel all sporty when I am off roading. I can easily use 5th that way.

And... I don't know about the clutch. I mean, I know what a bad clutch feels like, but I am not certain on the truck. I thought the same thing the other day, and could have sworn I could smell it, but it just doesn't seem fully like the clutch. If it is slipping, it is not obvious.





It does have a few small exhaust leaks, not sure about the valves though. And the cat could certainly be clogged. It is the original and I bought it from a guy who used it as a farm truck.

Would replacing the cat be a good starting point? Or should I check something else first?




-Thanks for you're replies, I appreciate it.

camo31_10.50

well for starters, do you only have the one O2 sensor after the cat?

if so, remove the cat and see if it runs better?

Mark1260

I don't have any o2 sensors after my cat. Is that bad? There is no CEL.

TNRabbit

It sounds as though the knock sensor is not working & is retarding your spark advance. Could also be the TPS is bad or needs adjustment. I would check those two things first.

Have you checked for codes or are you basing that on no check engine light? You can have stored codes with no light...

Mark1260

Thanks for the advice, I will check those.

As far as the codes, I was basing that on no CEL as I did not know it could through codes without the light. I can go get it scanned to see if anything is up.

Thanks

ChzSoda

Having the EXACT situation as described by the OP in my 91 PU 3VZE.
Last time I checked codes (fishing out some other issue at the time) it had a stored 51, which I've heard is related to TPS possibly?
No CEL while driving in mine either.
Latest development for me was lastnight it began to hesitate at highway speed, sort of jerky rpm's. Got off the freeway and drove 35'ish for a while to give it a break, didn't seem to do it the rest of the way home.

ThatGuy1295

I know its an overstated solution, but this actually does sound like fuel related issue. Filter, injectors, pump. Just sound starved. Stick your ear on the gas tank while she's idling. Should be consistent humming. Not erratic. Mine sounded like nitro circus before it went out.

92dlxman

i second the tps suggestion. high rpm power to me negates any fuel problem. . . .to me

dont pay money for a code read, look up the process and become enlightend. . . .gotta love obdI

ChzSoda

Yeah, I almost think it's both, after all of my hunting on this. As soon as I have any spare time and spare sun, I'm going to check both the TPS and fuel pump.

One of the strange things though, as mentioned by the OP, is when you're accelerating it'll just bog... bog... hit second... bog... bog... 3300 BAM JET ENGINE.

crazy4runner

Bro sound like you'll be needing a new motor=5vz lol....

Bassinfool

Sounds like the TPS. My old '92 did the same thing after I rebuilt the top-end. Finally got the TPS correctly adjusted after several attempts (PAIN IN THE BUTT!) and it ran like a champ.

ChzSoda

Not sure if it's related or not, wondering if the OP can chime in if he's having similar symptom, but every once in a while, seemingly random, truck will do a hard (really hard) hiccup.
For about 1/2 a second, everything dies, but then pops right back again.
It's enough to scare the sh*z out of you if you haven't felt it before.
Haven't been able to find a pattern yet.
It will do it hot/cold, heavy load, easy load, uphill, downhill, dry out, wet out, full tank of gas, low on gas, third gear, fifth gear...
If anyone thinks it's related (OP?) let me know, otherwise we can ignore it in this thread.

Mark1260

I don't have anything quite like that. When my engine is cold, and I give it full throttle it will stutter really bad, but I am assuming thats because the engine is 21 years old.

I am going to try and play with the TPS to see if that is my culprit.

I'll keep you all updated if I figure anything else.

blake.nemitz

i had a similar problem. let me ask when it hesirates then takes off, does it take off harder when it does if your only half throttle? mine ended up being a few mixed up vacuum lines to the egr that caused it to open when it shouldnt and made it hesitate bad. what's your timing set at?

Mark1260

I am not sure what you are asking, exactly. But the hesitation is always below 3,000 RPM regardless of quarter, half, or full throttle, and when it actually starts speeding up, it does so in a matter that mimics the throttle position.

It is not the TPS, I checked it out today. It is in specs, adjusted it a smidge and all it did was lower to idle.

I am thinking it might be the clogged cat. The only thing is, though, if the cat were clogged, wouldn't it be a constant power loss? Not being revived at ~3300RPM?

As far as the vacuum lines, thanks for the suggestion, I will check them out tomorrow.

Mark1260

I can look into those, but as was mentioned, it just doesn't seem like that to me. Of course, I could be very wrong!

Agree about the not being a fuel problem.
Do you possibly have a link about the 'process'? Do you mean I can see if it is throwing any codes without the fancy shmancy computer? Cuz that would be awesome, and I would love to learn.

Best description ever! That is exactly what it is like. Sucks living where I do though, 80% of my driving is on hills... Nothing like getting passed by Semi's

Yes, I have been thinking about a swap. I heard the 4.7 was a pretty straightforward job. Thats what I would probably try for

Mark1260

Well. still no luck figuring this one out. That bad thing is, I think it is getting worse. Same issues as before, however most of the time it simply will not gain speed. Flooring it only makes it slower lol.


Could this be cause by it running to lean?