95 blazer runs real rough

[travtug123]

I have been working on my blazer for about a month's. I have replace several new parts.

FUEL PUMP This will be second one
PLUGS & WIRES
CAP
TROTTLE BODY SENSOR
O2 SENSOR BANK 1
Coolant temp sensor
EGR Value
fuel pressure regulator


We have check the fuel pressure it seems to be okay. We also hook it up to a computer it came up with a random misfire po300. The truck run at a idle really well. However, when you take it down the road t falls on its face. When you push to the floor it gets up and goes but runs real rough. We are losing fuel pressure. We replaced the fuel pressure regulator now it will not start. So we also replace the fuel pump again thinking that we got a bad one. It still will not start please Help.

Does anyone have a clue PLEASE.

[blazerbob91]

The fuel pressure regulator is connectd to the spider assembly under he plenum. Get a fuel pressure gauge and check the pressure at the schraeder valve on the drivers side an the back of the plenum. You should have 60psi. Watch the gauge after you shut it down. It should maintain pressure for a whilel

[Blazernick]

I am having simmillar problems. My truck Idles great. But when i start going between 2000 and 3500 rpm my truck bucks and skips, it sounds like weak fuel pressure. I put on new wires plugs cap and rotor. but im getting the missfire code. I need help. IM going to check the fuel pressure like blazerbob says

[travtug123]

Thank you for responding. I check the fuel pressure it was not okay. So replace the fuel pump again and the fuel pressure regulator. It started for a few minutes then died now it will not restart. Now what do we look for?

[MT-2500]

What engine code?
What is the fuel presure reading?
Does it have good hot blue spark to all spark plugs?
Will it start with a shot of carb cleaner?

[travtug123]

We did not have any codes except the po300 random misfire. Yes there spark to all the plugs. The fuel pressure is now between 60-62psi and stays. No it will not start no matter what we do.

[travtug123]

Now they think that it is the control module ing., camshaft sensor, or the crankshaft sensor. I can not keep putting money in this truck.

[travtug123]

Why would all these sensor go bad at once?

[MT-2500]

Originally Posted by travtug123

Why would all these sensor go bad at once?

Sounds like you have a THROW PARTS AT IT MECHANIC.
Proper testing will tell you the problem.


Got compression?
Pull plugs and check compression and see if plugs are wet or dry on the ends.
Is the plug wiring right?
Is it a flat top dist or old style dist cap?
What is the engine vacuum readings at idle and at 2K rpm?

[travtug123]

Originally Posted by MT-2500

Sounds like you have a THROW PARTS AT IT MECHANIC.
Proper testing will tell you the problem.


Got compression?
Pull plugs and check compression and see if plugs are wet or dry on the ends.
Is the plug wiring right?
Is it a flat top dist or old style dist cap?
What is the engine vacuum readings at idle and at 2K rpm?

Yes the truck has compression and the plugs are wet. The truck has a flat top dist. Yes the wiring is right as well. I do not know of any vaccum leaks because the truck will not start.

The truck ran up to just a few days ago. We put the parts on one at a time. Everything was okay with the starting until we put on the new fuel regulator. And then it started for a few minutes then died. We found there was a vacumm leaks and fix it. The truck started again for a few seconds and died. It sound go no hesitation or nothing it just died. It has not started since. And still did not have fuel pressure so we put the second fuel pump on got the fuel pressure back to 60-62psi and stays. But truck will not start.

[MT-2500]

Is it getting good hot blue spark to all plugs?

[Schrade]

Originally Posted by travtug123

Thank you for responding. I check the fuel pressure it was not okay. So replace the fuel pump again and the fuel pressure regulator. It started for a few minutes then died now it will not restart. Now what do we look for?

What fuel pressure did you check?
Static motor off?
Idle with vacuum off of FP regulator?
Idle with vacuum ON FPR?
Pedal down test in second gear - guage taped to windshield, to check for acceleration enrichment / vacuum response???

Random misfire shouldn't be too hard to trace. Start from the rotor, and work back to coil, ignition module, etc. Inspect first!

[Schrade]

Originally Posted by MT-2500

Sounds like you have a THROW PARTS AT IT MECHANIC.
Proper testing will tell you the problem.

Yup.

Get it out of his hands YESTERDAY, and get it elsewhere.

If a mechanic cannot trace a 'random misfire', he is NOT a mechanic, he's a fisherman.

[travtug123]

Originally Posted by MT-2500

Is it getting good hot blue spark to all plugs?

Yes it is getting good fire.

[travtug123]

I guess you can take the control module ing. can be tested so I am going to have it tested.