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TBI Throttle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.

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Old 10-04-2008, 03:26 AM   #1
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engine starts to stumble and run rough after warm up

well the other day i was driving home i stopped by the store and pick up crap to take home...not important um after i started back up and pulled out of my parking spot it bogged and died, started right back up and ran good for about 2 blocks and then died again, tried to start it back up nothing, waited a hour ran for about 2 mins then bogged and died, i can hear my fuel pump coming on and i replaced the fuel filter not too long ago. After i got it towed home wednesday nite i left it alone thursday and now today i started it right up, ran good and then after it got warm the rpm jumped around a bit but not drastic maybe 200rpms from 900 to 700 or so. i shut it off before it could die. i'm hoping to post a video up later so for now this is all . please help and thnx guys.
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Old 10-04-2008, 10:37 PM   #2
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Re: engine starts to stumble and run rough after warm up

If it seems to be running rich as it warms up, check the CTS (coolant temp sensor). On an L03 it's screwed into the manifold near the thermostat housing toward the passenger side.

If you check the resistance between the two terminals on the sensor it should be ~3K ohms when cold and near 200 ohms around 200 deg F.

When mine was bad the resistance was around 30K ohms as the engine warmed up - opposite of what it should be. The resistance should go down as the engine warms up. In fact, the engine ran better with it disconnected. But, it would also throw a SES code

It's about a $15-20 part at most auto part stores. But, I would only change it if it doesn't check out.
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Old 10-05-2008, 06:30 AM   #3
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Re: engine starts to stumble and run rough after warm up

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Originally Posted by 89IROCZ28 View Post
If it seems to be running rich as it warms up, check the CTS (coolant temp sensor). On an L03 it's screwed into the manifold near the thermostat housing toward the passenger side.

If you check the resistance between the two terminals on the sensor it should be ~3K ohms when cold and near 200 ohms around 200 deg F.

When mine was bad the resistance was around 30K ohms as the engine warmed up - opposite of what it should be. The resistance should go down as the engine warms up. In fact, the engine ran better with it disconnected. But, it would also throw a SES code

It's about a $15-20 part at most auto part stores. But, I would only change it if it doesn't check out.
would this also cause it to stall? i'm going to check it out tomorrow first thing.
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Old 10-05-2008, 08:21 AM   #4
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Re: engine starts to stumble and run rough after warm up

I had a problem like this and it ended up being a stuck EGR valve.
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Old 10-05-2008, 09:04 PM   #5
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Re: engine starts to stumble and run rough after warm up

Yes, it would eventually stall and be impossible to restart until the engine cooled down. Then it would start and run until it warmed up again. Although, it became more difficult to restart each time as the plugs became fouled. I ended up replacing a brand new set of plugs b/c they were so badly fouled from running too rich.
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Old 10-05-2008, 09:37 PM   #6
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Re: engine starts to stumble and run rough after warm up

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Yes, it would eventually stall and be impossible to restart until the engine cooled down. Then it would start and run until it warmed up again. Although, it became more difficult to restart each time as the plugs became fouled. I ended up replacing a brand new set of plugs b/c they were so badly fouled from running too rich.
wow what you just said is exactly what is happening with the car, it would not restart until it will cool off. thnx foe the advice
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Old 10-08-2008, 02:36 PM   #7
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Re: engine starts to stumble and run rough after warm up

Hey guys just giving you an update, i replaced the EGR valve (dirty as ****) and non-op. i checked the resistance on the CTS (engine coolant temp sensor) and i was 2.041kOhms cold and 146ohms hot. So I still have to replace the sensor because i busted the connector on top when i was putting it back on heheits ok tho, it will still connect the only thing is that the plastic casing broke off. but I'm am replacing because that thing is gonna start coroding sooner or later and it looks ghetto. Thank you guys for all the advice every thing was easy off n on parts. and good luck with your guys's rides.

BOB
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Old 10-08-2008, 08:13 PM   #8
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Re: engine starts to stumble and run rough after warm up

FireTurdWS626 - Good to hear you got it running.

WS685ta - Good call on the EGR.
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Old 10-13-2008, 09:49 PM   #9
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Re: engine starts to stumble and run rough after warm up

HAHAHAHA, guess what guys, she broke down on me today.

