eurojoe

I have an 89 Toyota pickup RWD. It's having a weird issue with sputtering at acceleration. Let me give you the whole story so you guys can get the whole picture, i want to be as informative as possible since my time and your time are both important.

I couldn't pass smog because the Cats filter was broken and the Exhaust Manifold had a large crack. I changed the following

-Exhaust manifold including gaskets and studs (From NAPA Auto)
-Downpipe WALKER 45405
-Catalytic converter WALKER 80941
-piping and muffler WALKER 48307
(all stock walker products)
-Denso 02 sensors, upstream and downstream DENSO 2344051 & DENSO 2344150

The truck passed smog fine! But I noticed an odd rumbling sound when I hit the gas almost like a diesel engine sound and it felt like the engine was holding back. It was an exhaust leak where the manifold met the downpipe and where the downpipe met the cat. I adjusted and tightened them down until there was no more leak.

Now that there is no exhaust leak the engine runs BADLY! I have two major symptoms.
1) When I am gassing it from STOP it sputters HARD to try and catch speed up until 40 MPH, after 40MPH It runs a lot better however I still feel like the engine has power loss.
2) After trying to drive it like this the exhaust smells like sulfur, rotten eggs, gunpowder, firecrackers etc. Whatever you want to call it it smells like that.
3) Sitting in D or R the engine runs steadily and then has a hard rumble about to stall for a second, it happens at the exact same intermittent time. Almost as if then when the exhaust valve goes it trips up

Here is what I have tried to do to remedy the issue.

1) Pulled and Checked the CAT Looks fine to me, it doesn't smell and the filter is intact
2) Pulled and Checked the 02 Sensors, their neither black and sooty nor white and foggy. Tan colored residue on the 02 Sensors.
3) Checked the AFM, as far as I can tell it is OK using multimeter (even opened up the casing and checked on the electrical mechanism and sealed it back up with silicone)
4) Checked the TPS, seems to be adjusted at the correct settings using multimeter (I HAVE NO CEL however if I try the Diag Jumper I get a code 41)

I feel it can be a few things
1) CAT is a cheap piece of ˟˟˟˟ rip off?
2) Fuel injectors issue?
3) TPS Circuit issue?

What I have already fixed in the past
1) Throttle body is cleaned and has a new gasket
2) New spark plugs and wires and distributor cap
3) restabbed the distributor
4) corrected the timing
5) new fuel pump (denso)
6) new fuel filter
7) adjusted the valves and put a new gasket with gasket maker on the half moons

REALLY I am stumped, it seems the CAT is the problem however it seems the CAT is fine.

Any ideas? I will try any test you suggest!

Here is a video of the sound of the engine sputtering on acceleration.

https://youtu.be/slsY3XHj-Dg

eurojoe

I forgot to mention, I am in California so the cat I bought is made for Cali emissions.

is it possible that the modern Cat is to filtering for such an old engine?

wallytoo

iTrader: (1)

you are going to have to troubleshoot the problem, unless you want to spend lots of money via the scattershot method. begin by performing diagnostic tests as described in the FSM.

one of the first things i now check with hesitation issues is fuel rail pressure. what's yours?

eurojoe

I absolutely agree with you, that's why I tested my AFM and TPS because I know how to, I do not know how to check the fuel rail pressure. I will check the FSM and online videos for testing procedures, any tips for testing fuel rail pressure are greatly appreciated. I will also be checking the EGR valve since I believe the issue is exhaust related.

eurojoe

So the fuel pressure is at ~35 when tapped into the cold start injector. I even left it plugged in and drove around while its stuttering pattern, the fuel pressure was not stuttering accordance with the stutter of the engine on acceleration.

I also tested the EGR ssytem as best as I could
- EGR Valve kills idle when activated by sucking on the vacuum hose to the valve
- EGR Valve Inducer creates a suction when revving engine
- VSV Clicks when jumpered to the battery

I feel this is an exhaust issue as it only got worse as I fixed my several exhaust leaks, after I buttoned up every last leak it runs the worst.
my theory is that the engine cannot get rid of the exhaust quick enough and it limits the engine from intaking in fresh air, I am not 100% sure how this engine works but could that theory be so?

Any more tests? I will gladly do any suggested tests.

here is a video of the engine while I rev it up from the throttle cable, after the engine stops revving the last thing I hear is a small hiss coming out from behind the valve cover. Is this normal? It's like a little puff of exhaust has found its way out somewhere and I cannot locate it. I am not sure if you could hear it in the video.

wallytoo

iTrader: (1)

excellent. fuel pressure is within spec, so you can focus on something else. in and of itself, the exhaust system is hard to test. if it doesn't leak, that's good. plugged cat can be an issue, not sure how to test.

eurojoe

Well I ran another test, I removed the cat and left the down-pipe open. When revving the car in Drive it does the same thing, stuttering at 2k RPM. So it is not the plugged CAT. It has to be a fuel delivery issue or an air/fuel ratio issue.

It only happens when in Drive though, not in Park. In park the engine revs beautifully and idles at 750 spec without any issue.

