More issues...engine intermittently stumbles under load.

notnilc20
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More issues...engine intermittently stumbles under load.

Postby notnilc20 » Tue Jul 24, 2018 12:10 pm

Well, if it's not one thing it's another. Engine is a 16v bluetop largeport. Today approx 30 mins while driving the 86 down a straight away in 4th gear the car started to stumble when I would give it gas. it would not accelerate but instead start bucking almost. The rpms were jumping up and down ~1000rpm....i'd let it out of gear and it idled fine.... so I was doing this limping home and then it went away and the car started to run normally.

Then a few blocks from my house it started doing it again. So much so that when I got down to first gear, it would not accelerate at all.

I then took it out of gear and tried to rev the car in neutral and it would not rev but only stumble. Then the car died on me. Waited a few seconds and I started the car again and it ran just fine all the way home and I pulled in the driveway and immediately came inside to write this message. Fuel pump? Please help! This car is driving me crazy!

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jondee86
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Re: More issues...engine intermittently stumbles under load.

Postby jondee86 » Tue Jul 24, 2018 2:37 pm

I think that you should be checking fuel pressure this time round :) Sounds
like something is getting clogged or the fuel pump is dying.

Cheers... jondee86
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notnilc20
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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Tue Jul 24, 2018 3:04 pm

jondee86 wrote:I think that you should be checking fuel pressure this time round :) Sounds
like something is getting clogged or the fuel pump is dying.

Cheers... jondee86


Yeah....i'll definantly take this advice....gonna search for a kit to tap a gauge into the fuel system....

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jondee86
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Re: More issues...engine intermittently stumbles under load.

Postby jondee86 » Tue Jul 24, 2018 4:45 pm

Something like this would do the job so long as you don't mind stopping
the car and lifting the hood to see what's going on...
http://www.bmracing.com/products/46054- ... th-laser/#

My car seems to run fine on the factory FPR so I'm not looking to install an
adjustable FPR with gauge. And I don't want any more gauges inside the car.
So if I needed a gauge for diagnostics I would most likely put something like
the B&M gauge on top of the filter.

Cheers... jondee86
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notnilc20
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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Wed Jul 25, 2018 8:18 am

jondee86 wrote:Something like this would do the job so long as you don't mind stopping
the car and lifting the hood to see what's going on...
http://www.bmracing.com/products/46054- ... th-laser/#

My car seems to run fine on the factory FPR so I'm not looking to install an
adjustable FPR with gauge. And I don't want any more gauges inside the car.
So if I needed a gauge for diagnostics I would most likely put something like
the B&M gauge on top of the filter.

Cheers... jondee86


Yeah, I'm the same way about gauges. That's a good idea though. I'm going to rent a tool from Autozone today and see if it can tap into the system somehow. In the fsm it says to tap in right at the cold start injector hose on the fuel rail.....we'll see after I get off work. Thanks again....

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Re: More issues...engine intermittently stumbles under load.

Postby davew7 » Thu Jul 26, 2018 3:21 am

The input side of the fuel filter is 1/4" NPT, just thread in a pressure gauge there. Min should be around 40 PSI.
DaveW7

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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Thu Jul 26, 2018 7:32 am

UPDATE: i was able to rent the tool from autozone...fuel pressure tester kit and they had a perfect fitting to fit at the cold start injector line on the fuel rail....so I tapped in and it seems all was well. But also note that I couldnt test it with the engine under load or in gear...i was just revving it in the garage. Here are the fsm numbers at a,b and c.
Image

So here is a lil vid I made....according to the fsm it seems ok but towards the end the pressure was dropping to 30psi even at 4000 rpm....but maybe it's because the vacuum wasnt high enough to demand as much fuel? What's your opinion.....I wish I could have shown the rpm at the same time but I did say what rpms i was at towards the end....anyway, thanks for watching and your help...

Ps- guy at autozone said I could have issue with fuel oressure regulator and it not hold vacuum. But what do you think about the pressures results? Thanks.
https://youtu.be/bFQBYS2ugKU

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Re: More issues...engine intermittently stumbles under load.

Postby oldeskewltoy » Thu Jul 26, 2018 1:38 pm

do you have a spare AFM?

A long time ago (mid 1990s) I had a similar problem. I replaced the AFM, and the problem was fixed. Btw, the issue I had didn't set any codes.......
OST Cyl head porting, - viewtopic.php?f=22&t=300

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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Thu Jul 26, 2018 2:22 pm

oldeskewltoy wrote:do you have a spare AFM?

