P0171 turning into a witch hunt 07Vibe

[BenGenVibe07]

Hi all. This is my first post on GenVibe. This forum has been very helpful in the past, Thanks!! I'm the happy second owner of a 2007 vibe(140k miles). I'm running out of ideas on how to fix this issue and I know there are some smart people on here that might be able to help.

Recently I had a P0171 code. I didn't have a chance to have it checked out and within a week or two of regular driving, it would not start. My inital thought was fuel filter or fuel pump. When I did get it started, I took it to a "trusted" mechanic and he told me the intake manifold was cracked. After a day, he called me back and said it was not cracked but that the fuel pump needed to be replaced(and Im the worlds biggest dope for not doing it myself). When I picked up the car, it started fine and seemed to run ok. When I tried to turn it on that evening, it did not start. Later I found out it would start cold but had a hard time starting after being driven. At this point the throttle response was getting worse and worse. There was rough idle and the acceleration was heavily affected. So, either not enough fuel, too much air, or the computer was getting it all wrong and the mixture was off. This is where the adventure begins.

Since my first trip to the mechanic, I used it sparely for short trips and was very careful with the throttle(I'm sure I did not help the lean issue by driving it more).
Since the fuel pump was replaced, I first started with the MAF and cleaned it thoroughly(I unplugged it while running and the car died, so I suspect the MAF sensor is ok). I then began checking hoses, squeezing/clamping and bending them. I took some hoses off completely and inspected them. A few hoses only show a little cracking around the ends(maybe 2-4mm of cracking) but the others were fine. I sprayed many sections of the motor with carb cleaner but no change in RPM or anything to suggest a vacuum leak. So, I changed the intake manifold gasket(the Fen-pro black one) and later I changed it again with the updated orange/red toyota gasket. At this point the car is still not running well, can't accelerate past 15-20mph. After this I changed both O2 sensors and I changed the spark plugs(I read a ton of online forums and some people fixed the issue so I figured for why not try). Still running poorly, I did a vacuum test with a gauge connected to the brake booster line. When starting the car, the needle would come up to green/120 and showed a good motor, but 4 seconds in, it drops about halfway down during rough idle but would struggle to come back up to green/20 on the gauge. It would go back and forth, up and down, mimicking the idle speed. I know this is bad, but I could not determine what is causing the needle to move like this on the gauge. When I give a rev(it bogs down but eventually struggles to rev) the needle drops to 0 like it's supposed to and swings past 20 and settles on 20. I thought maybe exhaust, maybe valves... So I started with exhaust, I took out the upstream sensor to bypass the cat. No change, still running poorly(and now super loud exhaust). Next I did a compression test on the cylinders and each cylinder was at about 180 on the gauge which is good. So the valves should be fine. Now I'm thinking it has to be fuel related. I have not cleaned or tested the fuel injectors. I did do the screwdriver test and all of them are clicking evenly. I'm running out of ideas and worried I could waste more money by changing/cleaning, perhaps breaking, the fuel injectors.

At this point, I could replace the injectors... and I could continue to test hoses, or just start replacing them. Does anyone have a recommendation?

[vibrologist]

How do the brakes feel?

First check if you have re-attached the brake booster hose to the intake manifold after changing the gasket the last time. It is hidden and easily missed!
Click on the link in my signature and scroll down about 3/4 of the way. there is a telling picture.


Maybe the brake booster itself failed.
Here is what I would do: clamp off the brake booster hose or disconnect it and plug it towards the intake manifold. Drive super carefully,always ready to step on the brake with both feet because definitely no boost! If the engine runs well and starts well even when warmed up then I would assume the membrane in the booster has failed.
Hopefully someone has a less risky method of testing the brake booster. I don't want you to get into an accident!


What you are describing is a BIG vacuum leak and I would not spend money on the fuel system. If the booster checks ok. I would systematically search for vacuum leaks. That would include the complete PCV system , even the the oil filler cap, and the EVAP system.

Just an anecdote: My wife's Ford Contour had a misfire. I used the carb cleaner method to search for a vacuum leak. I was spaying somewhere near the intake manifold and it changed the idle. But there was nothing on the IM. then I noticed the spray went way down towards the oil pan. And there was a hose that was part of the PCV.... Lesson learned: be aware where exactly the spray goes.

[BenGenVibe07]

Brakes feel good. It idles rough, comes up to a good idle for a few seconds then bogs down, back up again, and bogs down again. over and over. I wouldn't say the engine runs well, but it runs. There's almost no way to rev it without massive stuttering, so it's not drivable.

I'll continue to check the brake booster, but it really does sound like a huge vacuum problem. I replaced the PCV valve and the hose connected looked good. I could really use a smoke machine to test it, maybe I can do the cigar trick?