There are NO vacuum leaks anywhere.

eurojoe

So I did a more advanced test on the Air Flow Meter. I backprobed the VS pin with the key in the on position. I could hear the fuel being drawn in as I opened and closed the door on the AFM. However, there was no change in voltage at all. Which leads me to believe I did the test wrong. If there is no voltage, the car shouldn't even idle at all? Or at the very least the engine should even take off at all. Am I right?

wallytoo

iTrader: (1)

can you hear the injectors? are all working? you can use a flat blade screwdriver like a stethoscope to listen. any differences?

eurojoe

I will try this out soon, my question is will this reveal anything at idle since my idle is perfectly fine.

only when throttling in drive does it stutter

eurojoe

It sounds like they are all working. I put the blade end of the screwdriver on the fuel rail right before it connects off. They all were making a noise some higher some lower pitch and it was not the sound of the engine chatter. It was definitely the fuel injectors sound. So they were not exactly consistent in sound yet they were all making a sound. First time i've tried that test or tested any fuel line parts so bear with me.

It is odd to me that it only stutters when revving the engine in Drive. in park it is perfectly fine, really doesn't make sense to me, could it be a wiring issue? EGR issue? Is there someway I can temporarily delete the EGR by plugging a few lines real quick and testing that? I don't want to remove the whole EGR system only to discover its not the issue.

eurojoe

I've been able to recreate the engine issue so you can see what I mean. Here is the car in Drive and I am gassing it as I hold the brake.

Hear that sputtering? After doing it in Drive so much It happens at idle while in park and Drive for a bit than clears up again. It is induced by acceleration.

I guess It could be a fuel delivery issue. I already changed the fuel filter and afterwards I did a seafoam treatment. Maybe the fuel filter got gunked up? I am going to change it in the next few days.

thook

you said the cel wasn't flashing, but that you got a code 41? that's the throttle sensor. but, that could've been triggered at some point when you were working on it and had the ignition on and the sensor disconnected. pull the efi fuse or disconnect the battery for 5 or 10 min's, reconnect, drive it around, and see if it comes back

your problem only seems to manifest when the vehicle's under load....ie. accelerating while in motion? does it improve while cruising on a relatively flat surface and steady speed?

thook

you said the cel wasn't flashing, but that you got a code 41? that's the throttle sensor. but, that could've been triggered at some point when you were working on it and had the ignition on. pull the efi fuse or disconnect the battery for 5 or 10 min's, reconnect, drive it around, and see if it comes back

your problem only seems to manifest when the vehicle's under load....ie. accelerating while in motion? does it improve while cruising on a relatively flat surface and steady speed?

was it doing this before the smog test and the following repairs and adjustments?

how many miles on the truck, and have the injectors ever been removed and serviced?

eurojoe

This issue only appeared after the smog test and new exhaust system.

so let me write out the series of events that has gone down in the last days for you

i cleared the Code 41 and it stayed off. no codes, everything was nice except it still did the weird throttle stutter

i drove it for a day all around town and when i got home i held my brake and with the truck in D and gassed it to recreate the effect (you can see the video in my last post) so it does the throttle stutter in Drive even when NOT in motion. confirmed

that was yesterday. Today i drove the truck in the evening after it sat ALL DAY. guess what? No throttle issue at all, drove just fine!

I know the problem isn't over and will come back just for the hell of it i went to jumper my diag ports the same day just after driving it running fine and check for codes (there is no CEL though) there was code 31 and 24 both having to do with the AFM

I also notice, sometimes when i starts my car the battery symbol on the dash flickers to the rumble of the engine (im thinking i need to check my grounds and AFM circuit) any guides for these specific tests you can reccomend?

i have never had the injectors serviced.

wallytoo

iTrader: (1)

hold off on the injectors for a bit.

i'd go through and check/clean all the grounds under the hood. clean means bright shiny metal, with tight connections.

for sure test the afm to find out the source of the codes.

eurojoe

I have tested the AFM as one of my very first test and it seemed to work just fine. I will retest it again.

how can i test my AFM circuit? Anyway i can connect my multimeter to the circuiter and get a live readong as i recreate the stutter issue?

eurojoe

So i checked all the grounds, cleaned em with a wirse brush and brake cleaner.

Truck runs the same but now there are no codes! Just blinking CEL when i jumper the Diagnostic ports

how can i test the proper circuits for AFM and fuel injection? I beleive the issue is either AFM to ECU or ECU to injectors

i have a really good Bosch multimeter that reads ohms and volts and rpms

i dont know how to use it to its fullest ability though

any guides on checking the AFM circuit?

thook

find a fsm diagram and back probe the ecu. use the voltage function with the key on. there are links in the stickies on the main subforum page for the fsm

eurojoe

I found the FSM manual and I went through the steps into the attached photo. Step one was good step two was good and then step three I attached the result on my multimeter .

do not fully understand how resistance in ohms and volts work or exactly how this manual works, but from what I can gather the AFM is bad?

Isnt negative ohms bad?

This picture is the result of backprobing the AFM pins E2 and Vc as pictured in step (3) while the harness is plugged into the sensor and the key is turned to II