A long time ago (mid 1990s) I had a similar problem. I replaced the AFM, and the problem was fixed. Btw, the issue I had didn't set any codes.......


I have one for an mr2 4age 16v....but I did test the afm and everything was spot on... think I still should try it?

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Re: More issues...engine intermittently stumbles under load.

Postby jondee86 » Thu Jul 26, 2018 5:32 pm

notnilc20 wrote:But also note that I couldnt test it with the engine under load or in gear...i was
just revving it in the garage.

As you will have noticed while holding the revs steady, free revving only requires
a very small throttle opening and because there is no load on the engine, there is
very little fuel consumed.

The manifold vacuum also stays high (close to idle vacuum) because of the small
throttle opening, and you can see this in your video. The only time the manifold
vacuum drops (FPR raises rail pressure) is when you open the throttle rapidly and
the engine momentarily does some work as the crankshaft accelerates. And when
the engine decelerates, you get a little more vacuum.

So it seems that when you tested it in the garage, the fuel pump and fuel supply to
the engine were working fine. This is in line with your experience when driving...
car starts and runs fine for a while and then starts playing up. What you really need
to do is leave the gauge attached and drive until the engine is struggling to run,
then without turning it off, stop, pop the hood and check the gauge.

This may be possible if you use a rag for padding and secure the gauge somewhere
safe under the hood with zip ties. That's about the only way I can think of for catching
an intermittent fuel pressure fault. What I am thinking is maybe you have a lot of
crud in you tank and after driving for a while it gets stirred up enough to clog the in
tank filter, or the pump gets hot and starts to play up. Something along those lines.

Cheers... jondee86
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Re: More issues...engine intermittently stumbles under load.

Postby davew7 » Fri Jul 27, 2018 4:05 am

The best method for checking pressure is verifying the pressure with and without the vacuum line attached to the PR.
30 PSI fuel pressure is not going to cut it even with vacuum line attached! You really need higher pressure in the 34-35psi at a min with the vacuum attached. For accelerating you need higher pressure [38-40psi W/O vacuum]. 40PSI would be better. Think of the higher pressure as having the same effect as the accelerator pump on a carb. You need the extra gas at tip-in for enrichment, to reduce the stumble. It's probably time to invest in a new fuel pump and strainer. Davew7

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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Fri Jul 27, 2018 8:30 am

davew7 wrote:It's probably time to invest in a new fuel pump and strainer. Davew7


Thanks Davew7, I agree with this..... what fuel pump would you recommend?


jondee86 wrote:What I am thinking is maybe you have a lot of
crud in you tank and after driving for a while it gets stirred up enough to clog the in
tank filter, or the pump gets hot and starts to play up. Something along those lines.

Cheers... jondee86


I think you're right sir. I think I'm just going to invest in a new fuel tank and pump and filter. Should I go all out with a Walbro? Or would any pump for our car from Rockauto.com be sufficient?

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Re: More issues...engine intermittently stumbles under load.

Postby oldeskewltoy » Fri Jul 27, 2018 1:20 pm

notnilc20 wrote:
oldeskewltoy wrote:do you have a spare AFM?

A long time ago (mid 1990s) I had a similar problem. I replaced the AFM, and the problem was fixed. Btw, the issue I had didn't set any codes.......


I have one for an mr2 4age 16v....but I did test the afm and everything was spot on... think I still should try it?




Hmmmm, I don't know if the MR2 one will work, (it may). And what's the harm, plug it in, and drive it.... see what happens.

From memory (can be weak), the 1987 FX16 AFM is a direct fit replacement - https://www.rockauto.com/en/catalog/toy ... ensor,5128
OST Cyl head porting, - viewtopic.php?f=22&t=300

Building a great engine takes knowing the end... before you begin :ugeek:

Enjoy Life... its the only one you get!

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Re: More issues...engine intermittently stumbles under load.

Postby jondee86 » Fri Jul 27, 2018 3:06 pm

notnilc20 wrote:Should I go all out with a Walbro? Or would any pump for our car
from Rockauto.com be sufficient?

I bought a generic pump like this one...
https://www.trademe.co.nz/motors/car-pa ... 74e6f40939
Didn't come with a filter, but easy enough to clean and reuse the factory one. Was
a while ago but from memory I paid around $60 versus $350 for one from the Toyota
dealership. Pump dropped straight in and worked fine, so with a stock engine there
is no need to upgrade to a Walbro.

