Engine stumbling

[AJs72K5]

Took the truck out for a drive last night. It was a bit cool, truck cruised at 75mph @ 2200 and the temp gauge never went above 200. Drove great!

Was driving today, and it was a bit warmer (75* in San Antonio). At about 40mph, in either 2, 3, or 4 (overdrive, but converter not locked up) the engine starts stumbling really bad. When it stumbles, the tach starts bouncing a lot and it feels like the truck is gonna die. The temp gauge was @ about 220. It idles ok, and accelerates well up to about 35mph. Any ideas, or where should I start looking first?

 

[obijuan]

fuel delivery?

 

[az_762_nato]

if the tach was jumping around a lot it may be the module taking a crap on ya

 

[obijuan]

actually AJ i just replaced that and my truck runs great. mine was doing that so i replaced the transmission.

it was a sequence of events, one of which was the module.

 

[blazin_blazer]

definitely the fuel filter would be my 1st suspect. possibly the fuel itself/water in fuel, have you got gas from a gas station you've never used b4?

 

[AJs72K5]

Tach was only bouncing when the engine was stumbling....and it was from actual rpm and lower. I'm halfway thru a tank from the Exxon around the corner from my house. Not the 1st time I've used it. I hate to admit this one, but I don't think there's a filter on the fuel line....one of those PO things.

On the module...are we talking the HEI module on the distro? The tranny should be good, it's not even 6 months old.

 

[blazin_blazer]

u running a q-jet? if so theres an inline filter in the carb, and seen a many stop up and lets the engine empty the fuel bowls then it stumbles as fuel trickles back in.

 

[AJs72K5]

No, it's got a Holly 670.

Only place there might be a filter is inside the fuel rail. Never opened it up, so I dunno.

 

[blazin_blazer]

ok, i tap out...tag who's next, sounds like a fuel delivery or fuel problem 2 me, since tach is bouncing b/c engine rpm's are actually changing.

 

[resurrected_jimmy]

The high temp suggest running lean which point right back to fuel delivery, sorry a cannot be of more help

 

[Thunder]

If your problems show up after the engine is warmed. Try replacing the Distributor module.

 

[AJs72K5]

Definately a temp related issue. Went and drove the truck during lunch. It drove like a champ when cool. When the temp guage got to about 210*, it started stumbling again.

 

[bp71k5]

Odd. Any chance you have an electric fan other setup that's kicking on at 210 degrees?

 

[AJs72K5]

I do have an electric fan. The flexalite thermostat doesn't have an exact setting. It should be kicking in somewhere around 190 to 200.

 

[bp71k5]

I was just wondering if there was an electrical problem happening when the thermostat tells the fans to turn on. If you have a manual cutpff switch you could isolate that from the system to try and narrow it down. I guess you could also just disconnect the sender wire to test that theory out.

EGR clogged? Electric choke bad?