# Engine wants to die with a little pedal (350tbi)



## Banksy (Aug 31, 2005)

My Chevy has a small throttle issue. It starts just fine and idles fine (with what feels like a small bump or misfire some times, very slight). If I lightly give it just a little throttle, the engine starts to stall and sputter, but doesn't die and this is in Park or Drive. If I floor it, it doesn't do it at all. There is just that initial spot and after that it's fine. 

Ideas?


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## Banksy (Aug 31, 2005)

It barely takes 3 revolutions to fire up. Just thought I'd add that.


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## dieselss (Jan 3, 2008)

Assuming its only when its cold ??


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## Banksy (Aug 31, 2005)

Yes when cold. Can't remember when hot. I'll warm it up and check.


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## dieselss (Jan 3, 2008)

Ok. 2 of ours do it,,,,honestly I just tell the guys to warm them up. If I ever get time or really care I was Gunna look into the cap and rotor area but not top on my priority list


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## Banksy (Aug 31, 2005)

I just went out and let it warm all the way up and it pretty much goes away. Couple times there was a very slight hiccup, but maybe it's just 23 year old 1990's technology. Never owned a TBI before, so I guess I'll just have to get used to it's quirks. I don't even have it on the road yet, so I don't know all it's little quirks yet.


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## dieselss (Jan 3, 2008)

Ok....maybe someone else might chime in and say something else


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## T-Trim (Nov 8, 2005)

I would check the egr valve. I had a 92 k-5 that did the same thing. Once I replaced it. good at new. If you like I can check on "how to check a egr" just pm and have it att mike . we have three other people in ther company using the same log in.


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## Banksy (Aug 31, 2005)

Does my truck even have an EGR??


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## T-Trim (Nov 8, 2005)

Its between the upper rad hose and the TB. Its bolted to the manifold.


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## jasonv (Nov 2, 2012)

Throttle position sensor, mass air flow sensor.
I suppose it *could* be the EGR, but I doubt it. I had a really bad EGR in a TBI Nissan (stuck wide open), never hesitated, just ran rough.


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## Holland (Aug 18, 2010)

jasonv;1566998 said:


> Throttle position sensor, mass air flow sensor.
> I suppose it *could* be the EGR, but I doubt it. I had a really bad EGR in a TBI Nissan (stuck wide open), never hesitated, just ran rough.


No maf on a tbi. They are speed density.

I would start out checking the coolant temp sensor. Remember tho, there are two on this engine. One up by the t stat is for the ecm, other is for the gauges. Get ahold of a scanner and see what temp its reading.

Any questions at all hit me up. Thumbs Up


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## jasonv (Nov 2, 2012)

Holland;1567021 said:


> No maf on a tbi. They are speed density.


Hard to keep up with all the brands and what they like to call all the different parts that are really the same. On my Nissan, they called the part between the injector body and intake manifold the MAF. Whatever it is being called, it tells the thing how much air is going through. If that isn't working right, it will provide the wrong mix and timing.


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## dieselss (Jan 3, 2008)

Well,,,gm ain't a Nissan. Tbi is real primitive. Hardly any sensors compared to now adays


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## Holland (Aug 18, 2010)

jasonv;1567129 said:


> Hard to keep up with all the brands and what they like to call all the different parts that are really the same. On my Nissan, they called the part between the injector body and intake manifold the MAF. Whatever it is being called, it tells the thing how much air is going through. If that isn't working right, it will provide the wrong mix and timing.


No offense, but if you dont know the vehicle the op is talking about then how are you going to help him?


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## theholycow (Nov 29, 2002)

EGR was my first thought. While the EGR valve on my car, fully actuated, is incapable of stalling *my* engine, others can certainly stall other engines under certain conditions.



jasonv;1567129 said:


> Hard to keep up with all the brands and what they like to call all the different parts that are really the same. On my Nissan, they called the part between the injector body and intake manifold the MAF. Whatever it is being called, it tells the thing how much air is going through. If that isn't working right, it will provide the wrong mix and timing.


MAF is Mass Air Flow, it measures air by mass (weight). This system does not use any measurement of how much air is going through, neither by mass nor by volume. It uses MAP, Manifold Absolute Pressure. It *calculates* (rather than measures) how much air moves through based on air pressure in the intake manifold and RPM. (Side note: Systems equipped with the MAF sensor usually/always also have the MAP sensor but don't use it in the same way except if the MAF fails.)


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## Banksy (Aug 31, 2005)

I had a 351w carbed 1986 F250 and that thing would act just like this truck when it was cold. A TBI is really a fancy carb, in a manner of speaking. 

A new temo sensor and tps are el cheapo on rockauto.com.


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## Snowzilla (Oct 24, 2009)

The TBI may have been primitive, but my experience was it was very reliable. I had an '89 5.7L which is still running for a new owner. It would stall and left me stranded a few times. The solution for me was replacing the distributor. Maybe a shop could rule out ignition with diagnostics. I can't recall if the distributor had a vac advance on it. But may be something to check, cracked line,etc. 

I recall a few hiccups here & there at idle but I excused it as old age.


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## T-Trim (Nov 8, 2005)

did you figure it out?


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## matzke3 (Oct 15, 2008)

Those dist do not have any vac control. If the engine totally dies at idle and restarts just fine its usually the dist. I've had several of these tbi trucks and most of them with the 747 ecm (likely what you have) and an AUTO trans prom do that. It seems those programmed with a manual do not. I'm trying to program that out of my project plow truck (400 built tbi). I think it is a sag in the timing curve. Meanwhile I suggest resetting the timing to 0 degrees with the brown/white wire connector unhooked, and or finding an ecm or prom for a manual trans.


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## Banksy (Aug 31, 2005)

T-Trim;1568334 said:


> did you figure it out?


Off this weekend. I'll pull it into the garage then. It seems to only do it when cold and I don't have tags on it yet, so it hasn't been a priority.


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## T-Trim (Nov 8, 2005)

Banksy;1568621 said:


> Off this weekend. I'll pull it into the garage then. It seems to only do it when cold and I don't have tags on it yet, so it hasn't been a priority.


Well just pm I can look it up.


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## ServiceOnSite (Nov 23, 2006)

I have thrown countless dollars at this same problem on mine. Every single sensor to cam shaft and timing chain. When on the gas the truck dont miss a beat. When coming to a stop off throttle is when it seem to do it for me. My truck more or less has been completely restored and runs and plows great. Its just an annoying thing that the truck does that i haven't been able to figure out, My thought were even to if i put a new long block in that motor would do the same thing being controlled by the same computer. If you have any luck with this please let me know.


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## theholycow (Nov 29, 2002)

Now that this thread is bumped I wonder if the OP ever got it figured out.

ServiceOnSite, what have you replaced and checked?


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## 32vld (Feb 4, 2011)

A cold start problem can be a coolant temp senor. Though he says it starts up ok.

An EGR stuck open will cause the engine to not run at idle. His engine idles.

A bad TPS can have a bad spot where the throttle is just opened off idle but read correct every where else in the throttle movement range.

TPS system one should be able to remove air cleaner and observe injector spray pattern. There should be no drops but a fine consistant 360 d spray.

GM TBS does not use a MAF but uses a MAP sensor which costs a lot less money then a MAF. $350 vs $50 prices many years ago.

Coolant temp sensor can only be tested cold first because you need to see it's ohm value change from cold eng to warmed up eng.

Usually a bad sensor will read as if the engine is warmed up when in fact the engine is cold. This will tell the computer the engine is warm so no extra fuel is fed to "choke" a cold engine so it will start. Again he does not have a cold start problem but an off idle stumble.


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