Depending on how much time you have, since you have to drop the tank to replace
the pump, you may as well drain it and take a look inside. I got about half a gallon
of rusty sludge out of mine, and the inside had massive corrosion. Car sat for too
many years in a cold garage that allowed condensation to form inside the tank.

I replaced it with a spare tank I had that was shiney new inside. After market tanks
are not sold here as the shipping costs to NZ are too high.

Cheers... jondee86
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Re: More issues...engine intermittently stumbles under load.

Postby davew7 » Sat Jul 28, 2018 3:34 am

I actually have a Brute Power fuel pump, from Rock Auto. I'm very pleased with the pump, and it was on the lower price range in the pump selection group. I would get a new strainer for the pump, But unless you know there are issues with the fuel tank that sound like an extra $. You could always get a new fuel filter for piece of mind if it has not been changed in a while. Davew7

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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Sat Jul 28, 2018 6:06 am

Ok....thanks a lot for your help guys. FYI- i did take the fuel level sender out yesterday to look at the bottom of the fuel tank and there was a lot of rust particles settled at the bottom of the tank....couldn't see the fuel pump strainer though. I will drop the tank sometime soon and check things out further....wonder if the strainer was just blocked and preventing fuel from flowing freely as Jonde86 mentioned above? The fuel pump is new as well as the filter....

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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Sun Jul 29, 2018 4:41 pm

UPDATE 2:
Got home from work a little early today so I decided to drop the tank and pull the fuel pump out and see what it looks like. Well needless to say it was quite Rusty in the tank and the sock on the bottom of the fuel pump looked quite clogged as well. It just baffles me how or why the car was having the herky jerks and eventually just died on me...but then a few seconds later I start the car and it runs fine? opinions?

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Re: More issues...engine intermittently stumbles under load.

Postby Nick94tt » Sun Jul 29, 2018 5:37 pm

Neighbor had similar issues with a mid 50's 8N Ford tractor. Had rusty sludge in the tank, thought he was out of fuel so he opened the reserve - thus dumping all the sludge into the carb and a pair of filter screens. It'd start up and idle fairly well, but under load choked out lean and stumbled/died.

The filter sock probably clears off enough to restart and run a bit after sitting, but nowhere near enough fuel capacity for load. If you drop the tank, consider stripping and epoxy coating the inside.

Don't forget a new fuel filter as well. Dirt cheap on rock and will likely be half clogged along with the pump.

(I had the same thing happen on a '03 Suzuki sv650s that sat too long. Had to drain the tank, soak it in white vinegar to remove the rust, and then force cleaner through the fuel pump after cleaning the strainer. Ran fine ever since.)

Not fuel related, but I had similar symptoms because of a broken lead from the coil to the distributor cap. Was making intermittent contact and acted very similar. Someone (likely me) pulled the wire and fitting apart ever so slightly. Took a long time to find as I didn't suspect the brand new NGK wires, lol.

Hope it helps. ^_^

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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Sun Jul 29, 2018 6:28 pm

Nick94tt wrote:The filter sock probably clears off enough to restart and run a bit
Hope it helps. ^_^


Nick94tt...thanks a lot for your input! I appreciate it. I'm probably just gonna get a new tank and pump....and yes, as you mentioned, fuel filter . Also gonna blow the lines out too while they're disconnected.

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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Sun Aug 19, 2018 8:12 am

UPDATE:

Well I changed the fuel system from the filter back less the fuel lines everything is new....here is the vid I did on that....
https://youtu.be/FdRuKWdRGDs

Took it for a drive and everything runs good...but I need to take it on an extended drive to see if it acts up again like before...fingers crossed.

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Re: More issues...engine intermittently stumbles under load.

Postby Nick94tt » Mon Aug 20, 2018 4:37 pm

Nicely done. The long drive should tell you pretty much all you need to know. I'm not a huge fan of additives but some cheap injector cleaner or marvel mystery oil in the gas (stabil as well) may be worthwhile.

If you've got a stethoscope you can easily verify all the injectors are cycling correctly - or at least evenly. Given their age any car that sits would probably benefit from a serious cleaning. Sitting still can be the death of old cars, lol.

I recently put about 1400 miles on my supra (that doesn't see much of any long distance driving, still under 89k miles) and picked up a couple mpg after the extended drive and some system cleaner.

Nick. ^_^

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Re: More issues...engine intermittently stumbles under load.

Postby notnilc20 » Fri Sep 07, 2018 8:27 am

UPDATE:

Well after putting around 100 miles on the Corolla it looks like the issue is gone (knock on wood). Not even a slight hickup. So i'm very happy to have positive results. Once again, thanks to all of the help.

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