Great suggestions, thank you. I'm going to continue spraying and looking

I should say, it will rev to higher RPMs, but takes a ton of effort to get it there..

[vibrologist]

Could it be a malfunction of the throttle body position sensor?
What happens if you disconnect it?

[BenGenVibe07]

If I disconnect the throttle body sensor, it revs up to 2000rpm then comes back down to a rough idle and goes back up to 2000rpm then back to idle. Eventually after 4 or 5 of those, it goes down to a very low idle and nearly dies

[vibrologist]

I don't know what to conclude of that- I was hoping for a miracle-.

[BenGenVibe07]

That's alright, thanks for the suggestions!

I have a friend who is a certified toyota mechanic, he's stumped as well.

[vibrologist]

last and desperate hint:
Disconnect battery negative.
Disconnect all plugs from the ECM. Reconnect the ECM and battery negative.

Disconnecting and reconnecting cleans the contacts. You can do that with all harnesses under the hood as well.

[BenGenVibe07]

I just noticed the filler cap seal is missing... I'll be replacing it tomorrow and praying just maybe this is it. I would be surprised if it's that simple, but I suppose it's connected to the PCV, is that right?

[hogdoctor]

I would go with a fuel pressure test as the next step. I'm not convinced the fuel pump was any more than a shotgun guess.

Patrick

[vibrologist]

I just noticed the filler cap seal is missing... I'll be replacing it tomorrow and praying just maybe this is it. I would be surprised if it's that simple, but I suppose it's connected to the PCV, is that right?

Correct.

[BenGenVibe07]

Thanks guys.

Im going to do a fuel pressure test and replace the cap today. Does the vibe have a schrader valve to test pressure?

[vibrologist]

Don't know. but here is some very good general information on fuel pressure testing:
https://www.youtube.com/watch?v=AeVTZz0od7Y

[vibrologist]

Are there any oil leaks around your engine? Timing cover, oil pan, oil filler tube etc?

Read this thread: viewtopic.php?f=12&t=46175&p=519596&hil ... er#p519584

[BenGenVibe07]

No huge change with the filler cap, maybe a bit but not much. I still need to do the fuel pressure test

Now you got me thinking. There are parts of the motor, I believe near the timing cover, that are pretty dirty. I've never ever seen it drip oil, nothing that big, but even a very small leak could cause that problem. I'll have to get some dye to check

[vibrologist]

Clean the dirty areas with brake cleaner or TB cleaner. You could try putting some stiff grease or chewing gum etc. on suspected leaks.

[kostby]

OK. GenVibe somehow swallowed my original, much wordier post.

So here's the condensed version of what sounds like a similar problem from decades ago:
1988 1/2 Ford Escort GT, manual trans.
One winter it began driving very erratically. Started and ran fine at idle, but press the accelerator and it was either FULL THROTTLE, or none at all.
It drove OK on the highway, and most of my commute was highway, so I lived with it for a few weeks.

Engine computers weren't as sophisticated then, far fewer sensors, and far less diagnostic feedback.
Took the car to the dealer (under warranty) multiple times, but mechanic could never isolate and fix the problem.
Only showed a 'lean condition'.
After a couple of scary weeks, I parked the car at the dealership overnight, and told them to try it when cold the next morning.
Mechanic nearly crashed the car getting it out of the parking lot and into the service bay!
So that time, he kept looking!

It was an unseen tear on the underside of a molded seam of the 'hose' between the MAF (of that era) and the throttle body.

iu-3.jpg (25.46 KiB) Viewed 6820 times

The tear admitted huge amounts of unmetered air into the intake when the throttle was pressed, causing a lean condition.
Throttle body compensated with much more fuel. Let off the throttle, tear closes, engine returns to idle.
On the highway, the tear and the air admitted was relatively constant, so the engine adjusted and ran reasonably well.

Bottom line: Have you checked the condition of the similar 'hose' on the Vibe?

iu-2.jpg (94.14 KiB) Viewed 6820 times

[vibrologist]

Excellent advise Kostby!
In Mazda 323 and Protégé that intake hose is cracking as well. To check it you take the hose out and bend it so it will show the cracks. They were always in the ribbed area. In my son's Protégé I fixed it with duct tape preventatively. Duct tape is a totally acceptable repair in this case.
However, I never heard of that in our engines. Nevertheless it bares checking.
If it is not the intake hose I would plug all the vacuum lines that go into that hose. It should run perfectly then. Then you can add one line after the other to find the conduit for the unmetered air.

[vibrologist]

I am hoping for an update.

[jolt]

Thanks guys.

Im going to do a fuel pressure test and replace the cap today. Does the vibe have a schrader valve to test pressure?

