major engine problem

[redrover]

I have a '99 disco II with a major problem
Start up is fine, but engine wants to die right away. It will barely keep running and then after a few minutes rpm's steady out at around 800.
When trying to drive I can barely get it up over 15 or 20 mph and it hesitates badly, sputtering.
On Saturday - Have checked spark plugs - great condition, gap set correctly. Battery/alternator both good. Spark plug wires good. Plenum gasket replaced about 6 months ago. Tested vaccuum - about 11 @ startup, then immediately drops to 6, slowly working itself up to about 14 after a 5-minute period @ idle. At approx. 3,000 RPM (Holding throttle steady) it reads 16 & then drops to 9 - 10 about every 10 seconds. Has about 120,000 miles on engine. The problem of not going over 15 mph happened as of last night, after these tests. But, it was hesitating badly the last few days prior to testing, and have had an ongoing worsening problem at startup.
Any info would be greatly appreciated.
Sorry in advance I'm new to this.

 

[joey]

Fuel issues? Check the fuel pressure.
Cats gone bad? Have them checked or do you smell rotten eggs?

Are you getting any codes?

Do you have a decent OBDII scanner that can monitor the engine while it is running?

 

[redrover]

fuel pressure is ok
no problem with cat conv's
I'm trying to borrow a reader from a friend
maf cleaned
I'll post as soon as I get newest codes

Previously read codes before full failure were
p0133 sensor circuit slow response bank 1 sensor 1
p0134 sens circ no activity detected bank 1 sensor 1
p0171 system too lean bank 1
p0174 system too lean bank 2
p0300 random multi cylinder misfire detected
p0301 cyl 1 misfire
p0303 cyl 3 misfire
p0305 cyl 5 misfire
p0306 cyl 6 misfire
p0307 cyl 7 misfire
p0308 cyl 8 misfire

I hope that this helps with diagnosis
Thank you

 

[95d1]

Check stepper motor. Napa has them cheap for a 85 chev astro

 

[redrover]

I replaced the intake, plenum and valve cover gaskets.
I still have codes
p1300 manufacurer contrl. ignition system or misfire
p0305 cylinder 5 misfire detected
p0307 cylinder 7 misfire detected
p0733 gear 4 ratio incorrect
p0734 gear 4 ratio incorrect
p0300 random/multiple cylinder misfire detected
p0308 cylinder 8 misfire detected
I hope that this help
Any thoughts?
Thanks
Pat

 

[joey]

I would check the air filter and clean the MAF sensor as well as the butterfly in the intake...

Sounds crazy, but I have seen the MAF sensor put out weird codes.

 

[redrover]

MAF was just cleaned and the air filter was changed 10,000 miles ago
I am getting varying vacuum readings at start-up. Starting at 11 dropping to 6 (engine almost dies) then up to 14. Pushing on accelerator almost kills engine.
Could bad wires/plugs cause this if misfiring? Or O2 sensors? Also gassy smell on start-up. Fuel pressure is 50.
Thanks
Pat

 

[joey]

Could be a TPS issue, but with a gassy smell I would lean more toward possible bad injectors.... Could very well be injectors... you could get them leak tested..

 

[redrover]

Sorry what is TPS?
Do you think that it could possibly be the computer?
Pat

 

[joey]

Throttle Position Sensor (TPS).... could be the ECU, but I doubt it... normally it is the things that make the computer able to do things.