mcerwing

I have a 91 pickup 3VZE. A couple months ago, my truck started acting weird when I would start it up. It felt as though the engine was misfiring. The truck would run really rough, and I could hear the engine backfiring out of the exhaust (or afterfiring, I don't know what the term is). When the problem started, it only did it for a little bit, maybe a minute at most. Then it would run just fine like nothing was wrong. I ran some seafoam and the problem seemed to be intermittent; it would do it some days, and other days it would run just fine. The problem started getting worse, and it took longer and longer for the truck to run without lagging. I kept trying to clean different things (air filter, oil, seafoam, fuel injector cleaner) but I had no luck. The truck now runs horrible all the time, and it doesn't matter if the engine is warm or cold. when I get on the gas, it feels like I'm missing a cylinder because it lags so much. It constantly backfires (or is it afterfire?) out of the exhaust when I let off of the gas. I changed the O2 sensor a few days ago, but it didn't change a thing. I pulled up the FSM and checked the resistance of the cold start injector, and it is within specs. I didn't take it off and check the operation like they showed in the manual, though. I also took off the VAFM and tested the resistance between the terminals.

See here:
http://www.ncttora.com/fsm/1993/engine/33volumeai.pdf

I tested everything as stated, and I even did the inspection by moving the flap and checking the resistance. Everything seemed to check out, except the resistance between terminals E2 and VC. It seemed like it was just open with no resistance, but I am hesitant to spend 200 dollars on a new VAFM. I don't know if I am testing it wrong or what. I get resistance between E2 and VB and it is within specs, which throws me off. VB, VC, E2, and THA are all in the same line and connect with one another. how is it I can get everything within specs (including E2 and VB) but I can't get E2 and VC? Is there a resistor between VB and VC? I searched everywhere, but I am still stuck. If you don't know what all of this means, see the link I posted above and it shows all the terminals and the wiring schematic. Could there be another problem?

Thanks in advance for all the help! This website never fails to have information on how to fix my truck.


-MIKE

TNRabbit

Check for bad distributor....

abecedarian

igniter?
Yep. We just took you 180 away from the afm.

pulled / checked trouble codes?

mcerwing

I pulled the codes, and i got the code for running too rich. i believe it was 26. i replaced the cap, rotors, wires and plugs within the last 5000 miles. how do you check the igniter and distributor?

mcerwing

I just pulled all the plugs, and they were pretty fouled up with carbon. The number 1 cylinder was the worst, with the plug not only being really fouled up but also having a cracked ceramic tip. what now? Would the VAFM cause it to run rich? i.e. the engine thinks it's taking in more air than it really is, and the engine is trying to match that with the gas? It doesn't misfire at the high rpms like it does at the low rpms, but it does backfire once I let off the gas.

Any thoughts?

mcerwing

I hate seeing unfinished threads, so I just wanted to post up that I fixed the problem. I still couldn't get resistance between the E2 and VC terminals, so I decided to replace the VAFM and it fixed the problem (or so I hope). If the problem comes back, I will post up again, but for now my truck is running great

mrddk92

I just did a top end rebuild on my 3vze and it doesn't have very much power and the throttle response isn't very good either. I'm thinking it has to do with my vafm because when I was taking the wire harness off I had a brain fart and took the 2 screws out and tried to pull the connector out that way. When I got it all back together it had no spark so I ended up taking the vafm cover off and three of the connectors were broken, I resoldered them and was able to get spark but its not running right. I will probably just get a new one

mick cassidy

i would check the timing just for reference buy the dealer shop manual gotta face up to it you got a problem and you gotta learn or pay someone best pay your self as i say ok the tests for the distributors and all the sensors are in the book as far as the igniter goes i havnt been able to find a test for that i assume if you get a spark it works ~!NEVER DO ANY electrical resistance tests when the eng is hot or warm it will be way off if your timing is off ...9 YES BUY A INNOVA brand timing light) if the timing is off and your out of adj. on your distributor what has happened is your crank pulley has sheared the woodruff key it will mive the belt about 4 teeth and be luckey you dont hit valves to pistons try that and let me know this just happened to me a few weeks ago messed with my head for 2 weeks symptons ; zero power overheating 5' after tdc @ 800 rpm with the two terminals shorted per the book i dont think it is the flow meter
as there is a wire in there and if crud builds up on it it burns out and you get a error code but your filter catches all the crud before it hits that and there about $ 750 !!!

mrddk92

My timing is at 10 btdc (8 with te and te1 connected). My distributor resistances checked out within spec. Before I got my headers hooked up to my exhaust it was running a lot worse and would stall easily and when it would stall it would throw a code 14(ignitor). Everything was working fine before so it still should be in my opinion. Except for the VAFM which I know I messed up a little for sure. I need to find someone in az with a working one so I can swap it to be sure before I get one.