There is no schrader valve to hook a pressure tester to on the fuel line, at least on my 2009. Between the engine and the firewall is a fuel line connection. You need to take that spring loaded connector apart with the proper tool. You then need to add a "T" adapter in the line to connect a fuel pressure gauge to test the pressure. GM made a "T" hose adapter for this propose but I do not think they sell them anymore. The last ones I seen where on Ebay selling for around $100.00. You can make your own adapter if you can find the connector ends for the fuel line disconnect. The fuel pressure should be around 45 pis at idle, if I remember right. Here is what it would look like:

[jolt]

Has the MAP sensor been cleaned or checked? There can not be any air leaks between the MAP sensor and the throttle body as the post up above talks about cracks in the air hose. With the engine running, spray carb or throttle body cleaner around any hose connection if you expect an external vacuum leak is the problem. If the engine RPM's change in speed when spraying at a hose connection, you have an air leak there that needs to be fixed. What are your short and long term fuel trim readings? Do you have access to freeze frame data when the code was thrown? You can pinch off vacuum hoses as the engine is running and see if the idle improves as you also have vacuum lines going back to the fuel tank and the brake booster too. When the fuel pump was replaced, was it just the pump or the pump assembly with the fuel pressure regulator?

Witch hunts are made by making guesses and jumping around all over the place. Another thing that can really throw troubleshooting off is if a person has multiple problems but is trying to troubleshoot it as one problem. Proper testing and elimination of what is good will work your way to the problem. It is very hard to trouble shoot something if you do not have the tools to do it with. From that point a person is just guessing and playing the odds (gambling) with what the problem is. A forum can give you idea's to work with from the information you provide and that is about it.

[jolt]

This may help guide you to troubleshooting the P0171 problem, your at least get you going so your not jumping all over the place. If more info is needed, ask and people here will help.

[jolt]

Here is fuel pump testing and gauge hook up on gen 1 vibe:

[BenGenVibe07]

Hi all. I apologize for the delay, I gave up a while back and just now got back to working on the vibe.

The intake hose did have some small cracks but nothing that looks anything like a tear going through the entire piece of rubber.

It has a new fuel pump, but I am wondering if the regulator, the housing for the pump could be the issue. Thank you for the fuel pressure testing suggestions, I'm going to try that next

The car is running very rich now. The short term Fuel trim is like -7 and the long term gets down to -18 or more.

I'll report back after I try a few more things

[BenGenVibe07]

The MAP sensor connection to the throttle body looks good. No change with cleaner sprayed on it.

The car turns on no problem, it will nearly stall the first or second start, then it will idle roughly. Still lots of hesitation when pressing the gas and noise out of the exhaust. Just to update yall

[BenGenVibe07]

Oh an update I forgot about. I replaced injectors and MAF and the throttle body gasket(read my first post to see other things I changed) and there was an improvement for a while, the 0171 code went away and now I have a P1296 code.

The T connector in my fuel pressure kit is not the right size to insert for a fuel pressure test. I'll have to look around for the one you mentioned that might not be made any longer

[jolt]

The picture is for a second gen Vibe (09-10) and is not for the first gen Vibe. It was given as a reference. The onvein40.pdf file shows the pressure test for the first gen '03. The numbers shown in that pdf file are Toyota numbers as the Corolla/Matrix are close twins to the Vibe.

[vibrologist]

P1296:


Low coolant level
Defective Coolant Temperature Sensor
Open or shorted Coolant Temperature Sensor harness
Poor electrical connection in Coolant Temperature Sensor circuit


I bet that's the core problem you are having.

[vibrologist]

Ben: you owe us an update!

[tercelerator]

Hi Vibers,
(2016 2WD base automatic)
I am getting the P0171, intermittently.
I did notice a few times that it was idling funny, jumping around.
So am going to replace the intake manifold gasket.
Now, this the stupid part of question. How do I figure out which engine I have to get right gasket:

8 1.8L MFI DOHC
or
L 1.8L MFI DOHC

Thanks for your time
(First time on site, should I be piggy backing this p0171 thread or making a new one...)

[vibrologist]

They made Vibes in 2016?

The 8th position of the VIN indicates the engine type.

[zbyers]

Hi Vibers,
(2016 2WD base automatic)
I am getting the P0171, intermittently.
I did notice a few times that it was idling funny, jumping around.
So am going to replace the intake manifold gasket.
Now, this the stupid part of question. How do I figure out which engine I have to get right gasket:

8 1.8L MFI DOHC
or
L 1.8L MFI DOHC

Thanks for your time
(First time on site, should I be piggy backing this p0171 thread or making a new one...)

I am assuming you mean an '06 Vibe. Easy way to tell: if you have aluminum intake = L (2ZZ engine). If black plastic intake it is the 1ZZ engine. If it's auto = 1ZZ.

[tercelerator]

Oh jeez, yes. Meant 2006. Thanks so much for the help.