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Continued Hesitation / Stumbling, with VIDEO

dhcomp

dhcomp

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Hey guys,

I've been battling this issue for a while, and don't dare admit all the parts i've thrown at it trying to fix it. Then it dawned on me finally today to post up a video.

Symptoms: Bad stumbling, as can be heard, right off of idle. Worst when cold and right after startup. I can give it more gas and it goes away, but if i hold it where it stumbles it gets worse and worse.

I'll try and get some better video tmr, i really only get one chance each day, and should have moved it away from teh engine fan noise.

Any idea what would cause this condition/sound?

THanks in advance guys, this issue has been killing me. I move a lot of boats around a just above idle, and its embarrassing. Has even stalled out a couple times.

 
Last edited by a moderator:
It would help to know what parts you have replaced.
Any trouble codes?
problem could be caused by a number of things. would help to know what work was done on the truck

bad idle/stalling like that can be caused by the EGR valve stuck open.
 
Thunder said:
It would help to know what parts you have replaced.
Any trouble codes?
problem could be caused by a number of things. would help to know what work was done on the truck

bad idle/stalling like that can be caused by the EGR valve stuck open.
Click to expand...

Ok, here is what i can remember.

Cap/Rotor
TPS
IACV
Coil
TBI Gasket
EGR and Gasket
O2 Sensor

Had a very rare check engine light, finally checked it when the code came up on sat, and it was code 32, EGR. So i JUST changed the egr and gasket before the video was taken.
 
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Check fuel pressure. Pressure should be between 9-13psi while running.
 
4X4HIGH said:
Check fuel pressure. Pressure should be between 9-13psi while running.
Click to expand...

I've never done this on a TBI motor before. Is there some sort of diagnostic/pressure port that i can hook a gauge to?

Thanks scott.
 
dhcomp said:
I've never done this on a TBI motor before. Is there some sort of diagnostic/pressure port that i can hook a gauge to?

Thanks scott.
Click to expand...

No there isn't. You either need to buy (i recommend this way) the fuel gauge fitting and gauge that attach to the TBI replacing the factory inlet fitting OR you buy the fitting that goes in place of the fuel filter so you can "test" the pressure. I like the idea of having a gauge that can be left hooked up so you can check it anytime you want without having to remove a fuel filter and climb under the truck to check.

Here is a link for the pressure inlet fitting so you can run a gauge. http://marine-performance-parts.com/cfmtechfuelpsiguageadaptorforgmtbi2843505774.aspx

Here is a link on the same website for a gauge. http://marine-performance-parts.com/015fuelpsiguage.aspx

I like Autometer gauges though so that's what i'm running instead of some generic brand gauge. This is the gauge i run. http://www.summitracing.com/parts/ATM-2173/?image=large

If you are runniong stock pressures then this is the gauge i would suggest. http://www.summitracing.com/parts/ATM-2172/
 
Thanks for the detailed response scott.

Kinda bummed I need to spend $60 to test for this possibility though.

Any other cheaper parts i should check first?

If not, I'll bite the bullet and get the gauge setup. If the gauge tells me i am low when it is hesitating, what is my fix? Fuel pump or pressure regulator? I'm kinda worried that even with the gauge, it will be hard to check the pressure when i am having the symptoms.
 
dhcomp said:
Funny you say that, now that i look it up and know what is is:
http://shop.oreillyauto.com/ProductDetail.aspx?MfrCode=SMP&MfrPartNumber=AS165&PartType=414&PTSet=A

I was wondering what that damn thing was today, when i was replacing the EGR. Its right in the way.....

But no, no MAP sensor replaced. Maybe i'll test it......although ive been better at just throwing parts at this problem:doah:
Click to expand...

Don't throw money at parts hoping to fix the problem eventually. The money you've already spent could have bought the fuel pressure fitting and gauge (think never enough tools) and at least then you would be capable of diagnosing fuel related issues in the future. Just about every electrical part can be tested somehow, you just have to have the tools to do so. I would rather spend money on tools than money on unneeded parts.
 
4X4HIGH said:
Don't throw money at parts hoping to fix the problem eventually. The money you've already spent could have bought the fuel pressure fitting and gauge (think never enough tools) and at least then you would be capable of diagnosing fuel related issues in the future. Just about every electrical part can be tested somehow, you just have to have the tools to do so. I would rather spend money on tools than money on unneeded parts.
Click to expand...

Agreed. I was process of elimination, and wanting the assurance to KNOW a part is new and good. Some of the tests didn't leave me with a warm and fuzzy feeling, you know?

