[dave91sub]

Does anyone have anymore ideas for wanting to die at lights?

Mine is doing the same or sort of the same thing, along with the stop lights while coasting down hills, it wants to die too.but when running down the road its fine.

I have read all the posts and changed or checked every thing that can be checked. in my 91 its the ODB1, and I do not get any codes, when this is happening the check eng light does not come on, some times it runs like nothing is wrong but this is happening more and more.

I've checked for leaks and changed all tune up items, changed the alt, unpluged the AC, dont need that now in alaska, its gotten cold here but this was stalling when it was warm too.timing is good, I dont know what more to say I'm just at a loss now, any help please

 

[ChevyFan]

RE: 91 wanting to die at lights

What's your powerplant Dave? How many miles, etc?

 

[dave91sub]

RE: 91 wanting to die at lights

it has a 350 tbi with 700r4 trans, as far as miles- dont have a clue the odometer stoped at about 140,000 at my best guess that has to be at least 60-70000 miles ago,
i have checked and rechecked everything under the hood, but never checked the fuel pump, that is where im going now, the only problem is that it runs bad but not all the time so i might check something and it is good by the test but not all the time, the only part of the system that hasnt been checked or changed is the fuel pump, if you have a different outlook/idea please no one can seem to figure this out its been to two different mechanics and they come up with the same idea - buy a newer rig, this is not what i want to do . thanks dave

 

[ChevyFan]

RE: 91 wanting to die at lights

Well, the small block chevy at some point is going to break down in different areas. You're talking about something with 200,000 miles under the hood.

Now, that being said, you will notice that there are quite a few guys on here that have Suburbans with high miles. The secret is regular maintenance and replacing stuff when it goes out. So your point is well taken. Something is going wrong ... what is it?

If you've checked everything under the hood, I'll skip stuff like plugs and wires. Believe it or not, I had a car run rough once becuase the snap-connector on the plug wires was breaking ... go figure.

Do you have plans to work on fuel delivery and the pump?

 

[dave91sub]

RE: 91 wanting to die at lights

yes in the next few days (when i get some time- not much of that now adays) i plan to run a pressure test of the fuel system and see what i get the book says i should have 9-13 psi in the line to the tbi with this information i should know alot more, would there be anything else that i should be looking at before digging into the fuel system, i really dont want to change the pump but i dont want to break down in the cold, its been 20 below for the last 2 weeks,

 

[dave91sub]

tested the fuel system, psi was good so i started over testing everything, capping off the vac to the egr valve, test drive and it stopped wanting to die, last time i vac tested the egr valve not a running test, i am replacing it when it comes in and then rehook the vac line and see what happens, i guess this is what happens when you have a problem that is not there all the time.

 

[ChevyFan]

EGR could be the culprit. Either a bad unit or vacuum leak to it. The problem went away though when you capped it off?

 

[TrailLeadr]

Bad EGR Solenoid. Sounds like EGR is working fine.

 

[dave91sub]

now you got me thinking, should a egr valve hold a vac, mine does not. the vac lines test good, but the solenoid, i capped off the solenoid and the problem is gone, now i get a service eng light, i think it would be from the oxy sensor the way that the book reads on how the egr works, but i turn the truck off and then back on and the light does not come back on, it has only come on when i run at highway speeds, and now the idle is a little high

 

[TrailLeadr]

Just want to be sure, I understand this. You disconnected the vac line on the manifold side of the solenoid, tested the solenoid and it held no vac? If that is true, then the solenoid is bad, you should replace it.

 

[dave91sub]

i tested the egr valve itself, is this wrong? does the soleniod hold a vac itself i thought it was just manly a valve to be switched open by eletronic, the lines were tested by themself

 

[TrailLeadr]

Pull the vac line that comes from the manifold to the solenoid off at the solenoid, and do your vac test directly to the solenoid. Keep the engine off while testing. If the vac holds at the solenoid then it's possibly a faulty ECU. If the vac fails at the solenoid then the solenoid is bad, and it should be replaced.

With no voltage across the solenoid the valve is closed, when the voltage is applied via the ECU to the solenoid the valve is open, allowing the EGR to open.

i tested the egr valve itself, is this wrong?

Testing the EGR valve is just part of the process, but it won't help diagnose the solenoid.

You said before that when you capped off the valve the problem went away, but caused a SES light, and high idle. This leads me to believe that the EGR valve is working, because when there is a vac present the valve is opening, and when there is no vac, it's obviously not opening.

Keep us posted!

 

[dave91sub]

Ok did that, tested on the upside of the solenoid, it leaked off, there was one at the store, changed it out- didnt eleminate the problem, this is not rare for me to have multiple problems,(just my luck)

Today the little bit of high idle got alot more, i dont have a tach but it is more then i want it to be almost like something is sticking, possibly freezing up, i dont know, but i could kick it down by mashing the throttal, this is not wise to do on ice.

Back to the orginal problem, after changing the solenoid the stalling wasnt as bad but still there, but then for a little while it ran just fine with no stalling and no high idle, should i change the EGR valve or should i start looking at the ECU, I am at the point of starting to change one thing at a time untill it works right because when I have tested things they test good on the meter, TPS, IAC, this method might work but sounds like it might cost a bit of cash, but Im at that point,

Is there some kind of tester that you can run on ODB1 system to find out what is going on?, or is it just when there is codes.

 

[TrailLeadr]

Is there some kind of tester that you can run on ODB1 system to find out what is going on?

You can still pull info from it, but it won't be as detailed as OBDII. I can't suggest any specific scanner. For starters you might try disconnecting the battery. The ECU may have been trying to compensate for the failing solenoid for long enough that it's set new parameters.

Was the engine idling high when it first started? You wouldn't have a heated o2 sensor in your rig, unless you modified it. So typically when it firsts starts it's going to idle high, and should level out after a few minutes. Especially if it's cold enough to have ice on the ground.

 

[TrailLeadr]

I was just re-reading your previous posts. You said you tested the EGR valve and it didn't hold a vac? If that's true then the diaphragm in the EGR has hole or tear in it. The EGR should hold a vac as well. Sorry, I missed that before.

 

[dave91sub]

replaced the EGR, pulled the codes from the computer. the only code that came out was one for the VSS (this is from the odomiter not working but the speedo does, and I have changed the VSS already. I got one more code for the MAP sensor, but the book said that if you have a rough idle you will get this code. I filled up with supriem and injector cleaner, running down the road the engine hic-uped, i was running about 55mph, and after that the wanting to stall and the high idle has not come back, could it be the O2 senor cleaning up ? the cat. converter? I dont know what I did but it is running good now and no more codes have come up for 2 days

 

[ChevyFan]

Your computer maybe needed to cycle as well after you made the changes.

 

[TrailLeadr]

Sounds like you're on the road to recovery! Like Steve said, give your computer a couple days to cycle. Typically, if I change two or more things on the engine I'll disconnect the battery for a couple min, to let the computer reset. If you didn't already disconnect the battery, I wouldn't bother at this point. Just the ECU learn that's it's getting "Good" info now, and make it's own adjustments.

Happy Idling!

 

[dave91sub]

things are going good, so far I am always waiting for the next shoe to fall, today the temp droped again about 15 below, and it studdered once but not again, I hope things work them selfs out (but thats not my luck) Thanks for the help and the ideas I keep you posted