gixxer

I have a 91 pickup 4x4 22re with 274,000.

Truck runs fine when warm but lately I have a stumble /hesitation when first starting the engine in the mornings and trying to drive off in first gear, then second. The engine acts like water is passing thru the gas, and stumbles for afew seconds then it wakes up and runs.. I ran 2 cans of seafoam thru the tank, and a can of dry gas thinking it was water in the fuel causing the problems but it continued so I put in NEW plugs/wires/cap/rotor and fuel filter, but is still continues to stumble when first starting and it also stumbles when the truck starts to climb a hill ...it acts like a misfiring or stumble, then it usually works fine after about 2 seconds of stumbling.

Any Ideas as to what might be happening ? It runs fine on straight aways and seems to get better when the engine is fully warmed up.

Timing is correct also...It does not help if I retard or advance the timing..it still contiues to stumble when cold or start climbing a hill.

I also put on a brand new idle air control valve, and I blocked off the hole for the idle air , and it still had the stumble/hesitation.

Hugh_Mann

Did you also look at the plugs? How about the igniter?

gixxer

Plugs look fine..they are brand new NGk's. Color on them is correct. And I swapped out the igniter with a known good one, and it still did the same thing this morning. No codes are present...just a steady flashing check engine light when jumpering the diagnostic port.

gixxer

Swapped out the coil with brand new one....still having problems... Idles fine....but when you try to drive off..it stumbles and misses like its getting no spark or fuel....Once the engine warms up to correct temp..then the truck runs fine.

Any more ideas to what might be wrong ? I popped off the fuel return line from the regulator and fuel comes out at a steady flow, but seems to have air bubbles in the line.

Hugh_Mann

You could also test the fuel pump if you haven't already.

gixxer

Fuel pump is pumping but how do I test the correct pressure ? Where do I attach the pressure tester ? And what is the correct pressure reading supposed to be ?

gixxer

I tested the fuel pump and it tested within spec between 38-44psi.

wyoming9

iTrader: (1)

Like some women I know they just take a while to warm up!!

Does it run fine if you let it warm up??

Have you checked the cold start injector is working like it should. perhaps a bad sensor is telling the ecu the engine is all ready warm

gixxer

It starts right up in the cold/damp weather and hot weather. Idles fine when cold..idles fine when warm...Drive the truck out the driveway , either cold or warmed up, and it acts like its fouling a plug, starving for fuel...starts to buck ...then about 5 minutes later it starts working fine again....until you approach a slight hill...then it starts again , but no where near as bad as the first time.

Let the truck cool down , and the problem starts again.

Cold start injector seems fine

The truck sat for about 2 months, it ran fine before sitting...I put in a new battery, cat convertor, and tail pipe/muffler. Drain all the fuel from the tank, and replaced with fresh gas. New plugs /wires/cap rotor fuel filter

gixxer

Found the problem...turned out to be 2 bad spark plugs...I replaced the old with BRAND NEW NGK's..and the problem was still there....I tested all the sensors and everything was good....I couldn't find the problem.....so for the hell of it I tried another set of NEW PLUGS...and that fixed my issues I was having.

2 BRAND NEW PLUGS that were bad from the factory...The engine would Idle fine, and the spark was fine on all 4 plugs at idle, but once you put a load on the engine...the plugs must have been misfiring or grounding out.

I replaced all 4 plugs again, and everything works the way it should. Put 200 miles on today and everything seems fine now.