Runs badly

[jusssi]

Engine setup is quite stock; cam etc. Issue is that when start engine first it runs hi idle and after set set closed loop and low idle speed it runs good 30 sec and then starts to stumble, misfire etc. and frequently dies. Everytime same thing, first good then bad. Cap, rotor, wires etc. is new. Fuel pressure keeps good.

 

[atkonkler]

Re: Runs badly

Engine setup is quite stock; cam etc. Issue is that when start engine first it runs hi idle and after set set closed loop and low idle speed it runs good 30 sec and then starts to stumble, misfire etc. and frequently dies. Everytime same thing, first good then bad. Cap, rotor, wires etc. is new. Fuel pressure keeps good.

Disconnect the map sensor to see if it runs better....if it runs better....map sensor it is....replace....open a beer and enjoy!:tup:

 

[jusssi]

Re: Runs badly

Thanks for response, but I check'd map and its voltage readings are reasonable and I have tunerpro which shows same too. But I open that beer in any case...

 

[atkonkler]

Re: Runs badly

Thanks for response, but I check'd map and its voltage readings are reasonable and I have tunerpro which shows same too. But I open that beer in any case...

Just for shits. ..start the truck....unplug the map sensor to see if it runs better and follow that up with another beer. :tup: I had no code or anything with mine....it had a high idle and would die....just an fyi!

 

[sae]

Re: Runs badly

Does it only die at idle or while being driven too?

 

[Baythan]

Re: Runs badly

Cap, rotor, wires etc. is new. Fuel pressure keeps good.

If you just put in new wires, double check that you didn't cross any. If would def cause truck to stumble. (ask me how I know...)

 

[jimmyz79]

Re: Runs badly

Might be clogged catalytic converter?
Had same happen on an old Camaro, ran great cold, warmed up and krapped out...

 

[jusssi]

Re: Runs badly

It may die at idle. Wires, well they aren't so nicely there... I'll be thankful for tips and pics how is the best way to route them, especially dist cap end?
Catalytic converter is also new.

 

[sae]

Re: Runs badly

Maybe IAC if it starts and runs good to a point every time then stalls, but still drives fine

 

[RealFastV6]

If it starts getting shitty as soon as it goes into closed loop then the oxygen sensor would be a pretty good bet, no?


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[sae]

Re: Runs badly

If you just put in new wires, double check that you didn't cross any. If would def cause truck to stumble. (ask me how I know...)

While you're in there, make sure they aren't touching the down pipe if you bought generic 4.3 wires that tend to run a bit long. The wires before I bought the RPM set would sag and get really close to the downpipe and I'd get misfires too

 

[Jimmy]

Re: Runs badly

I'm half lit But it sounds to me that the coolant temperature sensor (is that what its called?)is ****ed.

Any codes?

 

[jusssi]

Re: Runs badly

Thanks for responses. It isn't map. No iac either I think, it misfires and stumble at rev too. O2 sensor is new and it keeps afr pretty well at closed loop. Coolant temp sensor check'd.
I'm quite sure it's ignition; It was running idle for awhile maybe 5 minutes, not bad but some stumbling and misfiring, but went badly... see video>>
VIDEO

 

[atkonkler]

Re: Runs badly

Test the ignition control module. Shot in the dark...

 

[Quickstop [UK]]

Re: Runs badly

Well, I've seen trucks run much worse. Plugs ok? I assume you changed them but didn't see that in the list. How is the fuel pump/filter? Any knock? Have you got Datamaster to log it idling?

 

[Davemc1963]

Re: Runs badly

I guess the ign coil is probably next to check, and/or the two harness/wires to them (1 x 2 wire, 1 x 4 wire). The short two wire harness is by the D/S fuel rail and a bit susceptable to heat damage, but easy to check.

Try substituting for a known good coil, or checking the pri/sec resistances. I'm assuming there are appropriate specs in the W/S manual, but dont know for sure. That said, I have had coils that measure ok, but break down under load or if they get hot.

 

[jusssi]

Re: Runs badly

Ok, icm should be ok. I put new ac module few years ago, but this truck is been in garage since then...

 

[TNPhoon]

Re: Runs badly

I'm half lit But it sounds to me that the coolant temperature sensor (is that what its called?)is ****ed.

Any codes?

FWIW this was the issue with mine once and it was doing the same thing. You stated you checked that though?

 

[jusssi]

Re: Runs badly

No codes, coolant temp sensor shows reasonable value on tunerpro and made I made some checks wit ohm meter. Tried with another coil and same. How about distributor, opinions? I made one log with tunerpro, if somebody can check it.?

 

[Mingus]

Re: Runs badly

Watching that tach jump all over the place I would try a new ignition control module. The fact yours is barely used doesn't mean much. I've had a couple go out that were almost new in a Blazer I used to own.