I need some help! 2.9 running rough

[KCBFord1]

my broncoII 2.9L fuel injected is having some issues. here are the symptoms.
when first started it will have an irratic idle, 500 rpm to 1500 rpm, about 5 min after it will smooth out

idle will very anywhere from 900 rpm to 1400 rpm, doesnt seem to have any sort of pattern, but it favors the higher rpm most of the time

when driving at a constant speed with the rpm between 1500 and 2100 rpm the engine will studder and jerk the truck, when reving engine in nutrel, engine seems to run ok for the full range of rpm's.

throtle set screw is all the way back, ive replaced the cylinder heads, the spark plugs, the coil, the fuel pressor regulator/diaphram, air filter.

i cant figure it out.
thanks guys

 

[91rangerxlt]

when driving at a constant speed with the rpm between 1500 and 2100 rpm the engine will studder and jerk the truck, when reving engine in nutrel, engine seems to run ok for the full range of rpm's.

got this problem with my 90 ranger with the 2.9 when im on the hiway it cuts out at about the same rpm. i think its just plugs on mine though

 

[BlackBII]

Have you tried cleaning the IAC?

 

[1987rangerxlt]

Codes

Use an analog vom to check for codes. There is a whole list of them here on the ranger station.

 

[KCBFord1]

No, but i will tonight! thanks for the tip.

Have you tried cleaning the IAC?

 

[KCBFord1]

Vom?

is that just a voltmeter? could you go in to detail. or is it a code reader?

Use an analog vom to check for codes. There is a whole list of them here on the ranger station.

 

[Psychopete]

is that just a voltmeter? could you go in to detail. or is it a code reader?

It's just a volt meter. You don't want to use a digital one because you can't see the pulses reliably. You could also use a 12 volt test light. Check out EEC-IV diagnostics in the technical library.

Pete

 

[KCBFord1]

Oh i see now, wow this is realy cool, thank you!!!!!!

It's just a volt meter. You don't want to use a digital one because you can't see the pulses reliably. You could also use a 12 volt test light. Check out EEC-IV diagnostics in the technical library.

Pete

 

[KCBFord1]

i just cleaned it, it seems to be working good now. thanks! its still ilding high but i think i have a vacume leak or intake gasket is bad.

Have you tried cleaning the IAC?