I only drove her 3 times(liqour store and back) since i replaced the EGR valve and CTS sensor. I was on my way to work in the firebird and didn't even make it there, it ran great for about 40 mins went to dmv by my place which was 5 miles away and then went of to work from there which is 17 miles from mile place and only made it 14 miles when she stumbled bogged ran shity and died, i was in the street so i fired it back up while flooring it and it sounded bad, gave me enough just to make it into a parking lot.(20 ft) so i wait 3 and 1/2 hours started it ran for about 1 min and shut off did that 5 times until it did not wanna start, just cranks. I replaced the coil cause i had money in my pocket for it and my buddy on the phone said it might be that. I installed it, same stuff. Gave my buddy a call, offerd me a tow to his shop (in my head *this is ****ing ****) i told him about it breaking down b4 and the parts i replaced. He offerd to look at it for me and He'll let me know what parts I'll need to change.


Mostlikley the fuel pump tho cause i had someone crank it for me while i had the air cleaner top off and injectors were not squirting, all fuses fine and thats it lol. I just got home had dinner and know i sit and wait but if you got any thoughts or opinions, shoot em my way guys.


THANK YOU REAlly for the help, all the parts sudgested did really need replacement but there was still more too it hehe.

Later on guys,

-Rob
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Old 10-13-2008, 10:26 PM   #10
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Re: engine starts to stumble and run rough after warm up

Yep! Check fuel pump, pressure regulator and injectors for sure. Check the injectors using a noid light to see if you're getting normal pulses when the engine is cranked...

There are a number of "no start" issues to look into, but the above is a good start. Please keep us informed.
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Old 10-13-2008, 11:53 PM   #11
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Re: engine starts to stumble and run rough after warm up

Quote:
Originally Posted by dctrumpet View Post
Yep! Check fuel pump, pressure regulator and injectors for sure. Check the injectors using a noid light to see if you're getting normal pulses when the engine is cranked...

There are a number of "no start" issues to look into, but the above is a good start. Please keep us informed.
I could see no fuel being spray from the injectors when i had some one crank it, but the car is currently at my buddy's shop as i stated so hes taking a look at it for me (free diag and tow) what a buddy. so as soon as i know whic well be tomorrow or wednesday. so cya laters
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Old 10-16-2008, 06:41 AM   #12
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Re: engine starts to stumble and run rough after warm up

5 bucks says the little 6 inch piece of fuel line inside the tank between the FP and the sending unit busted open
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Old 10-17-2008, 04:16 AM   #13
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Re: engine starts to stumble and run rough after warm up

so for some reason two problems occurred, coil went bad (gets up to temp and shuts off my ride) and my fuel pump was weak. so i swapped em out and car is fixed. So no worries guy the fireturd aint going down to easy and when she does shes not down for long, i treat my lady good :-D later days guys.

-Rob
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Old 10-19-2008, 03:06 PM   #14
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Re: engine starts to stumble and run rough after warm up

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Originally Posted by FireTurdWS626 View Post
so for some reason two problems occurred, coil went bad (gets up to temp and shuts off my ride) and my fuel pump was weak. so i swapped em out and car is fixed. So no worries guy the fireturd aint going down to easy and when she does shes not down for long, i treat my lady good :-D later days guys.

-Rob
Saying coil You mean igntion coil? Sorry, I have the same problem on my Camaro RS 1991. So I need to know what exact should I replace.
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Old 10-20-2008, 04:05 AM   #15
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Re: engine starts to stumble and run rough after warm up

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Saying coil You mean igntion coil? Sorry, I have the same problem on my Camaro RS 1991. So I need to know what exact should I replace.
yes i do mean ignition coil but my car truly needed the coil replaced
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Old 10-20-2008, 04:38 AM   #16
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Re: engine starts to stumble and run rough after warm up

It seams my car needs the same. I have allready replaced spark plugs, spark plug cables, EGR valve. I have installed the dual speed MARK VIII fan - didn't work. It was a real PITA for me. So now I will go for the rest - temperature sensor, coil, and fuel pump. I hope the problem will be solved.
But I think it is the coil as mine as it looks really rusty, so very old as well.
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Old 10-20-2008, 07:40 AM   #17
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Re: engine starts to stumble and run rough after warm up

My car is a TBI but this is a pic of my coil. Cost about $50.
The fuel pump, you can take the tank down or do a search in the fab section. I think it was either a trap door or access door, or fuel pump access door. Something like that. Pics and all.
Temp sensor is on top of the intake, buy the t-stat. Make sure you get the right one, that controls the computer, the guage is controled by another one.

Click the image to open in full size.

Click the image to open in full size.

Drivers side, if you look closely the tan behind the coil is the dizzy.
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Old 10-27-2008, 01:57 PM   #18
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Re: engine starts to stumble and run rough after warm up

Post the pics again, please.
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Old 10-27-2008, 01:57 PM
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