Ok, so gauge and fitting. Do i need some sort of a hose to mount the gauge in a good place? Any pics of where you mounted yours? Just want to understand it all before i place the order. Is it stupid to get a hose long enough to snake the gauge out the cowl so i can put it on the windshield for testing purposes? Or do this hose and setup with a quick release fitting of some sort, like the newer MPFI engines? Once this problem is solved, i doubt i'll ever look at the gauge again. If i was running something more custom than a stock 350tbi i would, but in my case, dont' see the need.

Thanks scott!
 
This is the only pic i can find of how my gauge is mounted. Yes you can buy a length of hose and run the gauge up beyond the hood so you can drive and still see the gauge. I actually am going to do something similar with a second gauge with a schrader valve arrangement so i can run a test gauge out the hood when needed. The fitting i linked you to has 2 spots for a gauge so i'll have the gauge in one location and a hose set-up in the other going to a fuel block on the firewall with a schrader valve where i can attach the "test" gauge.

1989 blazer engine 037.jpg
 
4X4HIGH said:
This is the only pic i can find of how my gauge is mounted. Yes you can buy a length of hose and run the gauge up beyond the hood so you can drive and still see the gauge. I actually am going to do something similar with a second gauge with a schrader valve arrangement so i can run a test gauge out the hood when needed. The fitting i linked you to has 2 spots for a gauge so i'll have the gauge in one location and a hose set-up in the other going to a fuel block on the firewall with a schrader valve where i can attach the "test" gauge.
Click to expand...


Ok, thats helpful. Does it fit under the stock air cleaner in that location?

Any reason i couldn't' put a schrader valve on the adapter directly, and get the proper hose and disconnect to do the primary gauge like this?

Where can i buy those fittings?

Thanks for all your help man!
 
dhcomp said:
Ok, thats helpful. Does it fit under the stock air cleaner in that location?

Any reason i couldn't' put a schrader valve on the adapter directly, and get the proper hose and disconnect to do the primary gauge like this?

Where can i buy those fittings?

Thanks for all your help man!
Click to expand...

Yes the gauge fits with the stock air cleaner assembly in place. If you can find a schrader valve that is 1/8" NPT i don't see why you couldn't thread it directly into the fitting and then use the hose as you're wanting to do. I have a schrader valve from a TPI fuel rail but it's not 1/8" NPT so that's why i plan on making a fuel block to mount on the firewall and use the TPI schrader valve in it with a standard 1/8" NPT to 1/8" NPT hose between the block and the inlet fitting.
 
just think of the stock pile of test parts your going to have next time you have a problem
 
Since you're motor is a stock TBI this may not work as well as the fitting Scott recommended, but I used a similar fitting that had a shraeder valve built in for a guage to screw onto. Then when you're done, you just unscrew the guage. The problem is that it doesn't replace the original fitting, it screws into it and makes the straight portion of you're return line longer which then may run into the coil or other stuff back there.

Mine is kinda like this one, but not as expensive. And I can use the guage for checking tire pressure. :)

http://www.toolsource.com/-p-95303.html
 
You replaced the EGR but how about the EGR solenoid? Your code 32 still makes me think you have an EGR problem. When the solenoid go bad sometimes they put vaccum to the egr at idle and open it up. Which will screw things up. EGR should not have vacuum at idle.
Pull the vacuum line off the EGR. Plug the vac line and see if the idle gets better.
As for the MAP disconnect the electrical connection to it. That will throw the system into bypass mode. If things get better with the MAP disconnected you most likely found your problem.
try those 2 tests and post results.
Do the EGR test before you disconnect the MAP.
At least try these things, they are free, before you mess with getting the stuff to test the fuel pressure.
 
Thunder said:
You replaced the EGR but how about the EGR solenoid? Your code 32 still makes me think you have an EGR problem. When the solenoid go bad sometimes they put vaccum to the egr at idle and open it up. Which will screw things up. EGR should not have vacuum at idle.
Pull the vacuum line off the EGR. Plug the vac line and see if the idle gets better.
As for the MAP disconnect the electrical connection to it. That will throw the system into bypass mode. If things get better with the MAP disconnected you most likely found your problem.
try those 2 tests and post results.
Do the EGR test before you disconnect the MAP.
At least try these things, they are free, before you mess with getting the stuff to test the fuel pressure.
Click to expand...


Those tests seem easy enough, i will give them a try. My Check engine light only happens once a month or so, for a matter of minutes on the freeway when "lugging" the motor in OD.
 
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